Species Finder Species Posted Mar 14, 2000 Coho Salmon Appearance Coho have dark metallic blue or greenish backs with silver sides and a light belly. While they are in the ocean, they have small black spots on their back and upper lobe of the tail. The gumline in the lower jaw has lighter pigment than on Chinook salmon. In fresh water, spawning coho are dark with reddish-maroon coloration on the sides. Spawning males develop a strongly hooked snout and large teeth. Before juvenile coho migrate to sea, they lose their parr marks, a pattern of vertical bars and spots useful for camouflage, and gain the dark back and light belly coloration of coho living in the ocean. Their gills and kidneys also begin to change at this time so that they can process salt water. Maximum Size Over 2 feet (61 cm) in length and can weigh up to 36 pounds (16 kg). However, the average weight of adult coho is 8 pounds (3.6 kg). Growth Rate Relatively slow in fresh water – it takes 1-2 years for a coho salmon to grow to a 4-5 inch (10-13 cm) long smolt. In marine waters, coho salmon grow rapidly; in fact, they are one of the fastest growing Pacific salmon species. Geographic Range Throughout the North Pacific Ocean and in most coastal streams and rivers from Alaska to central California. Most abundant in coastal areas from central Oregon to southeast Alaska. Habitat Salmon are anadromous – they live in the ocean but return to fresh water to spawn. Coho spend approximately the first half of their life cycle rearing and feeding in streams and small freshwater tributaries. The remainder of their life cycle is spent foraging in estuarine and marine waters of the Pacific Ocean. Life Span Usually 3-4 years. After 1-2 years in fresh water, juveniles develop into smolts and migrate to marine waters. After 1.5 years at sea, most coho salmon return to the freshwater streams where they were born. Some male coho salmon, called “jacks”, return to fresh water at a small size the same year that they migrate to sea as smolts. Food In fresh water, coho feed on plankton and insects; when in the ocean, they switch to a diet of small fishes such as herring, sandlance, anchovies, and sardines. They are also known to eat juveniles of other salmon species, especially pink and chum salmon, and juvenile sablefish. Reaches Reproductive Maturity At age 3 or 4 for most adults, depending on the amount of time spent in fresh water prior to smolting; for jacks, age 2 or 3, again depending on freshwater age. Reproduction Adult coho salmon migrate from the ocean into the freshwater streams and rivers where they were born in order to mate. They only spawn once and then die. Females prepare several nests, called redds, in stream bottoms with fairly specific characteristics such as clear, cool water and suitable gravel. The eggs are laid and incubate for six to seven weeks until they hatch into yolk sac larvae. The larvae remain in the gravel until the yolk sac is absorbed. The fry emerge, and after maturing into smolts capable of living in salt water, they migrate downstream to the ocean. Spawning Coho salmon spawn in fall and winter, in smaller streams and tributaries with stable gravel substrates from the San Lorenzo River in Monterey Bay, California to Point Hope, Alaska, and throughout the Aleutian Islands. Migrations Coho salmon are anadromous – they migrate from the ocean to fresh water to spawn. Young fish migrate back to the ocean and remain close to shore. As they grow, they move offshore. Some stocks of coho salmon migrate more than 1,000 miles in the ocean, while other stocks remain in marine areas relatively close to the streams where they were born. Predators Otters, seals, and a variety of fish and birds prey on juvenile coho. Adults are eaten by sharks, sea lions and seals, and orcas. Information courtesy of NOAA.