Endangered and Threatened Wildlife and Plants; Endangered Species Status for the San Francisco Bay-Delta Distinct Population Segment of the Longfin Smelt, 61029-61049 [2024-16380]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 89, Number 146 (Tuesday, July 30, 2024)]
[Rules and Regulations]
[Pages 61029-61049]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-16380]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R8-ES-2022-0082; FXES1111090FEDR-245-FF09E21000]
RIN 1018-BG07


Endangered and Threatened Wildlife and Plants; Endangered Species 
Status for the San Francisco Bay-Delta Distinct Population Segment of 
the Longfin Smelt

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Final rule.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), determine 
endangered species status under the Endangered Species Act of 1973, as 
amended (Act), for the San Francisco Bay-Delta distinct population 
segment (DPS) of longfin smelt (Spirinchus thaleichthys), a fish 
species of the Pacific Coast. This rule extends the protections of the 
Act to this DPS and adds it to the List of Endangered and Threatened 
Wildlife.

DATES: This rule is effective August 29, 2024.

[[Page 61030]]


ADDRESSES: This final rule is available on the internet at https://www.regulations.gov. Comments and materials we received on the proposed 
rule are available for public inspection at https://www.regulations.gov 
at Docket No. FWS-R8-ES-2022-0082.
    Availability of supporting materials: Supporting materials we used 
in preparing this rule, such as the species status assessment report, 
are available at https://www.regulations.gov at Docket No. FWS-R8-ES-
2022-0082.

FOR FURTHER INFORMATION CONTACT: Donald Ratcliff, Field Supervisor, 
U.S. Fish and Wildlife Service, San Francisco Bay-Delta Fish and 
Wildlife Office, 650 Capitol Mall, Suite 8-300, Sacramento, CA 95814; 
telephone 916-930-5603. Individuals in the United States who are deaf, 
deafblind, hard of hearing, or have a speech disability may dial 711 
(TTY, TDD, or TeleBraille) to access telecommunications relay services. 
Individuals outside the United States should use the relay services 
offered within their country to make international calls to the point-
of-contact in the United States.

SUPPLEMENTARY INFORMATION:

Executive Summary

    Why we need to publish a rule. Under the Act, a species (including 
a distinct population segment of a species) warrants listing if it 
meets the definition of an endangered species (in danger of extinction 
throughout all or a significant portion of its range) or a threatened 
species (likely to become endangered within the foreseeable future 
throughout all or a significant portion of its range). If we determine 
that a species warrants listing, we must list the entity promptly and 
designate the species' critical habitat to the maximum extent prudent 
and determinable. We have determined that the San Francisco Bay-Delta 
distinct population segment (DPS) of longfin smelt (hereafter Bay-Delta 
longfin smelt) meets the definition of an endangered species; 
therefore, we are listing it as such. Listing a species as an 
endangered species can be completed only by issuing a rule through the 
Administrative Procedure Act rulemaking process (5 U.S.C. 551 et seq.).
    What this document does. This rule lists the Bay-Delta longfin 
smelt as an endangered species under the Endangered Species Act and 
adds the Bay-Delta longfin smelt to the List of Endangered and 
Threatened Wildlife in title 50 of the Code of Federal Regulations at 
50 CFR 17.11(h).
    The basis for our action. Under the Act, we may determine that a 
species is an endangered or threatened species because of any of five 
factors: (A) The present or threatened destruction, modification, or 
curtailment of its habitat or range; (B) overutilization for 
commercial, recreational, scientific, or educational purposes; (C) 
disease or predation; (D) the inadequacy of existing regulatory 
mechanisms; or (E) other natural or manmade factors affecting its 
continued existence. We have determined that the Bay-Delta longfin 
smelt is endangered due to the following threats: altered hydrology 
(Factor A; largely attributable to water management, including water 
diversions and channel modifications), nonnative species (Factors C and 
E), and the effects of climate change (Factor E; by exacerbating 
drought, decreasing river and stream flows, and increasing air and 
water temperatures).
    Section 4(a)(3) of the Act requires the Secretary of the Interior 
(Secretary), to the maximum extent prudent and determinable, to 
designate critical habitat concurrent with listing. We will publish a 
proposed critical habitat rule in a future edition of the Federal 
Register.

Previous Federal Actions

    On October 7, 2022, the proposed rule to list the Bay-Delta longfin 
smelt published in the Federal Register (87 FR 60957). On February 27, 
2023, we published a document in the Federal Register (88 FR 12304) 
that announced a public hearing and reopened the comment period for the 
proposed rule. Please see the proposed listing rule for a detailed 
description of previous Federal actions concerning this species.
    On December 22, 2023, San Francisco Baykeeper (Baykeeper), a 
nonprofit corporation, filed a complaint in the U.S. District Court for 
the Northern District of California (San Francisco Baykeeper v. United 
States Fish and Wildlife Service, et al. (Case 4:23-cv-06601-LB)) 
challenging the Service's failure to complete its statutory obligations 
to make a final listing determination for the Bay-Delta longfin smelt. 
On April 5, 2024, the court issued an order requiring us to submit the 
final listing determination to the Office of the Federal Register by 
July 22, 2024. This document satisfies our requirement for completion 
of our final listing rule.

Peer Review

    A species status assessment (SSA) team prepared an SSA report for 
the Bay-Delta longfin smelt. The SSA team was composed of Service 
biologists, in consultation with other species experts including those 
from the California Department of Fish and Wildlife. The SSA report 
represents a compilation of the best scientific and commercial data 
available concerning the status of the Bay-Delta longfin smelt, 
including the impacts of past, present, and future factors (both 
negative and beneficial) affecting the species.
    In accordance with our joint policy on peer review published in the 
Federal Register on July 1, 1994 (59 FR 34270), and our August 22, 
2016, memorandum updating and clarifying the role of peer review of 
listing actions under the Act, we solicited independent scientific 
review of the information contained in the draft Bay-Delta longfin 
smelt SSA report (Service 2021, entire). As discussed in the proposed 
rule, we sent the 2021 SSA report to five independent peer reviewers 
and received three responses. The peer reviews can be found at https://www.regulations.gov at Docket No. FWS-R8-ES-2022-0082 under supporting 
documents. In preparing the proposed rule, we incorporated the results 
of these reviews, as appropriate, into a revised draft SSA report 
(Service 2022, entire) and made this 2022 version available to the 
public on https://www.regulations.gov at Docket No. FWS-R8-ES-2022-0082 
during the open comment periods. We have since incorporated any 
additional edits as appropriate based on public comments received 
during the public comment periods into the current SSA report, which is 
the foundation for this final rule (Service 2024, entire). A summary of 
the peer review comments and our responses can be found in the Summary 
of Comments and Recommendations, below.

Summary of Changes From the Proposed Rule

    Since the October 7, 2022, proposed rule and February 27, 2023, 
document reopening the comment period and announcing a public hearing 
were published, we received comments from the public on the proposed 
listing rule and 2022 SSA report. After the second comment period 
closed on March 29, 2023, we also received additional comments on 
August 16, October 23, and December 12, 2023, from representatives of 
the Coalition for a Sustainable Delta. The Coalition also provided 
comments during the open comment periods for the proposed rule to 
https://www.regulations.gov at Docket No. FWS-R8-ES-2022-0082 (see 
documents FWS-R8-ES-2022-0082-0009 and -0024).
    After reviewing all the information we received, we updated and 
revised the 2022 SSA report to incorporate any grammatical edits, 
clarifications, and

[[Page 61031]]

formatting changes. We also revised the count-based population 
viability analysis (see Service 2024, appendix B) based on information 
received from comments on the proposed rule and peer review of the 
information associated with publication of the analysis (Tobias et al. 
2023, entire) in a scientific journal. The revisions to the analysis 
were associated with our methodology of estimating population growth 
rates and assisted in accounting for observation error in our 
estimates. Additionally, we also compared density-dependent model 
formulations to confirm sufficiency of our density-independent model. 
The changes made to the SSA report and appendix B did not significantly 
change our determination of status of the Bay-Delta longfin smelt in 
this final rule.
    Additionally, in the October 7, 2022, proposed listing rule, we 
determined the designation of critical habitat for the DPS to be not 
determinable due to a lack of necessary information to complete our 
analysis. We are currently in the review process of determining 
critical habitat for the DPS, and a proposed rule will be forthcoming 
(see Critical Habitat, below).

Summary of Comments and Recommendations

    In the proposed rule published on October 7, 2022 (87 FR 60957), 
and reopening document published on February 27, 2023 (88 FR 12304), we 
requested that all interested parties submit written comments on the 
proposal by December 6, 2022, and March 29, 2023, respectively. We also 
contacted appropriate Federal and State agencies, scientific experts 
and organizations, and other interested parties and invited them to 
comment on the proposal. A newspaper notice inviting general public 
comment was published in the Sacramento Bee on October 10, 2022 
(McClatchy 2022, entire). On November 21, 2022, we received a written 
request from the public for a public hearing (Barajas et al. 2022, 
entire). We held a virtual public hearing on the proposed listing rule 
on March 14, 2023, as described in our February 27, 2023, Federal 
Register document (88 FR 12304 at 12305) reopening the comment period 
and announcing the virtual public hearing. All substantive information 
received during both comment periods or subsequently has either been 
incorporated directly into this final determination as appropriate or 
is addressed below.

Peer Reviewer Comments

    As discussed in Peer Review above, we received comments from three 
peer reviewers on the draft SSA report (Service 2021, entire). We 
reviewed all comments we received from the peer reviewers for 
substantive issues and new information regarding the information 
contained in the 2021 SSA report. The peer review comments primarily 
fell into two main categories: (1) comments that provided grammatical 
or editorial corrections or minor clarifications of fact or that had no 
suggestions for changes to the SSA report but were either just 
expressing agreement or opposition and (2) comments that would affect 
the interpretation of available data and information presented in the 
SSA report. Peer review greatly assisted us to clarify our presentation 
of the substantial body of scientific information on Bay-Delta longfin 
smelt in the revised draft SSA report (Service 2022, entire) and the 
current SSA report (Service 2024, entire). Peer reviewer comments are 
addressed in the following summary. As discussed above, because we 
conducted this peer review prior to the publication of our proposed 
rule, we had already incorporated all applicable peer review comments 
into 2022 version of the SSA report, which was the foundation for the 
proposed rule. Additional comments received from the public have also 
been incorporated into the current version of the SSA report as 
necessary (Service 2024, entire) and together they are the foundation 
of this final rule.
    (1) Comment: One peer reviewer stated that use of survey indices is 
not a good metric for data analysis and suggested using catch data 
instead.
    Our response: We acknowledge that survey indices are not absolute 
census measures. However, we did compare existing Bay-Delta longfin 
smelt catch data (catch-per-unit-effort (CPUE) values from Stompe et 
al. 2020, entire) to the survey indices used in our analysis and got 
very similar results to what is presented in appendix B of the 2022 and 
2024 SSA reports (Service 2022, pp. 110-123, Service 2024, pp. 115-
128). As noted in the introduction of the technical note, CPUE and the 
Interagency Ecological Program (IEP) estimates both constitute indices 
of Bay-Delta longfin smelt abundance. Our use of abundance indices was 
not to determine the exact number of Bay-Delta smelt individuals but to 
use the multiple survey indices to determine trend information for the 
Bay-Delta longfin smelt. We consider the multiple survey efforts, which 
use varying sampling methods, as an appropriate measure to determine 
such trend information.
    (2) Comment: One peer reviewer mentioned that our analysis included 
a ``temporal bias'' in the 20-mm and fall midwater trawl (FMWT) survey 
data (referring to the ``wet'' period starting the data series compared 
to the recent dry period). The reviewer suggested that we consider 
comparing wet periods to wet periods and dry periods to dry periods to 
more appropriately demonstrate the decline.
    Our response: The section of the draft SSA report referred to by 
the reviewer (Service 2021, pp. 124-158) was intended to be a 
descriptive discussion on the statistical analysis of the abundance 
indices by the various survey efforts through time. In the revised 
draft SSA report (Service 2022, pp. 107-192), we revised the section to 
focus more on the descriptive statistics without calculating percent 
declines to avoid any possible perception of false precision within a 
decades-long data series. In the population viability analysis 
presented in our revised draft SSA report (Service 2022, appendix B) 
and now the updated modeling effort (the analysis has since published 
as Tobias et al., 2023, entire) described in appendix B of the current 
SSA report (Service 2024, appendix B), we interpret the full-time 
course of the suite of available data that includes any variance 
between wet or dry years.
    (3) Comment: One peer reviewer suggested that the geographic and 
depth bias to FMWT make it ineffective as a survey for longfin smelt 
due to the fact that the FMWT does not sample the entire estuary or the 
entire water column.
    Our response: The comment correctly points out that there are 
differences in spatial coverage both geographically and within the 
water column amongst the various survey efforts. However, we did not 
rely entirely on the FMWT as the only information in our analysis. To 
avoid any bias from any one survey effort, we used the information from 
all survey efforts in our modeling and overall analysis. Because none 
of the currently existing long-term monitoring surveys' sampling 
designs provides estuary-wide and full water column coverage, we 
consider that our methodology as identified in appendix B of the 
current SSA report (Service 2024) to determine trend information and 
extinction risk is a robust technical analysis as it helps reduce the 
effects of inflated variance through inverse weighting and is based on 
the best available scientific information available.

[[Page 61032]]

    (4) Comment: One peer reviewer disagreed with our description of 
the importance of freshwater flow into the San Francisco Bay estuary 
and cited an analysis that indicated that freshwater flow was not the 
primary factor contributing to the decline of Bay-Delta longfin smelt 
(Phillis 2019, entire). The peer reviewer points to information 
indicating that freshwater flow into the estuary did not cause as 
substantial population rebound during recent wet periods as has been 
observed in prior decades and that the relationship between freshwater 
flow and population abundance is weakening (Tamburello et al. 2019, 
entire). The peer reviewer further points out that juvenile-to-adult 
survival was not significantly affected by freshwater flow into the 
estuary (Nobriga and Rosenfield 2016, entire).
    Our response: We acknowledge that the relationship between 
increased freshwater flow and population abundance has recently been 
found to be decreasing. As a result, we have amended the SSA report to 
state that freshwater flow, while a primary driver of abundances, is 
not necessarily the primary driver influencing abundance of the current 
population (Service 2024, pp. 28-43). However, the peer reviewer's 
statement overlooks the influence of a massively declining adult 
population on the abundance of offspring that can be produced when 
favorable freshwater flow conditions exist. Other factors such as the 
size of the current adult breeding population and food resource 
limitations also play a role in the current status of the DPS, and we 
made clarifications in the current SSA report to also point to these 
other factors (Service 2024, pp. 35-36).

