Salmo salar

Distinct regional stocks have been identified using morphometric and biochemical characters (Claytor and McCrimmon 1988).

See taxonomy comments for the Gulf of Maine population.

Large breeding range in streams draining into the North Atlantic; many populations in the U.S. have been extirpated or have declined, but there are many occurrences and large numbers elsewhere; principal threats are habitat loss/degradation and overharvest.

North Atlantic, south to Portugal in the east, south to Connecticut and Housatonic rivers in the west (possibly formerly to Delaware); north to Ungava Bay (northern Quebec) and to the Nastapoka River in eastern Hudson Bay (Morin 1991); inland in North America to Lake Ontario, where now extirpated; widely stocked in lakes but seldom successfully. A spawning population, evidently derived from feral adults used for aquaculture, appears to be established in the Tsitika River in British Columbia, and freshwater and marine recoveries are well documented in Alaska (Volpe et al. 2000). Locally common, but depleted or extirpated from western and southern parts of range (Page and Burr 1991). The only remaining populations that are believed to consist, at least in part, of native fishes in U.S. rivers occur in Maine: Dennys, Machias, East Machias, Narraguagus, Pleasant, Ducktrap, and Sheepscot rivers (Colligan and Nickerson 1996); a few populations have been partially restored through hatchery production (Federal Register, 20 January 1994).

This species is represented by a large number of subpopulations and locations.

Native U.S. populations south of Maine are essentially extirpated due primarily to the effects of dams and water pollution; excessive harvest of adults by humans, stream acidification, sedimentation of spawning and holding habitat, and possibly changes in water temperature regimes contributed to the decline in some areas. Evidence from New England indicates that landlocked populations of Atlantic salmon may be negatively influenced as abundance of northern pike and/or Esox hybrids increases. In the U.S., some of these threats have been alleviated; water quality has improved in recent decades, and fish ladders have been constructed at many dams; reintroduction programs are in progress. Poor marine survival continues to result in reduced returns to U.S. rivers (USFWS 1995, Anderson et al. 2000); depletion of forage species by commercial fisheries and freshwater exposure of juveniles to an endocrine disrupter (leads to mortality in marine phase) are suggested possible causes. Escaped farmed salmon may pose a threat to native populations in coastal Maine rivers (USFWS 1995). See USFWS (1995), NMFS (Federal Register, 29 September 1995), Colligan and Nickerson (1996), and Anderson et al. (2000) for further information on threats to North American populations.