Modeling growth and reproduction of chilipepper rockfish under variable environmental conditions

Chilipepper rockfish (Sebastes goodei), a long-lived, highly fecund commercial species in the California Current ecosystem, contend with a variable environment on several time scales. Using a bioenergetics model, we simulated alternate strategies of energy allocation by female chilipeppers under variable conditions, and examined resulting patterns in age-dependent size and fecundity. Variable conditions consisted of single climate events (one anomalous year, one 4-year regime shift, or one 10-year regime shift) that occurred at different points over the lifespan of the fish and were either “poor” or “good” relative to baseline conditions. Poor years or regimes reduced growth and fecundity, while good years or regimes increased growth and fecundity. Fecundity losses during poor conditions could be mitigated by partially or fully reallocating energy from gonadal production into somatic growth, thereby increasing potential fecundity in future years. However, when mortality was incorporated, those energetic re-routing strategies only increased lifetime reproductive output if we assumed that old (≥age 8) females produce more viable larvae than young females, and if the event occurred prior to age 8. Young females also increased output of larvae beyond age 8 if they skipped spawning or reallocated reproductive energy during good conditions, instead investing the surplus energy into additional somatic growth and enhancing future fecundity. Our results are consistent with recent estimates of growth rate variability in the chilipepper population, and with observations of young females of other rockfish species skipping spawning during poor conditions. Models like this may help improve stock assessment parameters and biological reference points for species with environmentally driven variability in size at age.

Research highlights
► We model chilipepper rockfish growth and fecundity under contrasting conditions.
► Poor conditions led to declines in growth and fecundity.
► Lost fecundity was partly offset by diverting energy from reproduction to growth.
► Diverting energy produced long-term reproductive benefits only for young females.
► Climate-driven changes in growth, fecundity affect results of stock assessments.