Comparisons within and between years resulting in contrasting recruitment of pacific hake (Merluccius productus) in the california current system

摘要

In a search for correlates and possible causes of the difference in recruitment success of Pacitic hake (Merluccius productus) of the 1981 and 1984 year-classes, we analyzed (by optical plankton counter) the distribution into sizes of preserved zooplankton samples from stations with and without larval hake in winter and spring of these two years. We also assessed the onshore/offshore distributions of larvae, potential for geostrophic and Ekman transport, and their overall survival rates. Cluster analyses of biovolume spectra led to the development of a simple ratio of "medium" to "small + large" zooplankton that statistically separated stations within a year where larval hake were likely to be found from those where they were unlikely to be found.This biovolume ratio was independent of temperature, and the same ratio statistically distinguished stations where larval hake tended to occur in spring 1998. However, we found no property or process that might explain why the 1984 year-class was spectacularly successful.