Sharks in catch: A view from the initial findings

Accurate identification of sharks is a critical step for understanding shark biodiversity in a region. It will provide a scientific basis for the management and conservation of sharks in each country. DNA barcoding is a powerful tool for this task, and the picture of shark fishing in Vietnam became clearer as we started analysing the samples. Even though lab work is under progress, we have found some important results. First, it is obvious that one of the most commonly collected species is the blue shark, Prionace glauca. It is found in all survey areas, in both forms of fins and bodies. The International Union for Conservation of Nature (IUCN) has classified the blue shark as Near Threatened (NT), despite its popularity and global distribution in deep temperate and tropical waters. This is caused by its population decrease due to overfishing. Through exchanging information with fishermen, we realise that the blue shark is not their main target while fishing. Actually, this shark is usually caught as bycatch by handline that is used to fish tuna.

Another commonly exploited species is the spot-tail shark, Carcharhinus sorrah. Compared to the blue shark, the spot-tail shark is less widespread. It is found in the tropical Indo-Pacific region, including Vietnam. It is not surprising that spot-tail shark samples are common because this shark is fished commercially over much of its range, not only in Vietnam. However, similar to the blue shark, the spot-tail shark is classified as NT by the IUCN.

A blue shark, one of the commonly identified threatened species in Vietnam shark fishing. Photo © Byron Dilkes | Save Our Seas Foundation

Also, we found highly threatened species such as pelagic thresher, Alopias pelagicus and shortfin mako shark, Isurus oxyrinchus. Both of these sharks are classified as endangered on the IUCN red list. Fishing of these two species is also prohibited by the regulations of the Vietnamese government. However, illegal fishing still exists, and fishermen usually cut shark fins before their boats arrive in the ports. Of course, fins and bodies are concealed from fishery managers.

Even though the project is in progress, all species found to date are listed on the IUCN red list. Currently, we are continuing to analyse samples in the lab, and this work is just finished when all samples are identified. The remaining samples are promising and more species will be identified. Some fishery managers and conservationists already contacted the project leader to share the results after the project is completed. The findings will be important to serve long-term conservation of sharks in Vietnam.

The bodies of the pelagic thresher (Alopias pelagicus) after their fins were cut. Photo © Tinh Dinh Do