Coho salmon

The Latin name for Coho salmon is Oncorhynchus kisutch.

The Coho salmon can weigh between 3-7 kg. It can be up to one meter long. As with the other Pacific salmon species (Oncorhynchus), the anal fin has 13–19 rays. The body is silver colored with a dark back and a tail fin that shows black spots.

They feed on other smaller fish and are carnivores.

The Coho salmon’s dark back alternates between blue and green. The sides are grayish or whitish with dark spots on the back. There is a faint horizontal darker stripe near where the spots end. When it’s time for spawning, both females and males adopt a pink to reddish tone along their usually bland sides. They live around the Arctic and Pacific from Alaska to Monterey Bay, California. It rarely moves further south than Chamalu Bay, Baja California. They also occur in Northeast Asia.

Coho salmon was introduced into the Baltic Sea during the days of the Soviet Union. During the 80’s, large quantities of Coho salmon were caught. Today it is unclear if there are any left there. The Coho salmon is not known to reproduce in the Baltic Sea area.

As they approach two years, they have reached their maturity and their journey begins. They are looking for the spawning location during the autumn. The male changes by developing a hump on his back. The jaws become crooked and can no longer be closed completely. In Lake Michigan, and its tributaries in Wisconsin, the eggs are collected during their movement as there is no natural reproduction of Coho’s salmon there. To maintain the fish population there, it is a necessity. Temperature changes and the search for food cause the salmon to move. Warmer temperatures drive the fish to the deeper cooler areas of the lakes, and there is also more food for them.

The eggs hatch in late winter or early spring after six to seven weeks in the nest. After they have hatched, they stay in the nest and barely move for the first 6-7 weeks. They are then called alevin when they are newly hatched salmon that are still attached to the yolk sac. They no longer have a protective eggshell and get their nourishment from the yolk sac during their growth. It is a very sensitive stage for the Coho salmon from other aquatic animals, environmental changes and contaminants in the water. It is only when the entire yolk sac has been absorbed that the fish is ready to leave the nest. The Coho spend the first two years around the same place where they were born in the freshwater. The next stage is the Smolt stage. Then they are between 10-15 cm long and their characteristic silver scales begin to dominate. Smolt migrate to the sea from late March to July.

Some fish leave the freshwater in the spring, spend the summer in brackish water and then return in the fall. Coho salmon live in salt water for one to three years before returning to spawn. There are some males that return after only two years to spawn, they are called “jacks”.