Environmental Drivers of the Spatial and Temporal Distribution of Spawning Blue Crabs Callinectes sapidus in the Western Gulf of Mexico

Abstract

The blue crab Callinectes sapidus is an economically important shellfish found in the Gulf of Mexico and elsewhere. Recent declines in abundance of this species have driven progressive management actions throughout its range, including protection of spawning females by establishing “no-take” zones on the Atlantic coast. To date, no-take zones have not been established in the western Gulf of Mexico, although annual closures associated with mitigation of derelict traps exist in both Texas and Louisiana. In this study, we used long-term data acquired via fishery-independent sampling by the Texas Parks and Wildlife Department to assess spatial and seasonal distribution of spawning females in order to inform future evaluations of no-take areas. The presence of spawning females was modeled statistically by using water quality and spatial variables as predictors. Distance to the nearest Gulf pass was the most reliable predictor of presence, accounting for over 43% of the deviance observed in models from two independent sampling eras. Salinity (>21% of deviance) and temperature (>12% of deviance) were also reliable predictors, and the values of salinity and temperature that were associated with peak presence remained consistent over an approximately 30-year span despite increasing mean annual values of both variables through time. Peak presence in spawning grounds now occurs in early spring (March–April), contrasting with historical peak presence in the summer (June–July). These data imply seasonal shifts in spawning behavior despite relative spatial consistency through time, suggesting that Gulf pass areas would be ideal for protection of spawning blue crabs via no-take zones if such a measure is deemed necessary.

Received March 6, 2017; accepted May 18, 2017 Published online July 19, 2017

ACKNOWLEDGMENTS

We are grateful to the many TPWD fishery-independent monitoring staff members who were responsible for sampling. M. Fisher and three anonymous reviewers provided helpful comments on the initial draft of this manuscript during internal (TPWD) review. Fishery-independent sample collection was funded in part by a federal grant administered through the U.S. Fish and Wildlife Service’s Wildlife and Sport Fish Restoration program.