Fishers’ knowledge and risk assessment: a combined approach to studying endangered large-bodied sharks in the central Mediterranean

Abstract Mediterranean large-body sharks face a high risk of extinction, with population declines that could potentially be worse than the global trend. However, in the basin, there is little quantitative information on the long-term pattern of their populations. Here, we relied on local ecological knowledge (LEK) by tapping into the collective memory of professional fishers to tracing back the spatiotemporal changes in catch and abundance of four large-bodied sharks—hammerheads ( Sphyrna spp.), sandbar shark ( Carcharhinus plumbeus ), shortfin mako ( Isurus oxyrinchus ), and blue shark ( Prionace glauca )—inhabiting the waters off the Pelagie Archipelago (Strait of Sicily, Central Mediterranean) over three different periods (1961–1980s, target shark fishery; 1981–2000s, declining shark fishery; and 2001–2020s, no target shark fishery). A Productivity Susceptibility Analysis (PSA) was then conducted to combine fishers’ knowledge and biological data to assess the vulnerability of the four shark species in each period. Fishers reported a general perception of a reduction in abundance and catches over 60 years. Overall, a significant reduction in catches was observed for C. plumbeus (87%) and Sphyrna spp . (100%) , and three major aggregation sites were suggested. Vulnerability was high for all species across the three time periods, except for P. glauca, classified as moderately vulnerable until the 2000s. Notably, fishers reported that C. plumbeus and Sphyrna spp. were specifically targeted from the 1960s until the 1990s, with Sphyrna spp. potentially suffering decades of targeted fishing pressure. These results showed that in a data-poor fishery region, integrating fishers’ knowledge into ecological risk assessments effectively identifies the most vulnerable shark species throughout the history of the fishery and facilitates the development of urgent conservation actions needed for potentially extirpated and locally threatened shark populations.