Struggles beneath the waves: Unveiling the incidental capture of sea turtles by artisanal fisheries in Angolan waters

Abstract

The modernization and intensification of fishing practices have raised the threat to sea turtles, with escalating unintentional captures endangering turtles of all life stages. In this study, we examined the impact of artisanal fishing on sea turtles in two coastal regions of Angola, southern Africa. Between August 2015 - March 2016, through participatory monitoring (n = 8) and interviews with fishers (n= 41), we documented unintentional turtle captures occurring year-round during fishing activities. A total of 405 turtles, 403 olive ridley (Lepidochelys olivacea) and 2 green (Chelonia mydas), were caught in gillnets by fishers engaged in participatory monitoring. Net characteristics, including length and proximity to the shoreline, as reported by the interviewed fishers, correlated with those used by the monitoring group. We estimated approximately 1219 turtles captured by the 41 interviewed fishers over the 8-month study period. Most captures occurred within 100 m from the shoreline. The likelihood of accidental turtle captures increased significantly with proximity to the beach, larger mesh sizes, and greater net lengths and number of hauls. We calculated a survival rate of 41%, and a mortality rate of 59% for captured turtles. Number of turtles caught as bycatch varied throughout the year, with the highest Catch Per Unit Effort (CPUE) reported for Oct. – Dec. Since this period aligns with the nesting season, most captured turtles are likely to be females. The high mortality rate reported in this study emphasizes the immediate threat posed by accidental captures to sea turtle populations, underscoring the critical importance of conservation efforts, particularly in artisanal gillnet fisheries.

Keywords

• Lepidochelys olivacea
• Africa
• Sea turtle
• Bycatch