Coho Salmon Interior Fraser population
Scientific Name: Oncorhynchus kisutch
Taxonomy Group: Fishes
Range: British Columbia, Pacific Ocean
Last COSEWIC Assessment: November 2016
Last COSEWIC Designation: Threatened
SARA Status: No schedule, No Status
Image of Coho Salmon
The Coho Salmon currently living in the interior Fraser watershed are genetically distinct. They can be separated from salmon in other areas of Canada, including those in the lower Fraser River watershed. The Fraser River Canyon is a natural boundary that separates many fish populations, and the salmon in the upper Columbia watershed, which may have been most closely related to those in the Interior Fraser population, are now extinct. The Coho Salmon Interior Fraser population is of national significance, and is made up of at least five sub-populations.
Coho and other Pacific salmon can be distinguished from trout and char by the presence of 12 or more rays in the anal fin. The presence of white gums at the base of the teeth in the lower jaw separates adult Coho from other salmon. As well, black spots, when present on the tail fin, usually only occur on the upper lobe. During the early stages of growth, Coho Salmon have distinct dark vertical bars along each side, and an orange tint on all but the dorsal fin. As they develop into smolts, the dark markings gradually fade and the backs become green with dark spots. As they mature, male Coho Salmon darken, often becoming bright red, their upper jaw develops an elongated hooked snout, and their teeth become more conspicuous. Females are usually less brightly coloured, and their upper jaw development is less pronounced. Adult Coho Salmon typically weigh 2 to 5 kg and are 45 to 70 cm long. An exceptional individual may exceed 9 kg.
Distribution and Population
Coho Salmon occur naturally only within the Pacific Ocean and its tributary drainage. The interior Fraser watershed is part of the Southern Mountain COSEWIC Ecological Area. Coho Salmon are widespread throughout the Thompson River system, the largest watershed in the Fraser River system. Their distribution in non-Thompson tributaries of the interior Fraser is not well known. Coho Salmon spawned in the interior Fraser River have been recovered in fisheries from Alaska to Oregon, but most were caught off the west coast of Vancouver Island and in the Strait of Georgia. The number of spawning Coho Salmon in the North and South Thompson watershed peaked in the mid-1980s, declined rapidly until about 1996, and has perhaps been stable or increasing since then. The proportion of adults caught in fisheries averaged 68% until 1996. In response to conservation concerns, exploitation was reduced to about 40% in 1997 and averaged 6.5% the next three years. Counts made between 1998 and 2000 reveal that slightly more than half of the total estimated population of 24 000 occur within the North and South Thompson watersheds. Productivity has declined to the point where many local populations are not replacing themselves — even with the major reductions in fishing impacts. Recent marine survivals have been 3% or less, much lower than during the 1970s and 1980s.
Spawning habitat for Coho Salmon is usually clumped within watersheds, often at the heads of riffles in small streams, and in side channels of larger rivers. Females generally build nests in areas of shallow water (approximately 30 cm deep) where the gravel is less than 15 cm in diameter, and there is good circulation of well-oxygenated water. To survive the winter, young Coho Salmon need areas of slow-moving water with enough places to shelter — such as around large rocks or rotting tree trunks. Juveniles migrate down the Fraser River and spend an unknown time in the highly developed Fraser River estuary. The majority of the time they are in the ocean is usually spent near the coast of southern British Columbia.
Coho Salmon from the Interior Fraser population return to fresh water in the fall and spawn during fall and early winter. Spawning generally occurs at night. The female digs a nest, called a redd, and deposits 2400 to 4500 eggs. As the eggs are deposited, they are fertilized with sperm by the male. Fry emerge from the gravel the following spring and usually reside in fresh water for a year before migrating to sea as smolts. Coho Salmon initially feed on insects; as they grow, their diet expands to include sand lance, herring, copepods, and crab larvae. In their second year at sea, their growth rate increases, and they feed heavily on squid, herring, sand lance, and large zooplankton. Almost all Coho spend 18 months at sea before returning to fresh water and therefore have a three-year life cycle. Some males, known as jacks, mature earlier and return after only six months in the ocean. Unlike the other salmon species, which generally migrate long distances in the open ocean, Coho remain in coastal waters.
The main reason for the decline in the Coho Salmon Interior Fraser population is excessive fishing that resulted when harvest rates were not reduced quickly enough in response to climate-driven declines in marine productivity. Coho declines also can be related to the intensity of human disturbance in the freshwater habitat. Much of the interior Fraser watershed has been logged and is used for a variety of agricultural activities. Reduction of shade cover heats up the stream temperature, and siltation makes the stream channel too muddy for the salmon and their eggs to survive. The low marine survival observed recently also makes the population more vulnerable to other threats.
The responsibility for managing salmon and salmon habitat in BC is shared between the federal and provincial governments. A variety of legislative processes, some international, are in place to ensure salmon conservation. The federal Fisheries Act provides the authority for the management and regulation of fish and fish habitat.
Provincial and Territorial Protection
Status of Recovery Planning
Recovery Strategies :
Name Conservation Strategy for Coho Salmon (Oncorhynchus kisutch) in Canada (Interior Fraser population)
Status Approvals process initiated
PLEASE NOTE: Not all COSEWIC reports are currently available on the SARA Public Registry. Most of the reports not yet available are status reports for species assessed by COSEWIC prior to May 2002. Other COSEWIC reports not yet available may include those species assessed as Extinct, Data Deficient or Not at Risk. In the meantime, they are available on request from the COSEWIC Secretariat.
6 record(s) found.
- COSEWIC Status Reports (1 record(s) found.)
- COSEWIC Assessments (1 record(s) found.)
- Response Statements (1 record(s) found.)
- Orders (2 record(s) found.)
- Consultation Documents (1 record(s) found.)
COSEWIC Status Reports
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