Short-term effects of commercial fishing on the distribution and abundance of walleye pollock (Theragra chalcogramma)

Replicate acoustic surveys conducted near Kodiak Island, Alaska, USA, during summers 2001, 2004, and 2006 showed that the short-term effect of commercial fishing activities on walleye pollock (Theragra chalcogramma) during this period was small, in most cases too small to detect. An area with commercial fishing and a nearby comparison area where commercial fishing was prohibited were surveyed before and during the fishery. Acoustic data were used to assess changes in the abundance, geographical and vertical distributions, and small-scale spatial patterns of walleye pollock, which may have occurred after the fishery commenced. A decrease in biomass after fishing began was detected only in 2004. No changes were detected in geographical or vertical distributions that could be attributed to the fishery in any year. Adults did not appear to aggregate or disperse in response to the fishery. Juvenile aggregations did differ between the prefishery and fishery surveys in 1 of the 2 years when juveniles were present. These data suggest that changes in walleye pollock abundance and distribution caused by the fishery are likely quite small compared with natural fluctuations.