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CFR Citation: 50 CFR Part 226

Docket ID: [Docket No. 0808061060-81062-01]

RIN ID: RIN 0648-AW77

NOTICE: PROPOSED RULES

ACTION: Endangered and Threatened Species:

DOCUMENT ACTION: Proposed rule; request for comments.

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

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.

DOCUMENT 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.

SUMMARY: Proposed Critical Habitat for the Gulf of Maine Distinct Population Segment of Atlantic Salmon,

SUPPLEMENTAL INFORMATION

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 riverspecific hatchery populations of Atlantic salmon, having historical riverspecific 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 (http://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 midJuly (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 seawinter (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 Riverwere 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
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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 (GustafsonMarjanen 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 searun 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 preadapted to make a direct entry into seawater with minimal acclimation (McCormick et al., 1998). This preadaptation to seawater is necessary under some circumstances where there is very little transition zone between freshwater and the marine environment.

The spring migration of postsmolts 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). Postsmolts 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 postsmolts exhibit active, directed swimming in areas with strong tidal currents. Studies in the Bay of Fundy and Passamaquoddy Bay suggest that postsmolts 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 postsmolts tend to use the open ocean for a nursery zone, while North American postsmolts appear to have a more nearshore distribution (Friedland et al., 2003). Postsmolt distribution may reflect water temperatures (Reddin and Shearer, 1987) and/or the major surfacecurrent vectors (Lacroix and Knox, 2005). Postsmolts 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 postsmolts 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 (multisea 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 postsmolts 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 overwinter in the area of the Grand Banks before returning to their natal rivers to spawn (Reddin and Shearer, 1987). Reddin and Friedland (1993) found nonmaturing 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 postsmolts 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 smallscale 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 wateruse 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) ``subwatersheds'' being the smallest (avg. 41163 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 subwatershed 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
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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 GISbased 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
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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 midOctober and midNovember (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 subsurface movement of water to provide adequate oxygen for survival and growth (Decola, 1970). Water velocity and permeability of substrate allow for adequate transport of welloxygenated 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 sitandwait 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 sitandwait 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 overwintering 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, deadwaters (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 dewatering (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 nearfreezing 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
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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, prespawned 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 coevolutionary 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, doublecrested cormorants
(Phalacrocorax auritus), and ospreys (Pandion haliaetus). The migration time of prespawned 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 postsmolts 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 longterm 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 outmigrating 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).

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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, 10961100).

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 coextensive 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 landuse 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.

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Agricultural practices may also reduce habitat complexity and channel stability through physical stream alterations such as: Channelization, bank armoring, and removal of large woody debris (LWD) and riparian vegetation (Spence et al., 1996). These effects often result in streams with higher width to depth ratios which exhibit more rapid temperature fluctuations and may also be subject to increased embeddedness as a function of decreased water velocity affecting habitat use in sites for spawning, juvenile rearing, and migration (Fay et al., 2006).

Clearing of land for agricultural practices such as livestock grazing and crop cultivation typically loosens and smoothes land surfaces, increasing soil mobility and vulnerability to surface erosion, thereby increasing sedimentation rates in affected streams (Waters, 1995; Spence et al., 1996). Increased sedimentation can have significant effects on Atlantic salmon habitat by embedding substrates and increasing turbidity in spawning and rearing sites. Increased turbidity can reduce light penetration and result in a reduction of aquatic plant communities used for cover and foraging in juvenile rearing sites. Sedimentation from agricultural practices can also increase the inputs of nutrients such as phosphorus and ammonia as well as contaminants such as pesticides and herbicides throughout a watershed. An increase in nutrients can lead to eutrophication and potential oxygen depletion in surface waters. Exposure of contaminated sediments to anaerobic environments (lacking oxygen) often results in the release of organically bound chemicals (EPA, 2003), possibly creating a toxic environment for biotic communities downstream of these agricultural areas.

Agricultural practices can affect stream hydrology through removal of vegetative cover, soil compaction, and irrigation. Removal of vegetation and soil compaction can increase runoff which can increase the frequency and intensity of flooding (Hornbeck et al., 1970). Increases in frequency and intensity of flood events can increase erosion, increase sedimentation and scour affecting sites for spawning and rearing. Direct water withdrawals and groundwater withdrawals for crop irrigation can directly impact Atlantic salmon habitat by depleting streamflow (MASTF, 1997; Dudley and Stewart 2006; Fay et al., 2006). Currently, the cumulative effects of individual irrigation impacts on Maine rivers is poorly understood; however, it is known that adequate water supply and quality are essential to all life stages of Atlantic salmon and life history behaviors including adult migration, spawning, fry emergence, and smolt emigration (Fay et al., 2006).

Fertilizer runoff can increase nutrient loading in aquatic systems, thereby stimulating the growth of aquatic algae. If nutrient loading due to fertilizer runoff is significant, resulting algal blooms may have numerous detrimental impacts on multiple processes occurring within the affected aquatic ecosystem. Surface algal blooms that block sunlight can kill submerged aquatic vegetation important for juvenile rearing. Loss of submerged vegetation can lead to a loss of habitat for invertebrates and juveniles fishes and the decomposition of dead algae consumes large quantities of oxygen, an impact which, at times, can result in significant oxygen depletion (NMFS and FWS, 2005). A reduction in submerged aquatic vegetation and dissolved oxygen (DO) can cause both direct and indirect harm to salmon by affecting not only the physiological function of salmon (e.g., oxygen deprivation) but by impacting prey species and other necessary ecological functions sites for rearing. We conclude that the spawning and rearing and migration PCEs in each HUC 10 are and will likely continue to be negatively affected by agricultural practices well into the future, and, therefore, may require special management or protections which may include increasing the riparian buffer between agriculture lands and aquatic ecosystems that contain salmon habitat to prevent erosion and the runoff or leaching of contaminants and nutrients.

(b). Forestry

Forestry practices influence all specific areas proposed for designation and negatively impact PCE sites for spawning and rearing and migration. Timber harvest can significantly affect hydrologic processes. In general, timber removal increases the amount of water that infiltrates the soil and reaches the stream by reducing water losses from evapotranspiration (Spence et al., 1996). Soi

FOR FURTHER INFORMATION CONTACT Dan Kircheis, NMFS, at 207-866-7320, dan.kircheis@noaa.gov; Mary Colligan, NMFS, at 9782819116; or Marta Nammack, 3017131401.