Endangered and Threatened Wildlife and Plants; 12-month Finding on a Petition to list the Sacramento Splittail as Endangered or Threatened, 62070-62095 [2010-24871]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 75, Number 194 (Thursday, October 7, 2010)]
[Proposed Rules]
[Pages 62070-62095]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-24871]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R8-ES-2010-0013]
[MO 92210-0-0008-B2]


Endangered and Threatened Wildlife and Plants; 12-month Finding 
on a Petition to list the Sacramento Splittail as Endangered or 
Threatened

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 12-month petition finding.

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SUMMARY: We, the U.S. Fish and Wildlife Service, announce a 12-month 
finding on a petition to list the Sacramento splittail (Pogonichthys 
macrolepidotus) as endangered or threatened under the Endangered 
Species Act of 1973, as amended. After review of all available 
scientific and commercial information, we find that listing the 
Sacramento splittail is not warranted at this time. However, we ask the 
public to submit to us any new information that becomes available 
concerning the threats to the Sacramento splittail or its habitat at 
any time.

DATES: The finding announced in this document was made on October 7, 
2010.

ADDRESSES: This finding is available on the Internet at https://www.regulations.gov at Docket Number FWS-R8-ES-2010-0013. Supporting 
documentation we used in preparing this finding is available for public 
inspection, by appointment, during normal business hours at the U.S. 
Fish and Wildlife Service, San Francisco Bay Delta Fish and Wildlife 
Office, 650 Capitol Mall, Sacramento, CA 95814. Please submit any new 
information, materials, comments, or questions concerning this finding 
to the above street address.

FOR FURTHER INFORMATION CONTACT: Dan Castelberry, San Francisco Bay 
Delta Fish and Wildlife Office (see ADDRESSES); by telephone at 916-
930-5632; or by facsimile at 916-930-5654. If you use a 
telecommunications device for the deaf (TDD), please call the Federal 
Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION:

Background

    Section 4(b)(3)(B) of the Endangered Species Act of 1973, as 
amended (Act) (16 U.S.C. 1531 et seq.), requires that, for any petition 
to revise the Federal Lists of Endangered and Threatened

[[Page 62071]]

Wildlife and Plants that contains substantial scientific or commercial 
information that listing the species may be warranted, we make a 
finding within 12 months of the date of receipt of the petition. In 
this finding, we will determine that the petitioned action is: (1) Not 
warranted, (2) warranted, or (3) warranted, but the immediate proposal 
of a regulation implementing the petitioned action is precluded by 
other pending proposals to determine whether species are tendangered or 
threatened, and expeditious progress is being made to add or remove 
qualified species from the Federal Lists of Endangered and Threatened 
Wildlife and Plants. Section 4(b)(3)(C) of the Act requires that we 
treat a petition for which the requested action is found to be 
warranted but precluded as though resubmitted on the date of such 
finding, that is, requiring a subsequent finding to be made within 12 
months. We must publish these 12-month findings in the Federal 
Register.

Previous Federal Actions

    Please refer to the final listing rule (64 FR 5963) for a 
discussion of Federal actions that occurred prior to February 8, 1999. 
Please refer to the Notice of Remanded Determination of Status for the 
Sacramento Splittail (68 FR 55139) for a discussion of Federal actions 
that occurred after February 8, 1999, and prior to September 22, 2003. 
It is our intent, in this document, to reiterate and discuss only those 
topics directly relevant to this decision.
    On September 22, 2003, the Service published a Notice of Remanded 
Determination of Status for the Sacramento Splittail in the Federal 
Register (68 FR 55139) that removed the Sacramento splittail from the 
List of Endangered and Threatened Wildlife (50 CFR 17.11(h)). On August 
13, 2009, the Center for Biological Diversity (CBD) filed a complaint 
in U.S. District Court for the Northern District of California, 
challenging the Service on the merits of the 2003 determination 
alleging improper political influence. In a settlement dated February 
1, 2010 (Case4:09-cv-03711-PJH), the Service agreed to open a 30-day 
public comment period for a new 12 month finding to allow for the 
submission of additional information by the public. The Service also 
agreed to submit to the Federal Register a new status review and 12-
month finding as to whether listing the Sacramento splittail is 
warranted or not warranted. If warranted, the Service further agreed to 
publish, concurrently with the 12-month finding, a proposed rule to 
list the Sacramento splittail before September 30, 2010 and a final 
determination on or before September 29, 2011.

Definitions

    To assist the reader in understanding terminology used in this 
determination, we have provided below several terms with their 
corresponding definitions as they are used in this document. As used in 
this determination, the term ``Delta'`` refers to all tidal waters 
contained within the legal definition of the San Francisco Bay-
Sacramento-San Joaquin River Delta, as delineated by section 12220 of 
the State of California's Water Code. Generally, the Delta is contained 
within a triangular area that extends south from the City of Sacramento 
to the confluence of the Stanislaus and San Joaquin Rivers at the 
southeast corner and Chipps Island in Suisun Bay at the southwest 
corner. The term ``Estuary'' as used in this determination, refers to 
the collective tidal waters contained in the Sacramento and San Joaquin 
Rivers, the Delta, and San Pablo and San Francisco bays.

Species Information

Species Description

    The Sacramento splittail is a fish species native to central 
California and represents the only extant species in its genus in the 
world (Baerwald et al. 2007, p. 160). Splittail can grow to a length of 
40centimeters (cm) (15 inches (in.)), and have an elongate body, small 
head, and enlarged upper tail lobe. Their body coloration is dusky 
olive gray on the back and silver on the sides. During breeding season, 
their fins become tinged with red-orange. Additionally, males develop 
white tubercles on their heads and become darker in color during the 
breeding season (Moyle 2002, p. 146).

Taxonomy

    Splittail were first described in 1854 by W.O. Ayres as Leuciscus 
macrolepidotus and by S.F. Baird and C. Girard as Pogonichthys 
inaeqilobus. Although Ayres' species description is accepted, the 
species was assigned to the genus Pogonichthys in recognition of the 
distinctive characteristics exhibited by the two splittail species P. 
ciscoides and P. macrolepidotus (Hopkirk 1973, p. 24). Pogonichthys 
ciscoides, endemic to Clear Lake, Lake County, California, has been 
extinct since the early 1970s. The Sacramento splittail is currently 
classified as Pogonichthys macrolepidotus. Recent studies have revealed 
two populations of splittail that differ in their genetic makeup, one 
in the Napa/Petaluma drainages (hereafter referred to as the San Pablo 
population) and one in the greater Central Valley drainage (hereafter 
referred to as the Delta population) (Baerwald et al.2007, pp. 159-
167).

