Tuesday, October 27, 2009

Coho Salmon-What You Need To Know

The Coho salmon, Oncorhynchus kisutch, (from the Russian кижуч kizhuch) is a species of anadromous fish in the salmon family. Coho salmon are also known as silver salmon "silvers" or “torpedos”. 

Coho Description

During their ocean phase, Coho have silver sides and dark blue backs. During their spawning phase, the jaws and teeth of the coho become hooked, and they develop bright red sides, bluish green heads and backs, dark bellies with dark spots on their back. Sexually maturing coho develop a light pink or rose shading along the belly and the males may show a slight arching of the back. Mature coho salmon have a pronounced red skin color with darker backs and average 28 inches in length and 7 to 11 pounds in weight, although coho weighing up to 36 pounds have been reported. Mature females may be darker than males, with both showing a pronounced hook on the nose.

Male Ocean Coho

Coho Reproduction

The eggs hatch in the late winter or early spring after 6 to 7 weeks in the redd. Once hatched, they remain mostly immobile in the redd as the alevin life-stage, which lasts for 1–2 weeks. The alevins no longer have the protective egg shell, or chorion, and rely on their yolk sac for nourishment during growth. The alevin life stage is very sensitive to aquatic and sediment contaminants. When the yolk sac is completely resorbed by the alevin it will swim up out of the redd. Young coho spend one to two years in their freshwater natal streams,often spending the first winter in off-channel sloughs, before undergoing a transformation to the smolt life-stage. 

Smolts are generally 100-150 mm and their parr marks are faded and the silver scales characteristic of the adult life-stage start to dominate. Smolts migrate to the ocean in late March through July. Some fish leave fresh water in the spring, spend summer in brackish estuarine ponds and then migrate back into fresh water in the fall. Coho salmon live in the salt water for one to three years before returning to spawn. Some precocious males known as "jacks" return as two-year-old spawners. Spawning males develop a 
 strongly hooked snout and large teeth.

Male Freshwater Coho

Source: Wikipedia

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