Item talk:Q149808

Monitoring long-term changes in forage fish distribution, abundance and body condition

We collected data on forage fish abundance, distribution and body condition in Prince William Sound, Alaska during summers in 2012 through 2016. This included acoustic – trawl surveys, aerial-acoustic surveys, opportunistic sampling where we encountered forage aggregations, and concurrent measurements of forage fish habitat. Acoustic indices of density suggest low abundance of age-0 walleye pollock (Gadus chalcogrammus), capelin (Mallotus villosus), and krill (Euphausiacea), but higher abundance of age-0 (< 80 mm), age-1 (80-140 mm) herring, and gelatinous zooplankton in 2015. Aerial school density of adult herring was highest in 2015 compared to 2014 or 2016, but acoustic indices of adult Pacific herring (Clupea pallasii) did not follow the same pattern. Weight-length-age relationships differed significantly among years for capelin and Pacific sand lance (Ammodytes personatus), with higher body condition in 2013 and 2012 than in 2014 and 2015. This work has provided information on prey resources in coastal areas of the Gulf of Alaska that is consistent with recent observations in the larger Gulf of Alaska region. Ongoing analyses will be important in understanding the marine ecosystem response to anomalously warm conditions beginning in 2014.