Endangered and Threatened Species; Proposed Critical Habitat for the Gulf of Maine Distinct Population Segment of Atlantic Salmon, 51747-51781 [E8-20603]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 73, Number 173 (Friday, September 5, 2008)]
[Proposed Rules]
[Pages 51747-51781]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E8-20603]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 226

[Docket No. 0808061060-81062-01]
RIN 0648-AW77


Endangered and Threatened Species; Proposed Critical Habitat for 
the Gulf of Maine Distinct Population Segment of Atlantic Salmon

AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and 
Atmospheric Administration (NOAA), Commerce.

ACTION: Proposed rule; request for comments.

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SUMMARY: We, the National Marine Fisheries Service (NMFS), propose to 
designate critical habitat for the Gulf of Maine Distinct Population 
Segment (GOM DPS) of Atlantic salmon (Salmo salar). We previously 
determined that naturally spawned and several hatchery populations of 
Atlantic salmon which constituted the GOM DPS warrant listing as 
endangered under the Endangered Species Act of 1973, as amended (ESA). 
We are required to designate critical habitat for the GOM DPS as a 
result of this listing. We propose to designate as critical habitat 45 
specific areas occupied by Atlantic salmon at the time of listing that 
comprise approximately 203,781 km of perennial river, stream, and 
estuary habitat and 868 square km of lake habitat within the range of 
the GOM DPS and on which are found those physical and biological 
features essential to the conservation of the species. The entire 
occupied range of the GOM DPS in which critical habitat is being 
proposed is within the State of Maine. We propose to exclude 
approximately 1,463 km of river, stream, and estuary habitat and 115 
square km of lake habitat from critical habitat pursuant to section 
4(b)(2) of the ESA.

DATES: Comments on this proposal must be received by November 4, 2008. 
Two public hearings on the proposed rule will be held in conjunction 
with the Atlantic salmon proposed listing rule (See the notice, 
Proposed Endangered Status for the Gulf of Maine Distinct Population 
Segment of Atlantic Salmon, published in the Proposed Rules section of 
the September 3, 2008, issue of the Federal Register) and we will alert 
the public of the locations and dates of those hearings in a subsequent 
Federal Register notice.

ADDRESSES: You may submit comments, identified by RIN 0648-AW77, by any 
of the following methods:
     Electronic Submission: Submit all electronic public 
comments via the Federal eRulemaking Portal: https://
www.regulations.gov. Follow the instructions for submitting comments.
     Mail: Assistant Regional Administrator, Protected 
Resources Division, NMFS, Northeast Regional Office, Protected 
Resources Division, One Blackburn Drive, Gloucester, MA 01930.
     Facsimile (fax) to: 207-866-7342, Attention: Dan Kircheis.
    Instructions: All comments received are a part of the public record 
and will generally be posted to https://www.regulations.gov without 
change. All personal identifying information (for example, name, 
address, etc.) voluntarily submitted by the commenter may be publicly 
accessible. Do not submit confidential business information or 
otherwise sensitive or protected information. NMFS will accept 
anonymous comments (enter N/A in the required fields, if you wish to 
remain anonymous). Attachments to electronic comments will be accepted 
in Microsoft Word, Excel, Word Perfect, or Adobe PDF file formats only.
    The proposed rule, list of references and supporting documents, 
including

[[Page 51748]]

the Biological Valuation, Economic Analysis, IRFA Analysis, and 4(b)(2) 
Report, are also available electronically at the NMFS Web site https://
www.nero.noaa.gov/prot_res/ altsalmon/.

FOR FURTHER INFORMATION CONTACT: Dan Kircheis, NMFS, at 207-866-7320, 
dan.kircheis@noaa.gov; Mary Colligan, NMFS, at 978-281-9116; or Marta 
Nammack, 301-713-1401.

SUPPLEMENTARY INFORMATION: 

Background

    NMFS and the U.S. Fish and Wildlife Service (USFWS; collectively 
``the Services'') issued a final rule listing the GOM DPS of Atlantic 
salmon as endangered on November 17, 2000 (65 FR 69459). The GOM DPS 
was defined in the 2000 rule as all naturally reproducing wild 
populations and those river-specific hatchery populations of Atlantic 
salmon, having historical river-specific characteristics found north of 
and including tributaries of the lower Kennebec River to, but not 
including, the mouth of the St. Croix River at the U.S.-Canada border 
and the Penobscot River above the site of the former Bangor Dam.
    In September of 2006, a new Status Review for Atlantic salmon in 
the United States (Status Review report) was made available to the 
public (https://www.nmfs.noaa.gov/pr/pdfs/statusreviews/
atlanticsalmon.pdf). The 2006 Status Review report identified the GOM 
DPS of Atlantic salmon as being comprised of all anadromous Atlantic 
salmon whose freshwater range occurs in the watersheds of the 
Androscoggin River northward along the Maine coast to the Dennys River, 
including all associated conservation hatchery populations used to 
supplement natural populations; currently, such populations are 
maintained at Green Lake and Craig Brook National Fish Hatcheries. The 
most substantial difference between the 2000 GOM DPS and the GOM DPS 
described in the 2006 Status Review report is the inclusion of the 
Androscoggin, Kennebec, and Penobscot River basins. Subsequent to the 
2006 Status Review report, the Services proposed to list Atlantic 
salmon in the GOM DPS as endangered (See the notice, Proposed 
Endangered Status for the Gulf of Maine Distinct Population Segment of 
Atlantic Salmon, published in the Proposed Rules section of the 
September 3, 2008, issue of the Federal Register).
    This proposed rule would designate critical habitat for the GOM DPS 
pursuant to section 4(b)(2) of the ESA. Critical habitat is defined by 
section 3 of the ESA as ``(i) the specific areas within the 
geographical area occupied by the species, at the time it is listed * * 
* on which are found those physical and biological features (I) 
essential to the conservation of the species and (II) which may require 
special management considerations or protections; and (ii) specific 
areas outside the geographical area occupied by the species at the time 
it is listed * * * upon a determination by the Secretary that such 
areas are essential for the conservation of the species.'' Section 3 of 
the ESA (16 U.S.C. 15332) defines the terms ``conserve,'' 
``conserving,'' and ``conservation'' as ``to use, and the use of, all 
methods and procedures which are necessary to bring any endangered 
species or threatened species to the point at which the measures 
provided pursuant to this chapter are no longer necessary.''
    Section 4(b)(2) of the ESA (16 U.S.C. 1533) requires that, before 
designating critical habitat, we consider the economic impacts, impacts 
on national security, and other relevant impacts of specifying any 
particular area as critical habitat. Further, the Secretary may exclude 
any area from critical habitat upon a determination that the benefits 
of exclusion outweigh the benefits of inclusion, unless excluding an 
area from critical habitat will result in the extinction of the species 
concerned.
    Once critical habitat for Atlantic salmon in the GOM DPS is 
designated, section 7(a)(2) of the ESA (16 U.S.C. 1536) requires that 
each Federal agency in consultation with and with the assistance of 
NMFS, ensure that any action it authorizes, funds, or carries out is 
not likely to result in the destruction or adverse modification of 
critical habitat.
    This proposed rule summarizes the information gathered and the 
analyses conducted in support of the proposed designation, and 
announces our proposal to designate critical habitat for Atlantic 
salmon in the GOM DPS proposed for listing under ESA.