Public Comments

Influences on Water Temperature and Salinity
    (5) Comment: We received several comments contending that the 2022 
SSA report and proposed rule mischaracterize the relationship between 
water temperatures and San Francisco Bay Delta outflow. The commenters 
stated that estuary water temperatures are governed by a multitude of 
complex factors related to prevailing atmospheric conditions and are 
not influenced by San Francisco Bay Delta outflow.
    Our response: In the 2022 SSA report and proposed rule, we 
acknowledge the complexity of factors influencing water temperature in 
the San Francisco Bay Delta. We agree with commenters that estuary 
water temperatures are governed by a multitude of complex factors and 
that atmospheric forcing is the dominant factor in determining water 
temperature in the estuary. However, existing literature suggests 
increased inflow can influence San Francisco Bay Delta temperatures. 
Some studies have found evidence that increased San Francisco Bay Delta 
inflow can lead to cooler than predicted temperatures in the San 
Francisco Bay Delta over short timespans (Wagner et al. 2011, p. 551; 
Wagner 2012, p. 78). The current SSA report better clarifies the 
relationship between San Francisco Bay Delta inflow/outflow and water 
temperatures (Service 2024, pp. 27-28).
    (6) Comment: One commenter suggested that our conclusions regarding 
water temperature conditions are not accurate. Specifically, the 
commenter stated that temperature conditions in the San Francisco Bay-
Delta never exceed 20 degrees Celsius ([deg]C) (68 degrees Fahrenheit 
([deg]F)) in the winter-spring in the low-salinity zone, suggesting 
that high water temperatures are not a threat to larval and post-larval 
Bay-Delta longfin smelt.
    Our response: The commenter's statement that water temperatures 
never exceed 20 [deg]C (68 [deg]F) in the winter and spring within the 
low-salinity zone is incorrect. Water temperatures in May within the 
low-salinity zone have been found to exceed this temperature 
(California Department of Water Resources 2020, entire). Lab studies 
sampling Bay-Delta longfin smelt collected within the San Francisco Bay 
have shown that water temperatures above 20 [deg]C (68 [deg]F) cause 
molecular stress responses (Jeffries et al. 2016, entire) and that 
temperatures greater than 15 [deg]C (59 [deg]F) may impair the 
viability of larval Bay-Delta longfin smelt (Yanagitsuru et al. 2021, 
entire). Water temperatures are predicted to increase in the estuary as 
a result of climate change and are likely to be an important factor in 
the future condition of the DPS (Service 2024, pp. 63-71).
Food Limitation
    (7) Comment: A commenter stated that the 2022 SSA report fails to 
support the conclusion that food limitation may act as a stressor on 
the Bay-Delta longfin smelt.
    Our response: In our discussion of prey availability and the 
decline of the DPS in the 2022 SSA, we presented the current scientific 
understanding and our conclusions are based on the best scientific 
information available (Service 2022, pp. 35-36). We acknowledge in the 
current SSA report that the prey species Eurytemora affinis has not 
been statistically linked to the survival of larval longfin smelt 
(Service 2024, pp. 35-36). We also acknowledge in the 2024 SSA report 
that although DPS abundance was observed to decline following the 
overbite clam (P. amurensis) invasion, no direct statistical support 
for a bottom-up longfin-mysid link has been established (Service 2024, 
pp. 35-36). The two primary prey taxa of the DPS have substantially 
declined compared to historical levels when overbite clam was not 
present (Kimmerer and Orsi 1996, p. 412). Research into the invasion of 
the nonnative overbite clam into the estuary, although not definitive, 
does suggest there is a possible link between the invasion and the 
subsequent decline of longfin smelt (Kimmerer 2002, p. 47; Feyrer et 
al. 2003, pp. 284-286; Thomson et al. 2010, p. 1443) with more recent 
research finding a significant positive correlation between available 
prey biomass and feeding success of Bay-Delta longfin smelt in the 
estuary, suggesting prey availability could influence growth and 
survival (Barros et al. 2022, p. 1773). The inability to statistically 
link declines in prey directly with declines in the DPS does not 
eliminate the likelihood that prey abundances are somehow linked to 
survival, but it suggests that factors affecting survival are complex 
and they may be partly attributable to prey abundances.
Entrainment
    (8) Comment: We received two comments regarding entrainment rates 
of the DPS as a result of water diversion from the estuary. One 
commenter suggested the entrainment rates cited in the 2022 SSA report 
were overestimates because estimates were based on data that did not 
cover the full geographic extent of DPS larvae within the San Francisco 
Bay-Delta. The other commenter stated that the 2022 SSA report 
underestimates entrainment in the studies cited in the 2022 SSA report 
because the models excluded juvenile/adult entrainment, underestimated 
the length of time larvae are vulnerable to entrainment, and failed to 
account for indirect mortality.
    Our response: The research discussed in the 2022 SSA report 
regarding entrainment has since been published and is publicly 
available (Gross et al. 2022, entire; Kimmerer and Gross 2022, entire). 
The authors of these papers acknowledged longfin smelt extend beyond 
the geographic extent of the sampling scheme used in these studies and 
took measures to correct for this bias. The results of these studies 
suggest that under current Old and Middle Rivers (OMR) flow management 
strategies, entrainment of Bay-Delta longfin smelt has not been 
substantial

[[Page 61033]]

enough to affect DPS population dynamics. Estimates from these two 
studies currently represent the best commercial and scientific data 
available and are discussed in the current SSA report (Service 2024, 
pp. 41-43). A pilot study examining entrainment of larval smelts is 
ongoing and aims to answer some of the current uncertainties. Over the 
next few years, life cycle modeling work by the Service will better 
quantify the cumulative impact of entrainment of multiple life stages 
on the DPS.
Contribution of Bay Tributaries
    (9) Comment: We received multiple comments expressing concerns 
regarding how the 2022 SSA report and proposed rule addressed portions 
of the population that inhabit areas outside of the sampling footprint 
of most long-term surveys, particularly areas in and around Bay 
tributaries. Some of these commenters claim the Service disregarded 
this portion of the population in our determination and ignored the 
contribution of San Francisco Bay-Delta tributaries and recent 
restoration efforts of these areas to the DPS's current abundance, 
pointing to recent research (i.e., Lewis et al. 2019a and 2019b) as 
evidence of population redundancy. The commenters concluded that 
because the Service did not consider the DPS's use of these areas in 
evaluating abundance of the Bay-Delta longfin smelt, the DPS is not 
experiencing population declines as evidenced by continued inhabitation 
of all geographic units in its range, and, therefore, the DPS is not at 
substantial risk of extinction or extirpation in any portion of its 
documented range.
    Our response: Both the 2022 and 2024 SSA reports frequently 
acknowledge the inhabitation of Bay tributaries and recognize the 
important role they may have in reproduction, particularly in wet years 
(Service 2022, pp. 12, 19, 24; Service 2024, pp. 12, 21, 25). However, 
substantial contributions of recruits from these tributaries appear to 
be limited to wet years, and typically the majority of suitable 
spawning and rearing habitat is still the estuary's major low-salinity 
zone, which is usually located between Suisun Bay and the Delta 
(Kimmerer et al. 2013, figure 2, p. 7; Lewis et al. 2019a, p. 3; Lewis 
et al. 2019b, p. 6). Targeted sampling of some of these habitats in Bay 
tributaries has begun only recently; therefore, no time series exist on 
the time scale required to analyze population trends in these habitats. 
As such, there was no practical method to include data from these 
limited studies to inform our statistical analyses. However, recruits 
that hatched in Bay tributaries are available to the San Francisco Bay 
Study (SFBS) once they enter the larger Bays, so population 
contributions from Bay tributaries should be captured by SFBS indices.
    We agree with commenters that restoration of the Bay tributaries 
would provide valuable benefits to the DPS. However, these benefits 
would likely occur during the spawning and rearing season of wet years 
rather than during the extended summer/fall occupancy of these habitats 
as the commenters suggested. During the summer and fall when Bay-Delta 
longfin smelt are occupying these areas, they appear to be mostly 
inhabiting deeper habitat as evidenced by the higher catch in the otter 
trawl surveys compared to the mid-water trawl surveys (Rosenfield and 
Baxter 2007, p. 1586). As such, restoration of shallower tidal wetlands 
in the lower Bay tributaries may not provide suitable habitat during 
the summer and early fall, as temperatures in these shallow habitats 
can approach and exceed the thermal tolerance of Bay-Delta longfin 
smelt during these times.
    We disagree with the statement that the Bay-Delta longfin smelt is 
not experiencing population declines as evidenced by continued 
inhabitation of all geographic units in its range. The complex 
hydrodynamics of the estuary results in planktonic larvae and post-
larvae with limited mobility to be widely distributed throughout the 
estuary, regardless of whether the habitat is suitable for any length 
of time. Likewise, spawning adults appear to be primarily oriented to 
cool water temperatures, which results in inhabitation of the 
ephemerally cool temperatures of Bay tributaries (Lewis et al. 2019b, 
p. 19). Inhabitation and spawning in these waters beyond the wettest 
years likely acts as a population sink as opposed to a source, as was 
observed by lack of recruitment from these habitats in most years. Lack 
of successful recruitment in most years from these tributaries suggests 
these habitats do not provide meaningful population redundancy.
Outflow-Abundance Relationship
    (10) Comment: Some commenters took issue with our discussion on the 
relationship between freshwater flow and Bay-Delta longfin smelt 
abundance and questioned the validity and predictive power of the 
outflow-abundance relationship pointing to recent years when observed 
abundance indices were below indices predicted by the relationship.
    Our response: The relationship of freshwater flow and longfin smelt 
production has consistently been reaffirmed for decades based on the 
published literature (Stevens and Miller 1983, pp. 431-432; Jassby et 
al. 1995, p. 285; Kimmerer 2002, p. 47; Rosenfield and Baxter 2007, p. 
1585; Sommer et al. 2007, p. 274; Kimmerer et al. 2009, p. 381; 
MacNally et al. 2010, p. 1422; Thomson et al. 2010, pp. 1439-1440; 
Maunder et al. 2015, p. 108; Nobriga and Rosenfield 2016, p. 53; 
Kimmerer and Gross 2022, fig. 2, p. 2735). Nonetheless, we acknowledge 
that freshwater outflow is not a perfect predictor of Bay-Delta longfin 
smelt abundance due to the complexity and variable nature of habitat 
within the estuary and Bay-Delta longfin smelt population dynamics. The 
2022 and 2024 SSA reports acknowledge what may be step-declines (where 
populations decline to a lower abundance level and do not rebound to 
previous levels) or changes in the intercept of the relationship 
(Service 2022, pp. 35-37; Service 2024, pp. 35-37) and acknowledge the 
decreasing explanatory power of the flow-abundance model (Service 2022, 
p. 37; Service 2024, p. 37). The decline of adult stock and its 
resulting egg supply is the most parsimonious reason why observed 
indices have been below what were predicted from data in the 
increasingly distant past. The SSA reports illustrate the point that 
when declining spawning stock is considered in the outflow-abundance 
model, the explanatory power of the flow-abundance model did not 
degrade over time (Service 2022, fig. 3.3, p. 38; Service 2024, p. 38). 
Understanding the biological mechanisms behind the flow-abundance 
relationship is an ongoing topic of research for the Service and the 
broader scientific community in the estuary.
Low-Salinity Zone Mechanism
    (11) Comment: We received a comment suggesting the expansion of the 
low-salinity zone due to increased freshwater flow should not be 
considered a mechanism by which freshwater flow might influence Bay-
Delta longfin smelt productivity. The commenter cited Kimmerer et al. 
(2013) as evidence that the volume of low-salinity habitat in the 
estuary is unrelated to the DPS's abundance.
    Our response: We agree that current literature suggests higher 
outflow expanding the volume of the low-salinity zone is inadequate in 
explaining the population growth observed during wet years. In the 2022 
SSA report, we acknowledged that expansion of the low-salinity zone may 
be beneficial to larvae but did not suggest this

[[Page 61034]]

