Atlantic salmon have an elongate, slightly compressed body and a rounded snout. In breeding males a hook develops on the lower jaw. In the sea the back and top of the head may be green,blue or brown; the sides are silver and the underside is silvery white. On entering freshwater, the adults become darker in colour and lose their silvery appearance.
The Atlantic salmon is a cold water species and like most migratory fish has a different habitat for each stage of it's life history. Marine Atlantic salmon return from the sea to freshwater streams to spawn and then return to the lake. In Canada Atlantic salmon spawn in October and November, depending on the region. Landlocked or permanently freshwater salmon move from the lake to tributary streams to spawn and then return to the lake. During their upstream migration salmon have the ability to surmount obstacles to reach the spawning grounds and may pass over waterfalls and rapids. The spawning site is usually a gravel-bottom riffle area above or below a pool of water. The female salmon excavates the redd ( nest ) with her caudal fin and when spawning is over she covers the eggs with gravel. The eggs hatch in about 110 days and the young emege from the gravel in May or June. The young salmon remain in the rapid water until they are about 2.5 inches or 65 mm long. The age at which parr ( young salmon ) go to sea, as smolts, varies with the region and can be from 2 to 3 years old in the Maritimes to 4 to 8 years old in the Ungava region of Quebec. When at sea they may remain within the estuary or travel up to 1500 miles as far as Greenland. Marine salmon feed upon a variety of organisms including crustaceans and such fish as smelt, herring, mackerel and small cod. Parr in streams feed upon aquatic insect larvae.
Atlantic salmon was one of the first fishes to disappear from the Great Lakes region due to the effects of hydroelectric dam construction and environmental pollution. One of the greatest threats to the survival of anadromous salmon stocks is the high seas fishery. Salmon require pristine rivers and streams for their spawning hence logging operations and agricultural operations which create polluted rivers and streams is a major concern. Salmon require rivers and streams that are clear, cool and well-oxygenated for reproduction and for the first few years of rearing parr. Survival through the marine phase of the species life history is very poor and the continued existence of the Atlantic population depends on a captive rearing program. The salmon population historically suffered from dams that have impeded spawning migrations and have flooded spawning and rearing habitats. Negative effect of interbreeding or ecological interactions with escaped domestic salmon is another threat. Atlantic salmon once bred in 32 rivers tributary to the inner Bay of Fundy and stocks consisted of an estimated 40 thousand individual fish. In 2008 only 200 individual Atlantic salmon were left of this stock and there is no likelihood of rescue as neighbouring regions harbour severely depleted, genetically dissimilar populations.
photo courtesy of DFO