Atlantic Salmon Life History

    Atlantic salmon have a complex life history that includes 
territorial rearing in rivers to extensive feeding migrations on the 
high seas. During their life cycle, Atlantic salmon go through several 
distinct phases that are identified by specific changes in behavior, 
physiology, morphology, and habitat requirements.
    Adult Atlantic salmon return to rivers from the sea and migrate to 
their natal stream to spawn. Adults ascend the rivers of New England 
beginning in the spring. The ascent of adult salmon continues into the 
fall. Although spawning does not occur until late fall, the majority of 
Atlantic salmon in Maine enter freshwater between May and mid-July 
(Meister, 1958; Baum, 1997). Early migration is an adaptive trait that 
ensures adults have sufficient time to effectively reach spawning areas 
despite the occurrence of temporarily unfavorable conditions that occur 
naturally (Bjornn and Reiser, 1991). Salmon that return in early spring 
spend nearly 5 months in the river before spawning; often seeking cool 
water refuge (e.g., deep pools, springs, and mouths of smaller 
tributaries) during the summer months.
    In the fall, female Atlantic salmon select sites for spawning. 
Spawning sites are positioned within flowing water, particularly where 
upwelling of groundwater occurs to allow for percolation of water 
through the gravel (Danie et al., 1984). These sites are most often 
positioned at the head of a riffle (Beland et al., 1982b), the tail of 
a pool, or the upstream edge of a gravel bar where water depth is 
decreasing, water velocity is increasing (McLaughlin and Knight, 1987; 
White, 1942), and hydraulic head allows for permeation of water through 
the redd (a gravel depression where eggs are deposited). Female salmon 
use their caudal fin to scour or dig redds. The digging behavior also 
serves to clean the substrate of fine sediments that can embed the 
cobble/gravel substrate needed for spawning and reduce egg survival 
(Gibson, 1993). As the female deposits eggs in the redd, one or more 
males fertilize the eggs (Jordan and Beland, 1981). The female then 
continues digging upstream of the last deposition site, burying the 
fertilized eggs with clean gravel. A single female may create several 
redds before depositing all of her eggs. Female anadromous Atlantic 
salmon produce a total of 1,500 to 1,800 eggs per kilogram of body 
weight, yielding an average of 7,500 eggs per 2 sea-winter (SW) female 
(an adult female that has spent two winters at sea before returning to 
spawn) (Baum and Meister, 1971). After spawning, Atlantic salmon may 
either return to sea immediately or remain in freshwater until the 
following spring before returning to the sea (Fay et al., 2006). From 
1967 to 2003, approximately 3 percent of the wild and naturally reared 
adults that returned to rivers where adult returns are monitored--
mainly the Penobscot River--were repeat spawners (USASAC, 2004).
    Embryos develop in the redd for a period of 175 to 195 days, 
hatching in late March or April (Danie et al., 1983). Newly hatched 
salmon, referred to as

[[Page 51749]]

larval fry, alevin, or sac fry, remain in the redd for approximately 6 
weeks after hatching and are nourished by their yolk sac (Gustafson-
Greenwood and Moring, 1991). Survival from the egg to fry stage in 
Maine is estimated to range from 15 to 35 percent (Jordan and Beland, 
1981). Survival rates of eggs and larvae are a function of stream 
gradient, overwinter temperatures, interstitial flow, predation, 
disease, and competition (Bley and Moring, 1988). Once larval fry 
emerge from the gravel and begin active feeding they are referred to as 
fry. The majority of fry (> 95 percent) emerge from redds at night 
(Gustafson-Marjanen and Dowse, 1983).
    When fry reach approximately 4 cm in length, the young salmon are 
termed parr (Danie et al., 1984). Parr have eight to eleven pigmented 
vertical bands on their sides that are believed to serve as camouflage 
(Baum, 1997). A territorial behavior, first apparent during the fry 
stage, grows more pronounced during the parr stage as the parr actively 
defend territories (Allen, 1940; Kalleberg, 1958; Danie et al., 1984). 
Most parr remain in the river for 2 to 3 years before undergoing 
smoltification, the process in which parr go through physiological 
changes in order to transition from a freshwater environment to a 
saltwater marine environment. Some male parr may not go through 
smoltification and will become sexually mature and participate in 
spawning with sea-run adult females. These males are referred to as 
``precocious parr.''
    First year parr are often characterized as being small parr or 0+ 
parr (4 to 7 cm long), whereas second and third year parr are 
characterized as large parr (greater than 7 cm long) (Haines, 1992). 
Parr growth is a function of water temperature (Elliott, 1991), parr 
density (Randall, 1982), photoperiod (Lundqvist, 1980), interaction 
with other fish, birds, and mammals (Bjornn and Resier, 1991), and food 
supply (Swansburg et al., 2002). Parr movement may be quite limited in 
the winter (Cunjak, 1988; Heggenes, 1990); however, movement in the 
winter does occur (Hiscock et al., 2002) and is often necessary, as ice 
formation reduces total habitat availability (Whalen et al., 1999a). 
Parr have been documented using riverine, lake, and estuarine habitats; 
incorporating opportunistic and active feeding strategies; defending 
territories from competitors including other parr; and working together 
in small schools to actively pursue prey (Gibson, 1993; Marschall et 
al., 1998; Pepper, 1976; Pepper et al., 1984; Hutchings, 1986; Erkinaro 
et al., 1998; Halvorsen and Svenning, 2000; Hutchings, 1986; O'Connell 
and Ash, 1993; Erkinaro et al., 1998; Dempson et al., 1996; Halvorsen 
and Svenning, 2000; Klemetsen et al., 2003).
    In a parr's second or third spring (age 1 or age 2, respectively), 
when it has grown to 12.5 to 15 cm in length, a series of 
physiological, morphological, and behavioral changes occur (Schaffer 
and Elson, 1975). This process, called ``smoltification,'' prepares the 
parr for migration to the ocean and life in salt water. In Maine, the 
vast majority of naturally reared parr remain in freshwater for 2 years 
(90 percent or more) with the balance remaining for either 1 or 3 years 
(USASAC, 2005). In order for parr to undergo smoltification, they must 
reach a critical size of 10 cm total length at the end of the previous 
growing season (Hoar, 1988). During the smoltification process, parr 
markings fade and the body becomes streamlined and silvery with a 
pronounced fork in the tail. Naturally reared smolts in Maine range in 
size from 13 to 17 cm, and most smolts enter the sea during May to 
begin their first ocean migration (USASAC, 2004). During this 
migration, smolts must contend with changes in salinity, water 
temperature, pH, dissolved oxygen, pollution levels, and predator 
assemblages. The physiological changes that occur during smoltification 
prepare the fish for the dramatic change in osmoregulatory needs that 
come with the transition from a fresh to a salt water habitat (Ruggles, 
1980; Bley, 1987; McCormick and Saunders, 1987; McCormick et al., 
1998). Smolts' transition into seawater is usually gradual as they pass 
through a zone of fresh and saltwater mixing that typically occurs in a 
river's estuary. Given that smolts undergo smoltification while they 
are still in the river, they are pre-adapted to make a direct entry 
into seawater with minimal acclimation (McCormick et al., 1998). This 
pre-adaptation to seawater is necessary under some circumstances where 
there is very little transition zone between freshwater and the marine 
environment.
    The spring migration of post-smolts out of the coastal environment 
is generally rapid, within several tidal cycles, and follows a direct 
route (Hyvarinen et al., 2006; Lacroix and McCurdy, 1996; Lacroix et 
al., 2004, 2005). Post-smolts generally travel out of coastal systems 
on the ebb tide, and may be delayed by flood tides (Hyvarinen et al., 
2006; Lacroix and McCurdy, 1996; Lacroix et al., 2004, 2005); although 
Lacroix and McCurdy (1996) found that post-smolts exhibit active, 
directed swimming in areas with strong tidal currents. Studies in the 
Bay of Fundy and Passamaquoddy Bay suggest that post-smolts aggregate 
together and move near the coast in ``common corridors'' and that post-
smolt movement is closely related to surface currents in the bay 
(Hyvarinen et al., 2006; Lacroix and McCurdy, 1996; Lacroix et al., 
2004). European post-smolts tend to use the open ocean for a nursery 
zone, while North American post-smolts appear to have a more near-shore 
distribution (Friedland et al., 2003). Post-smolt distribution may 
reflect water temperatures (Reddin and Shearer, 1987) and/or the major 
surface-current vectors (Lacroix and Knox, 2005). Post-smolts live 
mainly on the surface of the water column and form shoals, possibly of 
fish from the same river (Shelton et al., 1997).
    During the late summer/autumn of the first year, North American 
post-smolts are concentrated in the Labrador Sea and off of the west 
coast of Greenland, with the highest concentrations between 56 [deg]N. 
and 58 [deg]N. (Reddin, 1985; Reddin and Short, 1991; Reddin and 
Friedland, 1993). The salmon located off Greenland are composed of both 
1SW fish and fish that have spent multiple years at sea (multi-sea 
winter fish, or MSW) immature salmon from both North American and 
European stocks (Reddin, 1988; Reddin et al., 1988). The first winter 
at sea regulates annual recruitment, and the distribution of winter 
habitat in the Labrador Sea and Denmark Strait may be critical for 
North American populations (Friedland et al., 1993). In the spring, 
North American post-smolts are generally located in the Gulf of St. 
Lawrence, off the coast of Newfoundland, and on the east coast of the 
Grand Banks (Reddin, 1985; Dutil and Coutu, 1988; Ritter, 1989; Reddin 
and Friedland, 1993; and Friedland et al., 1999).
    Some salmon may remain at sea for another year or more before 
maturing. After their second winter at sea, the salmon over-winter in 
the area of the Grand Banks before returning to their natal rivers to 
spawn (Reddin and Shearer, 1987). Reddin and Friedland (1993) found 
non-maturing adults located along the coasts of Newfoundland, Labrador, 
and Greenland, and in the Labrador and Irminger Sea in the later 
summer/autumn.

