Ontogenetic habitat partitioning among four shark species within a nursery ground

Abstract

Context Nursery areas provide refuge from predators, rich foraging grounds, and physical conditions conducive to growth and development of juvenile inhabitants. Specifically, the Mississippi Sound in the northern Gulf of Mexico is likely a nursery ground for multiple large and small coastal sharks. Aims and methods Using over a decade of shark survey catch data, we employed habitat modelling approaches to identify preferred environmental conditions and spatial distribution, and quantify core habitat overlap within the Mississippi Sound for young-of-year (YOY), juvenile and adult life stages of four coastal shark species. Results YOY Atlantic sharpnose (Rhizoprionodon terraenovae), blacktip (Carcharhinus limbatus) and finetooth (Carcharhinus isodon) sharks showed a preference for a combination of shallow, warm, low salinity, low dissolved oxygen and turbid waters. Corresponding to shared environmental preferences, spatial distributions of YOY sharks showed a high degree of overlap, particularly in the northern portion of the Mississippi Sound where few adult sharks were observed, suggesting that these life stages partition themselves to avoid predation. Conclusion and implications With a continued rise in US coastal shark populations, we hope this study can help further refine essential fish habitat for these coastal species and provide a framework analysis that can be used to understand habitat partitioning in other regions.