Historical review of capelin (Mallotus villosus) consumption in the Gulf of Alaska and eastern Bering Sea

Abstract

Capelin (Mallotus villosus) is an important forage species in the marine ecosystem. In the Bering Sea and Gulf of Alaska, capelin has been documented as an important prey of seabirds and marine mammals. However, a thorough study of the capelin as prey of marine fish has not yet been done.

This study reviews the consumption of capelin by marine fishes in the eastern Bering Sea and Gulf of Alaska. Data from the years 1970 to 2001 in the eastern Bering Sea and data from 1981 to 2001 in the Gulf of Alaska are used to show annual geographic distributions of capelin in the stomach contents of different predators. These distributions suggest that capelin were a key diet item for groundfish in the inner domain area (< 50 m) of the eastern Bering Sea, and in the shelf area (< 100 m) of the Gulf of Alaska. Capelin, in the eastern Bering Sea, seem to prefer the colder areas where temperature was lower and the ice extent moved farther south.

The main fish predators of capelin included arrowtooth flounder (Atheresthes stomias), Pacific cod (Gadus macrocephalus), Pacific halibut (Hippoglossus stenolepis), and walleye pollock (Theragra chalcogramma). Indices of capelin abundance (expressed as percentage of total stomach contents weight) by sub-region were estimated to show the relative abundance of capelin consumed each year by groundfish in both the eastern Bering Sea and Gulf of Alaska. Capelin abundance ranged between 1.3% of Pacific cod stomach contents and 8.8% of arrowtooth flounder stomach contents in the eastern Bering Sea. In the Gulf of Alaska, capelin abundance ranged from 0.38% of Pacific cod stomach contents to 2.49% of Pacific halibut stomach contents.

Estimates of the total amount of capelin consumed by the groundfish population during each summer feeding season of each year ranged from 21,168 metric tons (t) in 1999 and 221,408 t in 1990 for the Gulf of Alaska. In the eastern Bering Sea, the estimate was between 19,155 t in 1994 and 47,988 t in 1993.


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