Abstract

The spinner shark, Carcharhinus brevipinna, is widely distributed throughout the US Atlantic (ATL) and Gulf of Mexico (GOM) and is regularly caught in commercial and recreational fisheries. However, limited research has been conducted on this species to determine if the life history characteristics are similar between these regions. This study aimed to clearly characterize the reproductive biology of C. brevipinna in the ATL and GOM to better define population dynamics for the western Atlantic basin. This study found that length-at-maturity estimates differed between locations, with ATL males maturing at a smaller size (127.0-cm FL) than GOM males (128.6-cm FL), and ATL females maturing at a larger size (141.9-cm FL) than GOM females (124.5 cm FL). Male age-at-maturity estimates also differed between region, ATL (4.5 years) and GOM (7.1 years) but were comparable for females, ATL (6.6 years) and GOM (6.8 years). Carcharhinus brevipinna from both locations exhibited a seasonal reproductive cycle in which mating occurred during late Spring/Summer, followed by an 11–12-month gestation period with parturition in June/July and exhibited a similar average brood size, ATL (5.07 ± 0.33) and GOM (5.6 ± 0.4). Reproductive periodicity was assigned based on a subset of females and was determined to be biennial in the ATL and a mix of annual and biennial in the GOM; however, further research will be needed to better define periodicity in the GOM. These results are impactful for future management of this species within US waters of the western North Atlantic.