Critical Habitat

Methods and Criteria Used To Identify Proposed Critical Habitat

    Critical habitat is defined by section 3 of the ESA (and 50 CFR 
424.02(d)) as ``(i) the specific areas within the geographic area 
occupied by the species, at the time it is listed in accordance

[[Page 51750]]

with the provisions of [section 4 of this Act], on which are found 
those physical or biological features (I) essential to the conservation 
of the species and (II) which may require special management 
considerations or protection; and (ii) specific areas outside the 
geographical area occupied by the species at the time it is listed in 
accordance with the provisions of [section 4 of this Act], upon a 
determination by the Secretary that such areas are essential for the 
conservation of the species.'' The Department of the Interior and the 
Department of Commerce provide further regulatory guidance under 50 CFR 
424.12(b), stating that the Secretaries shall ``focus on the principal 
biological or physical constituent elements within the defined area 
that are essential to the conservation of the species * * * Primary 
constituent elements may include, but are not limited to, the 
following: roost sites, nesting grounds, spawning sites, feeding sites, 
seasonal wetland or dry land, water quality or quantity, host species 
or plant pollinator[s], geological formation, vegetation type, tide, 
and specific soil types.''

Identifying the Geographical Area Occupied by the Species and Specific 
Areas Within the Geographical Area

