The walleye or Alaska Pollock (Gadus chalcogrammus) is another species in the true cod family Gadidae. For a long time, taxonomists placed walleye pollock in a separate genus from Pacific cod, but researchers have recently shown pollock are closely related to Pacific and Atlantic cod, and most taxonomists now include walleye pollock in the genus Gadus.
Pollock are more streamlined than their gray cod cousins, but like cod, pollock have olive-green to tan mottled markings their backs. This coloration helps camouflage them from predators and prey when they rest and swim near the sandy ocean bottom. Pollock have silvery sides, white bellies, three dorsal fins, and two anal fins. Pollock have either no chin barbel or only a tiny barbel.
Pollock range from the Sea of Japan and the Sea of Okhotsk west to the Bering Sea and the Gulf of Alaska and south to Northern California. They migrate in a circular pattern, moving inshore to relatively shallow waters from 295 to 460 ft. (90 to 140 m) to breed and feed in March and then returning in December to the warmer, deeper waters of the continental shelf to 525 to 984 ft. (160 to 300 m). Pollock are semi-demersal (semi-bottom dwelling) but can be found anywhere from the surface to 1640 ft. (500 m).
Pollock spawn from March to mid-June. They form dense schools when spawning and broadcast eggs and sperm into the water. Fertilized eggs are planktonic, and depending on the temperature of the water, they incubate for approximately 10 to 27 days. When the larvae hatch, they have a yolk sac and float upside down at the water surface until the sac is absorbed.
Young pollock eat zooplankton, but as they grow, they begin adding fish to their diet. Adults feed on young pollock and other fish. Pollock grow rapidly and can reach a length of 3.4 ft. (105 cm) and a weight of 13.3 lbs. (6.05 kg). They usually don’t, live more than 10 years, but biologists in Alaska have recorded pollock as old as 22 years.
Alaska pollock is the largest fishery by volume in the United States and the second most important fishery in the world. The Alaska pollock has been called, “The largest remaining source of palatable fish in the world.”
From 1964 through 1980, only foreign vessels harvested Alaska pollock. U.S. vessels began to enter the fishery in 1980, and by 1987, U.S. boats harvested 99% of the quota. Since 1988, only U.S. vessels have operated in the Eastern Bering Sea pollock fishery. From 2002 to 2006, the Eastern Bering Sea pollock catch averaged 1.48 million metric tons worth $500 million annually.
While biologists do not believe pollock have been overfished, stocks have declined in recent years. The pollock fishery was originally a bottom fishery and trawls were dragged across the ocean bottom to catch the fish. As concerns about habitat degradation from bottom trawling grew, fishermen switched to pelagic trawl gear, which is deployed above the seabed. Controversy also swirls around the use of pelagic trawl gear, though, since the trawl is not specific to pollock but catches and often kills any fish it encounters.
Pollock is an important food for Steller sea lions, and when sea lion populations began decreasing, managers reduced fishery time and implemented area closures for pollock near critical sea lion habitat.
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Next week I plan to take a short break from fish and set the stage for a wonderful guest post from a fellow author the following week. Three weeks from now, I will write about lingcod. As always, thanks for visiting my blog.
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Robin Barefield is the author of three Alaska wilderness mystery novels, Big Game, Murder Over Kodiak, and The Fisherman’s Daughter. To download a free copy of one of her novels, watch her webinar about how she became an author and why she writes Alaska wilderness mysteries. If you like audiobooks, check out her audiobook version of Murder Over Kodiak. Also, sign up below to subscribe to her free, monthly newsletter on true murder and mystery in Alaska.