Distribution

    Historically, Sacramento splittail were found as far north as 
Redding on the Sacramento River. Splittail were also found in the 
tributaries of the Sacramento River as far as the current Oroville Dam 
site on the Feather River and Folsom Dam site on the American River 
(Rutter et al. 1908, p. 131). Along the San Joaquin River, splittail 
were harvested by native peoples in Tulare and Buena Vista Lakes where 
splittail bones have been found in archeological middens (Moyle et al., 
2004, p. 7). In the San Francisco Bay area, splittail have historically 
been reported at the mouth of Coyote Creek in Santa Clara County and 
the Southern San Francisco Bay (Snyder et al. 1905, pp. 327-338). 
Splittail were documented in Suisun and Napa marshes as well as Suisun 
Bay in the 1950's (Caywood . 1974, p. 29-65).
    Splittail occur in the San Francisco estuary and its tributaries 
and are found most often in slow moving sections of rivers and sloughs 
including dead end sloughs and shallow edge habitats (Moyle 2002, p. 
147; Daniels and Moyle 1983, p. 653; Feyrer et al. 2005, pp. 164-165). 
Recent studies have shown the splittail's range in the Sacramento, San 
Joaquin, Napa, Mokelumne and Petaluma rivers is significantly greater 
than previously thought when it was first petitioned in the early 
1990's as a threatened species (Sommer et al. 2007, pp. 27-28; Sommer 
et al. 1997, p. 970). The following chart created by Sommer and 
featured in his splittail paper follows (Sommer et al. 2007, p. 28).

[[Page 62072]]



Table 1. Upstream-most locations of historical and recent splittail collections (1998-2002). River kilometer (rkm) is the distance from the mouth of the
                                                      river. Location (rkm) of splittail collection
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                            Recent (Freyer et al.
            River System             Historic (Rutter 1908)    1970s (Cawood 1974)   Mid- 1990s (Sommer et     05) unless noted      Distance to first
                                                                                           al. 1997)              otherwise                dam\a\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Sacramento                           483                     387                     331                    391\b\                 387
--------------------------------------------------------------------------------------------------------------------------------------------------------
Feather                              109                     Present                 94                     94\c\                  109
--------------------------------------------------------------------------------------------------------------------------------------------------------
American                             49                      37                      19                     No new data            37
--------------------------------------------------------------------------------------------------------------------------------------------------------
San Joaquin                          Widespread              Present                 201                    218.5\d\               295
--------------------------------------------------------------------------------------------------------------------------------------------------------
Mokelumne                            NA                      25                      63                     96\e\                  63
--------------------------------------------------------------------------------------------------------------------------------------------------------
Napa                                 NA                      21                      10                     32                     NA
--------------------------------------------------------------------------------------------------------------------------------------------------------
Petaluma                             NA                      25                      8                      28                     NA
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Lowest dams in reach of river are Red Bluff (Sacramento), Oroville (Feather), Nimbus (American), Sack (San Joaquin), and Woodbridge (Mokelumne).
  Woodbridge is a seasonal dam. Napa River is not dammed within the range of splittail; first dam was removed from the Petaluma River in 1994.
\b\ D. Killam, California Department of Fish and Game, personal communication.
\c\ B. Oppenheim, NOAA Fisheries, personal communication.
\d\ R. Baxter, California Department of Fish and Game, unpublished data.
\e\ J. Merz, East Bay Municipal Utility District, November 2000.

    Distribution on the Sacramento River over the past 30 years has 
consistently ranged at least 232 to296 river kilometers (rkm) (144 
to184 miles (mi)) upstream of the estuary (Feyrer et. al. 2005, pp. 
163-167). The consistent finding of splittail more than 200 rkm (124 
mi) upstream of the Estuary may represent a population persisting there 
or may reflect the long distance that splittail migrate during dry 
years (Feyrer et al. 2005, pp. 165-166). Juvenile splittail have been 
recorded at the Glenn-Colusa Irrigation District Intake at rkm 331 (206 
mi) on the Sacramento River year-round from 1994 - 2001. It is unknown 
why these individuals do not migrate downstream after spawning as do 
the majority of splittail (Feyrer et al. 2005, pp 165-166). Splittail 
have been documented on the Toulumne River to rkm 27.4 (mi 17) (Heyne 
2003, pers. comm.) and on the Merced River to rkm 20.9 (13 mi) ( Heyne 
2003, pers. comm.). Splittail have been recorded in recent times from 
within Salt Slough (Baxter 1999a, p. 10; 1999b, p. 30). A 1998 
California Department of Fish and Game (CDFG) gillnet survey of the 
tidal reaches of the Lower Walnut Creek found splittail to be the most 
abundant fish in the creek (Leidy et al. 2007). Splittail are found in 
the Napa Marsh during years with high freshwater flow, but are rare 
during years of low freshwater outflow (Baxter 1999a, p. 11).
    Splittail can utilize a variety of habitats and having no known 
collection in an area does not mean that splittail are not there 
because it is impractical to survey the entire Delta. Splittail have 
been observed in a number of tributaries of major rivers such as the 
Sacramento and San Joaquin and are likely distributed much more widely 
in small creeks and marshes throughout the lower portions of the 
Estuary than known collections indicate (Kratville 2010, pers comm.). 
Suisun Marsh and Bay contain the largest areal extent of shallow water 
habitat available to the splittail and likely have the greatest 
concentrations of the species.
    Splittail's spawning habitat includes the natural and newly-
restored floodplains of the Cosumnes River, managed floodplains such as 
the Yolo and Sutter bypasses, and disjunct segments of floodplain 
adjacent to the Sacramento and San Joaquin rivers and tributaries. 
These areas approximate the large, open, shallow-water areas which once 
existed throughout the Delta (Sommer et al. 1997, p. 971). The largest 
portion of splittail spawning habitat occurs in the Yolo Bypass and 
higher splittail young-of-the-year abundances are strongly correlated 
with the flooding of the Yolo Bypass. The best spawning conditions for 
splittail occur in the bypass when water remains in the bypass until 
fish have completed spawning (at least 30 days), and larvae are able to 
swim out on their own during the draining process.
    In years where the Yolo and Sutter bypasses are not inundated for 
at least 30 days, splittail spawning is confined primarily to the 
natural and newly restored floodplains of the Cosumnes River and the 
margins of rivers and other floodplain features that are inundated at 
lower river stages. The Cosumnes River is unique in that it is the only 
major river flowing into the Delta that does not host a major dam. 
There are indications, based on presence of larvae and juveniles, that 
spawning in the Sacramento River occurs relatively far upstream at 
Colusa (Baxter 1999a, p. 8; 1999b, p. 29). Splittail also utilize the 
San Joaquin River for spawning in wet years when river flow exceeds the 
capacity for storage and flooding occurs. The Tuolumne, Cosumnes, 
Feather, American, Napa, and Petaluma Rivers, and numerous other 
smaller waters also support splittail spawning activity.
    In summary, the geographic distribution of the splittail has not 
decreased detectably over the last several decades and is in fact 
larger than estimated in our last listing decision (Sommer et al. 2007, 
pp.27-28; 68 FR 55139).