    To designate critical habitat for Atlantic salmon, as defined under 
Section 3(5)(A) of the ESA, we must identify specific areas within the 
geographical area occupied by the species at the time it is listed.
    The geographic range occupied by the GOM DPS of Atlantic salmon 
includes freshwater habitat ranging from the Androscoggin River 
watershed in the south to the Dennys River watershed in the north (Fay 
et al., 2006), as well as the adjacent estuaries and bays through which 
smolts and adults migrate.
    The geographic range occupied by the species extends out to the 
waters off Canada and Greenland, where post-smolts complete their 
marine migration. However, critical habitat may not be designated 
within foreign countries or in other areas outside of the jurisdiction 
of the United States (50 CFR 424.12(h)). Therefore, for the purposes of 
critical habitat designation, the geographic area occupied by the 
species will be restricted to areas within the jurisdiction of the 
United States. This does not diminish the importance of habitat outside 
of the jurisdiction of the United States for the GOM DPS. In fact, a 
very significant factor limiting recovery for the species is marine 
survival. Marine migration routes and feeding habitat off Canada and 
Greenland are critical to the survival and recovery of Atlantic salmon, 
but the regulations prohibit designation of these areas as critical 
habitat.
    Because Atlantic salmon are anadromous, spending a portion of life 
in freshwater and the remaining portion in the marine environment, it 
is conceivable that some freshwater habitat may be vacant for up to 3 
years under circumstances where populations are extremely low. While 
there may be no documented spawning in these areas for that period of 
time, they would still be considered occupied because salmon at sea 
would return to these areas to spawn.
    Current stock management and assessment efforts also need to be 
considered in deciding which areas are occupied. In addition to the 
stocking program managed by USFWS and the Maine Department of Marine 
Resources (MDMR), there are small-scale stocking efforts carried out by 
non profit organizations. Furthermore, in addition to stocking 
programs, straying from natural populations can result in the 
occupation of habitat.
    Hydrologic Unit Code (HUC) 10 (Level 5 watersheds) described by 
Seaber et al. (1994) are proposed as the appropriate ``specific areas'' 
within the geographic area occupied by Atlantic salmon to be examined 
for the presence of physical or biological features and for the 
potential need for special management considerations or protections for 
these features.
    The HUC system was developed by the United States Geological Survey 
(USGS) Office of Water Data Coordination in conjunction with the Water 
Resources Council (Seaber et al., 1994) and provides (1) a nationally 
accessible, coherent system of water-use data exchange; (2) a means of 
grouping hydrographical data; and (3) a standardized, scientifically 
grounded reference system (Laitta et al., 2004). The HUC system 
currently includes six nationally consistent, hierarchical levels of 
divisions, with HUC 2 (Level 1) ``Regions'' being the largest (avg. 
459,878 sq. km.), and HUC 12 (Level 6) ``sub-watersheds'' being the 
smallest (avg. 41-163 sq. km.).
    The HUC 10 (Level 5) watersheds were used to identify ``specific 
areas'' because this scale accommodates the local adaptation and homing 
tendencies of Atlantic salmon, and provides a framework in which we can 
reasonably aggregate occupied river, stream, lake, and estuary habitats 
that contain the physical and biological features essential to the 
conservation of the species. Furthermore, many Atlantic salmon 
populations within the GOM DPS are currently managed at the HUC 10 
watershed scale. Therefore, we have a better understanding of the 
population status and the biology of salmon at the HUC 10 level, 
whereas less is known at the smaller HUC 12 sub-watershed scale.
    Specific areas delineated at the HUC 10 watershed level correspond 
well to the biology and life history characteristics of Atlantic 
salmon. Atlantic salmon, like many other anadromous salmonids, exhibit 
strong homing tendencies (Stabell, 1984). Strong homing tendencies 
enhance a given individual's chance of spawning with individuals having 
similar life history characteristics (Dittman and Quinn, 1996) that 
lead to the evolution and maintenance of local adaptations, and may 
also enhance their progeny's ability to exploit a given set of 
resources (Gharrett and Smoker, 1993). Local adaptations allow local 
populations to survive and reproduce at higher rates than exogenous 
populations (Reisenbichler, 1988; Tallman and Healey, 1994). Strong 
homing tendencies have been observed in many Atlantic salmon 
populations. Stabell (1984) reported that fewer than 3 of every 100 
salmon in North America and Europe stray from their natal river. In 
Maine, Baum and Spencer (1990) reported that 98 percent of hatchery-
reared smolts returned to the watershed where they were stocked. Given 
the strong homing tendencies and life history characteristics of 
Atlantic salmon (Riddell and Leggett, 1981), we believe that the HUC 10 
watershed level accommodates these local adaptations and the biological 
needs of the species and, therefore, is the most appropriate unit of 
habitat to delineate ``specific areas'' for consideration as part of 
the critical habitat designation process.
    Within the United States, the freshwater geographic range that the 
GOM DPS of Atlantic salmon occupy includes perennial river, lake, 
stream and estuary habitat connected to the marine environment ranging 
from the Androscoggin River watershed to the Dennys River watershed. 
Within this range, HUC 10 watersheds were considered occupied if they 
contained either of the primary constituent elements (PCEs) (e.g., 
sites for spawning and rearing or sites for migration, described in 
more detail below) along with the features necessary to support 
spawning, rearing and/or migration. Additionally, the HUC 10 watershed 
must meet either of the following criteria:
    (a) Naturally spawned and reared Atlantic salmon have been 
documented in the HUC 10 watershed or the watershed is believed to be 
occupied

[[Page 51751]]

based on the biological valuation of HUC 10 watershed (See Biological 
Valuation of Atlantic Salmon Habitat in the Gulf of Maine Distinct 
Population Segment (2008)) and best professional judgment of state and 
Federal biologists;
    (b) The area is currently managed by the MDMR and the USFWS through 
an active stocking program in an effort to enhance or restore Atlantic 
salmon populations, or the area has been stocked within the last 6 
years through other stocking programs, including those efforts by the 
``Fish Friends'' program, where juvenile salmon could reasonably be 
expected to migrate to the marine environment and return to that area 
as an adult and spawn.
    Within the range of the GOM DPS, 105 HUC 10 watersheds were 
examined for occupancy based on the above criteria. Based on our 
analysis, we considered 48 of these HUC 10 watersheds within the 
geographic range to be occupied. Estuaries and bays within the occupied 
HUC 10s in the GOM DPS are also included in the geographic range 
occupied by the species.
    Occupied areas also extend outside the estuary and bays of the GOM 
DPS as adults return from the marine environment to spawn and smolts 
migrate towards Greenland for feeding. We are not able at this time to 
identify the specific features characteristic of marine migration and 
feeding habitat within U.S. jurisdictional waters essential to the 
conservation of Atlantic salmon and are, therefore, unable to identify 
the specific areas where such features exist. Therefore, specific areas 
of marine habitat were not proposed as critical habitat.

Physical and Biological Features in Freshwater and Estuary Specific 
Areas Essential to the Conservation of the Species

    We identify the physical and biological features essential for the 
conservation of Atlantic salmon that are found within the specific 
occupied areas identified in the previous section. To determine which 
features are essential to the conservation of the GOM DPS of Atlantic 
salmon, we first define what conservation means for this species. 
Conservation is defined in the ESA as using all methods and procedures 
which are necessary to bring any endangered or threatened species to 
the point at which the measures provided by the ESA are no longer 
necessary. Conservation, therefore, describes those activities and 
efforts undertaken to achieve recovery. For the GOM DPS, we have 
determined that the successful return of adult salmon to spawning 
habitat, spawning, egg incubation and hatching, juvenile survival 
during the rearing time in freshwater, and smolt migration out of the 
rivers to the ocean are all essential to the conservation of Atlantic 
salmon. Therefore, we identify features essential to successful 
completion of these life cycle activities. Although successful marine 
migration is also essential to the conservation of the species, we are 
not able to identify the essential features of marine migration and 
feeding habitat at this time. Therefore, as noted above, marine habitat 
areas are not proposed for designation as critical habitat.
    Within the occupied range of the Gulf of Maine DPS, Atlantic salmon 
PCEs include sites for spawning and incubation, sites for juvenile 
rearing, and sites for migration. The physical and biological features 
of the PCEs that allow these sites to be used successfully for 
spawning, incubation, rearing and migration are the features of habitat 
within the GOM DPS that are essential to the conservation of the 
species. A detailed review of the physical and biological features 
required by Atlantic salmon is provided in Kircheis and Liebich (2007). 
As stated above, Atlantic salmon also use marine sites for growth and 
migration; however, we did not identify critical habitat within the 
marine environment because the specific physical and biological 
features of marine habitat that are essential for the conservation of 
the GOM DPS (and the specific areas on which these features might be 
found) cannot be identified. Unlike Pacific salmonids, some of which 
use nearshore marine environments for juvenile feeding and growth, 
Atlantic salmon migrate through the nearshore marine areas quickly 
during the month of May and early June. Though we have some limited 
knowledge of the physical and biological features that the species uses 
in the marine environment, we have very little information on the 
specifics of these physical and biological features and how they may 
require special management considerations or protection. Therefore, we 
cannot accurately identify the specific areas where these features 
exist or what types of management considerations or protections may be 
necessary to protect these physical and biological features during the 
migration period.
    Detailed habitat surveys have been conducted in some areas within 
the range of the GOM DPS of Atlantic salmon, providing clear estimates 
of and distinctions between those sites most suited for spawning and 
incubation and those sites most used for juvenile rearing. These 
surveys are most complete for seven coastal watersheds: Dennys, East 
Machias, Machias, Pleasant, Narraguagus, Ducktrap, and Sheepscot 
watersheds; and portions of the Penobscot Basin, including portions of 
the East Branch Penobscot, portions of the Piscataquis and 
Mattawamkeag, Kenduskeag Stream, Marsh Stream and Cove Brook; and 
portions of the Kennebec Basin, including a portion of the lower 
mainstem around the site of the old Edwards Dam and portions of the 
Sandy River. Throughout most of the range of the GOM DPS, however, this 
level of survey has not been conducted, and, therefore, this level of 
detail is not available. Therefore, to determine habitat quantity for 
each HUC 10 we relied on a GIS-based habitat prediction model (See 
appendix C of the Biological Valuation of Atlantic Salmon Habitat 
within the Gulf of Maine Distinct Population Segment (2008)). The model 
was developed using data from existing habitat surveys conducted in the 
Machias, Sheepscot, Dennys, Sandy, Piscataquis, Mattawamkeag, and 
Souadabscook Rivers. A combination of reach slope derived from contour 
and digital elevation model (DEM) datasets, cumulative drainage area, 
and physiographic province were used to predict the total amount of 
rearing habitat within a reach. These features help to reveal stream 
segments with gradients that would likely represent areas of riffles or 
fast moving water, habitat most frequently used for spawning and 
rearing of Atlantic salmon. The variables included in the model 
accurately predict the presence of rearing habitat approximately 73 
percent of the time. We relied on the model to generate the habitat 
quantity present within each HUC 10 to provide consistent data across 
the entire DPS and on existing habitat surveys to validate the output 
of the model.
    Although we have found the model to be nearly 75 percent accurate 
in predicting the presence of sites for spawning and rearing within 
specific areas, and we have an abundance of institutional knowledge on 
the physical and biological features that distinguish sites for 
spawning and sites for rearing, the model cannot be used to distinguish 
between sites for spawning and sites for rearing across the entire 
geographic range. This is because: (1) Sites used for spawning are also 
used for rearing; and (2) the model is unable to identify substrate 
features most frequently used for spawning activity, but rather uses 
landscape features to identify where stream gradient conducive to both 
spawning and rearing activity exists. As such, we have chosen to group 
sites for

