OCEANIC FACTORS INFLUENCING DISTRIBUTION OF YOUNG ROCKFISH (SEBASTES) IN CENTRAL CALIFORNIA: A PREDATOR'S PERSPECT WE

Abstract

We used the diet of a seabird, the common murre (Uria aalge), to assess the abundance ofjuvenile rockfish (Sebactes spp., mostly S. jorduni? in the Gulf of the Farallones, California, 1973-90. On the basis of an exploratory analysis of the data and of several oceanographic factors, we hypothesize that availability of fish in the study area during June-July was a function of advection during the January-February period of rockfish parturition. When upwelling or downwelling was persistent in winter, there were fewjuveniles in late spring, but when upwelling had been mild or pulsed, juveniles were abundant. Rockfish availability also decreased when turbulence, sea level, and sea-surface temperature were high during winter. Stepwise multiple regression analyses indicated that, among these variables, advective transport significantly affects the distribution ofjuvenile rockfish. RESUMEN Usamos la dieta del ave marina alca piquilarga (Uria aalge) para estimar la abundancia de rocot juveniles (Sebustes spp., principalmente s. jordunq en el Golfo de Farallones, California, 1973-90. Basindonos en un anilisis exploratorio de 10s datos asi como en factor- oceanogr6ficos. presentamos la hip6tesis que la disponibilidad de peca en Junio-Julio fue funci6n de la advecci6n durante Enero-Febrero (la temporada de m’a 10s rocot). Cuando hub0 surgencias o hundimientos de masas de agua penistentes en invierno. disminuy6 la abundancia de juveniles en primavera tardia, mientras que cuando las surgencias heron poco intensas u ocurrieron intermitentemente, la abundancia de 10s juveniles incrcment6. La disponibilidad de 10s rocot disminuy6 cuando en invierno hub0 valores altos de turbulencia. nivel del mar o temperatura superficial. Andlisis de regresi6n mriitiple por pasos indicaron que de entre &as variables. la advecci6n afecta significativamente la distribucidn de rocotjuveniles.