Habitat Requirements

    Although primarily a freshwater species, splittail tolerate 
salinities as high as 10 to 18 parts per thousand (ppt) (Moyle and 
Yoshiyama 1992). Salinity tolerance in splittail increases in 
proportion to body length; adults can tolerate salinities as high as 29 
ppt for short periods in laboratory conditions, but experience loss of 
equilibrium (bodily balance) when salinities exceed 23 ppt (Young and 
Cech 1996, p. 668). Hospitable temperatures for non-breeding splittail 
range from 5 to 24[deg] Celsius (C) (75[deg] Fahrenheit (F)) although 
acclimated fish can survive temperatures up to 33[deg]C (91[deg] F) for 
short periods of time (Young and Cech 1996, pp. 667-675). Splittail are 
also tolerant

[[Page 62073]]

of low dissolved oxygen and can be found in water where levels are 
around 1 mg O\2\ L -\1\ (Moyle et al. 2004, p. 13).
    Splittail are frequently found in areas subject to flooding because 
they require flooded vegetation for spawning and rearing. Historically, 
the major flood basins (e.g., Colusa, Sutter, American, and Yolo 
basins; Tulare, Buena Vista, and Kern lakes) distributed throughout the 
Sacramento and San Joaquin valleys provided spawning and rearing 
habitat. These flood basins have all been reclaimed or modified for 
flood control purposes (i.e. as bypasses), and much of the floodplain 
area adjacent to the rivers is now inaccessible behind levees.
    Splittail make use of the Sutter Bypass, and particularly heavy use 
of the Yolo Bypass, for spawning under certain hydrologic conditions. 
The shallow, vegetated waters of the bypasses provide excellent rearing 
conditions for juvenile fish (Sommer et al. 2001, p. 11). The bypasses 
are primarily flood control facilities and secondarily, passively 
operated as agricultural lands. These lands are also managed for 
waterfowl and other wildlife habitat. Splittail using the bypasses are 
subject to the same threats found elsewhere, such as habitat loss, 
environmental contamination, harmful reservoir operations, competition 
with and predation by non-native fish, and so forth.
    The bypasses are only fully flooded when flows in the Sacramento 
River reach a certain level. The Yolo Bypass becomes inundated when the 
Sacramento River flow rate at the Freemont Weir exceeds 1,600 cubic 
meters per second (cms) (56,503 cubic feet per second (cfs)). This 
occurs when the River reaches approximately 9.0 meters (m) (30 feet 
(ft.) (National Geodetic Vertical Datum standard) in depth at the 
Freemont Weir (Sommer et al. 2001, pp. 7-8). Partial flooding of the 
Yolo Bypass via high flows from Cache and Putah creeks can occur 
independently regardless of Sacramento River flows. Due to the 
unpredictable flooding frequencies and duration of the bypass, 
splittail, having migrated long distances upstream, could arrive at 
floodplains that have not been inundated and therefore the splittail 
could be denied the opportunity to spawn. In those cases where adult 
splittail successfully spawn, the eggs or larvae could become trapped 
and killed if waters recede too rapidly. Insufficient duration of 
floodplain inundation could also force egress of juvenile splittail 
before they have attained a size and swimming ability sufficient to 
avoid predation. The annual splittail spawning and reproductive success 
is strongly correlated with frequency and duration of Yolo bypass 
inundation (Sommer et al. 2007, pp. 33-34).
    The Fremont Weir has been overtopped--resulting in Yolo Bypass 
inundation--19 of the last 31 years with 10 of these years producing 
inundation durations of more than 30 days (DWR 2010a, pp. 1-2). 
Inundation durations of 30-90 days are needed to produce robust 
splittail year classes on the bypass (Kratville 2010, pers. comm.). 
According to the ST5 (T. C. Foin) model, the inundation of floodplains 
that splittail utilize as spawning habitat must occur at a minimum of 
every 7 years for a minimum of 30 days for splittail populations to 
persist. Bypasses and other floodplains have historically been 
exceeding these parameters and we have no evidence that suggests they 
will not continue to do so in the foreseeable future.
    The Yolo Bypass supports agricultural crops such as corn and 
safflower and can support tomatoes in non-flood years. Optimal flooding 
conditions for the splittail (February through May) have negative 
effects on agricultural production in the area destroying and damaging 
crops, eroding soils and decreasing overall yields (Yolo Bypass 
Management Strategy 2001, ch. 2 p. 6). Because Yolo Bypass inundation 
is likely to be one of the most important factors in determining the 
continued production of high splittail population numbers, cooperation 
on the flood management between the landowners of the bypass and 
resource management agencies is essential.
    Splittail spawning occurs over flooded vegetation in freshwater 
marshes, sloughs, and shallow reaches of large rivers with depths of at 
least 1m (3.3 ft) (Moyle et al. 2007 , pp. 1-27). Observations of 
splittail spawning have indicated the species spawns at depths of less 
than 1.5 m (4.9 ft) in the Cosumnes River floodplain and at depths of 
less than 2 m (6.6 ft) in Sutter Bypass (Moyle et al. 2004, pp. 16-17). 
These studies show that splittail spawn in water depths between 1 to 2 
m (3.3 to 6.6 ft) depending on location of spawning. Splittail may not 
spawn again in the year following a successful effort (Moyle et. al. 
2004, p. 32).
    It is speculated that Suisun Marsh is the late-stage rearing area 
for juvenile splittail hatched and reared in the extensive spawning 
habitat found within the Yolo Bypass because water flowing out of the 
Yolo Bypass tends to stay on the north side of the delta and be drawn 
into Suisun Marsh (Moyle et al. 2004, p. 31).

