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 84 cm (2 ft 9 in) in length and weigh 2.3 to 7 kg (5–15 lb). Juveniles remain in freshwater until they are ready to migrate to the ocean, over distances of up to 1,600 km (1,000 mi). 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. Oncorhynchus comes from Ancient Greek ὄγκος (ónkos), meaning 'bend', and ῥύγχος (rhúnkhos), meaning 'snout'. The specific name nerka is the Russian name for the anadromous form. The name "sockeye" is an anglicization of suk-kegh (sθə́qəy̓ ), 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). Suk-kegh means 'red fish'.
Description The sockeye salmon is sometimes called red or blueback salmon, due to its color. Sockeye are blue tinged with silver in color while living in the ocean. When they return to spawning grounds, their bodies become red and their heads turn green. Sockeye can be anywhere from 60 to 84 cm (2 ft 0 in – 2 ft 9 in) in length and weigh from 2.3 to 7 kg (5–15 lb). Two distinguishing features are their long, serrated gill rakers that range from 30 to 40 in number, and their lack of a spot on their tail or back.
Range and habitat Sockeye salmon range as far south as the Columbia River in the eastern Pacific (although individuals have been spotted as far south as the 10 Mile River on the Mendocino Coast of California) and in northern Hokkaido in Japan in the western Pacific. They range as far north as the Bathurst Inlet in the Canadian Arctic in the east and the Anadyr River in Siberia in the west. The farthest inland sockeye salmon travel is to Redfish Lake, Idaho, over 1,400 km (900 mi) by river from the ocean and 2,000 m (6,500 ft) in elevation. In the United States, populations of sockeye salmon have been extirpated from Idaho and Oregon.
Landlocked populations
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 35 cm (14 in) 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. The fish, which is native to western North America, was stocked in Nantahala Lake in the mid-1960s by the NC Wildlife Resources Commission in an attempt to establish the species as a forage fish for other predator fishes in the lake. This stock has remained and become a favorite target for anglers, though the kokanee population there has recently been hurt by competition from illegally introduced blueback herring. 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
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
… excerpt ends here. Continue reading the full article.
