The smooth hammerhead shark and the common thresher shark belong to the fishery resources off northern Peru, which could be particularly sensitive to climate change. A study in Scientific Reports compared 35 economically important species and species groups in the tropical eastern Pacific up to the year 2055.
Twelve experts assessed climate exposure and sensitivity
The researchers did not use a direct prediction of future population sizes. Instead, they combined a trait-based climate risk analysis with expert knowledge. Twelve experts assessed ten environmental factors ā including water and air temperature, salinity, pH, chlorophyll, primary production, precipitation, and sea level rise ā as well as twelve biological and population-related traits.
The projections refer to the period from 2006 to 2055 compared to 1956 to 2005 and use the high-emission scenario RCP 8.5. An area between approximately three and six degrees south latitude before Tumbes and Piura was evaluated. This transitional zone between tropical waters and the northern Humboldt Current combines mangroves, river mouths, rocky coasts, islands, and open sea areas.
Five resources received the category highly vulnerable
None of the 35 resources examined were classified as very highly vulnerable. Five reached the high category: three benthic invertebrates as well as smooth hammerhead shark (Sphyrna zygaena) and common thresher shark (Alopias vulpinus). Seventeen resources were in the medium range and 13 in the low range. Overall, benthic species were most affected, followed by pelagic species.
In sharks, slow growth, late sexual maturity, and low offspring generally increase sensitivity to additional pressure. The study takes into account not only climate factors but also such biological characteristics. It thus shows relative priorities within the group studied, not the timing of a possible population collapse.
Data gaps can skew the result upwards
The research team explicitly points out uncertainties. Because only limited information is available on the reaction of the two shark species to individual climate factors, their vulnerability could be overestimated. In a sensitivity test, the smooth hammerhead shark dropped from high to medium when a single evaluation criterion was omitted. It is precisely this instability that makes additional measurement and stock data a priority.
For the fishery, it is about more than two species of sharks
The study area is home to around 41 percent of the industrial fishing fleet Perus and delivered an average of about 601,250 tons of marine products per year between 2013 and 2022. Climate-related shifts can change fishing grounds, fuel requirements, and the composition of catches. The authors therefore see their ranking as a tool for monitoring and adaptive fisheries management ā not as a replacement for species-specific stock analyses.
For Peru, climate pressure adds to existing burdens. The trade in shark fins and controversial export quotas show how important reliable origin, catch, and stock data already are today. The new study expands this debate to the question of which species will need additional protection and adaptation measures first under changing marine conditions.