Biology

    Splittail are relatively long-lived and larger fish may be 8 to 10 
years old (Moyle 2002). Splittail reach about 110 millimeters (mm) (4.3 
in) standard length (SL) (tip of the snout to the posterior end of the 
last vertebra)in their first year, 170 mm (6.6 in) SL in their second 
year, and 215 mm (8.4 in) SL in their third year (Moyle 2002, p. 148). 
Male and female splittail generally mature by the end of their second 
year, but some males mature in their first year and some females do not 
mature until their third year (Daniels and Moyle 1983, p.650).
    Estimates of splittail fecundity have shown high variability in 
numbers of eggs produced. Caywood (1974, p. 4015) found a mean of 165 
eggs per mm of SL of fish sampled and reported a maximum of 100,800 
eggs in one female. Feyrer and Baxter (1998, p. 123) found a mean of 
261 eggs per mm of SL and a fecundity range of 28,416 to 168,196 eggs. 
Bailey et al. (1999) examined fish held for a considerable time in 
captivity and found that fecundity ranged from 24,753 to 72,314 eggs 
per female, which most closely agrees with Caywood's (1974, p. 4015) 
observations.
    Splittail are benthic (feeding in the bottom of the water column) 
foragers that mainly feed in the daytime. Composition of splittail gut 
contents has revealed that they feed almost exclusively on aquatic 
invertebrates with chironomid larvae making up the largest portion of 
the diet in all areas except the Petaluma River where copepods make up 
the largest portion of the diet (Feyrer et al. 2007a, p. 1398). Until 
the 1980's, opossum or mysid shrimp (Neomysis mercedis), made up a 
large portion of the diet along with amphipods and harpacticoid 
copepods (Moyle et al. 2004, p. 14). Introductions of the Asiatic clam 
(Corbicula fluminea) in 1945 and more importantly the overbite clam 
(Corbula amurensis) first recorded from the estuary in 1986) were 
followed by a sharp decline in shrimp abundance that started in 1987 
and continued through 1999 (Feyrer et al. 2003, p. 283). Splittail have 
shifted their diet from prey items such as mysid shrimp to a diet 
increasingly focused on bi-valves, in particular the overbite clam. 
Opossum shrimp in splittail gut contents were reduced from 24 percent 
(historically) to 2 percent by 2003 (Feyrer et al. 2003, pp. 277-288; 
Kratville 2010, pers comm.). In the Estuary, clams, crustaceans, insect 
larvae, and other invertebrates also are found in the adult diet. 
Larvae feed mainly on plankton composed of small

[[Page 62074]]

animals (zooplankton), moving to small crustaceans and insect larvae as 
body size increases (Kurth and Nobriga 2001, EIP newsletter vol. 14, 
num.3, p. 41).
    Splittail populations fluctuate annually, depending on spawning 
success, which is positively well-correlated with freshwater outflow 
and the availability of shallow water habitat with submerged vegetation 
(Daniels and Moyle 1983; Sommer et al. 1997). Sexual maturity is 
typically reached by the end of their second year. Splittail are a 
migratory species that travel upstream into freshwater floodplain 
habitat to spawn. The onset of spawning is associated with rising water 
levels, increasing water temperatures, and increasing day length. Peak 
spawning occurs from February through May, although records of spawning 
exist for late January to early July (Wang 1986). One temporally stable 
cue for splittail is the timing of the vernal equinox (Feyrer 2006, p. 
221). Peak flow from the Central Valley enters the Estuary 
approximately at the same time as the vernal equinox (Feyrer 2006, p. 
221) and these coinciding events commence splittail migration. In some 
years, most spawning may take place within a limited period of time. 
For instance, in 1995, a year of high spawning activity, most splittail 
spawned over a short period in April (Moyle et al. 2004, p. 16). Within 
each spawning season, older fish reproduce first, followed by younger 
individuals (Caywood 1974, p. 50).
    Bailey (1994, p. 3) has documented that splittail eggs hatch in 3 
to 5 days at 18.5[deg] C, (65.3[deg] F). Bailey (1994, p. 3) also found 
that at 5 to 7 days after hatching, the yolk sac is absorbed and the 
diet begins to include small rotifers. Splittail larvae remain in 
shallow, weedy areas close to spawning sites for 10 to 14 days and move 
into deeper water as they mature and swimming ability increases (Sommer 
et al. 1997, pp. 961-976). When the flood waters recede juveniles 
typically leave the flooded areas and move downstream in May, June, and 
July to rear in estuarine marshes (Moyle et al. 2004, p. 17). Splittail 
can be easily identified at 20 to 25 mm (0.8 to 1.0 in) total length 
(TL) and become fairly active swimmers at this time (Moyle et al. 2004, 
p. 17).

Abundance

History of abundance models and evaluations
    An estimate of splittail abundance has never been performed; 
however, survey data have been used to construct indices of abundance 
that have been used in the past to assess population trends (Sommer et 
al. 2007, p 29; Moyle et al. 2004, p 7). In general, the applicability 
of survey data to a particular use arises from two factors: (1) How the 
data are collected; and (2) how the data are used to estimate or to 
index abundance. The key point with regard to the first factor is the 
degree to which the sample collected is representative of the sampled 
population. Gear type, configuration, and method of deployment all 
contribute to species, sizes, and life stages collected. Unequal 
vulnerability of different sizes of fish to a given sampling protocol 
results in systematic error in population estimation. Fish behavior, 
both between species and between life stages, also contributes to 
sampling error, as does habitat variation, because gear performance 
often differs among habitat types. The efficiency of open-water, or 
pelagic, sampling may be affected by physical factors such as flow 
velocity and turbidity, both in terms of gear performance and fish 
behavior.
    Splittail are a benthic (near-bottom-dwelling) species, often occur 
in shallow edge habitat, and feed most actively in early morning (Moyle 
et al. 2004, p 8; Moyle 2002, p 148). Splittail would not be expected 
to be collected efficiently in surveys that do not sample channel edges 
and bottom habitats effectively. Further, while combining data from the 
various surveys provides reasonably good coverage of the geographic 
range of splittail, individual surveys are often fairly limited in 
geographic scope. All surveys suffer from selection biases due to the 
type of gear deployed and the method of deployment (Ricker et al. 1975, 
pp 70-73; 92). None of the surveys used to construct the indices used 
to monitor the relative abundance of splittail was designed 
specifically to sample splittail, and each is limited in some manner in 
its ability to adequately represent splittail population trends. 
Therefore, the data collected do not represent a quantitative estimate 
of population size.
    The surveys and their limitations are described in the Service's 
Notice of Remanded Determination of Status for the Sacramento Splittail 
(68 FR 55139). Sommer et al. (2007, pp 29-30) and Moyle et al. (2004, 
pp 8-13) also explain some of the important limitations of the surveys 
with respect to splittail. A chart summarizing the surveys and their 
limitations is provided below.

