Oncorhynchus kisutch

Author: (Walbaum, 1792)

Oncorhynchus kisutch (Walbaum, 1792)

Status in World Register of Marine Species:
Accepted name: Oncorhynchus kisutch (Walbaum, 1792) (updated 2009-06-25)

Diagnosis: elongate, becoming deeper with age, spawning males a little hump-backed. Tip of upper jaw reaching well behind eye; snout and lower jaw becoming hooked and teeth enlarged in spawning males. Gillrakers 19-23. Pyloric caeca 45-81. Dorsal finrays iii-iv 8-10, and an adipose fin behind it; base below about middle of dorsal fin; anal finrays iv-v 12-14; caudal fin emarginate. Scales moderate, 120-140 in lateral line. Vertebrae 61-69. Colour: silvery, with black spots on upper flanks, base of dorsal fin and upper lobe of caudal fin in adults. Size: to 88 cm and 14 kg, usually spawning at 50-65 cm.

Habitat: pelagic, not forming shoals; juveniles inshore for first few months before migrating to open ocean. Food: predominantly fishes (pilchard, herring, anchovy, capelin), also squids, crustaceans; young in freshwater, mainly insect larvae; in freshwater, adults do not feed. Reproduction: entering rivers from late June and July, later in north, spawning from September to January or later, at 3-5 years old; adults die after spawning; rarely migrate far up rivers; young spend one year (rarely 2-3) in rivers, and 1-2 years in sea.

Distribution: a Pacific fish introduced into northern rivers of France, in 1974, 50,000 yearlings escaped into the Varenne (Normandy) from a fish farm, and 10,000 in 1975, with lesser numbers in southern France and southern Brittany in 1976-79; in 1975-77 up to 25 adults were caught in the Varenne, in rivers to the north, and around the Channel Is.