[[Page 51752]]

spawning and sites for rearing into one PCE. Therefore, sites for 
spawning and sites for rearing are discussed together throughout this 
analysis as sites for spawning and rearing.
    In the section below, we identify the essential physical and 
biological features of spawning and rearing sites and migration sites 
found in the occupied areas described in the previous section.
(A). Physical and Biological Features of the Spawning and Rearing PCE
    1. Deep, oxygenated pools and cover (e.g., boulders, woody debris, 
vegetation, etc.), near freshwater spawning sites, necessary to support 
adult migrants during the summer while they await spawning in the fall. 
Adult salmon can arrive at spawning grounds several months in advance 
of spawning activity. Adults that arrive early require holding areas in 
freshwater and estuarine areas that provide shade, protection from 
predators, and protection from other environmental variables such as 
high flows, high temperatures, and sedimentation. Early migration is an 
adaptive trait that ensures adults sufficient time to reach spawning 
areas despite the occurrence of temporarily unfavorable conditions that 
occur naturally (Bjornn and Reiser, 1991). Salmon that return in early 
spring spend nearly 5 months in the river before spawning, often 
seeking cool water refuge (e.g., deep pools, springs, and mouths of 
smaller tributaries) during the summer months. Large boulders or rocks, 
overhanging trees, logs, woody debris, submerged vegetation and 
undercut banks provide shade, reduce velocities needed for resting, and 
offer protection from predators (Giger, 1973). These features are 
essential to the conservation of the species to help ensure the 
survival and successful spawning of adult salmon.
    2. Freshwater spawning sites that contain clean, permeable gravel 
and cobble substrate with oxygenated water and cool water temperatures 
to support spawning activity, egg incubation, and larval development. 
Spawning activity in the Gulf of Maine DPS of Atlantic salmon typically 
occurs between mid-October and mid-November (Baum, 1997) and is 
believed to be triggered by a combination of water temperature and 
photoperiod (Bjornn and Reiser, 1991). Water quantity and quality, as 
well as substrate type, are important for successful Atlantic salmon 
spawning. Water quantity can determine habitat availability, and water 
quality may influence spawning success. Substrate often determines 
where spawning occurs, and cover can influence survival rates of both 
adults and newly hatched salmon.
    Preferred spawning habitat contains gravel substrate with adequate 
water circulation to keep buried eggs well oxygenated (Peterson, 1978). 
Eggs in a redd are entirely dependent upon sub-surface movement of 
water to provide adequate oxygen for survival and growth (Decola, 
1970). Water velocity and permeability of substrate allow for adequate 
transport of well-oxygenated water for egg respiration (Wickett, 1954) 
and removal of metabolic waste that may accumulate in the redd during 
egg development (Decola, 1970; Jordan and Beland, 1981). Substrate 
permeability as deep as the egg pit throughout the incubation period is 
important because eggs are typically deposited at the bottom of the egg 
pit.
    Dissolved oxygen (DO) content is important for proper embryonic 
development and hatching. Embryos can survive when DO concentrations 
are below saturation levels, but their development is often subnormal 
due to delayed growth and maturation, performance, or delayed hatching 
(Doudoroff and Warren, 1965). In addition, embryos consume more oxygen 
(i.e., the metabolism of the embryo increases) when temperature 
increases (Decola, 1970). An increase in water temperature, however, 
decreases the amount of oxygen that the water can hold. During the 
embryonic stage when tissue and organs are developing and the demand 
for oxygen is quite high, embryos can only tolerate a narrow range of 
temperatures.
    These sites are essential for the conservation of the species 
because without them embryo development would not be successful.
    3. Freshwater spawning and rearing sites with clean, permeable 
gravel and cobble substrate with oxygenated water and cool water 
temperatures to support emergence, territorial development and feeding 
activities of Atlantic salmon fry. The period of emergence and the 
establishment of feeding territories is a critical period in the salmon 
life cycle since at this time mortality can be very high. When fry 
leave the redd, they emerge through the interstitial spaces in the 
gravel to reach the surface. When the interstitial spaces become 
embedded with fine organic material or fine sand, emergence can be 
significantly impeded or prevented. Newly emerged fry prefer shallow, 
low velocity, riffle habitat with a clean gravel substrate. Territories 
are quickly established by seeking out areas of low velocities that 
occur in eddies in front of or behind larger particles that are 
embedded in areas of higher velocities to maximize drift of prey 
sources (Armstrong et al., 2002). Once a territory has been 
established, fry use a sit-and-wait strategy, feeding opportunistically 
on invertebrate drift. This strategy enables the fish to minimize 
energy expenditure while maximizing energy intake (Bachman, 1984).
    These sites are essential for the conservation of the species 
because without them fry emergence would not be successful.
    4. Freshwater rearing sites with space to accommodate growth and 
survival of Atlantic salmon parr. When fry reach approximately 4 cm in 
length, the young salmon are termed parr (Danie et al., 1984). The 
habitat in Maine rivers currently supports on average between five and 
ten large parr (age one or older) per 100 square meters of habitat, or 
one habitat unit (Elson, 1975; Baum, 1997). The amount of space 
available for juvenile salmon occupancy is a function of biotic and 
abiotic habitat features, including stream morphology, substrate, 
gradient, and cover; the availability and abundance of food; and the 
makeup of predators and competitors (Bjornn and Reiser, 1991). Further 
limiting the amount of space available to parr is their strong 
territorial instinct. Parr actively defend territories against other 
fish, including other parr, to maximize their opportunity to capture 
prey items. The size of the territory that a parr will defend is a 
function of the size and density of parr, food availability, the size 
and roughness of the substrate, and current velocity (Kalleberg, 1958; 
Grant et al., 1998). The amount of space needed by an individual 
increases with age and size (Bjornn and Reiser, 1991). Cover, including 
undercut banks, overhanging trees and vegetation, diverse substrates 
and depths, and some types of aquatic vegetation, can make habitat 
suitable for occupancy (Bjornn and Reiser, 1991). Cover can provide a 
buffer against extreme temperatures; protection from predators; 
increased food abundance; and protection from environmental variables 
such as high flow events and sedimentation.
    These features are essential to the conservation of the species 
because without them, juvenile salmon would have limited areas for 
foraging and protection from predators.
    5. Freshwater rearing sites with a combination of river, stream, 
and lake habitats that accommodate parr's ability to occupy many niches 
and maximize parr production. Parr prefer, but are not limited to, 
riffle habitat associated with diverse rough gravel substrate. The 
preference for these habitats by parr that use river and stream 
habitats supports a sit-and-wait feeding strategy intended to

