Written by Kennedy Osuka
Photo by Melita Samoilys
Region Update: Africa
IUCN SSC Shark Specialist Group | Africa Regional Group | Member CORDIO East Africa
Gillnets are widely used gears among Kenya’s coastal artisanal fishers. However, their mesh sizes are inadequately monitored or regulated; therefore, their impacts on threatened species are poorly understood. For the first time, a team of researchers from Coastal Oceans Research and Development in the Indian Ocean - CORDIO - East Africa assessed the effects of different gillnet mesh sizes on fish and fishers’ catches in Kenya’s coastal waters. The study, which has been published in the African Journal of Marine Science, found that large mesh gillnets ranging from 20.3 to 30.5 cm in stretched-mesh sizes were the primary gillnet type that captured >60% of threatened shark and ray species. The proportion of species assessed as Near Threatened, Vulnerable, or Endangered on the IUCN Red List of Threatened Species was double that of the medium mesh sizes (7.6 to 12.7 cm stretched-mesh size). The dominant species caught in medium and large mesh sizes were Mackerel Tuna (Euthynnus affinis) and the Vulnerable
Coach Whipray (Himantura uarnak). Other notable Vulnerable species captured in large mesh sizes comprised the Blacktip Reef Shark (Carcharhinus melanopterus), Whitetip Reef Shark (Triaenodon obesus), and Spotted Eagle Ray (Aetobatus ocellatus). Endangered species included the Giant Manta Ray (Mobula birostris). The Whitespotted Guitarfish (Rhynchobatus djiddensis) and Bluespotted Lagoon Ray (Taeniura lymma) that were recently assessed as Critically Endangered and Least Concern, respectively, also formed part of the landings. The observed dominance of threatened species highlights the need for focused gillnet management regulations. In other words, it contradicts the general recommendation of large mesh sizes for artisanal fishing. Thus, phasing them out in Kenya’s coastal waters has a great potential of reducing the capture of threatened sharks and rays. This would also help in lowering the incidental capture of marine mammals and turtles. Instead, the least-damaging medium-mesh sizes should be promoted as an alternative. 48
