Density-Dependent Growth in Atlantic Menhaden: Impacts on Current Management

Abstract

Biological reference points (BRPs) are used to determine stock status and set management regulations. While BRPs rely on equilibrium life history data, conditions are not static, and density dependence can play a role. Our objective was to determine the relationship between recruitment strength (i.e., density) and mean length and weight at age for Atlantic Menhaden Brevoortia tyrannus in order to assess the impacts on BRP calculations used for management. Recruitment was tested for autocorrelation and related to time-varying mean lengths and weights at age. Spawning potential ratio (SPR) and yield per recruit (Y/R) benchmarks were calculated across a range of fishing mortality rates, F, and recruitment. Recruitment was autocorrelated and negatively related to mean lengths and weights at age. Both SPR and Y/R were not static under nonequilibrium assumptions about recruitment. To maintain SPR with recruitment increased above equilibrium, F would decrease, while maintaining Y/R would require increased F to maintain yield. Tracking recruitment gives managers the ability to track the population and its ability to withstand F in the short term and to make timely management decisions. Changes in life history information over time should be incorporated into BRP calculations and benchmarks, as opposed to it being equilibrium based, in order to ensure sustainability of the population while maximizing harvest.

Received May 9, 2016; accepted November 5, 2016 Published online February 22, 2017

Acknowledgments

We thank Nicholas Ballew and Kevin Craig for reviewing previous drafts of this manuscript.