Inter-Annual Variability in the Prey Quality of Planktivores in the Gulf of Alaska in 2013 and 2014

Zooplankton are an important prey resource to many marine planktivorous fish, and changes to the quality of the zooplankton would directly affect the nutritional status of their predators. Energy density and lipid content was measured for preferred prey of Gulf of Alaska planktivorous fish including juvenile salmon, rockfish, and pollock from the summer of 2013 and 2014, the energy density of these predators was also measured.  There was significant interannual variability in the quality of the prey. Energy density of the preferred prey was 2- to 3-fold higher in 2014 compared to 2013. Where the lipid content of the large copepod, C. marshallae, was comparable to most euphausiids (Thysanoessa sp.), the lipid content of stage CV C. marshallae was 4-times higher than that of stage CVI females (adults). Water temperatures in 2014 were anomalously warm and some zooplanktivorous species were notably large. These data reveal a mechanism by which physical factors directly influence a marine ecosystem.