                                 Table 2. Summary of splittail sampling surveys
----------------------------------------------------------------------------------------------------------------
             Survey               Brief Description          Years               Pros                Cons
----------------------------------------------------------------------------------------------------------------
CDFG Fall Mid--Water Trawl       Designed to sample   1967--present       Catches all         --Targets striped
                                  juvenile striped                         splittail size      bass
                                  bass.                                    classes            --Low adult catch
                                 100 sampling sites:                                           rate
                                 San Pablo Bay in                                             --Sampling does
                                  the west to Rio                                              not cover entire
                                  Vista on the lower                                           range
                                  Sacramento River.                                           --Does not sample
                                 and to Stockton on.                                           benthos or
                                 the San Joaquin                                               shallow channel
                                  River.                                                       edges
                                                                                              --Some years yield
                                                                                               no splittail
                                                                                              --Splittail are
                                                                                               better able to
                                                                                               see nets in
                                                                                              recent years due
                                                                                               to decreased
                                                                                               turbidity
----------------------------------------------------------------------------------------------------------------
San Francisco Bay Mid--Water     Samples west of the  1980--present       --Two types of      --Does not cover
 Trawl and Otter Trawl Survey     Delta                                    sampling            entire range
                                 seaward to south                          equipment and      --Non--specific;
                                  San Francisco Bay.                      frequent sampling.   targets entire
                                                                          --Capture all size   pelagic or
                                                                           classes.            benthic community
                                                                                              --Incomplete data
                                                                                               between 1989--
                                                                                               1999
                                                                                              --Splittail only
                                                                                               caught in 5
                                                                                               percent or less
                                                                                               of samples
----------------------------------------------------------------------------------------------------------------

[[Page 62075]]

 
University of California at      Long--term study of  1979--present       Samples all size    --Non--specific;
 Davis (UC Davis) Suisun Marsh    the                                      classes             targets entire
 Otter Trawl                     ecology of the                                               fish community
                                  entire fish                                                 --Geographically
                                  community of the                                             limited
                                  marsh at 21 sites                                           --Larger fish less
                                  and 9 sloughs.                                               vulnerable to
                                                                                               trawls
----------------------------------------------------------------------------------------------------------------
Chipps Island Survey             U.S. Fish and        1976--present       --Samples well      --Designed to
                                  Wildlife Service                         during high flow    sample juvenile
                                  conducts a                               years               salmonids
                                  sampling program                        --Good adult catch  --Geographically
                                  for juvenile                             rates.              limited
                                  salmon in the deep                                          --Samples near--
                                  water channel near                                           surface waters
                                  Chipps                                                       only
                                 Island, midwater                                             --High turbidity
                                  trawl is pulled at                                           in sampling area
                                  the.
                                 surface in 10 20--
                                  minute hauls per
                                  day during May and
                                  June.
----------------------------------------------------------------------------------------------------------------
FWS Beach Seine Survey           Samples 23 stations  1979--present       --Broadest          --Inconsistent
                                  around Delta with                        geographical        from 1983--1992
                                  15--m beach seine                        coverage of all    --Focused on out--
                                  in low velocity                          surveys             migrating
                                  areas near                              --Good adult         juvenile salmon
                                  shoreline                                catches.           ----Low adult
                                                                                               catch
----------------------------------------------------------------------------------------------------------------
Salvage Operations               The Central Valley   1979--present       Highest number of   --Geographically
                                  Project (CVP) and                        splittail caught    localized--mainly
                                  State Water                              out of any survey   reflective of San
                                  Project (SWP)                            for both adult      Joaquin River
                                  operate fish                             and juvenile        production
                                  screening                                catches            --Catches are
                                  facilities to                                                result of
                                  divert fish away                                             entrainment and
                                  from the pump                                                often cause
                                  intakes into                                                 mortality
                                  holding
                                 facilities where
                                  fish are counted,.
                                 measured, and
                                  released..
----------------------------------------------------------------------------------------------------------------

    Please refer to February 8, 1999, final listing rule (64 FR 5963) 
for a full discussion of methods used to estimate abundance in that 
rule. Please refer to the September 22, 2003, Notice of Remanded 
Determination of Status for the Sacramento Splittail (68 FR 55139) for 
a full discussion of methods used to estimate abundance for that 
document. In our January 6, 1994, proposed rule to list the Sacramento 
splittail as threatened (59 FR 862), we initially evaluated and 
analyzed splittail survey data using a method published by Meng and 
Moyle (1995, p. 541) in the Transactions of the American Fisheries 
Society. Meng and Moyle used a common data set from the years 1980-1992 
to compare point estimates with the Mann-Whitney U-test. We used this 
same method during the development of our 1999 final listing rule (64 
FR 5963, February 8, 1999), using abundance data provided and updated 
by CDFG, California Department of Water Resources (CDWR), and UC Davis. 
Using the aforementioned method, the 1999 finding concluded that the 
splittail had declined by 62 percent in abundance over the last 15 
years.
    In a document we published in the Federal Register on August 17, 
2001 (66 FR 43145), we requested public comments to assist us in 
reanalyzing our splittail abundance data. In that document, we 
presented a stratified Mann-Whitney U-test, which represented an 
improvement on what essentially remained a Meng and Moyle (1995, pp. 
538-549) statistical approach. Following careful consideration of 
comments we received from numerous respondents to this document, 
including those provided through the peer review process, we concluded 
that the abundance indices and Multiple Linear Regression (MLR) model 
jointly developed and submitted by CDFG and U.S. Bureau of Reclamation 
(USBR) in 2001 (hereafter referred to as the CDFG/USBR MLR Model) 
provided the best scientific data (method) available for statistically 
evaluating temporal trends of splittail abundance information. We used 
this CDFG/USBR MLR Model as the basis of our September 22, 2003, Notice 
of Remanded Determination of Status for the Sacramento Splittail (68 FR 
55139), instead of the original Meng and Moyle (1995, pp. 540-542) 
methodology. We input 20 discrete sets of age-specific abundance 
monitoring data into the model. These data sets were obtained from the 
surveys described in Table 2 above. Running the model in a ``worst case 
scenario'' (alpha < 0.2 significance), we found nine significant 
downward-trending data sets and two significant upward-trending data 
sets, and we concluded that the population was in decline.
Current evaluation of models and abundance
    In light of uncertainties in data for estimating splittail 
population abundance, alternative approaches for understanding 
population behavior and regulation have been developed. One such 
approach is the life history simulation model developed by T. C. Foin 
wherein splittail population characteristics can be explored and 
compared with known field biology to infer important life stage 
survival probabilities and potential conservation strategies (Moyle et 
al., 2004, pp. 32-37). Life history simulation models can be 
parameterized to the extent possible using relevant field/survey 
information, and then used in a series of ``what if'' exercises to 
explore simulated population dynamics under selected conditions. Using 
the model in this way for sensitivity analysis allows the experimenter 
to discern which life stage or life stage characteristic is crucial to 
long-term simulated survival, for example, or how often ``sub-optimal'' 
conditions must occur for the simulated population to be at risk for 
extinction. Such population viability analyses (PVAs) can form part of 
the basis for the Act's listing decisions where sufficient life stage 
parameter estimates are well-known (Shaffer 1981, pp. 131-133; Meffe 
and Carroll 1994, pp. 181-182). In the Estuary such a model was used to 
confirm field observations that flood plain dynamics and subsequent 
spawning response by splittail populations were critical to long-term 
population persistence in the absence of other exogenous drivers of 
splittail mortality (Moyle et al. 2004, pp. 32-27).
    In the present case of the Sacramento splittail, survey data appear 
sufficient to

