Spawner-Recruit Relationships of Demersal Marine Fishes: Prior Distribution of Steepness

Stock assessments use spawner-recruit functions to relate the reproductive capacity of a stock (e.g., total fecundity) to subsequent recruitment. The Beverton-Holt spawner-recruit function, perhaps the most widely used, is conventionally parameterized using a “steepness” parameter that describes the stock's productivity. This parameter highly influences predicted population dynamics and responses to exploitation. Unfortunately, steepness can also be difficult to estimate reliably from data typical of stock assessments. In such cases, estimation can be improved by drawing inference from other stocks with similar life-history patterns. In particular, Bayesian prior distributions can formally be incorporated into stock assessments to inform estimation of steepness. In the present study, we used a meta-analytic approach to compute a prior distribution of steepness, focusing on marine demersal fishes. We similarly computed a prior distribution of maximum lifetime reproductive rate, a parameter inextricably related to steepness. In addition, we tested relationships between steepness and two life-history parameters linked to longevity—natural mortality and age at maturity—to examine the common assumption that long-lived, “K-selected” species have lower steepness values. In neither case was steepness significantly related to the life-history parameter. Our results should be directly applicable in stock assessments that apply the Beverton-Holt (or Ricker) function to marine demersal fishes, such as reef-associated species of the southeast United States in Atlantic, Caribbean, and Gulf of Mexico waters.