mechanism was a primary driver of the outflow-abundance relationship 
(Service 2022, p. 21). Dr. Kimmerer provided an additional comment on 
the proposed rule suggesting a predominant mechanism behind the 
outflow-abundance relationship may be a result of favorable larval 
transport and retention in the low-salinity zone and elevated prey 
concentrations occurring during periods of greater freshwater flow, 
resulting in higher survival and abundance. In the 2022 SSA report, we 
identified and discussed this mechanism as well as other postulated 
mechanisms that may contribute to the outflow-abundance relationship 
(Service 2022, p. 32). In the proposed rule summarizing the information 
from the 2022 SSA report, we may have underrepresented the transport 
and retention mechanism. We have further described this mechanism in 
the 2024 SSA report (Service 2024, pp. 21-22) and this final rule (see 
Summary of Biological Status and Threats below).
    (12) Comment: We received a comment regarding the habitat use of 
larval/post-larval Bay-Delta longfin smelt. The commenter cited 
Yanagitsuru et al. (2022), Rahman et al. (2023), and a presentation to 
the Estuarine Ecological Team by Levi Lewis (2023) as new evidence that 
the Bay-Delta longfin smelt larvae are distributed further downstream 
and at higher salinities than previously thought.
    Our response: The 2024 SSA report acknowledges the range of 
salinities that larval smelt are known to utilize in the estuary 
(Service 2024, p. 34). The lab studies that the commenter cites are 
informative of the physiological salinity tolerances of larvae but are 
not necessarily indicative of habitat use within the estuary, as such 
studies ignore predation, hydrodynamics, and other relevant physical 
and ecological processes. In the wild, larval abundance has been shown 
to rapidly decline above 10 practical salinity unit (PSU) (Lewis et al. 
2019b, p. 30), and peak recruitment and abundance occur in the range of 
2 to 4 PSU (Hobbs et al. 2010, p. 564; Grimaldo et al. 2017, p. 8; 
Grimaldo et al. 2020, pp. 12-14).
DPS Status
    (13) Comment: We received comments stating that the San Francisco 
Bay-Delta longfin smelt does not meet the criteria of a DPS according 
to the Service's policy because it is not ``markedly separated'' from 
the rest of the longfin smelt population and that the Bay-Delta 
population is regularly mixing with other populations. The commenter 
points to research conducted since our 2012 DPS determination regarding 
dispersal and connectivity between the Bay-Delta population and nearby 
populations farther north along the California coast.
    Our response: Our DPS policy does not require absolute separation 
of a DPS from other members of its species, because this can rarely be 
demonstrated in nature for any population of organisms (61 FR 4724; 
February 7, 1996). Our determination that the Bay-Delta longfin smelt 
meets the criteria of a DPS was published in the April 2, 2012, Federal 
Register (77 FR 19756). In the 2022 and 2024 SSA reports as well as our 
proposed listing rule, we identified and considered more recent 
research and reaffirmed that the Bay-Delta longfin smelt is a valid DPS 
(87 FR 60958-60959; October 7, 2022); Service 2022, p. 10; Service 
2024, p. 10). Studies that have examined longfin smelt genetics have 
all found evidence that the Bay-Delta population is distinct from other 
northern populations (Israel and May 2010, p. 230; Sa[gbreve]lam et al. 
2021, p. 1793).
    We acknowledge that Sa[gbreve]lam et al. (2021) found evidence of 
northern dispersal of some individuals from the Bay-Delta population, 
as evidenced by some shared genetic structure with smaller populations 
in Northern California estuaries and the Columbia River. However, the 
study detected no significant gene flow from any northern estuaries 
southward into the Bay-Delta population, suggesting gene flow is 
unidirectional in a northerly fashion. These findings suggest the Bay-
Delta population is genetically isolated, as it does not appear to be 
receiving immigrants from any northern populations. Sa[gbreve]lam et 
al. (2021, pp. 1793, 1802) concluded that the Bay-Delta population was 
distinct and is likely an important source for maintaining nearby 
populations.
    A recent study published after the 2022 SSA report examined other, 
much smaller, longfin smelt populations along the California coast 
(Brennan et al. 2022, entire). The authors determined that estuaries in 
proximity of the San Francisco Bay estuary may not be permanently 
inhabited by longfin smelt, and that the Bay-Delta population may 
therefore lack the resilience typically provided by metapopulations. 
The authors also noted that abundance and distribution of longfin smelt 
appears to have declined in other estuaries along the California coast 
(Brennan et al. 2022, p. 12). This information may further support the 
hypothesis that reduction of the Bay-Delta longfin smelt abundance 
decreases the DPS's contribution to outside populations.
Population Viability Analysis
    (14) Comment: We received comments expressing numerous concerns 
regarding our population viability analysis (PVA) and its use of 
population survey indices rather than actual abundance estimates for 
our determination of the status for the Bay-Delta longfin smelt. 
Specifically, the commenters took issue that the PVA relies on 
population indices data, which they contend do not fully sample the 
entire water column or habitat strata and introduce too much 
uncertainty on the size of the population. The commenters state that, 
because of these issues, the Service may have underestimated the size 
of the population and therefore overestimated the impact of threats 
facing the DPS; and the Service cannot use the PVA to determine time of 
extinction or base a listing decision on such uncertain data.
    Our response: As we described in the 2022 and 2024 SSA reports 
(Service 2022, appendix B, pp. 111-123; Service 2024, appendix B, pp. 
115-128), exact population abundance information is not necessary. A 
count-based PVA can be applied to index values, where a population 
index represents some portion of the total population as long as the 
proportion of the population that is observed remains relatively 
constant over time (Morris and Doak 2002, p. 51). General 
interpretation of the abundance indices for longfin smelt or any other 
species also requires this assumption or a correction for major 
deviations or inconsistencies. In the SSA reports, we acknowledge the 
different limitations of the long-term surveys and utilize them 
collectively to reduce potential biases that may be present in any 
single survey. As we state in our description of the methods used to 
conduct the PVA (Service 2022, appendix B, pp. 111-123; Service 2024, 
appendix B, pp. 115-128), we incorporated and applied our analysis in 
the PVA using several datasets that index the abundance of Bay-Delta 
longfin smelt, and these data capture the landscape of the available 
information regarding the estimation of abundance for the DPS.
    In our review of the status of the Bay-Delta longfin smelt, we used 
all the best commercial and scientific information available to make 
our determination. The PVA was just one of the many tools we used in 
our analysis. We consider the PVA to be one of many appropriate tools 
that provide useful information for our decision on the listing status 
of the DPS. PVAs are best suited to test a range of possible conditions 
or demographic assumptions to provide a range of likely fates for a 
population (Morris et al.

[[Page 61035]]

1999, p. 2). We conducted sensitivity analyses to examine the effects 
of different potential starting population sizes and different minimum 
viable population sizes (quasi-extinction thresholds). The sensitivity 
analyses showed that in most demographic scenarios tested, the 
population is at a high risk of quasi-extinction in the near future 
(Service 2024, figures 3 & 4, pp. 121 and 122). It is noteworthy that 
the count-based PVA presented in appendix B predicts the time to quasi-
extinction under current environmental conditions and does not account 
for the worsening environmental conditions associated with increases in 
drought intensity or frequency, warming water temperatures, and sea-
level rise that are occurring and are predicted to continue.
    (15) Comment: Some public commenters noted that the meta-analysis 
was conducted on multiple surveys and as a result obscured data from 
the San Francisco Bay study otter-trawl (SFBS OT) age-1 survey. The 
commenters stated that the mean population growth rate for the SFBS OT 
age-1 survey estimated in the PVA indicated a trend of increasing 
abundance and therefore is inconsistent with the Service's finding that 
the DPS is currently in danger of extinction.
    Our response: In an effort to include all available data and 
produce the best estimates of population growth rates, a meta-analysis 
was performed using all surveys. The meta-analysis presented in 
appendix B of the 2022 and 2024 SSA reports (a method proposed by a 
reviewer of the 2021 SSA report) illustrates how pooling information 
from the full suite of available survey data can help reduce 
uncertainty in our overall estimate of the mean population growth rate. 
Two important features of a meta-analysis are that the meta-mean will 
be closer to the population mean on average than any of the individual 
surveys (sample means) and the confidence interval will be narrower, 
making it a more precise estimator of the population mean than the 
estimates from the samples.
    Based on review and comment of the meta-analysis (Service 2022, 
appendix B, pp. 111-123), we revised our methods slightly for 
estimating mean population growth rates for the DPS. As a result of 
this modification, we obtained different estimates for each survey than 
were reported in the 2022 SSA report (Service 2022, appendix B, p. 
120). Results indicate that all of the abundance indices show long-term 
population declines, and all except for the SFBS age-0 otter trawl are 
statistically significant downward trends (Service 2024, appendix B, 
table 2). In both the original and revised analyses, seven of the eight 
surveys examined indicate a negative mean growth rate. To exclude 
evidence from all seven other surveys and base our decision off the 
single potentially positive survey time series would sacrifice a 
substantial volume of available data and bias the results of the 
analysis.
    (16) Comment: Several commenters stated that the 2022 SSA report 
and proposed rule indicate confirmation bias by relying on data from 
the FMWT survey without acknowledging the limitations of those data or 
evaluating competing data from the SFBS OT age-1 survey, which 
indicates that Bay-Delta longfin smelt DPS abundance is not declining. 
They further state that the FMWT survey should not be used as the 
primary determinant due to its limited extent in areas surveyed and 
that it may underrepresent the abundance of the DPS due to its sampling 
methods.
    Our response: In the 2022 and 2024 SSA reports, we do not rely on 
the FMWT data any more than any other survey and acknowledge 
limitations of all available surveys within the estuary (Service 2022, 
pp. 107-109; Service 2024, pp. 108-110). As stated above, we utilized 
information from the entire suite of surveys including the SFBS OT. As 
previously discussed, the commenter's statement that the SFBS OT data 
imply that the DPS is not declining is not supported by analyses of 
those data (Tobias et al. 2023, entire).
    In the SSA reports, we acknowledge that the FMWT does not sample 
the entire range of Bay-Delta longfin smelt during the fall; however, 
the survey does sample all of the low-salinity zone and some of the 
mesohaline water west of the low-salinity zone when Bay-Delta longfin 
smelt return to the upper estuary in the fall and early winter (Service 
2022, pp. 43-46; Service 2024, pp. 43-47). Research on the Bay-Delta 
longfin smelt has found that a significant proportion of age-0 (fish 
younger than 1 year of age) and older individuals inhabit the low-
salinity zone prior to and during spawning, making FMWT sampling in 
this region a reasonable index for population abundance (Rosenfield and 
Baxter 2007, p. 1590). We also acknowledge that the FMWT does not 
specifically target benthic habitat; however, except for a few 
particularly deep sampling stations, fish within a geographic location 
can still be sampled by the FMWT whether they are in the middle or the 
bottom of the water column (Service 2022, p. 44; Service 2024, p. 44). 
The ability of the FMWT to track changes in the DPS population is 
evidenced by its high correlation with SFBS data (Rosenfield and Baxter 
2007, p. 1590). Ultimately, both the FMWT and SFBS OT surveys use their 
own standardized methods that are capable of indexing changes in 
relative abundance.
    (17) Comment: One commenter pointed to the increase of FMWT 
abundance indices in the years of 2021-2022 as evidence of population 
resilience and stated that the Service needs to evaluate this 
information.
    Our response: In our 2022 SSA report, we included analyses of the 
2021 FMWT abundance indices (Service 2022, appendix B, p. 119) and 
considered this information in our proposed rule to list the Bay-Delta 
longfin smelt. Because the 2022 index was calculated after we had 
concluded our analyses and published our proposed rule, we reviewed the 
2022 indices in making our final determination. The Bay-Delta longfin 
smelt population has historically had highly variable population growth 
and declines, and such short-term population changes are not unexpected 
based on the trend information over the full FMWT survey effort 
(Service 2024, p. 47). Similar increases in abundance have occurred in 
2000, 2006, 2011, 2013, and 2017; however, all of these increases 
resulted in abundance estimates that are well below those prior to the 
declines experienced in the 1980s when population numbers were several 
orders of magnitude greater than those currently experienced by the 
DPS.
    (18) Comment: Several comments point to the wide confidence 
intervals of estimated growth rates in the count-based PVA and 
interpret these intervals as evidence that the Bay-Delta longfin smelt 
population may be stable or increasing.
    Our response: The commenters are correct in their interpretation of 
the confidence intervals around the mean growth rates for individual 
surveys. Bay-Delta longfin smelt population growth rates are highly 
variable from year to year depending on prevailing environmental 
conditions and spawning stock size. The wide confidence intervals are a 
result of this variation where in some years the population grows even 
though in most years it declines. To account for this variability and 
differences in confidence intervals of the studies, we developed the 
meta-analysis to pool estimates of the population growth rates from the 
individual surveys to get a more precise estimate. Based on the overall 
population trend over the length of all the studies, we determined that 
the Bay-Delta longfin smelt population is in decline.

[[Page 61036]]

    (19) Comment: One commenter provided a technical review of the 
analyses presented in the appendices of the 2022 SSA report and stated 
the information presented in appendix B required additional 
documentation of the evaluation of the assumptions, reconsideration of 
how the analysis accounts for sample error, and comparisons of density-
independent and density-dependent formulations of the models. In 
response, the commenter provided their own meta-analysis utilizing 
alternative methods to capture uncertainty.
    Our response: The analysis and text of appendix B has gone through 
revisions since the publication of the 2022 SSA report and some of the 
points and corrections identified by the commenter have been addressed 
in our current SSA report (Service 2024, appendix B). Regarding the 
commenter's alternative analysis, we could not fully incorporate it 
because the methods used are not sufficiently described for us to fully 
evaluate them. However, taking their reported results at face value, an 
increase in confidence limits would suggest a less stable population 
growth rate than was reported in the SSA report. This scenario would 
tend to produce a shorter time to quasi-extinction, likely offsetting 
the small increase in mean that they also report. Therefore, we 
conclude that this alternative analysis would also support a conclusion 
that the DPS is at risk of quasi-extinction.
Contemporary Versus Pre-Development Outflow
    (20) Comment: We received a comment that there has been no 
statistically significant reduction in outflow throughout the winter-
spring period, nor on an annual basis when comparing contemporary to 
pre-development conditions. The commenter also critiqued our use of 
Reis et al. (2019) in the SSA report, stating that the study failed to 
account for evapotranspiration that occurred prior to development in 
the estuary.
    Our response: One study comparing the pre-development conditions 
and contemporary conditions of the Central Valley and potential changes 
in the annual average San Francisco Bay Delta outflow found that the 
outflow has not changed substantially (Fox et al. 2015, pp. 4267-4271). 
However, annual average San Francisco Bay Delta outflow is not 
biologically relevant to Bay-Delta longfin smelt. Contemporary water 
operations have resulted in less San Francisco Bay Delta outflow during 
the winter and spring months and increased outflow during the summer 
months (Hutton et al. 2017a, fig. 5, p. 2507; Gross et al. 2018, fig. 
4, p. 10). Winter and spring months are when Bay-Delta longfin smelt in 
the estuary spawn and larvae rear in the low-salinity zone, and reduced 
outflow in the winter and spring months has been repeatedly linked to 
reduced juvenile Bay-Delta longfin smelt production (Stevens and Miller 
1983, pp. 431-432; Jassby et al. 1995, p. 285; Kimmerer 2002, p. 47; 
Rosenfield and Baxter 2007, p. 1585; Sommer et al. 2007, p. 274; 
Kimmerer et al. 2009, p. 381; MacNally et al. 2010, p. 1422; Thomson et 
al. 2010, pp. 1439-1440; Maunder et al. 2015, p. 108; Nobriga and 
Rosenfield 2016, p. 53; Kimmerer and Gross 2022, fig. 2, p. 2735). The 
reductions in February, April, and May outflows have been primarily 
attributed to reductions in San Francisco Bay Delta outflow as a result 
of water diversions (Hutton et al. 2017b, table 3, p. 2523).
    We do not agree with the commenter's critique of Reis et al. 
(2019). Differences in evapotranspiration rates are primarily a concern 
when comparing pre-development and post-development outflows in the 
estuary because extensive wetlands and floodplains pre-development 
theoretically increased evapotranspiration (reducing San Francisco Bay 
Delta outflow), but levees constructed during development largely 
disconnected floodplains and resulted in decreased evapotranspiration. 
By 1930, almost the entire San Francisco Bay Delta had been leveed and 
reclaimed (Whipple et al. 2012, p. 25). Reis et al. (2019) examined the 
years 1930-2018 when no substantial changes in estuary 
evapotranspiration occurred. As a result, the authors were able to 
reasonably assess the relative impact of water operations on San 
Francisco Bay Delta outflows.
Underestimate of Threats
    (21) Comment: One commenter stated that the Service understated the 
risk to the DPS by not considering specific current proposals to 
increase diversions of freshwater from the San Francisco Bay estuary 
and its watershed and that if realized these projects could result in 
changes to outflow in the estuary and further impact the Bay-Delta 
longfin smelt. The commenter points to several proposed projects 
including the Delta Conveyance Project, Sites Reservoir, and the State 
Water Resources Control Board's voluntary agreement process.
    Our response: In the 2022 SSA report and proposed rule, we 
identified reduced freshwater flow and diversion as one of the primary 
threats driving the current and future status of the Bay-Delta longfin 
smelt (Service 2022, pp. 28-30; 71-73). In our analysis of future 
conditions, we also acknowledged that changes in water demand may be 
more severe as the information used in our analysis identified impacts 
only out to the year 2030 due to the uncertainty and difficulty in 
accurately identifying changes with the necessary specificity (Knowles 
et al. 2018, p. 7638). However, due to the ongoing refinement of these 
proposed projects a specific assessment of each project was not 
possible within the timeframe for completion of our final rule. These 
projects, and any attendant risk or benefits to Bay-Delta longfin 
smelt, will be evaluated as they are implemented through appropriate 
regulatory processes, including section 7 consultations and/or section 
10 permits, and future recovery planning and implementation for the 
Bay-Delta longfin smelt.
    (22) Comment: One commenter stated that neither the 2022 SSA report 
nor the proposed rule evaluated the threat posed by harmful algal 
blooms (HABs) such as the one observed in the summer of 2022.
    Our response: We agree that in our 2022 SSA report and proposed 
rule, we did not include HABs as a threat to the Bay-Delta longfin 
smelt or a growing stressor to fish populations in the estuary. We 
agree that marine and brackish water HABs, such as the bloom that 
occurred in parts of San Francisco Bay in 2022, could plausibly affect 
Bay-Delta longfin smelt individuals in localized areas, but the impact 
of such blooms on the DPS overall is not well studied, and the best 
available information to date does not support a conclusion that HABs 
are a substantial threat to the status of the DPS. However, we agree 
that recent events are concerning. As emerging threats are defined and 
better understood, they will inform future consultations, permits, and 
recovery planning.

