The sockeye salmon (Oncorhynchus nerka), also called red salmon, kokanee salmon, blueback salmon, or simply sockeye, is an anadromous species of salmon found in the Northern Pacific Ocean and rivers discharging into it. This species is a Pacific salmon that is primarily red in hue during spawning. They can grow up to in length and weigh . Juveniles remain in freshwater until they are ready to migrate to the ocean, over distances of up to . Their diet consists primarily of zooplankton. Sockeye salmon are semelparous, dying after they spawn. Some populations, referred to as kokanee, do not migrate to the ocean and live their entire lives in fresh water.
Classification and name origin
The sockeye salmon is the third-most common Pacific salmon species, after pink and chum salmon. comes from Ancient Greek (), meaning 'bend', and (), meaning 'snout'. The specific name is the Russian name for the anadromous form. The name "sockeye" is an anglicization of (), its name in Halkomelem, the language of the indigenous people along the lower reaches of the Fraser River (one of British Columbia's many native Coast Salish languages). means 'red fish'.
Description
The sockeye salmon is sometimes called red or blueback salmon, due to its color. In the United States, populations of sockeye salmon have been extirpated from Idaho and Oregon.
Landlocked populations
thumb|right|Male spawning-phase sockeye
Some sockeye salmon populations are completely landlocked. Sockeye that live and reproduce in lakes are commonly called kokanee, which is red-fish name in the Sinixt Interior Salish language and silver trout in the Okanagan language. They are much smaller than the anadromous variety and are rarely over long. In the Okanagan Lake and many others, there are two kinds of kokanee populations – one spawns in streams and the other near lake shores. Landlocked populations occur in the Yukon Territory and British Columbia in Canada, as well as, in Alaska, Washington, Oregon, California, New York, Utah, Idaho, Montana, Nevada, Colorado, New Mexico, and Wyoming in the United States. Nantahala Lake is the only place in North Carolina where kokanee salmon are found.
In Japan, a landlocked relative of Sockeye salmon termed black kokanee, or "kunimasu" in Japanese, was thought to be extinct after 1940, when a hydroelectric project made its native lake in northern Akita Prefecture more acidic. However, the species seems to have been saved by transferring eggs to Saiko Lake in Yamanashi Prefecture, 500 kilometers to the south. This fish has been treated as a subspecies of sockeye Oncorhynchus nerka kawamurae, or even an independent species Oncorhynchus kawamurae.
Diet
Sockeye salmon use patterns of limnetic feeding behavior, which encompasses vertical movement, schooling, diel feeding chronology, and zooplankton prey selectivity. They can change their position in the water column, timing and length of feeding, school formation, and choice of prey to minimize the likelihood of predation. This also ensures they still get at least the minimum amount of food necessary to survive. All of these behaviors contribute to the survivability, and therefore fitness of the salmon. Depending on location and threat of predation, the levels of aggressive feeding behavior can vary.
Sockeye salmon, unlike other species of Pacific salmon, feed extensively on zooplankton during both freshwater and saltwater life stages. They also tend to feed on small aquatic organisms such as shrimp. Insects and occasionally snails are part of their diets at the juvenile stage.
Life cycle
thumb|Male sockeye salmon
Sockeye salmon exhibit many different life histories with the majority being anadromous where the juvenile salmon migrate from freshwater lakes and streams to the ocean before returning as adults to their natal freshwater to spawn. Similar to most Pacific salmon, sockeye salmon are semelparous, meaning they die after spawning once. Some sockeye, called kokanee, do not migrate to the ocean and live their entire lives in freshwater lakes. The majority of sockeye spawn in rivers near lakes and juveniles will spend one to two years in the lake before migrating to the ocean, although some populations will migrate to saltwater in their first year. Adult sockeye will spend two to three years in the ocean before returning to freshwater. Females will spawn in 3–5 redds over a period of several days. The eggs usually hatch within six to nine weeks and the fry typically rear in lakes before migrating to the ocean.
