Distribution and food habits of two similar species of Bothrocara (Perciformes: Zoarcidae) in the eastern Bering Sea

摘要

Six of the eight currently recognized species of the zoarcid genus Bothrocara are known from the eastern Bering Sea. Two of these species, B. brunneum and B. zestum, are widespread and commonly encountered on the upper continental slope, although B. zestum was not widely recognized as a distinct species in the region until 2004. During the summers of 2004 and 2008, large-scale bottom trawl surveys were conducted along the upper continental slope of the eastern Bering Sea from Bering Canyon to the U.S.-Russian border. Over the course of these surveys, distribution, relative abundance, length frequency, length-weight, and stomach contents information was collected for B. brunneum and B. zestum. Data collected on the surveys indicate that these two species have broadly overlapping geographic and bathymetric distributions in the region, but that their population numbers are substantially different. Length-weight regressions show that although these two species reach approximately the same maximum length, B. brunneum is substantially heavier than B. zestum at all lengths over about 40 cm. Stomach contents analysis indicates that the diet of B. brunneum consists primarily of various species of shrimps and mysids, while B. zestum is primarily piscivorous, consuming primarily bathylagids and other zoarcids. Therefore, despite their general morphological similarity, these two species function very differently in the eastern Bering Sea benthic ecosystem.