By Stephan Kennedy
Geographic Range
Sockeye salmon, Oncorhynchus nerka, are native to the western coast of North America in the Pacific Ocean. They can be located as far north as northern Alaska and as far south as northern California. During the mating season, Sockeye salmon travel inland as far as mid-west Idaho. Populations of this species have also been introduced in some areas of Asia and Russia. (Bickham, Wood, and Patton, 1995; Hasegawa et al., 2004; Quinn, 2005)
Biogeographic Regions:
nearctic 
(native ); palearctic (introduced ); pacific ocean (native ).
Other Geographic Terms:
holarctic .
Habitat
15 to 33 m
(49.21 to 108.27 ft)
Sockeye salmon are born in lakes, rivers, or streams, which are calmer than the Pacific Ocean. After fry, or young salmon, develop, they migrate to the Pacific Ocean where they spend most of their life. They are generally found at depths of 15 to 33 m. (Busch, 2000; Groot, 1966; Quinn, Terhart, and Groot, 1989; Wood and Foote, 1996)
These animals are found in the following types of habitat:
temperate ; polar ; saltwater or marine ; freshwater .
Aquatic Biomes:
pelagic ; lakes and ponds; rivers and streams; coastal ; brackish water .
Other:
estuarine .
Physical Description
1 to 4 kg
(2.20 to 8.82 lb)
63 cm (average)
(24.80 in (average))
When sockeye salmon hatch, they lack pigment and thus color. As they grow into fry, they become green and can have black spots. Sockeye salmon are typically blue in color until they reach reproductive age, when they brighten in color; their bodies turn read and their heads green. Additional distinctive markings appear on the head of males and sides of females during the spawning period. When ready to reproduce, sockeye salmon weigh 1 to 4 kg and measure on average 63 cm in length. Sockeye salmon are commonly misidentified. The otolith, or inner ear, of this species is distinct in size and shape from other members of the genus g. Oncorhynchus. This, however, is not always exact as there can be overlap among species in addition to intraspecific differences. (Busch, 2000; Casteel, 1974; Quinn, 2005)
Some key physical features:
ectothermic ; bilateral symmetry .
Sexual dimorphism: male more colorful.
Reproduction
Sockeye salmon breed once a year.
Sockeye salmon generally breed from July to October.
47 to 206
32 to 42 days
0 years (average)
4 to 5 years; avg. 4 to years
4 to 5 years
Sockeye salmon mate seasonally. Females lay their eggs and are then to select a mate. Males are chosen after they have come along her side and presented themselves multiple times. They are judged on their color and size. During this process, males can be attacked by females and other males. Larger dominant males reproduce more often than other males and, because sockeye salmon are polygynous, the dominant male can mate with many females. Some subordinate males may not have the opportunity to mate at all. (Busch, 2000; Foote, 1990; Quinn, 2005)
Mating systems:
polygynous .
Sockeye salmon breed from July to October, although some members of this speices located in the southern-most point of their geographic range have been known to breed into December. When females arrive, they create a nest in the gravel in which they lay their eggs. After fertilization, eggs stay in the gravel nest for 32 to 42 days. Females produce 47 to as many as 206 offspring. Sockeye salmon are independent when hatched and are able to reproduce at 4 to 5 years of age. (Busch, 2000; Lichatowich, 1999; Moore et al., 2007; Quinn, 2005)
Key reproductive features:
iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (external ); broadcast (group) spawning; oviparous .
Mothers invest time creating gravel nests, in which eggs incubate. After fertilization, however, the newly hatched alevin have no parental investment. (Quinn, 2005; Quinn, Hendry, and Wetzel, 1995)
Parental investment:
no parental involvement; female parental care ; pre-fertilization (protecting: female); pre-hatching/birth (provisioning: female).
Lifespan/Longevity
The average lifespan for sockeye salmon in the wild is 4 to 5 years. The oldest salmon caught was 8 years of age. Typically, sockeye salmon die after mating. ("Longevity, ageing, and life history of Oncorhynchus nerka", 2009; Groot, 1966)
Behavior
Sockeye salmon are social, and they swim in runs when migrating to freshwater streams to spawn. They also establish social hierarchies, usually at times of reproduction. Typically the largest male is most dominant. (Crutchfield and Pontecorvo, 1969; Quinn, 2005)
Home Range
Sockeye salmon have no home range and do not defend a territory. (Groot, 1966; Quinn, 2005)
Key behaviors:
natatorial ; motile ; migratory ; social .
