Pollock: Walleye

Walleye pollock, Alaska pollock

Walleye pollock (Theragra chalcogramma) is a member of the cod family and occurs in dense aggregations throughout the year. Pollock is both a demersal and pelagic species, spending time at the seafloor as well as throughout the water column. Pollock is found in the eastern and western Pacific Ocean, the Bering Sea, the Gulf of Alaska (GOA), the Sea of Okhotsk, and the Sea of Japan. Pollock is the most abundant groundfish species in the eastern Bering Sea, and the second most abundant groundfish species in the Gulf of Alaska, supporting the largest single-species fishery in the North Pacific. Pollock is a key species in the Bering Sea ecosystem, playing an important role as both predator and prey. Age-0 Pollock consume small zooplankton such as copepods and krill, while adult Pollock are cannibalistic. As a prey item, juvenile Pollock play an important role in the diet of many organisms, including older Pollock, Pacific cod (Gadus macrocephalus), Pacific halibut (Hippoglossus stenolepis), a number of seabirds, and marine mammals such as Steller sea lions(Eumetopias jubatus) and Northern fur seals (Callorhinus ursinus).

Pollock exhibit basic life history characteristics, such as early age at first maturity, that make them inherently resilient to fishing pressure. However, spawning aggregations of pollock are targeted by the commercial fishery but this is the only special behaviour that may increase the ease of capture of pollock. As a result, pollock are considered a “low” conservation concern.

In the U.S. federal waters of the Bering Sea, there are three stocks of pollock: the eastern Bering Sea stock, the Aleutian Islands stock, and the central Bering Sea stock. Both biomass and allowable fishing effort are greatest in the eastern Bering Sea region, and so this stock is primarily considered in this assessment. Pollock in the Bering Sea and the Gulf of Alaska are not overfished and overfishing is not occurring. The 2004 stock assessment for pollock in the eastern Bering Sea found that the current spawning stock biomass was above the maximum sustainable yield. The stock status of all pollock in the Bering Sea is considered a “low” conservation.

Pollock are caught in mid-water trawls which are described as having a low impact on the large bycatch species; seabirds, sea turtles, marine mammals, and sharks, and a medium impact on the bycatch of finfish and crabs. Since 1992, the discard rates for the Bering Sea pollock fishery have been at or below 10%, however, because of the scale of the pollock fishery, the absolute amount of bycatch is still high. None of the groundfish that occur as bycatch are listed as being overfished, or undergoing overfishing resulting in a rating of “low” conservation concern.

Mid-water trawls generally have little contact with the ocean bottom thus should have a very low impact on both the physical and biological components of seafloor habitat. On the other hand, the pollock fishery has often been cited as having substantial ecosystem effects. The fishery is likely one of several contributors to the decline of Steller sea lions as well as northern fur seals. Pollock fishery practises are rated as a “moderate” conservation concern due to the combination of minimal habitat effects and the ongoing concerns about the ecosystem effects of the pollock fishery.

In general, the stock productivity of pollock has been maintained in the Bering Sea and the Gulf of Alaska. Management has routinely set quotas at more conservative levels than recommended by its scientific advisors. Management measures have been implemented to address potential habitat effects, ecosystem effects, and bycatch associated with the pollock fishery and are continuously evaluated. Overall, management of the pollock fishery is considered “highly effective”.

Yes. This fishery was certified by MSC in 2005.