The sociality of Atlantic sturgeon and sand tiger sharks in an estuarine environment

Abstract

Social network analyses are used by ecologists to examine the various drivers of animal social structures. While social behaviours are found throughout the animal kingdom, their roles in structuring marine communities are poorly understood. Comparisons of sociality across marine fishes in the same location and time are rare. A large acoustic telemetry network in Delaware Bay allowed us to analyse the sociality of Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus , and sand tiger sharks, Carcharias taurus . Both species co-occur in the bay, are long-lived, make seasonal migrations and aggregate for unknown reasons. However, these species occupy distinctly different trophic positions and ecological niches. We found little evidence for sociality among Atlantic sturgeon. However, sand tigers exhibited evidence for preferential co-occurrence, modularity and assortment by maturity. In addition, we found that these species preferentially associate with conspecifics. Our findings suggest that sand tigers exhibit a higher degree of sociality than Atlantic sturgeon while in the Delaware Bay. From these findings, we outline the social structures of two evolutionary distinct species while they co-occur in the Delaware Bay. Additionally, we explored the influence that environmental acoustic conditions have on social network metrics and make recommendations for future analyses using acoustic telemetry in estuarine environments. • We analysed sociality of Atlantic sturgeon and sand tiger sharks in Delaware Bay. • Sand tigers exhibited preferential co-occurrence, modularity and maturity assortment. • Atlantic sturgeon exhibited little sign of sociality. • Sand tigers and Atlantic sturgeon preferentially assorted by species. • Environmental variables may influence network formation in short time windows.