I. Final Listing Determination

Background

    The longfin smelt is a small fish species 9-11 centimeters (cm) 
(3.5-4.3 inches (in)) in length with a relatively short lifespan of 
approximately 2 to 3 years. The Bay-Delta longfin smelt DPS occupies 
the San Francisco Bay estuary and areas of the Pacific Ocean out to the 
Farallon Islands (see figure 1). A thorough review of the taxonomy, 
life history, and ecology of the Bay-Delta longfin smelt is presented 
in the current SSA report (Service 2024, pp. 6-23).

[[Page 61037]]

[GRAPHIC] [TIFF OMITTED] TR30JY24.000

Regulatory and Analytical Framework

Regulatory Framework
    Section 4 of the Act (16 U.S.C. 1533) and the implementing 
regulations in title 50 of the Code of Federal Regulations set forth 
the procedures for determining whether a species is an endangered 
species or a threatened species, issuing protective regulations for 
threatened species, and designating critical habitat for endangered and 
threatened species. On April 5, 2024, jointly with the National Marine 
Fisheries Service, the Service issued a final rule that revised the 
regulations in 50 CFR part 424 regarding how we add, remove, and 
reclassify endangered and threatened species and what criteria we apply 
when designating listed species' critical habitat (89 FR 24300). On the 
same day, the Service published a final rule revising our protections 
for endangered species and threatened species at 50 CFR part 17 (89 FR 
23919). These final rules are now in effect and are incorporated into 
the current regulations. Our analysis for this final decision applied 
our current regulations. Given that we proposed listing this species 
under our prior regulations (revised in 2019), we have also undertaken 
an analysis of whether our decision would be different if we had 
continued to apply the 2019 regulations; we concluded that the decision 
would be the same. The analyses under both the regulations currently in 
effect and the 2019 regulations are available on https://www.regulations.gov.
    The Act defines an ``endangered species'' as a species that is in 
danger of extinction throughout all or a significant portion of its 
range, and a ``threatened species'' as a species that is likely to 
become an endangered species within the foreseeable future throughout 
all or a significant portion of its range. The Act requires that we 
determine whether any species is an endangered species or a threatened 
species because of any of the following factors:
    (A) The present or threatened destruction, modification, or 
curtailment of its habitat or range;
    (B) Overutilization for commercial, recreational, scientific, or 
educational purposes;
    (C) Disease or predation;
    (D) The inadequacy of existing regulatory mechanisms; or
    (E) Other natural or manmade factors affecting its continued 
existence.
    These factors represent broad categories of natural or human-caused 
actions or conditions that could have an effect on a species' continued 
existence. In evaluating these actions and conditions, we look for 
those that may have a negative effect on individuals of the species, as 
well as other actions or conditions that may ameliorate any negative 
effects or may have positive effects.
    We use the term ``threat'' to refer in general to actions or 
conditions that are known to or are reasonably likely to negatively 
affect individuals of a species. The term ``threat'' includes actions 
or conditions that have a direct impact on individuals (direct 
impacts), as well as those that affect individuals through alteration 
of their habitat or required resources (stressors). The term ``threat'' 
may encompass--either together or separately--the source of the action 
or condition or the action or condition itself.

[[Page 61038]]

    However, the mere identification of any threat(s) does not 
necessarily mean that the species meets the statutory definition of an 
``endangered species'' or a ``threatened species.'' In determining 
whether a species meets either definition, we must evaluate all 
identified threats by considering the species' expected response and 
the effects of the threats--in light of those actions and conditions 
that will ameliorate the threats--on an individual, population, and 
species level. We evaluate each threat and its expected effects on the 
species, then analyze the cumulative effect of all of the threats on 
the species as a whole. We also consider the cumulative effect of the 
threats in light of those actions and conditions that will have 
positive effects on the species, such as any existing regulatory 
mechanisms or conservation efforts. The Secretary determines whether 
the species meets the definition of an ``endangered species'' or a 
``threatened species'' only after conducting this cumulative analysis 
and describing the expected effect on the species.
    The Act does not define the term ``foreseeable future,'' which 
appears in the statutory definition of ``threatened species.'' Our 
implementing regulations at 50 CFR 424.11(d) set forth a framework for 
evaluating the foreseeable future on a case-by-case basis, which is 
further described in the 2009 Memorandum Opinion on the foreseeable 
future from the Department of the Interior, Office of the Solicitor (M-
37021, January 16, 2009; ``M-Opinion,'' available online at https://www.fws.gov/library/collections/national-listing-and-classification-guidance). The foreseeable future extends as far into the future as the 
U.S. Fish and Wildlife Service and National Marine Fisheries Service 
(hereafter, the Services) can make reasonably reliable predictions 
about the threats to the species and the species' responses to those 
threats. We need not identify the foreseeable future in terms of a 
specific period of time. We will describe the foreseeable future on a 
case-by-case basis, using the best available data and taking into 
account considerations such as the species' life-history 
characteristics, threat-projection timeframes, and environmental 
variability. In other words, the foreseeable future is the period of 
time over which we can make reasonably reliable predictions. 
``Reliable'' does not mean ``certain''; it means sufficient to provide 
a reasonable degree of confidence in the prediction, in light of the 
conservation purposes of the Act.
Analytical Framework
    The current SSA report documents the results of our comprehensive 
biological review of the best scientific and commercial data available 
regarding the status of the Bay-Delta longfin smelt, including an 
assessment of the potential threats to the DPS. The SSA report does not 
represent our decision on whether the DPS should be listed as an 
endangered or threatened species under the Act. However, it does 
provide the scientific basis that informs our regulatory decisions, 
which involve the further application of standards within the Act and 
its implementing regulations and policies.
    To assess the Bay-Delta longfin smelt's viability, we used the 
three conservation biology principles of resiliency, redundancy, and 
representation (Shaffer and Stein 2000, pp. 306-310). Briefly, 
resiliency is the ability of the species to withstand environmental and 
demographic stochasticity (for example, wet or dry, warm or cold 
years); redundancy is the ability of the species to withstand 
catastrophic events (for example, droughts, large pollution events), 
and representation is the ability of the species to adapt to both near-
term and long-term changes in its physical and biological environment 
(for example, climate conditions, pathogens). In general, species 
viability will increase with increases in resiliency, redundancy, and 
representation (Smith et al. 2018, p. 306). Using these principles, we 
identified the DPS's ecological requirements for survival and 
reproduction at the individual, population, and DPS levels, and 
described the beneficial and risk factors influencing the DPS's 
viability.
    The SSA process can be categorized into three sequential stages. 
During the first stage, we evaluated the individual DPS's life-history 
needs. The next stage involved an assessment of the historical and 
current condition of the DPS's demographics and habitat 
characteristics, including an explanation of how the DPS arrived at its 
current condition. The final stage of the SSA involved making 
predictions about the DPS's responses to positive and negative 
environmental and anthropogenic influences. Throughout all of these 
stages, we used the best available information to characterize 
viability as the ability of the DPS to sustain populations in the wild 
over time. We use this information to inform our regulatory decision.
    The following is a summary of the key results and conclusions from 
the current Bay-Delta longfin smelt SSA report (Service 2024, entire); 
the full SSA report can be found at Docket No. FWS-R8-ES-2022-0082 on 
https://www.regulations.gov.

Summary of Biological Status and Threats

    In this discussion, we review the biological condition of the DPS 
and its resources, and the threats that influence the DPS's current and 
future condition, in order to assess the DPS's overall viability and 
the risks to that viability.
    The needs of the Bay-Delta longfin smelt can be categorized into 
three main resource and biological condition categories, and include: 
(1) appropriate habitat salinity, by life stage; (2) appropriate 
habitat temperature conditions, by life stage; and (3) adequate food 
resources and availability, by life stage. As the Bay-Delta longfin 
smelt utilizes both freshwater and saline water conditions across its 
life cycle, its habitat is extremely variable. These variable 
conditions, along with other factors including the interaction among 
these dynamic variables, exert a strong influence on habitat 
suitability across space and time.
    Bay-Delta longfin smelt have temperature tolerances that impact the 
volume and seasonality of suitable habitat. It is logical to presume 
that the Bay-Delta DPS, inhabiting as it does the most southern portion 
of the species' range, has historically been (and is) at the uppermost 
temperature tolerance range of the species. Larvae appear to be adapted 
to cool water conditions. Larvae inhabit water temperatures between 8 
and 12 [deg]C (46 and 54 [deg]F) (Grimaldo et al. 2017, p. 8). 
Available research indicates that temperatures approaching and 
exceeding 15 [deg]C (59 [deg]F) impair larval viability, and hence this 
benchmark may be ecologically significant. At later larval stages, 
longfin smelt are still likely restricted to water temperatures below 
20 [deg]C (68 [deg]F) (Jeffries et al. 2016, p. 1709). In general, age-
1 and age-0 fish inhabit 16-18 [deg]C (61-64 [deg]F) water in summer 
and fall. Adults are thought to be limited by water temperature >22 
[deg]C (>72 [deg]F) during the summer and likely spend the majority of 
this time in cooler Bay habitats and the open ocean (see Service 2024, 
p. 25). Fish return to spawn where water quality conditions are 
favorable for egg survival. These conditions vary in location depending 
on Delta outflow, as well as flows from Bay Area tributaries. Spawning 
occurs at or below water temperatures of 13 [deg]C (55 [deg]F), but has 
been documented at up to 16 [deg]C (61 [deg]F) (see Service 2024, p. 
25).
    Bay-Delta longfin smelt have a defined salinity tolerance range 
that

[[Page 61039]]

increases as fish mature. This is consistent with their anadromous life 
history requiring spawning and early rearing in fresher San Francisco 
Bay Delta and Bay tributary waters. Yolk-sac larvae survive the longest 
and grow the largest at 5 and 10 parts per thousand (ppth) and are able 
to maintain water balance equally between 0.4 and 10 ppth, but the same 
lifestage is unable to survive at 32 ppth (ocean salinity). Yolk-sac 
larvae cannot complete yolk resorption in freshwater. In field surveys, 
peak yolk-sac larval densities have been found at 2-4 ppth (Grimaldo et 
al. 2017, p. 8), which is also concordant with the early life 
salinities that produce highest survival to later life stages (Hobbs et 
al. 2010, p. 564). The California Department of Fish and Wildlife's 
(CDFW) 20-mm surveys have also shown peak larval distribution near this 
same salinity zone (i.e., 2-4 ppth), although larvae have been detected 
in salinities as high as 12 ppth (see Service 2024, pp. 25-26). The 20-
mm survey gets its name from the size at which Bay-Delta longfin smelt 
are retained and readily identifiable at the fish facilities associated 
with the State and Federal pumping facilities.
    Available data clearly indicate a very strong association of Bay-
Delta longfin smelt to turbid water conditions. Aquatic turbidity 
provides simultaneous feeding and predator avoidance advantages for 
larval fishes (Utne-Palm 2002, p. 115; Pangle et al. 2012, pp. 10-11). 
Turbidity enhances prey avoidance at detection distances typical of 
predatory fish species. Further, the sediment and algal particles often 
backlight relatively translucent zooplankton, helping larval fishes see 
these prey more easily (Utne-Palm 2002, p. 119). In contrast, larger 
fishes that may prey on fish larvae have longer search and reactive 
distances so more sediment and algal particles are in between these 
larger fish and their potential prey (Utne-Palm 2002, pp. 122-123). We 
assume that these turbidity mechanisms that apply broadly to larval 
fishes also apply to later life stages of Bay-Delta longfin smelt. 
Taken together, recent laboratory experiments, combined with field 
results, provide an assessment of early-life habitat needs favoring 
more turbid conditions (Utne-Palm 2002, entire; Pangle et al. 2012, 
entire).
    Bay-Delta longfin smelt exhibit high prey-specificity. During the 
time that longfin smelt larvae and small juveniles are feeding in low-
salinity habitats, they appear to focus on only two prey taxa. Smaller 
larvae appear to primarily use the copepod Eurytemora affinis as prey, 
while larger larvae and small juveniles appear to require mysids as 
prey. Longfin smelt pre-spawning adults in Suisun Marsh have shown a 
strong dietary preference for mysids, while relying on copepods and 
amphipods when mysids are scarce (see Service 2024, pp. 26-27). As 
longfin smelt exhibit very little variation in prey use, they are 
considered more susceptible to food web changes than some other fishes 
(Feyrer et al. 2003, p. 281). The current SSA report (Service 2024, p. 
27) discusses some observations from various studies regarding affects 
to the low-salinity zone from invasion by the overbite clam 
(Potamocorbula amurensis) in the 1980s and potential impacts to the 
Bay-Delta longfin smelt as a food limitation stressor (see below, and 
also Service 2024, pp. 35-37).

