Assessing reproductive resilience: an example with South Atlantic red snapper Lutjanus campechanus

Abstract

We developed a conceptual model of reproductive resilience based on spatio-tempo- ral diversity in spawning activity and the 'big old fat fecund female fish' effect, i.e., trends in reproductive traits with size and age. We chose red snapper Lutjanus campechanus as our case study, as this species is highly fecund, currently overfished, and long-lived (50+ yr). The intrinsic reproductive resilience of red snapper was assessed in terms of spawning site distribution, vari- ability in time of spawning, and potential reproductive lifespan. To assess how age truncation might erode reproductive resilience, we evaluated the strength of the relationship between size and age and the following traits: spawning habitat, reproductive timing, batch fecundity, and egg quality. Few fish were older than 7 yr. Although younger fish occurred in a more restricted range of depths, there was no trend between size or age and depth. Spawning activity was well distrib- uted over space and time, with actively spawning females collected at 92 of 195 sampling sites over an extended spawning season. Larger, older females exhibited longer spawning periods and higher batch fecundities, but neither greater spawning frequency nor egg dry weight. The ratio of the effective to predicted reproductive lifespan at maximum sustainable yield was 31%. Many parameters estimated in this study are common to fish reproductive studies, but we hope that inte- grating them into a reproductive resilience framework will help focus the need for research on the underlying relationships between reproductive traits and stock productivity.