When Is Spawning Biomass a Good Proxy for Stock Reproductive Potential? A Case Study of Red Snapper (Lutjanus campechanus) in the Gulf of Mexico

Many tropical and subtropical fishes exhibit indeterminate fecundity and spawn multiple times over an extended period that may last much of the year. Several studies have demonstrated that the number of eggs produced during a spawning event (batch fecundity) increases with age or body length at a faster rate than does body weight. Moreover, evidence is emerging that spawning frequency also increases with age and body size.  As a result, egg production in tropical and subtropical species is probably less correlated to mature (spawning) biomass than has often been assumed for stock assessments.  We present a case example from a recent study of Red Snapper (Lutjanus campechanus) in the Gulf of Mexico where young fish are demonstrated to contribute substantially less to the reproductive potential of the stock than previously thought. We then demonstrate more generally how moving from a weight-based proxy (spawning biomass) to more direct measures of reproductive potential can affect the perceived correlations between spawning potential, larval surveys and recruitment.