[[Page 51753]]

minimize energy expenditure while maximizing growth. Overall, large 
Atlantic salmon parr using river and stream habitats select for diverse 
substrates that predominately consist of boulder and cobble (Symons and 
Heland, 1978; Heggenes, 1990; Heggenes et al., 1999).
    Parr can also move great distances into or out of tributaries and 
mainstems to seek out habitat that is more conducive to growth and 
survival (McCormick et al., 1998). This occurs most frequently as parr 
grow and they move from their natal spawning grounds to areas that have 
much rougher substrate, providing more suitable over-wintering habitat 
and more food organisms (McCormick et al., 1998). In the fall, large 
parr that are likely to become smolts the following spring have been 
documented leaving summer rearing areas in some headwater tributaries 
and migrating downstream, though not necessarily entering the estuary 
or marine environment (McCormick et al., 1998).
    Though parr are typically stream dwellers, they also use pools 
within rivers and streams, dead-waters (sections of river or stream 
with very little to no gradient), and lakes within a river system as a 
secondary nursery area after emergence (Cunjak, 1996; Morantz et al., 
1987; Erkinaro et al., 1998). It is known that parr will use pool 
habitats during periods of low water, most likely as refuge from high 
temperatures (McCormick et al., 1998) and during the winter months to 
minimize energy expenditure and avoid areas that are prone to freezing 
or de-watering (Rimmer et al., 1984). Salmon parr may also spend weeks 
or months in the estuary during the summer (Cunjak et al., 1989, 1990; 
Power and Shooner, 1966).
    These areas are essential to the conservation of the species to 
ensure survival and species persistence when particular habitats become 
less suitable or unsuitable for survival during periods of extreme 
conditions such as extreme high temperatures, extreme low temperatures, 
and droughts.
    6. Freshwater rearing sites with cool, oxygenated water to support 
growth and survival of Atlantic salmon parr. Atlantic salmon are cold 
water fish and have a thermal tolerance zone where activity and growth 
is optimal (Decola, 1970). Small parr and large parr have similar 
temperature tolerances (Elliott, 1991). Water temperature influences 
growth, survival, and behavior of juvenile Atlantic salmon. Juvenile 
salmon can be exposed to very warm temperatures (> 20 [deg]C) in the 
summer and near-freezing temperatures in the winter, and have evolved 
with a series of physiological and behavioral strategies that enable 
them to adapt to the wide range of thermal conditions that they may 
encounter. Parr's optimal temperature for feeding and growth ranges 
from 15 to 19 [deg]C (Decola, 1970). When water temperatures surpass 19 
[deg]C, feeding and behavioral activities are directed towards 
maintenance and survival. During the winter when temperatures approach 
freezing, parr reduce energy expenditures by spending less time 
defending territories, feeding less, and moving into slower velocity 
microhabitats (Cunjak, 1996).
    Oxygen consumption by parr is a function of temperature. As 
temperature increases, the demand for oxygen increases (Decola, 1970). 
Parr require highly oxygenated waters to support their active feeding 
strategy. Though salmon parr can tolerate oxygen levels below 6mg/l, 
both swimming activity and growth rates are restricted.
    These features are essential to the conservation of the species 
because high and low water temperatures and low oxygen concentrations 
can result in the cessation of feeding activities necessary for 
juvenile growth and survival and can result in direct mortality.
    7. Freshwater rearing sites with diverse food resources to support 
growth and survival of Atlantic salmon parr. Atlantic salmon require 
sufficient energy to meet their basic metabolic needs for growth and 
reproduction (Spence et al., 1996). Parr largely depend on invertebrate 
drift for foraging, and actively defend territories to assure adequate 
food resources needed for growth. Parr feed on larvae of mayflies, 
stoneflies, chironomids, caddisflies, blackflies, aquatic annelids, and 
mollusks, as well as numerous terrestrial invertebrates that fall into 
the river (Scott and Crossman, 1973; Nislow et al., 1999). As parr 
grow, they will occasionally eat small fishes, such as alewives, dace, 
or minnows (Baum, 1997).
    Atlantic salmon attain energy from food sources that originate from 
both allochthonous (outside the stream) and autochthonous (within the 
stream) sources. What food is available to parr and how food is 
obtained is a function of a river's hydrology, geomorphology, biology, 
water quality, and connectivity (Annear et al., 2004). The riparian 
zone is a fundamental component to both watershed and ecosystem 
function, as it provides critical physical and biological linkages 
between terrestrial and aquatic environments (Gregory et al., 1991). 
Flooding of the riparian zone is an important mechanism needed to 
support the lateral transport of nutrients from the floodplain back to 
the river (Annear et al., 2004). Lateral transport of nutrients and 
organic matter from the riparian zone to the river supports the growth 
of plant, plankton, and invertebrate communities. Stream invertebrates 
are the principal linkage between the primary producers and higher 
trophic levels, including salmon parr.
    These features are essential to the conservation of the species, as 
parr require these food items for growth and survival.
(B). Physical and Biological Features of the Migration PCE
    1. Freshwater and estuary migratory sites free from physical and 
biological barriers that delay or prevent access of adult salmon 
seeking spawning grounds needed to support recovered populations. Adult 
Atlantic salmon returning to their natal rivers or streams require 
migration sites free from barriers that obstruct or delay passage to 
reach their spawning grounds at the proper time for effective spawning 
(Bjornn and Reiser, 1991). Physical and biological barriers within 
migration sites can prevent adult salmon from effectively spawning 
either by preventing access to spawning habitat or impairing a fish's 
ability to spawn effectively by delaying migration or impairing the 
health of the fish. Migration sites free from physical and biological 
barriers are essential to the conservation of the species because 
without them, adult Atlantic salmon would not be able to access 
spawning grounds needed for egg deposition and embryo development.
    2. Freshwater and estuary migration sites with pool, lake, and 
instream habitat that provide cool, oxygenated water and cover items 
(e.g., boulders, woody debris, and vegetation) to serve as temporary 
holding and resting areas during upstream migration of adult salmon. 
Atlantic salmon may travel as far as 965 km upstream to spawn (New 
England Fisheries Management Council, 1998). During migration, adult 
salmon require holding and resting areas that provide the necessary 
cover, temperature, flow, and water quality conditions needed to 
survive. Holding areas can include areas in rivers and streams, lakes, 
ponds, and even the ocean (Bjornn and Reiser, 1991). Holding areas are 
necessary below temporary seasonal migration barriers such as those 
created by flow, temperature, turbidity, and temporary obstructions 
such as debris jams and beaver dams, and adjacent to spawning areas. 
Adult salmon can become fatigued when ascending high velocity riffles 
or falls and require resting areas

