Reconstructing historical catch trends of threatened sharks and rays based on fisher ecological knowledge
Leurs, Guido, Jabado, Rima W., Camará, Assana, Dos Santos, Lilísio, Nonque, Diosnes Manuel, Zuidewind, Thije J., Barry, Iça, Campredon, Pierre, Blaschke, Benja, de Boer, Karin, Hijner, Nadia, Olff, Han, Pontes, Samuel Ledo, Regalla, Aissa, Walsh, Matthew Bjerregaard, and Govers, Laura L. (2025) Reconstructing historical catch trends of threatened sharks and rays based on fisher ecological knowledge. Conservation Biology, 39 (5). 70059.
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Abstract
Small-scale fisheries often lack historical shark and ray catch information, hampering their management. We reconstructed historical catch trends and current fishing pressure by combining local ecological knowledge, satellite-based vessel counts, and a short-term landing-site survey. To test the effectiveness of this method, we focused on the Bijagós Archipelago (Guinea-Bissau, West Africa), where historical fisheries data are lacking. Benthic rays (stingrays [Dasyatidae] and butterfly rays [Gymnura spp.]), benthopelagic rays (duckbill eagle rays [Aetomylaeus bovinus] and cownose rays [Rhinoptera marginata]), guitarfish (Glaucostegus and Rhinobatos spp.), requiem sharks (Carcharhinidae), and hammerhead sharks (Sphyrna spp.) declined in abundance by 81.5–96.7% (species dependent) from 1960 to 2020. Fishing effort increased annually: fishing trip duration by 42.0% (SE 3.4), numbers of fishing vessels at sea as perceived by fishers by 36.3% (1.0) (1960–2020), and number of vessels by 12.0% (1.1) (2007–2022). We estimated that in 2020, fishing vessels collectively captured 61–264 sharks and 522–2194 rays per day in the archipelago, depending on the proportion of the fishing fleet that was active (i.e., low fleet activity of 18% and high fleet activity of 80%). We advocate for reducing shark and ray catches by regulating fleet size, reinforcing boundaries of protected areas, and collecting fisher-dependent information on shark and ray landings to safeguard these vulnerable species and coastal livelihoods. We demonstrated the effectiveness of using this 3-pronged approach to provide baseline data on shark fisheries, a common challenge in areas with small-scale fisheries and limited research capacity.
| Item ID: | 88719 |
|---|---|
| Item Type: | Article (Research - C1) |
| ISSN: | 1523-1739 |
| Keywords: | coastal ecology, conocimiento ecológico local, conservación, conservation, conservation ecology, ecología costera, ecología de la conservación, elasmobranchs, elasmobranquios, fisheries, Guinea-Bissau, Guinea-Bisáu, local ecological knowledge, pesquerías, pesquerías artesanales, small-scale fisheries, West Africa, África Occidental |
| Copyright Information: | © 2025 The Author(s). Conservation Biology published by Wiley Periodicals LLC on behalf of Society for Conservation Biology. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. |
| Date Deposited: | 23 Jun 2026 07:25 |
| FoR Codes: | 31 BIOLOGICAL SCIENCES > 3103 Ecology > 310305 Marine and estuarine ecology (incl. marine ichthyology) @ 100% |
| SEO Codes: | 18 ENVIRONMENTAL MANAGEMENT > 1805 Marine systems and management > 180502 Assessment and management of pelagic marine ecosystems @ 100% |
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