Tag Archives: Pacific Cod

Walleye Pollock (Gadus chalcogrammus)

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.

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Pacific Cod Commercial Fishery

Three weeks ago, I wrote about the collapse of the Pacific cod population in central and southwestern Alaska. Over the course of two years, cod went from one of the most prolific fish species in the area to nearly non-existent. The Alaska Department of Fish and Game slashed commercial fishing quotas in 2017, but there were so few cod, commercial fishermen struggled even to catch the allowed poundage. The economic ramifications from the crash of the Pacific cod fishery are just beginning to affect Alaska’s ports, and biologists believe it will be years before the launch of another viable cod fishery.

This week, I’ll explain more about the history of the Pacific cod fishery and commercial methods for harvesting cod in Alaska. First, though, I want to emphasize the importance of Pacific cod not only to fishermen but also to consumers. Most of us at some point in our lives have eaten cod; whether it was a fish stick, a fish sandwich, fried fish, or baked white fish, cod is one of the most popular fish served by restaurants from fast-food drive-ins to diners to gourmet bistros. Cod has a mild flavor and a dense, flaky white flesh. It freezes well and can be shipped long distances. Cod liver oil is made from cod livers and is an important source of vitamin A, vitamin D, vitamin E, and omega-3-fatty acids.

The Pacific cod fishery gained traction just as the Atlantic cod fishery began to crash. The Atlantic cod fishery lasted for more than 1000 years and was popular even during the Viking period, around 800 AD. The fishery was vital to Europe, Canada, and the U.S., but this widespread popularity of Atlantic cod led to its downfall. Atlantic cod populations survived centuries of human strife, ranging from plagues to wars, only to be fished to the point of annihilation because the many countries that commercially fished cod couldn’t agree on regulations to protect this valuable resource. With Atlantic cod no longer available, fish buyers looked to the Pacific.

Pacific cod have been commercially fished on a small scale since the 19th century, but the modern commercial fishery began in the early 1960s with the Japanese longline fishery in the Bering Sea/ Aleutian Island (BSAI) region.  Between 1980 and 1989, a U.S. trawl fishery and several joint venture fisheries began in both the BSAI and the Gulf of Alaska (GOA) regions, and by 1989 the U.S. commercial cod fishery overtook the foreign fishery in both the BSAI and GOA regions.

Multiple methods are now used to harvest Pacific cod, including trawl, longline, pot, and jigging. Between 1991 and 1999, trawl gear accounted for 52% of the cod catch, longline gear took 37% of the harvest, and pot gear caught 11%. After 2000, however, longline fishing became the most productive means of landing cod. Between 2000 and 2006, longline gear accounted for 46% of the catch, trawl gear 37%, and pot gear 16%.

According to recent NOAA Fisheries Service surveys of Pacific cod stocks taken only a few years before the population collapsed, the cod stocks in Alaskan waters were stable and were not being over-fished. In 2010, NOAA estimated the BSAI stock at 1 million metric tons and the GOA stock at 0.4 million tons. Biologists have closely regulated the Pacific cod fishery and have erred on the side of caution by setting strict quotas to protect not only the cod fishery but also marine mammals such as Steller sea lions that depend on cod for food.

Researchers are now working diligently to discover what happened to the Pacific cod. Why did the cod population crash in Alaska? The leading theory is the crash was caused by warmer-than-normal ocean temperatures which in turn caused a reduction in the biomass of phytoplankton and zooplankton in the North Pacific. Juvenile cod, like most young fish, depend on zooplankton as a food source. Because of the reduction of zooplankton in the North Pacific, juvenile cod had little to eat, and many starved to death.

If the zooplankton biomass in the North Pacific has decreased to the point where cod can’t find enough to eat, we should all be concerned, not only for cod but for all animals in this portion of the sea. Marine animals from the smallest fish and birds to the largest whales depend on phytoplankton and zooplankton to survive.

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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.

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Pacific Cod (Gadus macrocephalus)

True cod belong to the genus Gadus. The two most common members of the genus Gadus are the Atlantic cod (Gadus morhua) and the Pacific cod (Gadus macrocephalus). These two species are similar in appearance, reproductive biology, and lifecycles. Pacific cod are also known as grey cod, gray cod, greyfish, or grayfish.

