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Oncorhynchus nerka (Walbaum, 1792)
Sockey Salmon; Sockeye Salmon
Family: Salmonidae
Introduction to the Fish

Photograph

© Rick Howie     (Photo ID #12938)

Map


Distribution of Oncorhynchus nerka in British Columbia.
Source: Distribution map provided by Don McPhail for E-Fauna BC

Introduction


Sockey salmon is native to both the Asian and North American Pacific Coasts. It is a silvery, trout-like fish species that lacks spots. There are two forms of this species: the sea-going migratory marine form known as the sockeye, and the landlocked non-migratory freshwater form known as the kokanee. Both are generally referred to as sockeye salmon. The land-locked form evolved in many BC lakes, but do remain in contact with the sea-going form in many locations. The life history of these differs (read McPhail 2007 for a detailed discussion on this).

McPhail (2007) describes this species as follows: "At sea, or in the case of kokanee in lakes, the sexes have the same body shape, bright silver flanks, and a blue back. At they mature, however, sockey and kokanee chane shape and colour. In males, the head enlarges, the teeth on the jaws ncrease in size, and a down-turned hook develops on the end of the snout; to a lesser extent the tip of the lower jaw develops an upturned hook. Also, mature males develop a laterally compressed body and a fleshy hump anterior to the dorsal fin...these traits are not as pronounced in females."

Species Information

Dorsal spines (total): 0; Dorsal soft rays (total): 11 - 16; Anal spines: 0; Anal soft rays: 13 - 18; Vertebrae: 56 - 67. Both the sockeye and the kokanee are distinguished by the long, fine, serrated, closely spaced gill rakers on the first arch that number between 30 and 40, and by its lack of definite spot on the back and tail (Ref. 27547). Body fusiform, streamlined, laterally compressed, body depth moderate, slightly deeper in breeding males (Ref. 6885). Head bluntly pointed, conical, eye rather small, position variable with sex and condition; snout rather pointed (Ref. 6885). Lateral line straight (Ref. 27547). Pelvic fins with axillary process; caudal emarginate (Ref. 27547). Pre-spawning fish are dark steel blue to greenish blue on the head and back, silvery on the sides and white to silvery on the belly; no definite spots on the back, although some individuals may have dark speckling and irregular marks on the dorsal fin (Ref. 27547). At spawning, the head of the males becomes bright to olive green, with black on the snout and upper jaw; the adipose and anal fins turn red and the paired fins and tail generally become grayish to green or dark; females are generally less brilliantly colored than males (Ref. 27547). Various populations may show less brilliant colors, and a few turn dull green to yellowish, with little if any red (Ref. 27547).

Source: FishBase. Page, L.M. and B.M. Burr 1991 A field guide to freshwater fishes of North America north of Mexico. Houghton Mifflin Company, Boston. 432 p.

Biology

Species Biology

Epipelagic (Ref. 58426). There are two forms, the anadromous form known as the sockeye and the landlocked form (with a much smaller maximum size) known as the kokanee (Ref. 27547). Upon emergence from gravel, fry at first tends to avoid light, hiding during the day and emerging at night (Ref. 27547). In some populations, sockeye fry go to the sea during their first summer but most spend one or two (rarely three or four) years in a lake before migrating (Ref. 30333). In a few streams of the Copper River drainage in Alaska, young sockeye stay in the stream (Ref. 27547). Once in the lake, the young spend a few weeks inshore, feeding largely on ostracods, cladocerans and insect larvae. The fish then become pelagic and move offshore, where they feed on plankton in the upper 20 m or so (Ref. 27547). Seaward migration follows with the young individuals first staying fairly close to shore, feeding mainly on zooplankton, but also on small fishes and insects (Ref. 30343, 30346). With growth, they head out to sea and fish become important in the diet (Ref. 27547). Kokanee are confined to lake-stream systems, and most of its life is spent in the lake (Ref. 27547). They feed mainly on plankton, but also take insects and bottom organisms (Ref. 1998). Kokanee, wherever they are native, have been derived from anadromous populations, and each kokanee population apparently has evolved independently from a particular sockeye run (Ref. 30338, 30339). Offspring of kokanee occasionally become anadromous, and sockeye offspring occasionally remain in freshwater (Ref. 27547). Lifespan of the kokanee varies from two to seven years in different stocks (Ref. 27547)

Source: FishBase. Page, L.M. and B.M. Burr 1991 A field guide to freshwater fishes of North America north of Mexico. Houghton Mifflin Company, Boston. 432 p.

Distribution

BC Distribution and Notes

The sockeye salmon is also a genetically heterogeneous species and locally adapted populations are common. In the past, kokanee were often referred to as a subspecies, Oncorhynchus nerka kenneryli. We now know that most natural kokanee populations evolved from different populations of anadromous sockeye. Since shared common ancestors is a crucial component in defining any taxon, and the kokanee life-history form is clearly polyphyletic, it is inappropriate to assign the same subspecific name to all kokanee populations. This does not mean that kokanee are simply small sockeye. Some kokanee populations spawn sympatrically (i.e., in the same stream and at the same time) as anadromous sockeye but still retain a suite of inherited morphological, physiological, and behavioural differences from sockeye. Populations where kokanee and sockeye are sympatric for part of their life history are scientifically important and some should be protected. Also, there are lakes (e.g., Okanagan Lake) where two, or more populations, spawn in different habitats (i.e., beach and stream spawners). These situations are of scientific interest. There is also a mysterious population of deep-bodied kokanee in Seton Lake. Apparently, they spawn late in the year and at great depth. We know nothing about this unusual population.

Source: Information provided by Don McPhail for E-Fauna BC.
Global Distribution

North Pacific: northern Japan to Bering Sea and to Los Angeles, California, USA (Ref. 2850). Landlocked populations in Alaska, Yukon Territory and British Columbia in Canada, and Washington and Oregon in USA. Import restricted in Germany (Anl. 3 BartSchV).

Source: FishBase. Page, L.M. and B.M. Burr 1991 A field guide to freshwater fishes of North America north of Mexico. Houghton Mifflin Company, Boston. 432 p.
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Status Information

Scientific NameOrigin StatusProvincial StatusBC List
(Red Blue List)		COSEWIC
Oncorhynchus nerkaNativeS4No StatusNot Listed
Oncorhynchus nerka pop. 7NativeSNRNo StatusE (Dec 2017)
Oncorhynchus nerka pop. 8NativeSNRNo StatusE (Apr 2016)



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