Distributions of larval rockfishes Sebastes spp. across nearshore fronts in a coastal upwelling region

Abstract

We sampled larval fishes along cross-shelf transects off Granite Canyon, California, USA, during the upwelling seasons of 1993 and 1994 to determine whether coastal upwelling fronts affect the cross-shelf distribution of larval rockfishes Sebastes spp. during the earliest period of planktonic life. Rockfish larvae occurred in relatively high densities near surface fronts and were dis- tributed in patches oriented along sloping pycnoclines contiguous with surface fronts. Qualitative comparisons between observed distributions of larval rockfishes in relation to hydrographic structure and predictions from models of plankton distributions at convergent fronts support the hypothesis that convergent circulation contributes to observed distributions. Our results indicate that (1) coastal upwelling fronts influence larval rockfishes at an earlier life history stage than has previously been documented, and (2) the influence of upwelling fronts on distributions of larval rockfishes is similar to the influence of hydrographic fronts on distributions of larval fish reported for a variety of oceano- graphic settings. In light of the plausible effects of upwelling fronts on larval transport and ecology, our findings suggest that upwelling fronts merit further investigation for their potential role in trans- lating variability in upwelling dynamics into fluctuations in recruitment to coastal rockfish popula- tions along the west coast of North America.