Integrating long-term citizen science data and contemporary artisanal fishery survey data to investigate recreational and small-scale shark fisheries in Kenya

Abstract

Shark catches are common in small-scale (artisanal) and recreational fisheries; the magnitudes of these catches remain poorly known and understudied, particularly in developing countries. Data from three sources were used to assess the composition of shark landings in these fisheries in Kenya: boat-based recreational fishery tagging 1987–2016; observed landings from the Bycatch Assessment and Mitigation in the Western Indian Ocean Fisheries Project 2016–2017; and Catch Assessment Surveys landings data 2017–2020. Eighteen species were identified among 1,215 sharks recorded in small-scale fisheries between June 2016 and June 2017. Most of them belonged to the families Carcharhinidae (26%), Triakidae (23%) and Sphyrnidae (14%). Longlines (41%), drift gillnets (30%) and bottom-set gillnets (21%) recorded the highest proportions of catches. A total of 501 sharks comprising 16 species were recorded in the recreational tagging data between 1987 and 2016, caught using either trolling lines or rods and reels. The families Carcharhinidae (56%) and Sphyrnidae (12%) represented the highest proportion of the catch. A generalized linear model was used to assess the effect of year, gear type, season and vessel propulsion mode on the variation in catches of sharks in small-scale fisheries between 2017 and 2020. Catches were significantly higher in 2017 with high catch rates observed in longlines and handlines. Findings from this study highlight the importance of citizen science by recreational fishers in increasing awareness around the risks and threats to shark populations. Strengthening of existing monitoring of shark interactions with small-scale and recreational fisheries is important alongside the implementation of appropriate conservation and management measures such as reductions in fishing effort (e.g. prawn trawling) in nursery areas, prohibiting the capture of CITES-protected species, and enforcing catch-and-release practices by sport fishers to ensure the long-term sustainability of both the affected shark species and the livelihoods of the fishers.