Threats Influencing the Bay-Delta Longfin Smelt

    The threats facing the Bay-Delta DPS of the longfin smelt include 
habitat alteration (Factor A) and changes to hydrology associated with 
reduced and altered freshwater flows (Factor A); increased water 
temperatures (Factor A); reduced food resource availability (Factor E); 
predation (Factor C); entrainment from freshwater diversion facilities 
(Factor E); and contaminants (Factor E). We consider reduced and 
altered freshwater flows resulting from human activities and impacts 
associated with current climate change conditions (increased magnitude 
and duration of drought and associated increased temperatures) as the 
main threat facing the Bay-Delta longfin smelt due to the importance of 
freshwater flows to maintaining the life-history functions and species 
needs of the DPS. However, because the Bay-Delta longfin smelt is an 
aquatic species and the needs of the species are closely tied to 
freshwater input into the estuary, the impact of many of the other 
threats identified above are influenced by the amount of freshwater 
inflow into the system (i.e., reduced freshwater inflows reduce food 
availability, increase water temperatures, and increase entrainment 
potential).
Reduced and Altered Freshwater Flows
    The development of dams and water delivery infrastructure built 
throughout the Sacramento and San Joaquin River basins for flood 
protection and water supply for agriculture and human consumption has 
greatly impacted freshwater flows into the San Francisco Bay estuary 
(Service 2024, section 3.1.1). The creation of this water storage and 
delivery system, where water is stored during the wet season and 
conveyed to farms and cities during the dry season, has resulted in one 
of the largest human-altered water systems in the world (Nichols et al. 
1986, p. 569). Operation of this system has resulted in a broader, 
flatter hydrograph with less seasonal variability, thus changing the 
timing, magnitude, and duration of freshwater flows into the San 
Francisco Bay-Delta (Kimmerer 2004, p. 15; Andrews et al. 2017, p. 72; 
Gross et al. 2018, p. 8). It is estimated that the Federal and State 
water projects annually reduce an average of about 5 million acre-feet 
(MAF) of freshwater into the San Francisco Bay Delta, while other 
municipal or private reservoirs or diverters annually divert an 
additional 8 MAF of potential freshwater into the San Francisco Bay 
Delta (Hutton et al. 2017b, fig. 4, p. 2523). The cumulative effect of 
this annual average of about 13 MAF of freshwater supplies has resulted 
in a long-term decline in freshwater inflow into the estuary during the 
period of February through June relative to estimates of what flows 
would have been available absent water development (Gross et al. 2018, 
fig. 6, p. 12; Reis et al. 2019, fig. 3, p. 12). This situation has 
further increased the frequency of very low outflow years that, prior 
to water development, would have been very rare and associated only 
with extreme drought (Reis et al. 2019, fig. 3, p. 12).
    From 1956 to the 1990s, water exports (water removed from the San 
Francisco Bay Delta as a result of State (State Water Project) and 
Federal (CVP) water projects) increased, rising from approximately 5 
percent of the Delta freshwater inflow to approximately 30 percent of 
the Delta inflow (Cloern and Jassby 2012, p. 7). By 2012, an estimated 
39 percent of the estuary's unimpaired freshwater flow in total was 
either consumed upstream or diverted from the estuary (Cloern and 
Jassby 2012, p. 8). Water exports continue to the present day and are 
expected to continue in the future.
    A reduction in freshwater flows into the estuary influences and 
impacts the location and function of the low-salinity zone (spawning 
and rearing habitat for longfin smelt). Freshwater inflow into the 
estuary and other co-linear indicators of wet versus dry conditions 
during the winter and spring have been statistically associated with 
recruitment of larvae to the juvenile life stage of Bay-Delta longfin 
smelt (Service 2024, section 3.1.1). Prior to large-scale water exports 
and reduced freshwater flows, the location of the low-salinity zone (as 
represented by the 2 percent bottom salinity position, known as X2) 
reached the <=55-km (<=34-mi) point in the estuary (monthly averages 
from February

[[Page 61040]]

through May) in about half of all years. More recently the position of 
X2 reaching at least the 55-km (34-mi) point occurred only very rarely 
as a result of wet year conditions (Gross et al. 2018, fig. 6, p. 12 
and fig. 7, p. 13) (Service 2024, section 3.1.1). In the case of Bay-
Delta longfin smelt, optimal growth and rearing conditions (food and 
water conditions (salinity, turbidity, circulation patterns)), 
especially for early life stage fish, is directly linked to freshwater 
inflow to the estuary.
Drought Conditions
    California's precipitation patterns can be extremely variable, and 
several years of dry conditions have occurred over numerous extended 
periods resulting in varying levels of drought (California Department 
of Water Resources (DWR) 2020, entire). Drought periods can be 
characterized as having less freshwater flow, as well as shorter 
duration and lower magnitude of peak flows. The current trend in 
drought conditions has recently increased in frequency, duration, and 
magnitude (Swain et al. 2018, pp. 427-433). Prior to the 21st century, 
dry and critically dry years occurred approximately 33 percent of the 
time. However, since the year 2000, the dry and critically dry year 
frequency has increased to 43 percent. Based on soil moisture 
reconstruction, the period between 2000 and 2021 was probably the 
driest 22-year period on record (Williams et al. 2022, p. 1). As the 
existing impacts from climate change (i.e., warmer temperatures) 
increase evapotranspiration in the watershed, the aforementioned water 
supply needs can exacerbate the magnitude of realized dry conditions 
over and above these natural patterns in precipitation and reduced San 
Francisco Bay Delta freshwater inflow.
    Bay-Delta longfin smelt exhibit poor survival and reproduction 
during droughts (Thomson et al. 2010, pp. 1438-1446; Mahardja et al. 
2021, pp. 9-10). The survival of Bay-Delta longfin smelt through their 
early life stages is lower during dry conditions and higher during wet 
conditions, as evidenced by Bay-Delta longfin smelt abundance indices 
nearly always declining sharply during dry periods then rebounding when 
wet weather returns (Mahardja et al. 2021, pp. 9-10). However, such 
recovery does not always occur after each drought cycle, leading to 
lower baseline numbers for the DPS (Moyle 2002, p. 237; Sommer et al. 
2007, pp. 270-276). In addition, extended dry years compound the 
negative impacts to Bay-Delta longfin smelt as the DPS has not shown an 
ability to quickly recover and reoccupy upstream spawning habitats 
following drought. These drought conditions have exacerbated the impact 
of reduced freshwater flows from human activities and have been 
attributed to accelerating the establishment of the overbite clam 
(Potamocorbula amurensis) (see Reduced Food Resources and Pelagic 
Organism Decline (POD), below) by making saline water conditions more 
available throughout areas typically associated with more freshwater 
(Carlton et al. 1990, pp. 90-91).
Habitat Alteration
    Large-scale habitat alteration such as channelization and dredging 
of streams and bays, building of levees and canals, and draining of 
wetlands has occurred since the 1850s. The impacts of such in-water and 
adjacent upland habitat alterations greatly affected and continues to 
impact the bathymetry of the estuary by collectively making the estuary 
deeper and less hydrodynamically connected to the surrounding landscape 
(Andrews et al. 2017, fig. 5, p. 64). The altered waterways create more 
space and avenues for the incoming tides to bring more saline water 
landward. Specifically, landscape changes since 1850 are estimated to 
have resulted in an average landward shift of X2 of over 3 km (2 mi) 
(Andrews et al. 2017, p. 68). This change along with reductions in 
freshwater input into the estuary (see Reduced and Altered Freshwater 
Flows, above) has caused a winter-spring upstream (landward) shift of 
X2 on the order of 10-20 km (6-12 mi). Taken together, the landscape 
changes discussed above and changes to the estuary's flow regime have 
changed how mixing processes function, and thus altered the habitat and 
food resource opportunities available for the estuary's biota, 
including the Bay-Delta longfin smelt.
Water Temperature Alterations
    As described in the Life History and Biology section of the current 
SSA report (Service 2024, section 2.4), Bay-Delta longfin smelt 
spawning occurs within cool-water conditions below 16 [deg]C (61 
[deg]F), while larvae and young juveniles show a preference for 
temperatures below 15 [deg]C (59 [deg]F) and 20 [deg]C (68 [deg]F), 
respectively. The embryonic through early juvenile life stages are when 
Bay-Delta longfin smelt are believed to be most vulnerable to warming 
temperatures because these early life stages do not possess the ability 
to migrate to the cooler waters of central San Francisco Bay and the 
coastal ocean due to limited motility and increases in potential 
predation. Subadults and adults are thought to be limited to water 
temperature below 22 [deg]C (72 [deg]F). Studies and datasets indicate 
water temperatures in the San Francisco Bay Delta commonly exceed 22 
[deg]C (72 [deg]F) during the summer (Vroom et al. 2017, p. 9904; data 
from California Data Exchange Center, Central & Northern California 
Ocean Observing System, and U.S. Geological Survey (Blodgett et al. 
2011, entire). Age-1 to age-3 individuals should possess the capacity 
to move to cooler waters during such times, making them less vulnerable 
than larvae and age-0 juveniles. However, climate change is predicted 
to substantially increase the number of days that water temperatures 
are inhospitable to all life stages, likely decreasing the duration of 
suitable spawning and larval rearing windows (Service 2024, section 
4.2.2).
Reduced Food Resources
    As discussed above and in the current SSA report (Service 2024, 
section 3.1.2), the Bay-Delta longfin smelt historically limited their 
diet to a relatively small number of crustacean meso- and 
macrozooplankton taxa. Bay-Delta longfin smelt larvae have diets 
dominated by a copepod, Eurytemora affinis, that is common in the low-
salinity zone during the spring (CDFW, unpublished data). The two most 
common prey taxa for larger longfin smelt are epibenthic mysids and 
amphipods (Burdi 2022, pers. comm.; CDFW unpub. Diet Study Data). The 
copepod E. affinis was also at one time an important prey item for a 
now much-depleted mysid species, Neomysis mercedis (Knutson and Orsi 
1983, p. 478), a prey species of juvenile and adult Bay-Delta longfin 
smelt.
    Since the 1970s, the Eurytemora affinis population in the estuary 
has been in decline, but beginning in the late 1980s, the zooplankton 
community for the San Francisco Bay estuary started undergoing about a 
decade of rapid change in species composition, trophic structure, and 
utility for fish production (Winder and Jassby 2011, pp. 683-685; 
Kratina et al. 2014, p. 1070; Brown et al. 2016, p. 8). This decline 
coincided with the rapid invasion of the estuary by the nonnative 
overbite clam (Carlton et al. 1990, pp. 81 and 85, fig. 3) and with an 
extended drought in the Central Valley in the period 1987-1994 
(Rosenfield and Baxter 2007, p. 1589).
    The overbite clam is a filter feeder that is thought to have 
diverted food resources from the primary food sources of, or fed 
directly on, the nauplii (first larval stage) of common calanoid 
copepods and resulted in their decline. These native copepods are one 
of the

[[Page 61041]]

