Using fisher-contributed secondary fins to fill critical shark-fisheries data gaps

Small sharks, big problems: DNA analysis of small fins reveals trade regulation gaps and burgeoning trade in juvenile sharks

Many shark species have been overexploited for international markets, including fins for shark fin soup in Southeast Asia. Previous studies highlighted the value of large, threatened shark species, regulated under CITES Appendix II. However, sampling biases may have overlooked small shark species. Here, we address this by identifying species from ~4000 small shark fins in Hong Kong. These fins included species not recorded in previous surveys, raising the market's species diversity to 106. Nearly 75% of the small fins came from small shark species and 58.1% of small species were threatened with extinction. We identified an important CITES listing gap: Trade in 19 small, threatened species, especially from the family Triakidae, is unregulated. In addition, a quarter of small fins come from large sharks, indicating that substantial exploitation of juveniles is occurring and may be affecting fisheries sustainability. Enhanced surveillance of small shark fin trade is essential to ensure effective conservation under emerging trade regulations.

Phylogeography and population genetics of the cryptic bonnethead shark Sphyrna aff. tiburo in Brazil and the Caribbean inferred from mtDNA markers

Resolving the identity, phylogeny and distribution of cryptic species within species complexes is an essential precursor to management. The bonnethead shark, Sphyrna tiburo, is a small coastal shark distributed in the Western Atlantic from North Carolina (U.S.A.) to southern Brazil. Genetic analyses based on mitochondrial markers revealed that bonnethead sharks comprise a species complex with at least two lineages in the Northwestern Atlantic and the Caribbean (S. tiburo and Sphyrna aff. tiburo, respectively). The phylogeographic and phylogenetic analysis of two mitochondrial markers [control region (mtCR) and cytochrome oxidase I (COI)] showed that bonnethead sharks from southeastern Brazil correspond to S. aff. tiburo, extending the distribution of this cryptic species >5000 km. Bonnethead shark populations are only managed in the U.S.A. and in the 2000s were considered to be regionally extinct or collapsed in southeast Brazil. The results indicate that there is significant genetic differentiation between S. aff. tiburo from Brazil and other populations from the Caribbean (Φ_ST  = 0.9053, P < 0.000), which means that collapsed populations in the former are unlikely to be replenished from Caribbean immigration. The species identity of bonnethead sharks in the Southwest Atlantic and their relationship to North Atlantic and Caribbean populations still remains unresolved. Taxonomic revision and further sampling are required to reevaluate the status of the bonnethead shark complex through its distribution range.