Spatial variability in the growth of Sheepshead (Archosargus probatocephalus) in the Southeast US: Implications for assessment and management

Abstract

Understanding geographic variation in growth dynamics is essential for the management of exploited fish populations because such variation can be used to define stock structure and influence perceptions of stock productivity. Sheepshead (Archosargus probatocephalus) is a species targeted by both commercial and recreational fisheries, and is distributed throughout the north and central Atlantic Ocean and Gulf of Mexico. We analyzed fishery-dependent and –independent length-at-age and weight-at-length data from Texas, Louisiana, Mississippi, Alabama, Florida, South Carolina, North Carolina, and Virginia to investigate the geographic variation in growth of Sheepshead. We constructed a series of von Bertalanffy growth functions (VBGF) and length-weight power equations using a Bayesian framework that included sex, latitudinal, and regional effects. Median posterior VBGF parameter estimates of asymptotic length (L∞) for females ranged from 561 mm fork length in the Virginia Chesapeake Bay to 418 mm in Florida Gulf coast, while the posterior median growth coefficient (k) ranged from 0.42 yr−1 in Texas to 0.20 yr−1 in the Florida Atlantic. Predicted length-at-age and weight-at-length varied considerably among States. Predicted length-at-age for age-1 and -5 individuals was greater in the Gulf of Mexico than the Atlantic. However, predicted length-at-age for older age classes was greater in the Atlantic. Predicted weight-at-length decreased along latitudinal gradients in the Atlantic and the lowest values were found in Mississippi. Given the impact of growth on fisheries reference points, such geographic variation in growth can inform the development of assessment efforts for Sheepshead in the Gulf of Mexico and Atlantic.