main sources of prey of larval Bay-Delta longfin smelt (Carlton et al. 
1990, pp. 90-91; Kimmerer et al. 1994, p. 87; Feyrer et al. 2003, pp. 
284-286; Rosenfield and Baxter 2007, p. 1589). Mysids have experienced 
an over tenfold decrease in abundance and accounted for less than 4 
percent of total zooplankton biomass within the estuary after 1994 
(Winder and Jassby 2011, p. 684). In addition to lower abundance, the 
average individual sizes of mysids in the estuary have decreased over 
time, with a species composition shift towards Hyperacanthomysis 
longirostris, an invasive species that reaches maturity at a smaller 
mass than Neomysis species (Hennessy 2011, entire). Although Bay-Delta 
longfin smelt consume these nonnative species, they are not preferred 
and the change in food resources most likely results in an increased 
effort for the DPS to meet its food resource needs.
    To further exacerbate the impacts of the change in food resources, 
the decline of the Bay-Delta longfin smelt's historical prey base has 
not been accompanied by a large change in prey use by the DPS (Barros 
et al. 2019, p. 15; Feyrer et al. 2003, p. 285). This finding suggests 
that Bay-Delta longfin smelt had formed strong predator-prey 
interactions with their primary prey, a hypothesis supported by 
empirical data (MacNally et al. 2010, p. 1426). Because the DPS 
exhibits very little variation in prey use despite the reduction in 
natural prey availability, they are considered more susceptible to food 
web changes than some other fishes (Feyrer et al. 2003, p. 281). The 
decline in food resources is likely affecting juvenile and adult 
longfin smelt growth and fitness as well as increasing the effort 
needed to meet food resource demands (Kimmerer and Orsi 1996, pp. 418-
419; Feyrer et al. 2003, p. 281).
Predation
    In the proposed rule and 2024 SSA report, we discussed the role 
predation may play on individuals and various life stages of the Bay-
Delta longfin smelt (see the 2024 SSA report and proposed rule for 
additional information). Because little information is available on the 
exact predators of the Bay-Delta longfin smelt or the impact predation 
has on the status of the DPS, we do not consider the impacts from 
predation to be a primary driver, but we still include this 
consideration as part of the cumulative impact from all threats for the 
DPS, especially during poor habitat conditions when food is lacking.
Entrainment
    Freshwater diversion occurs throughout the estuary through intake 
structures for agricultural, municipal, and environmental purposes and 
in some cases may lead to entrainment of Bay-Delta longfin smelt. 
Entrainment occurs when the suction caused by pumping water creates an 
opportunity for fish to follow or be captured by the flow of water and 
become trapped and transported by the hydrodynamic footprint of those 
diversions. This entrainment may result in fish, especially early-life-
stage fish, being killed or removed from the estuary. Bay-Delta longfin 
smelt can be entrained in water exported by the major pumping 
facilities in the South Delta (see Water Project Exports, below) when 
adults and commingling age-1 individuals move upstream into the 
freshwater portions of the San Francisco Bay Delta (CDFW 2020a, fig. 
13, p. 53). Bay-Delta longfin smelt larvae and small juveniles that are 
either rearing or being tidally dispersed landward of X2 can also be 
entrained (CDFW 2020a, fig. 13, p. 53). During periods of high 
freshwater flow into the estuary, Bay-Delta longfin smelt (adults, 
juveniles, and larvae) are much less likely to be entrained by the 
major pumping facilities in the South Delta because the low-salinity 
zone is further downstream (or seaward) of the San Francisco Bay Delta. 
However, changes to the estuary's landscape (see Habitat Alteration, 
above) have caused the tidal flows to reach further into the Old and 
Middle Rivers (Andrews et al. 2017, p. 66), which, as discussed below, 
may further impact Bay-Delta longfin smelt (see Water Project Exports, 
below). Below we describe the types of freshwater diversions and 
exports and their impacts on Bay-Delta longfin smelt.
    Water Project Exports: The State of California through the DWR and 
the U.S. Bureau of Reclamation (Reclamation) operate freshwater 
diversion facilities and infrastructure associated with the SWP and 
CVP, respectively, which export fresh water from the Delta. The 
operation of these facilities can exert a strong influence on regional 
hydrodynamics (Kimmerer and Nobriga 2008, fig. 7, p. 12; Hutton et al. 
2019, fig. 7, p. 11). That hydrodynamic influence can result in the 
entrainment of fish, sometimes from considerable distances (Kimmerer 
2008, p. 2, fig. 1, p. 3). Several methods have been implemented to 
limit and offset the entrainment impacts at the SWP and CVP facilities, 
including construction of forebays (areas used to collect fish before 
they enter the pumps), fish screens, gate systems (used to divert fish 
away from pumps), and salvage operations (active collection and 
transport of fish back into the estuary). In most years, Bay-Delta 
longfin smelt have been collected (``salvaged'') in the fish facilities 
that are in front of each pumping plant. The salvage of fish is an 
indicator that individuals are being entrained by pumping of water at 
these facilities and either being killed or removed from the estuary. 
The peak of salvage of age-1 and older Bay-Delta longfin smelt 
typically occurred in January (Grimaldo et al. 2009, fig. 5, p. 1262). 
These adult and age-1 fish likely represented individuals searching for 
spawning habitats and immature individuals commingling with the adults. 
The peak of salvage of age-0 fish typically occurred in April or May as 
larval fish reach sizes at which they could be retained on the fish 
screens of the CVP and SWP fish collection facilities. However, it is 
likely some larvae began to be entrained once they started hatching in 
December or January, but remained undetected until about March, with 
salvage efficiency increasing in April-May as the fish grow larger.
    It is possible that past entrainment and loss of Bay-Delta longfin 
smelt may have reached levels of concern (CDFW 2020a, fig. 10, p. 47). 
However, since 2009, the entrainment of longfin smelt has not been 
substantial (Service 2024, fig. 3.4), perhaps partly due to monitoring 
and management of flows in the Old and Middle Rivers (OMR) between the 
Sacramento/San Joaquin River confluence and the export facilities. When 
net OMR flow is positive, San Joaquin River water is generally moving 
seaward through the San Francisco Bay Delta and away from the pumping 
facilities. The more net negative OMR is flowing, the more the water in 
the San Francisco Bay Delta is moving back upstream toward the pumping 
plants and the faster that water is moving south, thereby increasing 
entrainment potential. The additional negative flow causes Sacramento 
River water entering the northwest portion of the San Francisco Bay 
Delta to be diverted southward toward the pumping facilities rather 
than seaward, which allows saltier tidal flows to move further toward 
the San Francisco Bay Delta.
    In order to address and minimize effects to federally listed fish 
species (delta smelt (Hypomesus transpacificus), chinook salmon 
(Sacramento River winter-run and Central Valley spring-run salmon 
(Oncorhynchus tshawytscha), Central Valley steelhead (Oncorhynchus 
mykiss), and green sturgeon (Acipenser

[[Page 61042]]

medirostris)), restrictions to pumping and other water operations 
management strategies have been implemented by the DWR and Reclamation 
to limit negative OMR flows and associated entrainment through the 
section 7 process of the Act (Service 2008, entire; National Oceanic 
and Atmospheric Administration, National Marine Fisheries Service 
[NMFS] 2009, entire; Service 2019, entire; NMFS 2019, entire). In 
addition, the DWR has implemented similar measures for State-listed 
species (including longfin smelt) (CDFW 2009b Incidental Take Permit 
(ITP), entire; CDFW 2020b, ITP, entire).
    The results of two different analytical approaches using smelt 
larval survey (SLS) data suggest that entrainment of fish has not 
exceeded 3 percent since 2009 (Kimmerer and Gross 2022). Gross et al. 
(2022) coupled particle tracking modeling with the SLS data set and 
found an upper 95 percent credible interval of proportional entrainment 
was 2.9 percent in the critically dry winter of 2013 and nearly zero in 
the wet winter of 2017. Kimmerer and Gross (2022) analyzed all of the 
SLS data in the period 2009-2020. Similarly, this approach also found 
proportional entrainment was unlikely to have exceeded 3 percent (range 
= 0.5 to 2.9 percent) (Kimmerer and Gross 2022, table 1). We interpret 
these findings, as well as previously published information (CDFW 
2020a, entire), to indicate that the OMR management strategies in place 
since 2009 have been an effective conservation strategy for limiting 
the impact of entrainment and its consequences for the Bay-Delta 
longfin smelt. As a result, the best information currently available 
indicates that management actions for operating water diversion 
facilities are assisting in limiting entrainment impacts for the Bay-
Delta longfin smelt.
Contaminants
    The San Francisco Bay estuary has been identified as an impaired 
water body due to it containing numerous and persistent contaminant 
compounds (California State Water Resources Control Board 2018, 
appendix A). The list of contaminant compounds identified within the 
estuary includes elemental contaminants or `metals' (e.g., mercury and 
selenium), toxic organic compounds (dioxins, furans, polychlorinated 
biphenyls), and pesticides (chlordane dieldrin, DDT). Additional 
emerging contaminants of concern include newer pesticides, flame 
retardants, nutrients, naturally occurring toxins, microplastics, and 
pharmaceuticals and personal care products (i.e., plastic microbeads, 
insect repellant, sunscreen, cosmetics, etc.) (Klosterhaus et al. 2013, 
pp. 97-98, table 1; Sutton et al. 2017, entire). Ongoing analysis of 
water in the San Francisco Bay Delta suggests that on average 10 new 
synthetic organic pesticide chemicals are detected every year 
(California Department of Pesticide Regulation 2020, dataset). Water 
sampling in one study of the San Francisco Bay Delta indicated the 
presence of more than 50 chemical compounds from a single 1-liter (L) 
(34-ounce (oz)) water sample (Moschet et al. 2017, pp. 1557-1560).
    The sources of contaminants include discharge from municipal 
wastewater treatment plants, agricultural outfalls, stormwater runoff, 
anti-fouling paints on boat and ship hulls, and direct human 
application of pest and aquatic plant control compounds (Service 2024, 
section 3.1.6). Legacy contaminants in the Bay-Delta (those from 
historical loading, such as organochlorine chemicals (e.g., DDT) from 
past agricultural use and mercury from past mining activity) have been 
shown to persist in the environment and continue to impact ecosystems 
and can bioconcentrate through the food web, posing additional health 
risks (Connor et al. 2006, pp. 87-88; Marvin-DiPasquale and Cox 2007, 
p. 2). Regulation has reduced the use of some contaminants, only to be 
replaced by other more potent alternative water-soluble chemicals such 
as neonicotinoids, which have additional impacts on nontarget species 
such as aquatic invertebrates and fish (Buzby et al. 2020, pp. 15-21).
    Field-based toxicity is difficult to determine, as impacted fish 
are not recovered in order to be examined (i.e., fish either die from 
direct exposure and resulting disease, or are eaten). Risk of exposure 
and effect, as determined by comparison to other species (e.g., delta 
smelt and the introduced inland silverside (Menidia beryllina)), 
potentially include direct effects on development, growth, and 
reproduction; impacts resulting from impairments to bioenergetic 
demands; and impaired locomotion, reducing feeding success, which can 
lead to increased susceptibility to predation, disease, and entrainment 
(Brander et al. 2012, p. 2854; Connon et al. 2009, p. 12; Hasenbein et 
al. 2014, p. 696; Jeffries et al. 2015a, p. 17407; Jeffries et al. 
2015b, p. 55; Cole et al. 2016, p. 219; DeCourten and Brander 2017, p. 
2).
Pelagic Organism Decline (POD)
    Between the years 2002 through 2004, abundance indices for multiple 
fish species within the San Francisco Bay estuary declined abruptly in 
what is known as the pelagic organism decline, or POD. Specifically, 
the POD referred to a drop in survey catches of four fish species (Bay-
Delta longfin smelt, delta smelt, striped bass (Morone saxatilis), and 
threadfin shad (Dorosoma petenense)) (Sommer et al. 2007, p. 273). The 
POD event is generally recognized as a population step-decline for 
numerous fish species in the estuary. The coincident declines of 
multiple species suggested a possible common cause, but a single 
mechanism for decline that applied to all four fish has not been 
identified (MacNally et al. 2010, p. 1426; Thomson et al. 2010, pp. 
1442-1443). As a result, researchers have focused on multiple causes, 
from habitat changes, reductions in freshwater inflow, water 
diversions, food resource changes, competition, predation, and 
contaminants, as contributing to the POD (Sommer et al. 2007, pp. 271-
276; MacNally et al. 2010, p. 1418; Fong et al. 2016, pp. 20-21). As 
outlined above, all of these factors have been identified as threats 
impacting the Bay-Delta longfin smelt to varying degrees. Although the 
POD event is not a threat in itself, but is instead most likely a 
result of multiple threats, the subsequently smaller DPS population is 
more susceptible to poor habitat conditions and has a reduced 
capability of rebounding from lower abundance years.

Bay-Delta Longfin Smelt Current Condition

Current Abundance

    Several long-term survey efforts have been established for 
monitoring San Francisco Bay estuary fish populations including the 
Bay-Delta longfin smelt. These established survey efforts include the 
20-mm survey, the SFBS, and the FMWT. The 20-mm survey has been 
conducted since 1995, and although it does not produce an abundance 
index for Bay-Delta longfin smelt, we adapted the methods for the delta 
smelt abundance index for the Bay-Delta longfin smelt. Our methods and 
information on how we adapted the study information are outlined in the 
current SSA report (Service 2024, appendix B). The SFBS has sampled 
low-salinity to fully marine waters of the estuary using standardized 
sampling methods since 1980. However, sampling was more sporadic in the 
1990s and again in several recent years. The SFBS samples near bottom 
as well as midwater to surface-oriented fishes (Feyrer et al. 2015, 
Fig. 5, p. 3614) and provides separate abundance indices for ages 0, 1, 
and 2+ Bay-Delta longfin

[[Page 61043]]

smelt. The longest of these survey efforts is the FMWT, which was 
initiated in 1967 and has surveyed pelagic waters from the Delta into 
San Pablo Bay monthly from September through December each year. The 
FMWT captures mostly juvenile and adult fish 50-150 mm (2-6 in) in 
length and has been used to monitor the abundance of sampled fish 
species since the late 1970s (Stevens and Miller 1983, pp. 431-432). In 
the case of Bay-Delta longfin smelt, the FMWT samples adults and 
juveniles, most likely those returning from more marine environments to 
low-salinity and freshwater areas associated with spawning. Similar 
abundance estimates are reflected in the 20-mm survey, SFBS, and other 
modeling efforts (Service 2024, section 3.2.1). Collectively, these 
survey efforts encompass abundance estimates of all life stages of the 
Bay-Delta longfin smelt in the estuary.
    Figure 2 identifies FMWT abundance information for Bay-Delta 
longfin smelt since its inception in 1967 with emphasis on the years 
2000 to 2020. The FMWT time series is an index of fish numbers 
returning to spawn in the San Francisco Bay Delta, which is an 
indicator of abundance patterns as observed over this relatively longer 
time interval presented to give a simplified visual presentation of 
overall population trend during the last several decades. A more 
detailed analysis of overall trends and attendant risk is discussed, 
below.
[GRAPHIC] [TIFF OMITTED] TR30JY24.001

Population Trends and Risk of Quasi-Extinction

    All the best available field surveys for documenting long-term 
abundance trends indicate Bay-Delta longfin smelt numbers have 
substantially declined over time, with current relative abundance 
reflecting small fractions of the species' historical relative 
abundance and representing a decline of three to four orders of 
magnitude over the course of available historical abundance records. 
Even considering the small periodic increases in numbers in occasional 
years in the most recent survey results (past 20 years), the general 
trend over time has been lower highs and lower lows in abundance for 
the DPS. This finding supports the conclusion that abundance of all 
life stages has declined substantially over the course of several 
decades and that the overall decline has continued in recent years 
(Service 2024, section 3.2). A meta-analysis of annual population 
growth rates derived from the monitoring data showed that the DPS has a 
negative population growth rate (Service 2024, section 3.2.2). Figure 3 
displays quasi-extinction risk projections (including confidence 
intervals) over time for the Bay-Delta longfin smelt from our risk 
assessment (Tobias et al. 2023, fig. 4, p. 7; Service 2024, appendix 
B).