[[Page 51754]]

within and around high velocity waters where they can recover until 
they are able to continue their migration. Holding areas near spawning 
areas are necessary when upstream migration is not delayed and adults 
reach spawning areas before they are ready to spawn.
    These features are essential to the conservation of the species 
because without them, adult Atlantic salmon would be subject to 
fatigue, predation, and mortality from exposure to unfavorable 
conditions, significantly reducing spawning success.
    3. Freshwater and estuary migration sites with abundant, diverse 
native fish communities to serve as a protective buffer against 
predation. Adult Atlantic salmon and Atlantic salmon smolts interact 
with other diadromous species indirectly. Adult and smolt migration 
through the estuary often coincides with the presence of alewives 
(Alosa spp.), American shad (Alosa sapidissima), blueback herring 
(Alosa aestivalis), and striped bass (Morone saxatilis). The abundance 
of diadromous species present during adult migration may serve as an 
alternative prey source for seals, porpoises and otters (Saunders et 
al., 2006). As an example, pre-spawned adults enter rivers and begin 
their upstream spawning migration at approximately the same time as 
early migrating adult salmon (Fay et al., 2006). Historically, shad 
runs were considerably larger than salmon runs (Atkins and Foster, 
1869; Stevenson, 1898). Thus, native predators of medium to large size 
fish in the estuarine and lower river zones could have preyed on these 
1.5 to 2.5 kg size fish readily (Fay et al., 2006; Saunders et al., 
2006). In the absence or reduced abundance of these diadromous fish 
communities, it would be expected that Atlantic salmon will likely 
become increasingly targeted as forage by large predators (Saunders et 
al., 2006).
    As Atlantic salmon smolts pass through the estuary during migration 
from their freshwater rearing sites to the marine environment, they 
experience high levels of predation. Predation rates through the 
estuary often result in up to 50 percent mortality during this 
transition period between freshwater to the marine environment 
(Larsson, 1985). There is, however, large annual variation in estuarine 
mortality, which is believed to be dependent upon the abundance and 
availability of other prey items including alewives, blueback herring, 
and American shad, as well as the spatial and temporal distribution and 
abundance of predators (Anthony, 1994).
    The presence and absence of co-evolutionary diadromous species such 
as alewives, blueback herring, and American shad likely play an 
important role in mitigating the magnitude of predation on smolts from 
predators such as striped bass, double-crested cormorants 
(Phalacrocorax auritus), and ospreys (Pandion haliaetus). The migration 
time of pre-spawned adult alewives overlaps in time and space with the 
migration of Atlantic salmon smolts (Saunders et al., 2006). Given that 
when alewife populations are robust, alewife numbers not only likely 
greatly exceed densities of Atlantic salmon smolts, making them more 
available to predators, but the caloric content per individual alewife 
is greater than that of an Atlantic salmon smolt (Schulze, 1996), 
likely making the alewife a more desirable prey species (Saunders et 
al., 2006).
    These features are essential to the conservation of the species 
because without highly prolific abundant alternate prey species such as 
alewives and shad, the less prolific Atlantic salmon will likely become 
a preferred prey species.
    4. Freshwater and estuary migration sites free from physical and 
biological barriers that delay or prevent emigration of smolts to the 
marine environment. Atlantic salmon smolts require an open migration 
corridor from their juvenile rearing habitat to the marine environment. 
Seaward migration of smolts is initiated by increases in river flow and 
temperature in the early spring (McCleave, 1978; Thorpe and Morgan, 
1978). Migration through the estuary is believed to be the most 
challenging period for smolts (Lacroix and McCurdy, 1996). Although it 
is difficult to generalize migration trends because of the variety of 
estuaries, Atlantic salmon post-smolts tend to move quickly through the 
estuary and enter the ocean within a few days or less (Lacroix et al., 
2004; Hyvarinen et al., 2006; McCleave, 1978). In the upper estuary, 
where river flow is strong, Atlantic salmon smolts use passive drift to 
travel (Moore et al., 1995; Fried et al., 1978; LaBar et al., 1978). In 
the lower estuary smolts display active swimming, although their 
movement is influenced by currents and tides (Lacroix and McCurdy 1996; 
Moore et al., 1995; Holm et al., 1982; Fried et al., 1978). In 
addition, although some individuals seem to utilize a period of 
saltwater acclimation, some fish have no apparent period of acclimation 
(Lacroix et al., 2004). Stefansson et al., (2003) found that post-
smolts adapt to seawater without any long-term physiological 
impairment. Several studies also suggest that there is a ``survival 
window'' which is open for several weeks in the spring, and gradually 
closes through the summer, during which time salmon can migrate more 
successfully (Larsson, 1977; Hansen and Jonsson, 1989; Hansen and 
Quinn, 1998).
    These features are essential to the conservation of the species 
because a delay in migration of smolts can result in the loss of the 
smolts' ability to osmoregulate in the marine environment which is 
necessary for smolt survival.
    5. Freshwater and estuary migration sites with sufficiently cool 
water temperatures and water flows that coincide with diurnal cues to 
stimulate smolt migration. The process of smoltification is triggered 
in response to environmental cues. Photoperiod and temperature have the 
greatest influence on regulating the smolting process. Increase in day 
length is necessary for smolting to occur (Duston and Saunders, 1990). 
McCormick et al. (1999) noted that in spite of wide temperature 
variations among rivers throughout New England, almost all smolt 
migrations begin around the first of May and are nearly complete by the 
first week in June. However, the time that it takes for the 
smoltification process to be completed appears to be closely related to 
water temperature. When water temperatures increase, the smolting 
process is advanced, evident by increases in Na+, K+-ATPase activity--
the rate of exchange of sodium (Na+) and potassium (K+) ions across the 
gill membrane or the regulation of salts that allow smolts to survive 
in the marine environment (Johnston and Saunders, 1981; McCormick et 
al., 1998; McCormick et al., 2002). In addition to playing a role in 
regulating the smoltification process, high temperatures also are 
responsible for the cessation of Na+, K+-ATPase activity of smolts 
limiting their ability to excrete excess salts when they enter the 
marine environment. McCormick et al., (1999) found significant 
decreases in Na+, K+-ATPase activity in smolts at the end of the 
migration period, but also found that smolts in warmer rivers had 
reductions in Na+, K+-ATPase activity earlier then smolts found in 
colder rivers. Hence any delay of migration has the potential to reduce 
survival of out-migrating smolts because as water temperatures rise 
over the spring migration period, smolts experience a reduction in Na+, 
K+-ATPase reducing their ability to regulate salts as they enter the 
marine environment. Though flow does not appear to play a role in the 
smoltification process, flow does appear to play an important role in 
stimulating a migration response (Whalen et al., 1999b).

