Spatial and temporal use of New Jersey estuaries by sandbar sharks (Carcharhinus plumbeus)

Estuarine habitats are critical to the survival of early life history stages of many coastal shark species; however, the spatial and temporal use of smaller, non-principal estuaries remains understudied. In southern New Jersey, the Mullica River – Great Bay and Little Egg Harbor estuaries have been proposed as nursery areas for sandbar sharks (Carcharhinus plumbeus), but evidence has been limited. This study used acoustic telemetry to evaluate the spatial and temporal use of these estuarine habitats by sandbar sharks within these proposed nursery systems. Targeted nighttime sampling was conducted from June – October in 2023 and 2024. 32 captured sharks were measured, sexed, and surgically implanted with Innovasea V-16 acoustic transmitters. Shark movement was monitored through an array of 17 receivers deployed throughout the estuaries. Detection data were supplemented by records from the Atlantic Cooperative Telemetry (ACT) network to assess movements beyond the study area. Most tagged sharks were immature (80%), while mature individuals were mostly female (86%). Tagged individuals generated ~ 25,000 detections within the estuarine array. Sandbar sharks were detected within the estuaries from June – October, with juveniles showing the greatest use of inlet-associated receivers while mature adults favored protected back creek receivers. Among sharks tagged in 2023, 79% returned to the system in 2024. Newly tagged sandbar sharks spent an average of 23.8% of their available time within the system in 2023 and 8.2% in 2024, while returning individuals spent an average of 19.3% inside the estuarine system. Outside of the local telemetry array, tagged sandbar sharks were detected on receivers from New York to Florida, indicating connectivity with the broader western North Atlantic coastal corridor. These findings support southern New Jersey estuaries as important summer nursery habitat for juvenile sandbar sharks with high juvenile presence, summer residency, and interannual return. Identifying, understanding, and conserving these areas is essential as survival of juveniles is critical to rebuilding and sustaining adult populations of sharks, especially in the wake of compounded anthropogenic change.