Traditional fisher perceptions on the regional disappearance of the largetooth sawfish Pristis pristis from the central coast of Brazil

Abstract

Overfishing is considered one of the main threats to the health of global marine fish populations. Elasmobranchs that are characterized by low reproductive outputs may be particularly sensitive to intense fishing pressures. The sawfishes stand out as a highly threatened group, due in part to their life history in shallow coastal waters and their ease of capture. In Brazil, sawfish populations are now virtually extinct and these declines have gone undocumented, leaving their precise causes and timing poorly understood. Here, based on ecological and fisheries know - ledge of local fishers, we document the disappearance of largetooth sawfish Pristis pristis from 5 estuaries on the central Brazilian coast. Fisher knowledge, combined with an estuarine morphology perspective, revealed important insights on this species, along with a timeline of its decline. Furthermore, fishers' accounts of the protracted decline revealed clear inter-estuary differences in the timing of population declines, potentially influenced by local geomorphological features. The onset of sawfish population decline appears to have been earlier in estuaries with a direct connection to the sea than in estuaries connected to an inner bay, occurring in the former case from the 1930s onward. A second wave of intensifying decline began in the 1970s in more structurally complex estuaries. Pressures from artisanal and modern fishery practices appear to have led to an earlier population decline in structurally less complex estuaries, while in larger and more complex ones this decline occurred decades later. The replacement of traditional by more modern fishing practices may have triggered the initial phase of local sawfish extinctions.