Occurrence and Identification of Multiple Brooding in Rockfishes (Sebastes spp.)

Viviparous rockfishes (Sebastes spp.) most commonly produce one brood annually; however, multiple brooding within a reproductive season has been documented in a handful of rockfish species. Prevalence of multiple brooding appears to co-vary geographically and with size, with increased occurrence in southern California and in larger females, but the drivers of this process are unclear. Ambiguity surrounding frequency of multiple brooding complicates fisheries management. The production of multiple broods, especially if influenced by maternal size or age, adds further uncertainty to accurate estimation of annual fecundity. Although stock assessments typically account for size- or age- dependent fecundity when data are available, no assessments have yet formally addressed the issue of multiple-spawning, which could be another mechanism for size- or age- dependent fecundity if it occurs more frequently in larger, older individuals. Identification of multiple brooding, and determination of the proportion of occurrence, is essential for accurate projections of spawning output. We use three methods to identify multiple broods: macroscopic ovary examination, fresh microscopic inspection and histological analysis. Here we discuss this life history strategy, prevalence of multiple brooding in our field collections from central California, and compare the accuracy and efficiency of identification methods and their implications for management applications.