Abundance and distribution of rockfish (Sebastes) larvae in the Southern California Bight in relation to environmental conditions and fishery exploitation

In this study we describe seasonal, interannual, and long-term changes in t he larval abundance of six rockfish (Sebastes) taxa in relation to spawning biomass and to variability ill the ocean environment. We used rockfish lar vae from a total of 11.472 CalCOFI plankton rows taken in the Southern Cali fornia Bight from 1951 to 1998. Species included in the study were bocaccio (S. paucispinis), cowcod (S. levis), shortbelly rockfish (S. jordani). aur ora rockfish (S. aurora), and splitnose rockfish (S. diploproa). Interannua l trends in occurrance and abundance are described for each species in rela tion to biomass trends of adults and to changes in the ocean environment ca used by ENSO events and by the cool and warm regimes of the Pacific Decadal Oscillation (PDO). Larval abundance of S. paucispinis and S. levis decline d abruptly during the shift to a warm regime and continued to decline, as d id the adult biomass. Abundance of S. jordani larvae declined during the re gime shift but increased after the 1982-83 El Nino, reaching the peak value for the time series ill 1991. Within each regime, minor declines in larval occurrence and abundance were associated with ENSO episodes. The tightly g rouped series of three La Nina events in 1970-76 immediately preceded the s hift front the cool to the warm regime late in 1976 and may have contribute d to the marked decline ill larval occurrence and abundance that, for most species, continued through the 1982-83 El Nino. The decline in larval rockf ish abundance during the regime shift may be a consequence of the decline i n rockfish populations caused by the expanding rockfish fishery; however, t he ocean environment may be a causal factor, because larvae of S. jordani, an unexploited species, underwent declines similar to those of fishery targ et species during that period.