EPA's Vessel General Permit and Small Vessel General

1997, Somero and Hofmann 1997, Van der Kraak and Pankhurst 1997, Welch et al. 1998).
Atlantic salmon smolt growth is known to change with temperature, with a temperature increase
from 57º to 64ºF resulting in a greater than 10% decrease in growth rate (Handeland et al. 2008).
It should be noted that positive effects may also be realized by climate change and specifically
warmer water temperature. Increased opportunities for growth in spring and summer could
increase the percentage of fish that enter the upper size distribution of a population and smolt the
following spring (Thorpe 1977, Thorpe et al. 1980, Thorpe 1994). In addition, warmer rearing
temperatures during the late winter and spring have been shown to advance the timing of the
parr-smolt transformation in Atlantic salmon (Solbakken et al. 1994). There is, however, an
optimal temperature range and a limit for growth after which salmon parr will stop feeding due
to thermal stress. During this time, protein degradation and weight loss will increase with rising
water temperature (McCarthy and Houlihan 1997). The NRC (2004) concluded that some
degree of climate warming or change in hydrologic regime could be tolerated if other problems
affecting Atlantic salmon are reduced.
Critical habitat
On June 19, 2009, 45 specific areas occupied by Atlantic salmon at the time of listing
(approximately 19,571 km of perennial river, stream, and estuary habitat and 799 square
kilometers of lake habitat within the range of the GOM DPS) were established for Atlantic
salmon critical habitat (74 FR 29300). The PCEs for this critical habitat include:
� 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.
� 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 as well as support emergence, territorial development
and feeding activities of Atlantic salmon fry.
� Freshwater rearing sites with space to accommodate growth and survival of Atlantic
salmon parr.
� 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.
� Freshwater rearing sites with cool, oxygenated (6 mg/L) water and diverse food resources
(mayflies, stoneflies, chironomids, caddisflies, blackflies, aquatic annelids, and mollusks,
as well as numerous terrestrial invertebrates, alewives, dace, or minnows) to support
growth and survival of Atlantic salmon parr.
� 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 or prevent emigration of smolts to the marine environment.
� 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.
� Freshwater and estuary migration sites with abundant, diverse native fish communities to
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