Coho Salmon - Onchorhynchus kisutch  









Coho Salmon - Onchorhynchus kisutch

General

The Coho salmon is an anadromous fish native to western north america. The Coho salmon (Onchorhynchus kisutch) is identified by white gums, a black tongue, some spots on their upper half and silver-coloured square tails.

Size

It is a moderately sized usually between 6 to 12 pounds but can reach up to 31 pounds. They are bluish-black with silver sides in saltwater and have black spots on the back and a few on the upper part of the caudal fin.

Geographic Range

Coho can be found from central California to Alaska.

Reproduction

Coho usually return to their native streams to spawn after 3 years. There are some that return after 2 years and are called Jack salmon. Spawning occurs in small streams with stable gravel substrate between November and January. Coho prefer lower stream velocity, shallower water and smaller gravel than Chinook salmon.

Feeding

Juvenile coho feed on plankton and insects. Adult coho feed on small fish.

Life History

Coho spend about half of their life rearing and feeding in small streams and tributaries, moving seaward the following spring. They loose their parr marks when they transition to salt water, along with their gills and kidneys. The time spent in estuaries is critical to the development of the species. The remainder of their time is spent foraging in brackish and marine waters.

Oxygen

High dissolved oxygen levels

Temperature

Summertime stream temperatures of 10 to 15 degrees Celcius (Reiser and Bjornn, 1979)

Shade

Adequate stream cover is required and prefer reaches less than 10 metres wide.

Large Woody Debris

Juvenile coho prefer streams with abundant large woody debris (Bradford et. al, 1997 and Reeves et. al, 1989).

Historic

Poor forest practices and agricultural management can cause siltation siltation, which can adversly affect spawning beds or smother eggs. Physical obstructions such as dams and culverts can block or restrict fish passage and cause inadequate water flow which may affect oxyegen levels and water temperature. Shoreline development, residential drainages, and filling marshes and wetlands can affect Coho is estuaries where they are already subject to additional predation.







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