Shifting baselines among traditional fishers in São Tomé and Príncipe islands, Gulf of Guinea

Local ecological knowledge has filled baseline gaps in conservation biology, providing important information that has contributed to resource management policies both on land and at sea. Marine ecosystems are globally threatened by overfishing, yet we know little on if and how fishers perceive changes in fisheries composition through time. This is particularly important in developing nations where people rely on fishery resources as their main source of food and income. We interviewed 178 artisanal fishers to collect information regarding their perceptions on the trends and composition of reef fisheries in São Tomé and Príncipe islands, a marine biodiversity hotspot. In addition, we investigated the relative contribution of the possible factors causing changes in these reef fish assemblages according to fishers' perceptions. Of six reef fish species assessed, five exhibited significant declining catch trends. We found a declining trend in individual body size for targeted species based on reports from older (mean ± S.E. = 43.3 ± 2.6 kg) and younger (21.0 ± 0.7 kg) fishers' generations. Generations also differed in their perceptions of declines over time, all of the very experienced fishers reported decline, while only one-third of inexperienced fishers did so. The main causes for fish catch changes identified by experienced fishers (>40 years of fishing practice) were the increasing number of fishers (25%), destructive fishing practices (mainly blast fishing) (18%) and industrial fishing (29%). Our results suggest the occurrence of the shifting baseline syndrome phenomena among traditional fishers and provide baseline information for the conservation and management of São Tomé and Principe marine ecosystems.