Connectivity of scamp Mycteroperca phenax populations in the United States Gulf of Mexico and Atlantic Ocean

Abstract

Connectivity among marine fish populations not only arises through the movement of adults but also through larval dispersal facilitated by ocean currents. For species with long pelagic larval duration and high site fidelity as adults, larval dispersal can be the dominant mechanism of connectivity among otherwise spatially distinct populations. Therefore, when assessing the recruitment dynamics or population structure of such species, it is essential to evaluate how larval biology and reproductive ecology interact with oceanographic circulation. To investigate this interaction for scamp Mycteroperca phenax, a grouper found in the Gulf of Mexico and Atlantic Ocean, we simulated the dispersal of millions of virtual larvae throughout the scamp’s range near the southeastern USA. We found a pattern of local retention, with larvae tending to settle close to their spawning location. There was also, however, long-distance dispersal that consistently crossed the boundary between spatial management units. Due to directional patterns in oceanographic transport and spatial differences in abundance, almost one-third of the virtual larvae that settled in the Atlantic came from spawning locations in the Gulf of Mexico, although most of these settled near the boundary between the regions. These patterns were robust to a variety of sensitivity analyses, but the magnitude of connectivity between management units varied. This connectivity has significant implications for stock assessment and fishery management. It may increase the resilience of Atlantic populations, but it also means that the sustainability of Atlantic populations may rely, in part, on the health of spawning populations in the Gulf of Mexico.