Reproduction
thumb|Spawning sockeye salmon
thumb|Spawning bed
Males partake in competitive and sneaking tactics, formation of hierarchies, and non-hierarchical groupings around females who are ready to mate. Reproductive success varies more in males than females. The greater variability in male reproduction is associated with the greater average size and exaggerated shape of males. Reproductive success in females is determined by the number of eggs she lays, her body size, and the survival of the eggs, which is due in part to the quality of the nest environment. Male spatial distribution depends on shifts in reproductive opportunities, physical traits of breeding sites, as well as the operational sex ratio of the environment. Male social status is positively correlated to length and dorsal hump size. Larger females tend to spawn in shallower water, which is preferred over deeper water.
Females are responsible for parental care. They select, prepare, and defend a nest site until they die or are displaced. Males do not participate in parental care at all, and they move between females after egg deposition.
Sexual selection and natural selection
Sexual selection favors large males and females. Males choose females based on their readiness to spawn and their size in order to maximize their breeding opportunities. Larger bodies allow females to reproduce larger and more numerous eggs, better nest choice and ability to defend it, and the ability to bury eggs deeper and provide more protection. This shows natural selection against large bodies. Populations with higher levels of predation tend to evolve smaller body size. Without the threat of predation, salmon that breed early in the season live longer than those that breed late in the season.
Energy cost
Reproduction is marked by depletion in energy stores. Fat, protein, and somatic energy stores decrease from the final moments in marine migration through freshwater entry, spawning, and death. Reproduction in the sockeye salmon has to be accomplished with the energy stores brought to the spawning grounds. How the salmon use their energy during migration and spawning affects how successful they will be reproductively; energy used for migration cannot also be used for courtship. If they waste too much energy, they might not be able to spawn. Males must also make the decision whether to invest energy in fighting for a female or for longevity on the spawning grounds. High water temperatures also increase the energy expenditure of sockeye salmon as they migrate upriver.
Competition
thumb|Male sockeye salmon
Aggressive behavior displayed by dominant males is predominantly directed towards intruding dominant males. Sometimes sockeye salmon males behave aggressively towards subordinate males. These encounters are short, with the intruding male leaving after one or two aggressive interactions.
Fisheries and consumption
thumb|Global capture production of Sockeye(=Red) salmon (Oncorhynchus nerka) in thousand tonnes from 1950 to 2022, as reported by the [[Food and Agriculture Organization|FAO]]
The total registered fisheries harvest of the sockeye in 2010 was some 170,000 tonnes, of which 115,000 tonnes were from the United States and the rest was equally divided between Canada and Russia. This corresponds to some 65 million fish in all, and to some 19% of the harvest of all Pacific salmon species by weight.
thumb|Smoked sockeye salmon ready for consumption
Commercial fishermen in Alaska net this species using seines and gillnets for fresh or frozen fillet sales and canning. The annual catch can reach 30 million fish in Bristol Bay, Alaska, which is the site of the world's largest sockeye harvest.
Sockeye salmon have long been important in the diet and culture of the Coast Salish people of British Columbia.
The largest spawning grounds in Asia are located on the Kamchatka Peninsula of the Russian Far East, especially on the Ozernaya River of the Kurile Lake, which accounts for nearly 90% of all Asian sockeye salmon production, and is recognized as the largest spawning ground outside of Alaska. Illegal fishing in Kamchatka is subject to environmental concern.
Sockeye is almost never farmed. A facility in Langley, BC harvested its first salmon in March 2013, and continues to harvest farmed salmon from its inland facility.
Conservation status
United States
thumb|right|A school of sockeyes swimming upstream to spawn. In the foreground, an [[arctic char waits.]]
United States sockeye salmon populations are currently listed under the US Endangered Species Act by the National Marine Fisheries Service as an endangered species in the Snake River and as a threatened species in Lake Ozette, Washington. The Snake River sockeye salmon was listed as endangered in November 1991, after the Shoshone-Bannock Tribe at Fort Hall Indian Reservation petitioned the National Marine Fisheries Service.
