EPA's Vessel General Permit and Small Vessel General

Within days, the free-swimming fry enter the parr stage, moving downstream to areas with
adequate cover (rocks, vegetation, overhanging banks, and woody debris), water depths ranging
from approximately four to 24 inches, velocities between 1foot and 3 feet per second, and
temperatures near 61ºF (Beland 1984). When they finally reach their desired habitats, parr will
actively defend territories that vary in size depending on the amount of food available and the
density of other parr in the area (Symons 1971, McCormick et al. 1998, Armstrong et al. 1999).
Some male parr become sexually mature and can successfully spawn with sea-run adult females.
Water temperature, appetite, parr density, photoperiod, the level of competition and predation,
and food supply may all influence the growth rate of parr (Lundqvist 1980, Randall 1982, Hearn
1987, Fausch 1988, Metcalfe et al. 1988, Elliot 1991, Nicieza and Metcalfe 1997). Maine
Atlantic salmon parr densities are typically between three and nine parr per 1,075 feet 2 , with
years up to 16 parr per 1,075 feet 2 not uncommon (Beland 1996). There is no evidence of
density-dependent limitations at densities of 13 parr per 1,075 feet 2 (Whalen et al. 2000). Parr
feed on larvae of mayflies, stoneflies, caddisflies, chironomids, blackflies, annelids, and
mollusks, as well as numerous terrestrial insects that fall into the river (Scott and Crossman
1973a).
In a parr’s second or third spring, when it has grown 5 to 6 inches long, physiological,
morphological, and behavioral changes occur (Schaffer and Elson 1975). This process, called
smoltification, prepares parr for the dramatic change in osmoregulatory needs that comes with
the transition from a freshwater to a saltwater habitat (Hoar 1976, McLeese et al. 1994,
McCormick et al. 1998). In southern latitudes, including New England, most parr smolt after
one year, but in cooler areas, they may take two to four years in freshwater before smolting
(McCormick et al. 1998). Most smolts in New England rivers enter the sea during May and June
to begin their ocean migration. Maine rivers produce approximately three smolts per 1,075 feet 2
of habitat.
Atlantic salmon of US origin are highly migratory, undertaking long marine migrations from the
mouths of US rivers into the northwest Atlantic Ocean, where they are distributed seasonally
over much of the region (Reddin 1985). The marine phase starts with smoltification and
subsequent migration through the natal river and estuary. Upon completion of the physiological
transition to saltwater, the post-smolt stage grows rapidly and has been documented moving in
small, loosely aggregated schools near the surface (Dutil and Coutu 1988). After entering the
nearshore waters of Canada, the post-smolts become part of a mixture of stocks of Atlantic
salmon from various North American streams. Post-smolts appear to feed opportunistically on
macroinvertebrates, amphipods, euphausiids, and fish (Hansen and Pethon 1985, Hansen and
Quinn 1998, Andreassen et al. 2001). Once they mature to adult salmon, they travel individually
and primarily eat capelin, herring, and sand lance (Hansen and Pethon 1985, Reddin 1985,
Hansen and Quinn 1998).
Status and trends
The GOM DPS of anadromous Atlantic salmon was listed by the USFWS and NMFS as an
endangered species on November 17, 2000 (65 FR 69495). The GOM DPS encompasses all
naturally reproducing remnant populations of Atlantic salmon downstream of the former
Edwards Dam site on the Kennebec River northward to the mouth of the St. Croix River. To
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