[[Page 61044]]

[GRAPHIC] [TIFF OMITTED] TR30JY24.002

Effects of Threats Impacting the Bay-Delta Longfin Smelt

    Reduced and altered freshwater flows into the estuary greatly 
impact the physical and ecological processes important to Bay-Delta 
longfin smelt spawning and larval rearing habitat. Reductions in 
freshwater flow reduce the number of young that survive to later 
reproduce. Reduced freshwater flows also require the DPS to move 
farther inland to find appropriate low-salinity conditions for spawning 
and rearing. Although management actions to limit the impact of water 
diversions at export facilities have been implemented, this movement 
farther inland makes the DPS's larvae and young more vulnerable to 
entrainment as a result of water diversion from water export 
facilities.
    The amount of freshwater input into the estuary is dependent on 
natural wet/dry precipitation patterns. These patterns have been 
influenced by the effects of current climate change conditions, which 
have resulted in more frequent, prolonged, and intense drought 
conditions (reduced flows) and increased water temperatures (poor 
habitat conditions). Freshwater flows into the estuary have also been 
greatly influenced by human-caused alteration of rivers and streams 
leading into the estuary as well as diversion and export of freshwater 
from the estuary. These human-caused impacts of water management have 
exacerbated the impacts of environmental variability of natural wet/dry 
precipitation patterns.
    In addition to altered habitat conditions for the Bay-Delta longfin 
smelt, the available food resources for the DPS have also been severely 
impacted. A rapid change to the zooplankton community in the estuary 
beginning in the late 1980s along with the introduction of the 
nonnative species such as the overbite clam and others has greatly 
reduced the natural prey base for the DPS and replaced it with a 
smaller nonnative mysid. Because the fish in the DPS continue to 
exhibit very little variation in prey use despite the reduction in 
natural prey availability, they are considered more susceptible to food 
web changes than some other fishes. The decline in food resources is 
likely affecting juvenile and adult longfin smelt growth and fitness as 
well as increasing the effort needed to meet food resource demands.
    After the review of the threats of predation, entrainment, and 
contaminants, we have determined that they are not primary driving 
factors currently influencing the Bay-Delta longfin smelt. However, 
these threats are likely still contributing cumulatively to the overall 
impacts acting on the DPS.
    We note that, by using the SSA framework to guide our analysis of 
the scientific information documented in the SSA report, we have 
analyzed the cumulative effects of identified threats and conservation 
actions on the species. To assess the current and future condition of 
the species, we evaluate the effects of all the relevant factors that 
may be influencing the species, including threats and conservation 
efforts. Because the SSA framework considers not just the presence of 
the factors, but to what degree they collectively influence risk to the 
entire species, our assessment integrates the cumulative effects of the 
factors and replaces a standalone cumulative-effects analysis.

Resiliency, Redundancy, and Representation for the Bay-Delta Longfin 
Smelt

    In the current SSA report for the Bay-Delta longfin smelt (Service 
2024, chapter 3), we evaluated the Bay-Delta longfin smelt's 
resiliency, redundancy, and representation under our SSA framework 
(Service 2016, entire).
    Resiliency describes the ability of a species to withstand 
stochastic disturbance. Because the Bay-Delta longfin smelt is a 
single, intermixed population, we did not identify multiple resiliency 
units but looked at the population as a whole. As discussed above, the 
Bay-Delta longfin smelt is subject to multiple interacting threats, 
including saltwater intrusion and reduced freshwater flows, that are 
altering and degrading habitat conditions. The resulting impact of 
these threats limits the extent, duration, and availability of 
appropriate habitat conditions needed for spawning, rearing, and 
ultimate recruitment of individuals into the population. These threats 
include anthropogenic actions (such as freshwater management, 
freshwater diversion, and physical alterations to the bathymetry of the 
estuary) or poor or altered

[[Page 61045]]

environmental conditions (such as increased frequency and magnitude of 
drought resulting from current climate change conditions). Disruptions 
to the estuary's food web associated with reductions in freshwater flow 
or introductions of nonnative species are also limiting resiliency for 
the DPS.
    Redundancy is the ability of a species to withstand catastrophic 
events. The Bay-Delta longfin smelt is a single intermixed population 
and occurs in areas within the San Francisco Bay estuary as dictated by 
the extremely modified and altered habitat and resource conditions. The 
San Francisco Bay estuary is also subject to extreme environmental 
variability as a result of climate change conditions resulting in 
increased temperatures and frequency, magnitude, and duration of 
drought. As a result of these changes, the ability of the system and 
organisms within the estuary to withstand catastrophic events and 
rebound during periods of more favorable conditions is greatly reduced. 
Large-scale estuary-wide ecosystem population collapses of fish and 
native zooplankton have occurred in the estuary. Although no single 
cause for the collapses has been identified, both native and nonnative 
fish populations have not recovered. The result has been step-declines 
of the Bay-Delta longfin smelt population size since the mid-1980s, 
thereby reducing the redundancy of the DPS.
    Representation describes the ability of a species to adapt to 
changing environmental conditions over time. This definition includes 
the ability of a species to adapt to both near-term and long-term 
changes in its physical and biological environments. The Bay-Delta 
longfin smelt population occurs in the San Francisco Bay estuary and is 
a single, genetically indistinguishable population. The Bay-Delta 
longfin smelt represents the southern extent of the species as a whole 
and most likely is a source for populations along the coast north of 
San Francisco Bay, but the number of individuals contributing to 
populations further north has substantially declined. Due to ocean 
currents and the species' poor swimming capability, populations north 
of the San Francisco Bay are unlikely to have the ability to move south 
and assist in reestablishing a population in the San Francisco Bay-
Delta once they have been extirpated from the San Francisco Bay-Delta. 
The DPS's ability to adapt behaviorally to environmental changes (to 
have adaptive capacity) is also limited. This limitation is exemplified 
by the DPS's behavioral tendency of not adapting to food resource 
changes. As discussed, food resources for the DPS have changed 
significantly yet the DPS's behavior has not shifted to adapt to those 
changes.
    In our evaluation of the current condition of the Bay-Delta longfin 
smelt, we evaluated several population viability analyses (PVAs) that 
quantitatively derive probabilities of extinction over time based on 
the DPS's historical and current abundance estimates (Service 2024; 
appendix B). The PVAs used information from the existing suite of 
surveys, including the FMWT, the 20-mm survey, and the SFBS (Service 
2024, figure 3.11). The PVAs modeled extinction probability based on a 
continuation of existing threats currently facing the DPS under varying 
levels of population recruitment. Population growth rates were further 
synthesized by conducting a meta-analysis on the growth rates of the 
different surveys. The results of the count-based PVA meta-analysis 
identified that the probability of quasi-extinction for the Bay-Delta 
longfin smelt is estimated at 33 percent over 20 years and reaches 50 
percent in 30 years (Service 2024, appendix B).
    As a result of our review of the best scientific and commercial 
data available on the Bay-Delta longfin smelt, we have determined that 
the DPS's resiliency is low. Numerous decades of declining abundance 
indices for the Bay-Delta longfin smelt document the inability of the 
DPS to rebound during more favorable environmental conditions and 
respond to the threats it is facing in the contemporary San Francisco 
Bay estuary. The Bay-Delta longfin smelt also has extremely limited 
redundancy because it effectively represents a single, small population 
inhabiting the San Francisco Bay-Delta and nearshore ocean environment, 
and because it continues to be impacted by large-scale stochastic 
events and is subject to catastrophic events. We have determined that 
the representation of the Bay-Delta longfin smelt is limited as well, 
reflecting that same declining abundance trend and no discernible and 
quantifiable compensatory adaptation to current ecological conditions. 
Based on our evaluation of the current resiliency, redundancy, and 
representation for the Bay-Delta longfin smelt, we conclude the current 
ability of the DPS to maintain populations in the wild is low.

Future Conditions

    As part of the SSA, we also developed future-condition scenarios to 
capture the range of uncertainties regarding future threats and the 
projected responses by the Bay-Delta longfin smelt. To assess the 
future condition of the Bay-Delta longfin smelt, we used published 
information related to the varying environmental conditions of the San 
Francisco Estuary, including future climate change information and 
projected increases in water demand, and how these changes may impact 
how well the estuary can support the Bay-Delta longfin smelt into the 
future. In our analyses, we considered two plausible future scenarios 
based on representative concentration pathways (RCP) 4.5 and 8.5 as the 
bookends for our analysis. The scenarios assessed climate change 
information (temperature increases, changes in precipitation patterns, 
sea-level rise) through 2100, as published information was available. 
The information identified that declines in Bay-Delta longfin smelt 
population abundance will continue into the future under both the RCP 
4.5 and 8.5 scenarios. Because we determined that the current condition 
of the Bay-Delta longfin smelt was consistent with an endangered 
species (see Determination of the Bay-Delta Longfin Smelt's Status, 
below), we are not presenting the results of the future scenarios in 
this final rule. Please refer to the current SSA report (Service 2024, 
chapter 4) for the full analysis of future scenarios.

Conservation Efforts and Regulatory Mechanisms

    Numerous efforts have been initiated regarding conservation and 
regulation of the San Francisco Bay estuary and its resources, 
including managing water flows into and export from the estuary, 
improving water quality, conducting habitat restoration, and 
implementing measures or regulations to protect native fish. This 
effort includes establishment of multiagency collaborations such as the 
Interagency Ecological Program (IEP), which focuses on coordinating and 
prioritizing science needs and research to meet responsibilities under 
State and Federal regulatory requirements (IEP 2014, entire).
    The State of California listed the longfin smelt in the San 
Francisco Bay estuary and along the California Coast as a threatened 
species under the California Endangered Species Act in 2009 (CDFW 
2009a, entire; California Natural Diversity Database 2022, entire) and 
has issued restrictions and requirements for the export of water for 
the State Water Project (see Entrainment, Water Project Exports, 
above). Several other fish species (delta smelt, several salmonid 
species) are listed under both the Act and the California Endangered 
Species Act, and the Service and NMFS have also issued biological 
opinions regarding the effects to these species and their habitats for

[[Page 61046]]

delivery and export of water from the estuary (see Entrainment, Water 
Project Exports, above). The State Water Board is responsible for 
issuing water quality standards and monitors contaminants within the 
estuary (see Contaminants, above). However, despite efforts such as 
those identified above, the current condition of the estuary and 
continued threats facing the estuary and Bay-Delta longfin smelt, such 
as reduced freshwater inflow, severe declines in population size, and 
disruptions to the DPS's food resources, have not been ameliorated.

Determination of the Bay-Delta Longfin Smelt's Status

    Section 4 of the Act (16 U.S.C. 1533) and its implementing 
regulations (50 CFR part 424) set forth the procedures for determining 
whether a species meets the definition of an endangered species or a 
threatened species. The Act defines an ``endangered species'' as a 
species in danger of extinction throughout all or a significant portion 
of its range and a ``threatened species'' as a species likely to become 
an endangered species within the foreseeable future throughout all or a 
significant portion of its range. The Act requires that we determine 
whether a species meets the definition of endangered species or 
threatened species because of any of the following factors: (A) The 
present or threatened destruction, modification, or curtailment of its 
habitat or range; (B) Overutilization for commercial, recreational, 
scientific, or educational purposes; (C) Disease or predation; (D) The 
inadequacy of existing regulatory mechanisms; or (E) Other natural or 
manmade factors affecting its continued existence.

Status Throughout All of Its Range

    The Bay-Delta longfin smelt's current abundance and density 
throughout the San Francisco Bay estuary have substantially declined. 
Currently, the DPS exists in very low abundance despite periods when 
appropriate habitat conditions, which typically would allow for 
population rebounds, are available. The best scientific and commercial 
information available and our analysis of that information revealed 
that several threats are causing or contributing to this decline and 
currently pose a meaningful risk to the viability of the DPS. These 
threats have put the Bay-Delta longfin smelt largely into a state of 
chronic population decline due to habitat loss (reduction in freshwater 
flows into the estuary), which is exacerbated by limited food resources 
and the impacts associated with climate change, thereby limiting its 
resiliency and ability to withstand catastrophic events (reduced 
redundancy). This decline in numbers of the Bay-Delta longfin smelt is 
also a reflection of the DPS's ability to adapt to the ecosystem 
changes.
    As a result of the DPS's poor performance in adapting to the suite 
of stressors acting upon it, we consider the Bay-Delta longfin smelt's 
adaptive capacity and, therefore, its current representation to be low. 
The Bay-Delta longfin smelt's continued reduced population size makes 
the DPS vulnerable to varying habitat conditions from year to year due 
to both anthropogenic and environmental conditions that are being 
influenced by the effects of climate change. Historically, with a 
larger population size, the DPS was more resilient to such stochastic 
and catastrophic events due to its ability to rebound in abundance when 
habitat conditions and resources would allow. The habitat changes, 
limitations to food resources, and resulting small population size now 
limit the DPS's ability to maintain its current population.
    After evaluating threats to the DPS and assessing the cumulative 
effect of the threats under the section 4(a)(1) factors, we find that 
the threats facing the San Francisco Bay-Delta DPS of the longfin smelt 
are current and ongoing and include habitat degradation and loss from 
reduced freshwater flow into the estuary (Factor A), increased 
intrusion of saltwater into spawning habitat areas (Factor A), 
alteration of food resources and availability (Factor E), nonnative 
species competition and food resource effects (Factor E), and the 
effects associated with climate change such as increased temperatures 
and frequency, magnitude, and duration of drought (Factor E). Because 
these threats are ongoing and currently impacting the DPS, and have 
already been shown to have caused a significant decline in the DPS's 
current resiliency, redundancy, and representation, the DPS meets the 
Act's definition of endangered status.
    Thus, after assessing the best scientific and commercial 
information available, we determine that the San Francisco Bay-Delta 
DPS of the longfin smelt is in danger of extinction throughout all of 
its range.

Status Throughout a Significant Portion of Its Range

    Under the Act and our implementing regulations, a species may 
warrant listing if it is in danger of extinction or likely to become so 
in the foreseeable future throughout all or a significant portion of 
its range. We have determined that the San Francisco Bay-Delta DPS of 
the longfin smelt is in danger of extinction throughout all of its 
range and accordingly did not undertake an analysis of any significant 
portions of its range. Because the San Francisco Bay-Delta DPS of the 
longfin smelt warrants listing as endangered throughout all of its 
range, our determination does not conflict with the decision in Center 
for Biological Diversity v. Everson, 435 F. Supp. 3d 69 (D.D.C. 2020), 
because that decision related to significant portion of the range 
analyses for species that warrant listing as threatened, not 
endangered, throughout all of their range.

Determination of Status

    Our review of the best scientific and commercial information 
available indicates that the San Francisco Bay-Delta DPS of the longfin 
smelt meets the definition of an endangered species. Therefore, we are 
listing the San Francisco Bay-Delta DPS of the longfin smelt as an 
endangered species in accordance with sections 3(6) and 4(a)(1) of the 
Act and our February 7, 1996, policy regarding distinct population 
segments (61 FR 4722).

Available Conservation Measures

    Conservation measures provided to species listed as endangered or 
threatened species under the Act include recognition as a listed 
species, planning and implementation of recovery actions, requirements 
for Federal protection, and prohibitions against certain practices. 
Recognition through listing results in public awareness, and 
conservation by Federal, State, Tribal, and local agencies, foreign 
governments, private organizations, and individuals. The Act encourages 
cooperation with the States and other countries and calls for recovery 
actions to be carried out for listed species. The protection required 
by Federal agencies, including the Service, and the prohibitions 
against certain activities are discussed, in part, below.
    The primary purpose of the Act is the conservation of endangered 
and threatened species and the ecosystems upon which they depend. The 
ultimate goal of such conservation efforts is the recovery of these 
listed species, so that they no longer need the protective measures of 
the Act. Section 4(f) of the Act calls for the Service to develop and 
implement recovery plans for the conservation of endangered and 
threatened species. The goal of this process is to restore listed 
species to a point where they are secure, self-sustaining, and 
functioning components of their ecosystems.