Sockeye is an exception to 2010's forecast resurgence of Oregonian fish stocks. Spring Chinook, summer steelhead, and Coho are forecast to increase by up to 100% over 2008 populations. The sockeye population peaked at over 200,000 in 2008 and were forecast to decline to just over 100,000 in 2010. As an early indication of the unexpectedly high sockeye run in 2010, on July 2, 2010, the United States Army Corps of Engineers reported over 300,000 sockeye had passed over Bonneville Dam on the Columbia River. Lower temperatures in 2008 North Pacific waters brought in fatter plankton, which, along with greater outflows of Columbia River water, fed the resurgent populations.
Proposed legislative efforts, such as the Northern Rockies Ecosystem Protection Act, are attempting to protect the headwaters of the sockeye salmon by preventing industrial development in roadless areas.
Record numbers of a once-waning population of sockeye salmon have been returning to the Northwest's Columbia Basin (as of June 2012), with thousands more crossing the river's dams in a single day than the total numbers seen in some previous years.
Canada
thumb|120px|left|Sockeye salmon jumping over a beaver dam, [[Aleknagik Lake, Alaska, United States ]]
The conservation status of sockeye populations in Canada is under review by Fisheries and Oceans Canada as part of its Wild Salmon Policy strategy to standardize monitoring of wild salmon status. Salmon runs of particular note are the Skeena and Nass river runs, and the most famous is the Fraser River sockeye run.
The Fraser River salmon run has experienced declines in productivity since the 1990s, mirroring a similar decline in the 1960s.
The return abundance (population) of Fraser River sockeye in 2009 was estimated at a very low 1,370,000, 13% of the pre-season forecast of 10,488,000.
That represented a decline from the recent (1993) historical cycle peak of 23,631,000
and the return abundance was the lowest in over 50 years. The reasons for this (former) decline remain speculative. According to a consortium of scientists assembled to review the problem, the decline highlights the uncertainty in forecasting salmon returns.
After the low returns, the Government of Canada launched a formal inquiry into the decline, the Commission of Inquiry into the Decline of Sockeye Salmon in the Fraser River.
The Commission has been tasked with investigating all the factors which may affect Fraser River sockeye salmon throughout their life cycle. According to the terms of reference,
While the commission was holding public hearings, in the late summer of 2010, the largest run of sockeye since 1913 returned to the Fraser River system.
Final counts show that approximately 30 million salmon returned to the Fraser River and its tributaries in 2010. In total, approximately 11,591,000 Fraser sockeye were caught by Canadian fishers and 1,974,000 Fraser sockeye were caught by American fishers. The final projected escapement (fish which were not caught) was 15,852,990 fish.
Recent unpredictable fluctuations in runs are speculated to be due to changing water temperatures. There is high variation in thermal tolerance among the different sockeye salmon populations that migrate up the Fraser River. The Chilko River sockeye salmon population is able to maintain cardiorespiratory function at higher temperatures, which may make them more resilient to the effects of rising river temperatures. In one study examining possible physiological mechanisms underlying these population differences in thermal tolerance, juvenile sockeye salmon from the Chilko River and Weaver Creek did not show any differences in force-frequency response of the heart or cardiac pumping capacity when reared in common garden temperatures at 5 °C and 14 °C. Therefore, the physiology underlying these differences in thermal tolerance has yet to be determined.
Gallery
<gallery>
File:kokaneespawn.jpg|Spawning Kokanee salmon in the Sawtooth Range of Idaho
File:Sockeye adult male.jpg|Male ocean-phase sockeye
File:Oncorhynchus_nerka_2.jpg|Female (top) and male (bottom) in spawning colors
File:August 2004, Bristol Bay sockeye "mob" (7136827903).jpg|Sockeye salmon in Bristol Bay, Alaska
File:Zombie_Fish_(Kokanee_Salmon)_(22583777446).jpg|Closeup of a kokanee salmon
</gallery>
References
External links
- FishBase entry for Oncorhynchus nerka
- Animal Diversity Web entry for Oncorhynchus nerka
- Species Profile
- National Geographic Sockeye salmon
- Watershed Watch Salmon Society A British Columbia advocacy group for wild salmon
- Salmon/Steelhead page of the USDA Forest Service, Pacific-Northwest Fisheries Program.