[[Page 62076]]

point to supra-annual patterns of abundance (abundance changes over 
several or many years), but do not appear to support parsing into sub-
annual or life-stage specific characterization of splittail population 
biology. Inaccuracies associated with intra-annual sampling and both 
relative and absolute gear inefficiencies make it very difficult to 
discern splittail population dynamics on a sub-annual basis. Life 
history traits of the splittail including their dependence on 
floodplain hydrology and seasonal flooding of riparian and floodplain 
lands make this species quite suited to exploration using population 
simulation approaches (Moyle et al., 2004,pp. 13-18, 32).
    The T. C. Foin splittail population simulation model (ST5) and 
related models have led to the following conclusions regarding 
Sacramento splittail population variability and longer-term population 
forecasts (Moyle et al., 2004, pp. 32-37). Splittail populations are 
highly variable and driven in large measure by rainfall and flooding; 
high variability in splittail populations can be modeled focusing on 
reproductive effort in those years with substantial added floodplain 
inundation. Simulations indicate that several dry years in succession 
are not likely to imperil splittail populations. Despite downward 
trends in simulated populations of splittail, this model indicates that 
low numbers of splittail reproducing along river margins can sustain 
the population through long drought periods and that a long series of 
dry years is unlikely to drive the splittail to extinction (Moyle et 
al. 2004, pp. 36-37). However, a large-scale, regional catastrophe 
combined with low population might lead to stochastic extinction. Adult 
mortality considered in isolation does not appear to be driving the 
population dynamics of splittail in the Estuary or in the models. 
Periodic (i.e., a minimum of every 7 years) floodplain inundation seems 
essential to long-term population persistence. High variability is a 
fundamental property of splittail populations; therefore, little can be 
discerned regarding population status within a given survey year from 
annual indices of abundance.
    The splittail population model ST5 and additional splittail models 
built in support of CALFED Science Program objectives use as a 
foundation biological characterization supplied by field biologists and 
species specialists (Moyle et al. 2004, pp.32-37). Noted in splittail 
life history is adaptation to ``estuarine waters with fluctuating 
conditions'' (Moyle 2002, p. 147). This includes the ability to respond 
to abrupt water level changes and the ability to utilize seasonally 
inundated floodplains for spawning. Sacramento splittail are highly 
fecund, with some large females reportedly able to produce over 100,000 
eggs (Moyle 2002, p. 148). As an iteroparous (producing offspring in 
successive cycles), moderately long-lived (5 to 8 years) species with 
high reproductive potential, it is not surprising that splittail life 
history characteristics allow the species to persist even in the face 
of only moderately predictable conditions year-to-year. As long as 
favorable spawning conditions occur at a minimum of every 7 years, 
populations can remain at relatively low levels and rebound when 
favorable spawning conditions occur (Moyle 2002, pp. 34-38). Recent 
survey records provided via Interagency Ecological Program (IEP) survey 
efforts for the Sacramento splittail have shown this pattern (Meng and 
Moyle 1995, pp. 548; Sommer et al., 1997;DWR 2010c, p. 16). This was 
demonstrated in 1995 when populations retained a high reproductive 
capacity after a substantial decline following several years of drought 
(Sommer et al. 1997, p. 971)., Due to the deficiencies in the survey 
data discussed above, we are unable to discern a trend in adult 
abundance. The young-of-year splittail population experiences a natural 
fluctuation in numbers due to drought cycles in the region.

Evaluation of Information Pertaining to the Five Threat Factors

    Section 4 of the Act (16 U.S.C. 1533) and implementing regulations 
(50 CFR part 424) set forth procedures for adding species to, removing 
species from, or reclassifying species on the Federal Lists of 
Endangered and Threatened Wildlife and Plants. Under section 4(a)(1) of 
the Act, a species may be determined to be endangered or threatened 
based on any of the following 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.
    In making this 12-month finding, information pertaining to the 
Sacramento splittail in relation to the five factors provided in 
section 4(a)(1) of the Act is discussed below. In making our 12-month 
finding on the petition we considered and evaluated the best available 
scientific and commercial information.
    In considering what factors might constitute threats to a species, 
we must look beyond the exposure of the species to a factor to evaluate 
whether the species may respond to the factor in a way that causes 
actual impacts to the species. If there is exposure to a factor and the 
species responds negatively, the factor may be a threat and we attempt 
to determine how significant a threat it is. The threat is significant 
if it drives, or contributes to, the risk of extinction of the species 
such that the species warrants listing as endangered or threatened as 
those terms are defined in the Act.

Factor A. The present or threatened destruction, modification, or 
curtailment of its habitat or range

Habitat Loss
    The Bay Institute has estimated that intertidal wetlands in the 
Delta have been diked and leveed so extensively that approximately 95 
percent of the 141, 640 hectares (ha)(350, 000 acres(ac)) of tidal 
wetlands that existed in 1850 are gone (The Bay Institute 1998, ch. 4, 
p. 17), and that 90 percent of the riparian forest and riparian 
wetlands of the Sacramento Valley have been cleared, filled, or 
otherwise eliminated. Diking, dredging, filling of wetlands, and 
reduction of freshwater flows through more than half of the rivers, 
distributary sloughs, and the Estuary for irrigated agriculture and 
urban use have widely reduced fish habitat and resulted in extensive 
fish losses (Moyle et al. 1995, p. 166-168). San Joaquin River flows 
have been degraded to a higher extent than flows in the Sacramento 
River (Feyrer et.al. 2007a, p. 1396).Limited spawning can take place in 
river and stream habitats, but the persistence of the splittail is now 
dependent on seasonal floodplains including the Yolo and Sutter 
bypasses and Cosumnes River.
    Loss and degradation of shallow, near-shore habitat is a historic, 
current and future threat to the splittail. Riparian and natural bank 
habitats are features that historically provided splittail with 
spawning substrate, organic material, food supply, and cover from 
predators. Vast stretches of the Sacramento and San Joaquin Rivers, 
their tributaries, and distributary sloughs in the Delta have been 
channelized and much of the shallow nearshore habitat has been leveed 
and riprapped. The prevention of channel meandering by the placement of 
riprap is causing a continual loss of low

