Extinction risk of high value sharks

There is a rapid decline in the abundance and biodiversity of the world’s species, both on land and in the oceans. Sharks and rays are among the worst affected, largely because of intentional and accidental catches in fisheries.

Now, KAUST researchers, together with scientists in Zanzibar, Kenya, the United Kingdom and Australia, have studied small-scale shark fisheries in Zanzibar and Kenya to determine the value of species to local people, with the aim of informing future sustainable management policies^[1].

“In areas where shark harvesting is intentional, it is because these species are of social and economic value to local people. Understanding this value is a critical step in determining the needs of fisheries and developing viable management strategies,” says Andrew Temple, a postdoc under the KAUST Global Fellowship Program, who worked on the project with KAUST’s Michael Berumen and co-workers.

The team examined the link between economic and social (nutritional) value and the extinction risk of sharks and rays in small-scale fisheries. Shark fisheries are often located in poor rural areas and can represent a considerable proportion of the local economy and nutritional needs. For this study, Temple and co-workers collected sales data from 16 landing sites across Kenya and Zanzibar and conducted interviews with 476 local fishers.

“Our results showed that the species with the highest economic and social value are also the most endangered,” says Temple. “This pattern creates conditions for an economically incentivized feedback loop, where vulnerable fishers persistently overfish declining species.”

On an individual basis, the most economically valuable species — including devil rays, wedgefish and bull, silky and mako sharks — tend to be large and slow to reproduce. This means they are more likely to be threatened with extinction.

In the study, shark catches were dominated by endangered species. The overall value of these fisheries and associated livelihoods are under threat because they are relying on endangered creatures. To protect sharks, shark fishers and dependent communities, the feedback loop must be broken through careful local management measures.

“Sustainable small-scale shark fisheries do exist, but they are few and far between,” says Berumen. “Rolling out sustainable solutions in such complex socio-economic situations is challenging. We would not advocate for blanket bans on shark and ray fishing, for example.”

Blanket bans are very difficult to enforce effectively and, if they harm the fishers’ income and wellbeing and there is no substitute in place, such bans can understandably lead to rule-breaking.

“You can end up with uncontrolled, hidden black markets instead,” notes Temple. “We outline some potential avenues for managers to consider, but there is no ‘silver bullet’ that works worldwide. Managers must decide what is achievable within their resources and the local context and culture.”

The team is continuing their research into value in fisheries, and how this can play a role in assessing risk to species across different scales.