Pacific cod range from Japan to the Bering Strait and the Gulf of Alaska and south as far as Northern California. Pacific cod are bottom dwellers and are usually found between depths of 40 to 1800 ft. (12-549 m). They tend to move into deeper water in the fall and winter.

A Pacific cod’s body is elongate and ranges in color from grey to brown on the back and sides to a pale cream on the stomach. Mottled spots or pale areas cover the backs and sides. A cod has a triangular tail, three rounded dorsal fins, and two anal fins. The fins are dusky colored and have white edges. The upper jaw of a cod extends over the lower jaw, and it is easy to identify a Pacific cod by its single chin barbel, or whisker, that has a length nearly equal to its eye diameter. Female cod can grow to 58 inches (147 cm) in length and weigh 55 lbs. (25 kg) Males are slightly smaller and can reach a length of 55 inches (141 cm) and weigh 44 lbs. (20 kg).

Female cod reach sexual maturity when they are four to five years old at a length of 20 to 23 inches (50-58 cm). In Alaska, most spawning activity occurs in March. Males court females by displaying their fins and grunting. A male and female then pair, and the male swims upside down under the female while she releases her eggs and he releases his sperm. The fertilized eggs then sink to the bottom where they remain for eight to 23 days before the hatch. A newly-hatched cod enters a planktonic phase for the next ten weeks while its body weight increases by 40-fold. When it is approximately 0.79 inches (2 cm) the cod moves to the sea floor and begins eating benthic crustaceans, such as isopods and small crabs. After six months, the cod is approximately 3.1 inches (8 cm) long, and by the end of the first year, it has attained a length of 5.5 – 7.1 inches (14-18 cm). Small cod eat mostly invertebrates, while larger Pacific cod feed on invertebrates and fish.

Cod live a maximum of 18 years. They are plagued by parasites, including the cod worm, Lernaeocera branchialis. Cod worms have a complex lifecycle. They begin as free-swimming larvae but then hook to the front of a flatfish or a lumpsucker. The worms penetrate the flesh of the fish with a fine filament and suck the blood of their host. The worms then mate, and the female worm finds a cod and clings to the cod’s gills, where it then penetrates the body of the cod and enters its heart. The front part of the worm forms branches and burrows into the main artery of the cod and extracts nutrients for itself and its eggs from the cod’s blood. Other parasites also infect cod, and anglers commonly catch cod covered by sores.

Cod are important food fish for larger fish, sharks, and marine mammals, including the endangered Stellar sea lion. They are also a commercially valuable food fish for humans.
Next week, I’ll write more about the importance of cod as a commercial species, and I’ll discuss the various methods of harvesting them.

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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.

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What is a Cod?

Four species of fish in the Gulf of Alaska have the common name “cod,” but only two of these species, the tomcod and Pacific grey cod, are true cod. Common fish names are often misleading and confusing. For example, brown trout (Salmo trutta) belong to the genus Salmo, while cutthroat trout (Oncorhynchus clarki) and rainbow trout (Oncorhynchus mykiss) are in the genus Oncorhynchus. To confuse the issue even more, brook trout (Salvelinus fontinalis), lake trout (Salvelinus namaycush), and Dolly Varden trout (Salvelinus malma) are char, not trout. Also, in the southern United States, bullheads are catfish, while in Alaska, we call sculpins bullheads.

True Cod and Imposter Cod

Lingcod

Lingcod (Ophiodon elongatus) and black cod (Anoplopoma fimbria) are not only unrelatedto Pacific grey cod (Gadus macrocephalus) and Pacific tomcod (Microgadus proximus), but they look quite different from the two “true” cod species. Pollock (Gadus chalcogrammus), though, a species closely related to a Pacific grey cod, isn’t even referred to as a cod. With these confusing common names, we can forgive an angler for not knowing whether he has caught a “true cod” or some unrelated fish.

Pollock

Last week, I wrote about the crash of the Pacific cod population in the Gulf of Alaska. In that post, I was discussing only Pacific grey cod. Over the next few weeks, I’ll write posts about the true cod species as well as the cod imposters in Alaskan waters. I hope to clear up any confusion surrounding cod and their common names.