[[Page 61047]]

    The recovery planning process begins with development of a recovery 
outline made available to the public soon after a final listing 
determination. The recovery outline guides the immediate implementation 
of urgent recovery actions while a recovery plan is being developed. 
Recovery teams (composed of species experts, Federal and State 
agencies, nongovernmental organizations, and stakeholders) may be 
established to develop and implement recovery plans. The recovery 
planning process involves the identification of actions that are 
necessary to halt and reverse the species' decline by addressing the 
threats to its survival and recovery. The recovery plan identifies 
recovery criteria for review of when a species may be ready for 
reclassification from endangered to threatened (``downlisting'') or 
removal from protected status (``delisting''), and methods for 
monitoring recovery progress. Recovery plans also establish a framework 
for agencies to coordinate their recovery efforts and provide estimates 
of the cost of implementing recovery tasks. Revisions of the plan may 
be done to address continuing or new threats to the species, as new 
substantive information becomes available. The recovery outline, draft 
recovery plan, final recovery plan, and any revisions will be available 
on our website as they are completed (https://www.fws.gov/program/endangered-species), or from our San Francisco Bay-Delta Fish and 
Wildlife Office (see FOR FURTHER INFORMATION CONTACT).
    Implementation of recovery actions generally requires the 
participation of a broad range of partners, including other Federal 
agencies, States, Tribes, nongovernmental organizations, businesses, 
and private landowners. Examples of recovery actions include habitat 
restoration (e.g., restoration of native vegetation), research, captive 
propagation and reintroduction, and outreach and education. The 
recovery of many listed species cannot be accomplished solely on 
Federal lands because their range may occur primarily or solely on non-
Federal lands. To achieve recovery of these species requires 
cooperative conservation efforts on private, State, and Tribal lands.
    Once this species is listed, funding for recovery actions will be 
available from a variety of sources, including Federal budgets, State 
programs, and cost-share grants for non-Federal landowners, the 
academic community, and nongovernmental organizations. In addition, 
pursuant to section 6 of the Act, the State of California will be 
eligible for Federal funds to implement management actions that promote 
the protection or recovery of the San Francisco Bay-Delta DPS of the 
longfin smelt. Information on our grant programs that are available to 
aid species recovery can be found at: https://www.fws.gov/service/financial-assistance.
    Please let us know if you are interested in participating in 
recovery efforts for the San Francisco Bay-Delta DPS of the longfin 
smelt. Additionally, we invite you to submit any new information on 
this species whenever it becomes available and any information you may 
have for recovery planning purposes (see FOR FURTHER INFORMATION 
CONTACT).
    Section 7 of the Act is titled Interagency Cooperation and mandates 
all Federal action agencies to use their existing authorities to 
further the conservation purposes of the Act and to ensure that their 
actions are not likely to jeopardize the continued existence of listed 
species or adversely modify critical habitat. Regulations implementing 
section 7 are codified at 50 CFR part 402.
    Section 7(a)(2) states that each Federal action agency shall, in 
consultation with the Secretary, ensure that any action they authorize, 
fund, or carry out is not likely to jeopardize the continued existence 
of a listed species or result in the destruction or adverse 
modification of designated critical habitat. Each Federal agency shall 
review its action at the earliest possible time to determine whether it 
may affect listed species or critical habitat. If a determination is 
made that the action may affect listed species or critical habitat, 
formal consultation is required (50 CFR 402.14(a)), unless the Service 
concurs in writing that the action is not likely to adversely affect 
listed species or critical habitat. At the end of a formal 
consultation, the Service issues a biological opinion, containing its 
determination of whether the Federal action is likely to result in 
jeopardy or adverse modification.
    Examples of discretionary actions for the San Francisco Bay-Delta 
DPS of the longfin smelt that may be subject to consultation procedures 
under section 7 are land management or other landscape-altering 
activities on Federal lands administered by the Service, National Park 
Service, Department of Defense, Reclamation, U.S. Army Corps of 
Engineers, or U.S. Department of Agriculture, as well as actions on 
State, Tribal, local, or private lands that require a Federal permit 
(such as a permit from the U.S. Army Corps of Engineers under section 
404 of the Clean Water Act (33 U.S.C. 1251 et seq.) or a permit from 
the Service under section 10 of the Act) or that involve some other 
Federal action (such as funding from the Federal Highway 
Administration, Federal Aviation Administration, or the Federal 
Emergency Management Agency). Federal actions not affecting listed 
species or critical habitat--and actions on State, Tribal, local, or 
private lands that are not federally funded, authorized, or carried out 
by a Federal agency--do not require section 7 consultation. Federal 
agencies should coordinate with the local Service Field Office (see FOR 
FURTHER INFORMATION CONTACT) with any specific questions on section 7 
consultation and conference requirements.
    The Act and its implementing regulations set forth a series of 
general prohibitions and exceptions that apply to endangered wildlife. 
The prohibitions of section 9(a)(1) of the Act, and the Service's 
implementing regulations codified at 50 CFR 17.21, make it illegal for 
any person subject to the jurisdiction of the United States to commit, 
to attempt to commit, to solicit another to commit or to cause to be 
committed any of the following acts with regard to any endangered 
wildlife: (1) import into, or export from, the United States; (2) take 
(which includes harass, harm, pursue, hunt, shoot, wound, kill, trap, 
capture, or collect) within the United States, within the territorial 
sea of the United States, or on the high seas; (3) possess, sell, 
deliver, carry, transport, or ship, by any means whatsoever, any such 
wildlife that has been taken illegally; (4) deliver, receive, carry, 
transport, or ship in interstate or foreign commerce, by any means 
whatsoever and in the course of commercial activity; or (5) sell or 
offer for sale in interstate or foreign commerce. Certain exceptions to 
these prohibitions apply to employees or agents of the Service, the 
National Marine Fisheries Service, other Federal land management 
agencies, and State conservation agencies.
    We may issue permits to carry out otherwise prohibited activities 
involving endangered wildlife under certain circumstances. Regulations 
governing permits for endangered wildlife are codified at 50 CFR 17.22, 
and general Service permitting regulations are codified at 50 CFR part 
13. With regard to endangered wildlife, a permit may be issued: for 
scientific purposes, for enhancing the propagation or survival of the 
species. The statute also contains certain exemptions from the 
prohibitions, which are found in sections 9 and 10 of the Act.
    It is the policy of the Services, as published in the Federal 
Register on July 1, 1994 (59 FR 34272), to identify,

[[Page 61048]]

to the extent known at the time a species is listed, specific 
activities that will not be considered likely to result in violation of 
section 9 of the Act. To the extent possible, activities that will be 
considered likely to result in violation will also be identified in as 
specific a manner as possible. The intent of this policy is to increase 
public awareness of the effect of a listing on proposed and ongoing 
activities within the range of the species.
    As discussed above, certain activities that are prohibited under 
section 9 may be permitted under section 10 of the Act. In addition, to 
the extent currently known, the following activities will not be 
considered likely to result in violation of section 9 of the Act: (1) 
take of the longfin smelt outside the range of the DPS as identified in 
figure 1 above; (2) take as a result of recreational fishing as 
permitted by the State of California; or (3) recreational boating on 
open-water areas of the San Francisco Bay-Delta Estuary.
    This list is intended to be illustrative and not exhaustive; 
additional activities that will not be considered likely to result in 
violation of section 9 of the Act may be identified during coordination 
with the local field office, and in some instances (e.g., with new 
information), the Service may conclude that one or more activities 
identified here will be considered likely to result in violation of 
section 9.
    To the extent currently known, the following is a list of examples 
of activities that will be considered likely to result in violation of 
section 9 of the Act in addition to what is already clear from the 
descriptions of the prohibitions found at 50 CFR 17.21: (1) handling or 
collecting individuals of the DPS; (2) destruction/alteration of the 
Bay-Delta longfin smelt's habitat by discharge of fill material, 
dredging, draining, ditching, or stream channelization or diversion; 
(3) unauthorized diversion or alteration of surface flow into the San 
Francisco Bay-Delta estuary by removal of freshwater from rivers, 
streams, wetlands, and other aquatic features; (4) introduction of 
contaminants that may degrade water quality of the San Francisco Bay-
Delta estuary; or (5) introduction of nonnative species that compete 
with or prey upon the Bay-Delta longfin smelt or alter food resources 
for the DPS.
    This list is intended to be illustrative and not exhaustive; 
additional activities that will be considered likely to result in 
violation of section 9 of the Act may be identified during coordination 
with the local field office, and in some instances (e.g., with new or 
site-specific information), the Service may conclude that one or more 
activities identified here will not be considered likely to result in 
violation of section 9.
    Questions regarding whether specific activities would constitute 
violation of section 9 of the Act should be directed to the San 
Francisco Bay-Delta Fish and Wildlife Office (see FOR FURTHER 
INFORMATION CONTACT).

II. Critical Habitat

    Section 4(a)(3) of the Act and implementing regulations (50 CFR 
424.12) require that we designate critical habitat at the time a 
species is determined to be an endangered or threatened species, to the 
maximum extent prudent and determinable. In the October 7, 2022, 
proposed listing rule (87 FR 60957 at 60970), we determined that 
designation of critical habitat was prudent but not determinable 
because specific information needed to analyze the impacts of 
designation was lacking. Since the publication of the proposed listing 
rule, we have obtained the necessary information and are in the process 
of developing a proposed critical habitat designation for the Bay-Delta 
longfin smelt. We plan to publish a proposed critical habitat rule in 
the near future and complete a final designation as required by 
sections 4(a)(3) and 4(b)(6)(C)(ii) of the Act.

Required Determinations

National Environmental Policy Act (42 U.S.C. 4321 et seq.)

    It is our position that, outside the jurisdiction of the U.S. Court 
of Appeals for the Tenth Circuit, we do not need to prepare 
environmental analyses pursuant to the National Environmental Policy 
Act (42 U.S.C. 4321 et seq.) in connection with regulations adopted 
pursuant to section 4(a) of the Act. We published a notice outlining 
our reasons for this determination in the Federal Register on October 
25, 1983 (48 FR 49244). This position was upheld by the U.S. Court of 
Appeals for the Ninth Circuit (Douglas County v. Babbitt, 48 F.3d 1495 
(9th Cir. 1995), cert. denied 516 U.S. 1042 (1996)).

Government-to-Government Relationship With Tribes

    In accordance with the President's memorandum of April 29, 1994 
(Government-to-Government Relations with Native American Tribal 
Governments; 59 FR 22951, May 4, 1994), Executive Order 13175 
(Consultation and Coordination with Indian Tribal Governments), the 
President's memorandum of November 30, 2022 (Uniform Standards for 
Tribal Consultation; 87 FR 74479, December 5, 2022), and the Department 
of the Interior's manual at 512 DM 2, we readily acknowledge our 
responsibility to communicate meaningfully with federally recognized 
Tribes and Alaska Native Corporations on a government-to-government 
basis. In accordance with Secretaries' Order 3206 of June 5, 1997 
(American Indian Tribal Rights, Federal-Tribal Trust Responsibilities, 
and the Endangered Species Act), we readily acknowledge our 
responsibilities to work directly with Tribes in developing programs 
for healthy ecosystems, to acknowledge that Tribal lands are not 
subject to the same controls as Federal public lands, to remain 
sensitive to Indian culture, and to make information available to 
Tribes. No Tribal lands were identified within the range of the Bay-
Delta longfin smelt, and we did not receive any information during our 
development of the SSA report for the DPS or the two open public 
comment periods. We will continue to reach out and coordinate with 
Tribal entities during the development of our recovery planning and 
critical habitat designation processes for the Bay-Delta longfin smelt.

References Cited

    A complete list of references cited in this rulemaking is available 
on the internet at https://www.regulations.gov and upon request from 
the San Francisco Bay-Delta Fish and Wildlife Office (see FOR FURTHER 
INFORMATION CONTACT).

Authors

    The primary authors of this rule are the staff members of the Fish 
and Wildlife Service's Species Assessment Team and the San Francisco 
Bay-Delta Fish and Wildlife Office.

List of Subjects in 50 CFR Part 17

    Endangered and threatened species, Exports, Imports, Plants, 
Reporting and recordkeeping requirements, Transportation, Wildlife.

Signing Authority

    Martha Williams, Director of the U.S. Fish and Wildlife Service, 
approved this action on June 14, 2024, for publication. On July 22, 
2024, Martha Williams authorized the undersigned to sign the document 
electronically and submit it to the Office of the Federal Register for 
publication as an official document of the U.S. Fish and Wildlife 
Service.

Regulation Promulgation

    Accordingly, we amend part 17, subchapter B of chapter I, title 50 
of the Code of Federal Regulations, as set forth below:

[[Page 61049]]

PART 17--ENDANGERED AND THREATENED WILDLIFE AND PLANTS

0
1. The authority citation for part 17 continues to read as follows:

    Authority:  16 U.S.C. 1361-1407; 1531-1544; and 4201-4245, 
unless otherwise noted.

0
2. Amend Sec.  17.11 in paragraph (h), in the List of Endangered and 
Threatened Wildlife, by adding an entry for ``Smelt, longfin [San 
Francisco Bay-Delta DPS]'' in alphabetical order under FISHES to read 
as follows:


Sec.  17.11   Endangered and threatened wildlife.

* * * * *
    (h) * * *

----------------------------------------------------------------------------------------------------------------
                                                                                          Listing citations and
           Common name              Scientific name      Where listed         Status         applicable rules
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
                                                     Fishes
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
Smelt, longfin [San Francisco     Spirinchus          U.S.A. (CA).......  E              89 FR [INSERT FIRST
 Bay-Delta DPS].                   thaleichthys.                                          PAGE OF FEDERAL
                                                                                          REGISTER PUBLICATION],
                                                                                          7/30/2024.
 
                                                  * * * * * * *
----------------------------------------------------------------------------------------------------------------


Madonna Baucum,
Regulations and Policy Chief, Division of Policy, Economics, Risk 
Management, and Analytics of the Joint Administrative Operations, U.S. 
Fish and Wildlife Service.
[FR Doc. 2024-16380 Filed 7-29-24; 8:45 am]
BILLING CODE 4333-15-P