Communication and Perception
The eyes of sockeye salmon are located on opposite sides of their head, and they thus have a greater field of vision than animals with two eyes facing forward. The spectrum of visibility of sockeye salmon includes color, from indigo to red, as well as ultraviolet light. Members of this species have nostrils and an enhanced sense of smell. This also adds to their sense of taste. Additionally, sockeye salmon have lateral lines, which detect vibrations, allowing them to hear. (Busch, 2000; Groot, 1966)
Perception channels:
visual ; ultraviolet; tactile ; vibrations ; chemical .
Food Habits
While in the ocean, sockeye salmon primarily consume zooplankton. In freshwater environments, they are known to eat insects, and, when upstream, occasionally snails. (Graynoth, Bennett, and Pollard, 1986)
Primary Diet:
planktivore .
Animal Foods:
insects; mollusks; zooplankton .
Predation
- Brown Bear Ursus arctos
- Black Bear Ursus americanus
- Bald Eagle Haliaeetus leucocephalus
- Rainbow Trout Oncorhynchus mykiss)
- Cutthroat Trout Oncorhynchus clarki
- Sculpins Cottus asper
- Mountain Whitefish Prosopium williamsoni
- Arctic Turns Sterna paradisaea
- Lake Trout Salvelinus namaycush
- Squawfish Ptychocheilus oregonensis
- Mew Gulls Larus canus
- Humans Homo sapiens
Adult sockeye salmon are easily spotted and caught because of their size, and they are eaten by bears, including brown bears and black bears, and birds, such as the mew gull. Predators of frys (young sockeye salmon) include lake trout, squawfish, and mountain whitefish. Most predation occurs in streams and rivers. As frys, sockeye salmon can often escape predators because of their smaller size. Humans also consume a considerable about of sockeye salmon. (Groot and Margolis, 1991; Olson, Squibb, and Gilbert, 1998; Quinn and Kinnison, 1999)
Ecosystem Roles
Sockeye salmon are host to a variety of parasites, which are generally found within the kidney. Most of these parasites release spores when in freshwater where excretion of water by sockeye salmon is high. These parasites include Myxidium salvelini and Parvicapsula minibicornis, both myxosporeans. Sockeye salmon also contribute to the diet of black bears and brown bears. (Higgins, Margolis, and Kent, 1993; Jones et al., 2004; Kent, Whitaker, and Dawe, 1997)
Economic Importance for Humans: Negative
Salmon, including sockeye salmon, are caught in and destroyed by hydroelectric dams when they attempt to swim through to spawn. This decreases salmon populations and thus availability for fishing. (Pringle, 2001)
Economic Importance for Humans: Positive
Sockeye salmon are commonly fished and are the most common species of salmon caught around British Columbia and Alaska. (Iudicello, Weber, and Wieland, 1999; Walters and Martell, 2004)
Ways that people benefit from these animals:
food .
Conservation Status
IUCN Red List: [link]:
Not Evaluated.
US Federal List: [link]:
Endangered; Threatened .
CITES: [link]:
No special status.
State of Michigan List: [link]:
No special status.
Although listed as a species of least concern by the IUCN Red List, the U.S. Fish and Wildlife Service Species Report listed O. nerka as endangered in 1992. In some areas, sockeye salmon are only listed as threatened, as populations have stabilized. Many programs have been implemented to prevent over-fishing and to rejuvenate sockeye populations in areas where over-fishing has occurred. (Iudicello, Weber, and Wieland, 1999; Walters and Martell, 2004)
Contributors
Stephan Kennedy (author), Radford University.
Karen Francl (editor), Radford University.
Gail McCormick (editor), University of Michigan.
References
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Craig, J., C. Foote. 2001. Countergradient Variation and Secondary Sexual Color: Phenotypic Convergence Promotes Genetic Divergence in Carotenoid Use Between Sympatric Anadromous and Nonanadromous Morphs of Sockeye Salmon (Oncorhynchus nerka). Evolution, 55/2: 380-391.
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