[[Page 62077]]

velocity shallow water breeding habitat (Feyrer et. al. 2005, p. 167).
Beneficial Actions Offsetting Adverse Effects
    While habitat loss has occurred, a number of habitat restoration 
actions are also being undertaken.
    CALFED Habitat Restoration:The CALFED Bay Delta Program (CALFED) 
leadership has recently transitioned from the CALFED Bay Delta 
Authority to the Bay Delta Stewardship Council. This changed the name 
and governing structure of the program, but did not change the 2000 
Record of Decision (ROD) for CALFED or any goals or objectives of the 
CALFED plan.
    The CALFED plan exists as a multi-purpose (water supply, flood 
protection, and conservation) program with significant ecosystem 
restoration and enhancement elements, The program brought together more 
than 20 State and Federal agencies to develop a long-term comprehensive 
plan to restore ecological health and improve water management for all 
beneficial uses of the Bay-Delta system. The plan specifically 
addresses ecosystem quality, water quality, water supply, and levee 
system integrity.
    The CALFED Ecosystem Restoration Program (ERP) presented a 
strategic plan for implementing an ecosystem-based approach for 
achieving conservation targets (CALFED 2000a, pp. 1-3). The CDFG is the 
primary implementing agency for the ERP. The goal of ERP to improve the 
conditions for the splittail will remain whether the splittail is 
listed as threatened or endangered or not listed. In the CALFED 
process, the splittail's status could be adversely affected by program 
elements to: Increase water storage in the Central Valley upstream of 
the Delta; modify Delta hydrologic patterns to convey additional water 
south, and upgrade and maintain Delta levees. However, as noted 
previously CALFED has an explicit goal to balance the water supply 
program elements with the restoration of the Bay-Delta and tributary 
ecosystems and recovery of the splittail and other species. Because 
achieving the diverse goals of the program is iterative and subject to 
annual funding by diverse agencies, CALFED has committed to maintaining 
balanced implementation of the program within an adaptive management 
framework. Within this framework of implementation, it is intended that 
the storage, conveyance, and levee program elements would only be 
implemented in such a way that the splittail's status would be 
maintained and eventually improved.
    CALFED has identified 29 specific species enhancement conservation 
measures for splittail (CALFED 2000b. There are more than 150 projects 
that benefit the splittail or its habitat in the plan and more than 
half of those have been completed to date (2010 ERP database 
spreadsheets). Key accomplishments of the ERP include investments in 
fish screens, temperature control, fish passage and habitat protection 
and restoration (CALFED 2007, p. 2).
    Additional projects such as Cosumnes River floodplain restoration 
and Liberty Island restoration are ongoing. Major obstacles to the 
completion of these projects , especially the acquisition of land have 
been overcome. Although discussion of all 150 programs currently 
benefitting splittail will not be practical in this document, we have 
highlighted several projects that have played an important role in 
offsetting threats to the splittail into the foreseeable future.
    Liberty Island lies at the southern end of the Yolo bypass. After 
years of active agricultural production on Liberty island, the levees 
were breeched in 1997 and the island was allowed to return to a more 
natural state (Wilder 2010, PowerPoint s. 4). The CALFED program funded 
the purchase of the island in 1999 by granting money to the Trust for 
Public Lands for the acquisition of the island (Wilder 2010, PowerPoint 
s. 5). Splittail are utilizing the flooded island and have been 
documented in a number of surveys including the beach seine survey in 
which they were the most abundant fish caught from August 2002 to July 
2003 (Wilder 2010, PowerPoint s. 22; Liberty Island Monitoring Program 
2005, p. 37; Marshall et al. 2006, p. 1). Splittail are utilizing the 
southern portion of the island more than the northern portion of the 
island (Webb 2009, p. 1). In 2007, the Delta Juvenile Fish Monitoring 
program was awarded $2.5 million from the CALFED program for the Breach 
III study at Liberty Island. Work has been initiated and results will 
assist agencies in understanding the ecological system and developing 
recommendations for future restoration projects (Hrodey 2008). There 
are currently plans to remove additional levees by Wildlands 
Corporation which has acquired a portion of Liberty Island that it 
plans to return to natural floodplain habitat. Wildlands Corporation's 
actions may be approved and initiated within the next year, but cannot 
be counted as a conservation measures at this time (Roper 2010, pers. 
comm.). When these actions are implemented, they are expected to 
further increase splittail spawning grounds on Liberty Island.
    Restoration efforts have also been undertaken at the Cosumnes River 
Preserve (hereafter referred to as the Preserve) under management of 
the Bureau of Land Management (BLM), The Nature Conservancy, and a 
number of other agencies and private organizations. Restoration 
activities that benefit splittail include riparian enhancement and 
intentional breaching of levees to restore floodplain function. The 
Preserve opened 81 ha (200 acres) to flooding in October of 1995 by 
removing a 15.2 m (50 ft) section in a levee along the Cosumnes River 
(Cosumnes River Preserve Management Plan March 2008). Following floods 
in 1995 and 1997, the decision was made by the Preserve in coordination 
with the U.S. Army Corps of Engineers to not repair the portions of the 
levees breeched by the floods thus allowing for a more natural flood 
regime (Cosumnes River Preserve Management Plan March 2008, ch. 2 pp. 
6-7). Levees have been breached in a total of five locations to allow 
flooding of a variety of habitats including marshes and sloughs (Crain 
et al. 2004, p. 126). Restoration is ongoing and splittail are likely 
to benefit from these efforts, as the area has also been described as 
among the most important floodplain habitats still available to the 
species (Moyle et al. 2004, p. 17). Splittail used the Preserve 
floodplains during both years of a study conducted in 1999 and 2001 
(Crain et al. 2004, p. 140). Splittail larvae were present in 2001 when 
only a small portion of the floodplain in the study area was inundated. 
Although spawning was not observed, it is presumed to have occurred in 
the last week of March or the first week of April since larvae appeared 
shortly after. Larvae moved off the floodplain during cold-water flow 
pulses in the last week of April and the first week of May (Crain et 
al. 2004, p. 140).
Other Habitat Restoration Projects:
    The Yolo Bypass Wildlife Area (Wildlife Area), located within the 
Yolo Bypass, currently encompasses 6,787 ha (16,770 ac). This area has 
increased substantially since CDFG's original acquisition of 
approximately 1180 ha (2,917 ac) in 1991. The added area has allowed 
restoration actions that benefit splittail spawning efforts to proceed 
by creating new seasonal floodplains (Yolo Bypass Wildlife Management 
Land Management Plan, 2008, ch.1).
    In early 2002, the Sacramento River National Wildlife Refuge 
Complex (SRNWRC) began implementation of a Plan for Proposed 
Restoration Activities on the Sacramento River National Wildlife 
Refuge. The restoration

