Multiple spawning and the dynamics of fish populations: inferences from an individual-based simulation model

Abstract

We used an individual-based Monte Carlo simulation model to assess how aspects associated with multiple spawning (within a spawning season) affected survivorship, lifetime fecundity, cohort egg production, and yield-per-recruit of a highly exploited species. To make our model more realistic, we included and tested the effects of individual variability in growth and a seasonal growth pattern. Birth months influenced when fish first matured and became vulnerable to the fishery. There was a sixfold increase in mature fish at the beginning of their first spawning season associated with having been born early versus late the previous season. Early born fish had a lower average life-span than later born fish. Although early born fish had lower survivorship they produced the most eggs because of an early size at first maturity, low fishing mortality in the first year, and their larger size at age. These results suggest multiple spawning can have important implications for recruitment and adult population dynamics.