Preliminary investigation of reproductive hormone profiles in the blacktip shark (Carcharhinus limbatus), a placental viviparous species, in southern Florida

Accurate reproductive information is crucial for the effective management of sharks. Here, we used non-lethal methods to evaluate reproductive hormone profiles of blacktip sharks (Carcharhinus limbatus) off the coast of southern Florida (FL) as part of a preliminary investigation of this species' reproductive patterns in the region. Circulating testosterone concentrations in males ranged from 0.04 to 320.7 ng mL(-1), and concentrations peaked during months previously shown to represent peak spermatogenic activity. In females, circulating concentrations of oestradiol (E2) ranged from 12.5 to 941.4 pg mL(-1), and progesterone (P4) ranged from 30.1 to 821.2 pg mL(-1). E2 peaked during months with peak vitellogenic and ovulatory activity in previous studies; P4 displayed less variability among months. In general, changes in monthly hormone concentrations align well with the timing of reproductive events in C. limbatus in other regions. However, because of low monthly sample sizes and a lack of reproductive status confirmation, the female profiles raise interesting questions about this population's reproductive cycle that could be explored in future studies. Additional studies should collect larger monthly samples and incorporate supplementary data to provide more insight into the reproductive cycle of this species in southern FL.

Automated summary

Non-lethal methods were used to evaluate the reproductive hormone profiles of blacktip sharks off the coast of southern Florida. The study found that testosterone concentrations in males peaked during months of peak spermatogenic activity, while females displayed higher estradiol concentrations during months of peak vitellogenic and ovulatory activity. However, due to the limited sample sizes and lack of reproductive status confirmation, further research is needed to fully understand the reproductive cycle of this species in the region.