Relationships between Prey Concentration and Growth, Condition, and Mortality of Pacific herring, Clupea pallasi, Larvae in an Alaskan Subarctic Embayment

Abstract

We tested the hypothesis that growth, condition, and mortality of four "trace" cohorts of Pacific herring, Clupea pallasi, larvae in Auke Bay, Alaska, in 1988 were limited by concentration of prey. Hatching of herring larvae coincided with the spring maximum of copepod nauplii production, so prey concentration was high enough to support successful feeding and growth. However, growth and condition differed significantly among cohorts. Low growth and condition were not caused by density-dependent competition for food among herring larvae because larvae were too dilute to affect prey concentration and were unlikely to be caused by competition within the entire plankton community because there is no evidence that nonherring plankters interfered with feeding of herring larvae. Most larvae with low condition were from two cohorts that hatched from the upper zone, which suggests that desiccation and extremes of temperature may have disrupted embryonic development and produced larvae that were not competent to feed successfully. There were no among-cohort differences in instantaneous mortality. We conclude that growth, condition, and mortality of herring larvae in Auke Bay in 1988 were not limited by food, but by other factors such as predation and environmental conditions during egg incubation.