Growth and reproductive performance in cultured nearshore rockfish (Sebastes spp.)

The present study evaluates the extent to which the viviparous reproductive strategy that characterizes the genus Sebastes (rockfish) can be expressed in culture. In addition, the growth patterns of rockfish were examined during the early phases of growth pertinent to the culture of the species. Using grass rockfish (Sebastes rastrelliger) as our model, it was demonstrated that all phases of ovarian seasonal cyclicity could proceed under controlled environmental conditions. Rockfish successfully spawned in our facility and subsequently passed through successive phases of oocyte development during the normal reproductive season before follicular atresia was observed in the absence of fertilization. Fish introduced into culture in an advanced stage of vitellogenesis became pregnant in the absence of males 14–55 days later. This observation is consistent with the view that delayed fertilization occurs in rockfish and establishes that wild caught specimens for spawning purposes are not confined to pregnant females. By monitoring growth parameters in two groups of brown rockfish (S. auriculatus) introduced into culture during their first and second year of development a comprehensive picture of early growth was established. Overall changes in both weight and length followed a sigmoid curve comprising an early phase of exponential growth transitioning to a phase of exponential decay. The constituent phases of this curve, as expressed in the two age groups, and the combined growth data over a period of 1083 culture-days were precisely described by the Gompertz equation. This equation also described the growth of young-of-the-year copper rockfish (S. caurinus) with similar accuracy. Validation of the applicability of our Gompertz equation was achieved by reference to growth parameters of brown rockfish of known age raised from birth at UCSB. Our mathematical model precisely depicted growth with age from birth to the period of sexual maturity. These data on growth in relation to age may find broad application in fisheries management plans allowing for evaluation of population changes over time and be useful in determining and improving the culture potential of nearshore rockfish species.