[[Page 51755]]

    These features are essential to the conservation of the species 
because elevated water temperatures that occur in advance of a smolts 
diurnal cues to migrate can result in a decreased migration window in 
which smolts are capable of transitioning into the marine environment. 
A decrease in the migration window has the potential to reduce survival 
of smolts especially for fish with greater migration distances.
    6. Freshwater migration sites with water chemistry needed to 
support sea water adaptation of smolts. The effects of acidity on 
Atlantic salmon have been well documented. The effects of acidity cause 
ionoregulatory failure in Atlantic salmon smolts while in freshwater 
(Rosseland and Skogheim, 1984; Farmer et al., 1989; Staurnes et al., 
1996; Staurnes et al., 1993). This inhibition of gill Na+, K+-ATPase 
activity can cause the loss of plasma ions and may result in reduced 
seawater tolerance (Rosseland and Skogheim, 1984; Farmer et al., 1989; 
Staurnes et al., 1996; Staurnes et al., 1993) and increased 
cardiovascular disturbances (Milligan and Wood 1982; Brodeur et al., 
1999). Parr undergoing parr/smolt transformation become more sensitive 
to acidic water, hence water chemistry that is not normally regarded as 
toxic to other salmonids may be toxic to smolts (Staurnes et al., 1993, 
1995). This is true even in rivers that are not chronically acidic and 
not normally considered as being in danger of acidification (Staurnes 
et al., 1993, 1995). Atlantic salmon smolts are most vulnerable to low 
pH in combination with elevated levels of monomeric labile species of 
aluminum (aluminum capable of being absorbed across the gill membrane) 
and low calcium (Rosseland and Skogheim, 1984; Rosseland et al., 1990; 
Kroglund and Staurnes, 1999).
    These features are essential to the conservation of the species 
because Atlantic salmon smolts exposed to acidic waters can lose sea 
water tolerance, which can result in direct mortality or indirect 
mortality from altered behavior and fitness.

Special Management Considerations or Protections

    Specific areas within the geographic area occupied by a species may 
be designated as critical habitat only if they contain physical or 
biological features essential to the conservation of the species that 
``may require special management considerations or protection.'' It is 
the features and not the specific areas that are the focus of the ``may 
require'' provision. Use of the disjunctive ``or'' also suggests the 
need to give distinct meaning to the terms ``special management 
considerations'' and ``protection''. ``Protection'' suggests actions to 
address a negative impact. ``Management'' seems broader than 
protection, and could include active manipulation of the feature or 
aspects of the environment. The ESA regulations at 50 CFR 424.02(j) 
further define special management considerations as ``any methods or 
procedures useful in protecting physical and biological features of the 
environment for the conservation of listed species''. The term ``may'' 
was the focus of two Federal district courts that ruled that features 
can meet this provision because of either a present requirement for 
special management considerations or protection or possible future 
requirements (see Center for Biol. Diversity v. Norton, 240 F. Supp. 2d 
1090 (D. Ariz. 2003); Cape Hatteras Access Preservation Alliance v. 
DOI, 344 F. Supp. 108 (D.D.C. 2004)). The Arizona district court ruled 
that the provision cannot be interpreted to mean that features already 
covered by an existing management plan must be determined to require 
additional special management, because the term additional is not in 
the statute. Rather, the court ruled that the existence of management 
plans may be evidence that the features in fact require special 
management (Center for Biol. Diversity v. Norton, 1096-1100).
    The primary impacts of critical habitat designation result from the 
consultation requirements of ESA section 7(a)(2). Federal agencies must 
consult with NMFS to ensure that their actions are not likely to result 
in the destruction or adverse modification of critical habitat (or 
jeopardize the species' continued existence). These impacts are 
attributed only to the designation (i.e., are incremental impacts of 
the designation) if Federal agencies modify their proposed actions to 
ensure they are not likely to destroy or adversely modify the critical 
habitat beyond any modifications they would make because of listing and 
the requirement to avoid jeopardy. Incremental impacts of designation 
include state and local protections that may be triggered as a result 
of designation, and education of the public about to the importance of 
an area for species conservation. When a modification is required due 
to impacts both to the species and critical habitat, the impact of the 
designation is considered to be co-extensive with ESA listing of the 
species.
    The draft ESA 4(b)(2) (NMFS, 2008) Report and Economic Analysis 
(IEc, 2008a) describe the impacts in detail. These reports identify and 
describe potential future Federal activities that would trigger section 
7 consultation requirements because they may affect the essential 
physical and biological features.
    We identified a number of activities and associated threats that 
may affect the PCEs and associated physical and biological features 
essential to the conservation of Atlantic salmon within the occupied 
range of the GOM DPS. These activities, which include agriculture, 
forestry, changing land-use and development, hatcheries and stocking, 
roads and road crossings, mining, dams, dredging, and aquaculture have 
the potential to reduce the quality and quantity of the PCEs and their 
associated physical and biological features. There are other threats to 
Atlantic salmon habitat including acidification of surface waters. 
However, we are not able to clearly separate out the specific 
activities responsible for acidification, and therefore are unable to 
specifically identify a federal nexus.
    Specific activities that may affect the PCEs and associated 
physical and biological features are evaluated below based on whether 
the spawning and rearing PCE and/or the migration PCE may require 
special management considerations or protection. Specific areas where 
these activities occur are represented in a table following the 
evaluation of activities. Further evaluation of the activities listed 
below is presented in detail in section 5 of Kircheis and Liebich 
(2007).
(a). Agriculture
    Agricultural practices influence all specific areas proposed for 
designation and negatively impact PCE sites for spawning and rearing 
and migration. Physical disturbances caused by livestock and equipment 
associated with agricultural practices can directly impact the habitat 
of aquatic species (USEPA, 2003). Traditional agricultural practices 
require repeated mechanical mixing, aeration, and application of 
fertilizers and pesticides to soils. These activities alter physical 
soil characteristics and microorganisms. Tilling aerates the upper 
soil, but causes compaction of finely textured soils below the surface, 
which alters water infiltration. Use of heavy farm equipment and 
construction of roads also compact soils, decrease water infiltration, 
and increase surface runoff (Spence et al., 1996). Agricultural grazing 
and clearing of riparian vegetation can expose soils and increase soil 
erosion and sediment inputs into rivers.

[[Page 51756]]

    Agricultural practices m