Coho Salmon, Oncorhynchus kisutch

Coho Salmon, Oncorhynchus kisutch. Fish caught from coastal waters off Sikta, Alaska, June 2019. Length: 1.07 m (42 inches). Catch, photograph, and identification courtesy of Josh Leisen (joshadventures.com), Gaylord, Michigan.

Coho Salmon, Oncorhynchus kisutch. Fish caught from coastal waters off Sikta, Alaska, June 2019. Length: 1.07 m (42 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).

The Coho Salmon, Oncorhynchus kisutch, is a member of the Salmon and Trout or Salmonidae Family, and is also known as the Silver Salmon or Silvers and in Mexico as salmón plateado. Globally, there are seventeen species in the genus Oncorhynchus, of which two are found in Mexico’s freshwater systems.

The Coho Salmon has a deep fusiform body with a slender adipose fin. Oceanic fish are silver in color with dark-blue backs that transition to white ventrally with small black spots on their back and the upper lobe of the caudal fin. When spawning they develop hooked jaws and teeth and when they enter fresh-water they develop bright-red sides, bluish-green heads and backs and dark bellies and dark spots on their back. Sexually mature fish have a light-pink to rose color along the belly. The males are generally darker in color than the females and the males have a slightly arched back. Their anal fin has 12 to 17 rays; their dorsal fin has 9 to 13 rays. Their gill rakers are rough and widely spaced. They have a straight lateral line.

The Coho Salmon is anadromous spending various stages of their life in fresh water and in salt water. In the ocean they are found at depths up to 100 m (330 feet). They reach 1.08 m (2 feet 7 inches) in length and 15.2 kg (33 lbs) in weight. In freshwater Coho feed on plankton, aquatic invertebrates and terrestrial insects. In salt water they consume plankton and fish. In turn they are heavily preyed upon by sea birds, various fishes, California Sea Lions and the Pacific Harbor Seals. The adults return to the rivers where they were born. Eggs are deposited in small pit made by the females and then fertilized initially by one male and then by several males. Once fertilized the eggs are covered by the female and the process is repeated for several days. Once all the eggs have been deposited the females will die. After hatching in the early spring the juveniles remain for one or two years in their freshwater streams until they migrate to the ocean. Upon reaching the sea the juveniles remain close to shore consuming planktonic crustaceans. As the mature the migrate to deeper waters and consume fish, jellyfish, and squid and grow rapidly. They remain in salt water for one to three years and then collect in the fall at the mouths of rivers and streams and move upstream to reproduce when rains increase the water flow. They reach sexual maturity in approximately 2 years and have a lifespan of 5 years.

The Coho Salmon is found in Mexican waters of the Pacific but on a very limited basis and only from just north to San Quintín, Baja California, northward along the Northwest coast of the Baja.

The Coho Salmon is most likely confused with the Chinook Salmon, Oncorhynchus tshawytscha (large oval black spots), the Chum Salmon, Oncorhynchus keta (lack a blue back), the Pink Salmon, Oncorhynchus gorbuscha (spotting on the lower lobe of the caudal fin), and spawning Sockeye Salmon, Oncorhynchus nerka (red that extends to the bac and fins).

From a conservation perspective the Coho Salmon has not been formally evaluated. Globally salmonid species have experienced dramatic declines during the past several decades and a result of human and natural factors. Their spawning streams are negatively impacted by commercial timber harvesting as their larval stage is very sensitive to sedimental contaminants. The Coho Salmon is heavily pursued by both commercial and recreational fishermen. They are caught primarily with gill nets and seines by commercial fishermen. As a game fish they are pursued in both fresh and salt water from July to December on light tackle and by fly fishermen and are famous for their epic attacks on bait. They are considered to be an excellent human food fish. They have been an important component of Native Americans for centuries.