Spatial and temporal variability in the diet of juvenile Pacific herring (Clupea pallasi) in Prince William Sound, Alaska

The diet of juvenile Pacific herring, Clupea pallasi, from four bays in Pri nce William Sound, Alaska, varied spatially and seasonally. In Zaikof Bay, which was sampled in each season, stomach fullness of this herring was high est in May and declined significantly through the winter. Diversity of prey taxa in the diet was highest in June, after the spring phytoplankton bloom . In October, Oikopleura species were dominant in the fish diets of all bay s. In March, fish eggs, Cirripedia nauplii, small Calanoida, and large Cala noida were the dominant prey in Eaglek, Simpson, Whale, and Zaikof bays, re spectively. Energy density of stomach contents was highest in May, highligh ting the importance of high lipid copepod taxa in Zaikof Bay. Estimated ass imilation rates suggest that the diets of smaller age-0 herring provide clo se to maintenance levels of energy prior to winter. Therefore, variability in diet composition and diet energy density could account for relative diff erences in nutritional conditions of age-0 herring in Prince William Sound.