[[Page 62078]]

activities have resulted in the reestablishment or enhancement of 1707 
ha (4, 218 ac) of the SRNWRC (Silveria 2010, pers. comm.). This 
restoration is expected to benefit splittail through improvement of 
vegetative conditions on floodplains. Restoration and enhancement 
involve the removal of crops, orchards, and related infrastructure 
(pumping units, barns, sheds, etc.) followed by replacement with native 
vegetation appropriate to each site. In addition to restoration 
efforts, levees have been removed at the Flynn and Rio Vista units and 
a levee has been breached at the La Barracna unit (Silveira 2010, pers. 
comm.). These efforts allow for a more natural floodplain regime and 
increase native vegetation that benefits splittail.
Summary of Factor A
    Rip-rapping of river and stream habitat constitutes a potential 
threat to the Sacramento splittail. The implementation and magnitude of 
the CALFED, Central Valley Project Improvement Act (CVPIA) (discussed 
under Factor D) and other habitat restoration activities, which focus 
on the restoration of habitats that directly and indirectly benefit 
splittail go far beyond any foreseeable future habitat losses. The 
overall effect of habitat restoration activities is also expected to 
continue to be beneficial for splittail into the future.
    Efforts undertaken in the past decade have benefited the species by 
restoring its habitat. There is presently sufficient habitat to 
maintain the species, and inundation frequency and duration in key 
areas is sufficient to provide spawning to maintain the species. 
Furthermore, habitat restoration activities that have been completed 
are currently being implemented and those planned for the future are 
adding to the available habitat for the species.
    We conclude that the best scientific and commercial information 
available indicates that the Sacramento splittail is not now, or in the 
foreseeable future, threatened by the present or threatened 
destruction, modification, or curtailment of its habitat or range.

Factor B. Overutilization for commercial, recreational, scientific, or 
educational purposes

Recreational Fishing
    Splittail were historically abundant enough to be harvested by 
Native Americans and commercial fisheries, although no studies on 
abundance were begun until 1963 (Moyle et. al. 2004, p. 7). Today, 
splittail are harvested for bait by the sport fishery and as a food 
source, but take is limited by the California Fish and Gave Commission 
to two individuals per day as further discussed under Factor D. The 
largest splittail may be the first to engage in the spawning migration 
(Caywood 1974; Moyle et al. 2004, p. 15). The early-season fishery 
potentially targets and removes females with high reproductive 
potential. The effect of this fishery in the Sacramento River may be 
relatively greater in dry years, when splittail spawning is largely 
confined to river margins where fishing effort is concentrated. 
Splittail is known to be an effective bait fish for striped bass and is 
commonly caught by anglers for this use (Moyle et al. 2004, p. 19). The 
splittail fishery is the smallest fishery targeted in the CDFG angler 
survey (SFRA 2008). At present, there is no evidence of any trend in 
the available data suggesting that larger fish are being 
disproportionally removed from the population or that the size 
structure of the splittail population has been altered by this small 
fishery. There is no indication that the intensity of fishing or bag 
limits will increase in the future.
Scientific Collection
    Monitoring surveys conducted throughout the year, including the 
Fall Mid-Winter Trawl (FMWT), Summer Tow Net Survey (TNS), Beach Seine 
Survey, Chipps Island Trawl, Suisun Marsh Survey, and Spring Kodiak 
Trawl Survey (SKT) capture and record adult and juvenile splittail. 
These surveys sometimes result in the unintentional mortality of some 
individuals. Data from the last 12 years of surveys conducted by the 
Service are in Table 3.

 Table 3. Take (collection and release) and mortality by U. S. Fish and
                Wildlife Service surveys for 1999- 2010.
------------------------------------------------------------------------
             Survey                  Number Taken          Mortality
------------------------------------------------------------------------
Chipps Island                    6887                 339
------------------------------------------------------------------------
Mossdale                         146,854              1,856
------------------------------------------------------------------------
Service Beach Seine              207,137              2,394
------------------------------------------------------------------------

    An average of 383 splittail are killed every year in the course of 
conducting Service surveys. Adult splittail spawn up to 100,000 eggs 
per individual per fecundity event and the loss of a few thousand 
individuals from scientific collection over a 10 year period is not 
expected to have a significant effect at the population level. We have 
no information to indicate use of the species for other commercial, 
recreational, scientific, or educational purposes.
Summary of Factor B
    The new CDFG regulation enacted in March 2010 limiting take of 
splittail to two individuals per day has eliminated any potential 
threat that fisheries may have posed. The best available scientific and 
commercial data shows that this current level of take does not 
adversely affect the splittail population or that this level of 
mortality will increase in the future.
    Annual Service surveys result in an average of 383 splittail being 
killed each year. However, due to the high fecundity rate of splittail, 
the average yearly loss has not had a significant effect at the 
population level and the information obtain from the surveys is being 
used to monitor the splittail populations.
    We conclude that the best scientific and commercial information 
available indicates that the Sacramento splittail is not now, or in the 
foreseeable future, threatened by the overutilization for commercial, 
recreational, scientific or educational.

Factor C. Disease or predation

Disease
    The south Delta is fed by water coming from the San Joaquin River, 
where pesticides (e.g., chlorpyrifos, carbofuran, and diazinon), salts 
(e.g., sodium sulfates), trace elements (boron and selenium), and high 
levels of total dissolved solids are prevalent due to agricultural 
runoff (64 FR 5963, February 8, 1999). Of specific concern are the 
threats posed by heavy metals such as mercury, selenium, and 
pesticides. There is some possibility

[[Page 62079]]

that disease in splittail could be a function of increased contaminant 
loading and subsequent immune system depression. Disease related to 
contaminants is further discussed under Factor E below.
    Splittail naturally carry parasites like most fish, b