Fin‐to‐body weight ratios for shark species caught in the southern Gulf of Mexico's artisanal fishery: Insight into CITES enforcement for shark fin trade

Shark species are among the most vulnerable marine fishes facing impacts from fisheries. To ensure the international fin trade does not threaten their populations, several species have been listed in the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Appendix II. However, the lack of data on fin-to-body weight ratios makes it difficult to accurately estimate the biomass of harvested sharks based on their traded fins and weakens CITES enforcement. This study determines species-specific fin-to-body weight ratios for shark species caught by the artisanal fishery in the southern Gulf of Mexico. Wet fin weights of primary fins from 479 individuals, belonging to 19 species and six families, indicated that Carcharhinus leucas (43.6%), C. plumbeus (18.8%), C. obscurus (15.0%) and Sphyrna lewini (6.6%) were the most significant large-bodied species involved in the international shark fin trade from the southern Gulf of Mexico. The species-specific mean wet fin weight to total body weight ratios ranged from 1.22% to 3.44%, while wet fin weight to trunk weight ratios varied between 1.40% and 5.73%. Furthermore, the dry fin weight-to-trunk weight ratios oscillated from 0.52% to 1.71%, and the dry fin weight-to-trunk weight ratios ranged from 0.58% to 2.86%. The mean dry-to-wet fin conversion factor was estimated at 42.9%. Alopias superciliosus, C. altimus, C. leucas, C. obscurus, C. plumbeus and Isurus paucus exhibited the highest fin-to-body weight ratios. Our findings provided a practical tool for assessing shark population exploitation based on shark fin trade volumes, contributing to CITES enforcement and management strategies.