Shark Bycatch - Small Scale Tuna Fishery Interactions along the Kenyan Coast.

Abstract

In Kenya and to a great extent most parts of the WIO region, shark catches majorly occur as by-catch in artisanal tuna fisheries and prawn trawls, including sport fishing activities. However, the extent to which these various fisheries catch sharks is not known but may be significant. The species structure, distribution, catch rates and levels of fisheries-shark interactions are not well documented. This information is, however, necessary to assess exploitation levels of shark species and for setting regulatory, conservation and management frameworks. This study therefore aimed at filling this information gap. Data was collected from fisher landings at various sites along the Kenya coast and by observers on commercial and scientific trawl surveys. Landings at 5 beaches were inspected for 15 days per month for 12 months (August 2012 to July 2013). Specimens were identified to species and, sex, length and weight recorded for each shark landed or trawled as by-catch. Results indicate that the artisanal and the prawn trawl shark bycatch is dominated by Hammerhead sharks (Sphyrna lewini, 53.7%), Blacktip Reef shark (Carcharhinus melanopterus, 33.7%), and Grey Reef shark (Carcharhinus amblyrhynchos, 5.5%). Other species present in the catches in lower quantities (~7.1%) include Carcharhinus falciformis, Carcharhinus longimanus, Carcharhinus brevipinna, Sphyrna zygaena, Stegostoma fasciatum. Catch rates of species show spatial and seasonal variation in abundance with higher catches in Kenya’s north coast. Morphometrics of the dominant species are included, and size frequency distributions show mostly juveniles in the catches. There is need to continuously monitor the distribution and abundance of sharks, including shark-fishery interactions in the WIO region for purposes of conservation.