THE JET OFF POINT ARENA, CALIFORNIA - ITS ROLE IN ASPECTS OF SECONDARY PRODUCTION IN THE COPEPOD EUCALANUS-CALIFORNICUS JOHNSON

The most abundant large herbivorous copepod in the jet off Point Arena, California, was Eucalanus californicus. In July 1988, females were actively laying eggs and also had a sac of stored lipid. If egg production is a function of present food supply, food concentrations within the jet become the primary factor governing egg laying. However, if stored lipid is the nutritive source for egg production, the critical food supply governing egg laying can be quite distant in space and time from the actual egg laying. In this jet, present food concentration was the factor governing egg production. The size of the lipid sac was also positively correlated with egg production, suggesting that lipid was not being used for oogenesis. Such a life history strategy, in which egg laying and lipid storage are proceeding concurrently in females, has not been described before. Reproductive females were found primarily nearshore and along the southern edge of the jet; highest rates of egg laying and largest lipid reserves were also in these areas. We speculate that temperature affinities of Eucalanus californicus result in maximized abundance, egg production, and lipid sequestration at temperatures below approximately 13-degrees-C. In the Point Arena region, this results in a nearshore portion of the population inhabiting surface layers and showing potential for very high rates of secondary production. The jet acts to transport E. californicus from the nearshore zone into its offshore habitat on a regular basis. Eddies in the region may be the mechanism by which E. californicus is returned to the nearshore zone.