Pacific Tomcod

Tomcod

The Pacific tomcod (Microgadus proximus) is one of the smaller members of the cod family, reaching a maximum size of 12 inches (30.5 cm). Its body is slender and covered with small, thin scales, but it feels smooth to the touch. It ranges in color from olive green to brown on its dorsal surface and creamy white on its ventral surface. Like its cousin the grey cod, a tomcod has a barbel on its chin, three dorsal fins, two anal fins, a large head, and a large mouth with small teeth. A tomcod’s barbel is smaller than a Pacific grey cod’s barbel, and unlike a Pacific cod, a tomcod’s dorsal fins do not contain spines. Despite these differences, a tomcod looks very much like a small Pacific grey cod.

Tomcod range from central California to western Alaska and can be found anywhere from the surface to as deep as 700 feet. They feed on zooplankton, shrimp, worms, and small fish and in turn, are a food source for larger fish, seals, and sea lions. Because of their small size, tomcod are not an important species for either commercial or sport fishermen, but they are a good food fish and have a sweet, subtle flavor.

Next week, I’ll discuss grey cod. I have already posted about their declining numbers in Alaskan waters, but I’ll delve more into their biology, importance in the ecosystem, and their value as a human food source. The following week, I’ll point out the differences between Pacific and Atlantic cod.

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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.

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Sign Up for my free, monthly Mystery Newsletter about true crime in Alaska.

What Happened to the Pacific Grey Cod?

In October 2017, the National Oceanic and Atmospheric Administration (NOAA) made a shocking announcement. Pacific cod (or grey cod) stocks in the Gulf of Alaska had declined 71% since 2015 and 83% since 2013. Cod, once one of the most plentiful fish in Alaskan waters, suddenly became a rare catch, devastating one of the most lucrative commercial fisheries in the state. Biologists scrambled to learn why cod were dying and why the few cod caught weighed less than normal and appeared malnourished.

While researchers yet do not have empirical evidence to support their theory, they have a good idea why cod populations have crashed. During the winter of 2013/2014, scientists mapped an unusually warm, large, circular body of seawater in the North Pacific Ocean. This mass of water didn’t cool as winter progressed but instead hovered several degrees above the normal winter temperature. Scientists nicknamed the mass of warm water the “Blob.” In February 2014, the Blob remained 4.5° F (2.5°C) warmer than the average February ocean temperature.

Warm water temperatures persisted throughout 2014, and oceanographers noted these were the warmest temperatures ever measured in the North Pacific Ocean since climatologists began recording ocean temperatures. Along with these warm water temperatures, a static high-pressure region in the atmosphere persisted throughout much of 2014, resulting in a lack of the normal wind-generated currents that stir the surface waters of the North Pacific.

The Blob

This warm, calm mass of water produced far-reaching effects on the biology of the North Pacific. Without an upwelling of cooler water and nutrients, the surface waters of the warm Blob became stagnant, resulting in reduced phytoplankton production. Phytoplankton is the platform for the ocean food pyramid, and without a healthy supply of phytoplankton, the pyramid collapses. Zooplankton can’t survive unless they have phytoplankton to eat, and without zooplankton, many fish species, including the juveniles of most species, will starve. Plankton-eating fish provide the food supply for larger fish, and all fish, mammals, and birds dependent on marine life to survive will suffer from a reduction in phytoplankton productivity.

A lack of food was not the only problem Pacific cod faced, though. The increased ocean temperatures raised their metabolism while reducing the available food. With less food, the average size of the cod dropped. A 2015 NOAA survey showed cod were the skinniest ever recorded, and at this same time, mortality rates skyrocketed for the younger age classes of cod, an indication the cod population would not recover for many years. The warm water and lack of nutrients also negatively affected cod egg production.

Will the Pacific grey cod recover? Biologists don’t know the answer to this question, but even if cod populations begin to recover now, they will not be commercially viable until at least 2021. The crash of the cod fishery has had a negative impact on the economies of Alaska fishing ports, and the decline of cod is certain to impact the food web of the North Pacific.

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.

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Sign Up for my free, monthly Mystery Newsletter about true crime in Alaska.