Cosmas N. Munga

Species composition of fisheries resources of the Tana and Sabaki Estuaries in the Malindi-Ungwana Bay, Kenya

For over 30 decades, the Sabaki and Tana estuaries of the Malindi-Ungwana Bay, Kenya have supported both the artisanal fishery and semi-industrial bottom trawl sectors. Currently these estuaries in the bay support over 3 000 artisanal fishers and a maximum acceptable fleet of four medium-sized trawlers. These sectors have exerted pressure on the fisheries resources of the bay and will continue to do so due to the increasing artisanal fishing effort. We describe the present status of the fisheries resources of the estuaries in the bay following shore-based catch assessments between 2009 and 2011, and shallow-water bottom trawl surveys in early 2011. These aimed to determine species composition, relative abundance and distribution patterns of the penaeid shrimps and associated trawl fish bycatches, and fish catches from the artisanal fishers. Five shrimp species: Fenneropenaeus indicus, Penaeus monodon, Metapenaeus monoceros, Penaeus semisulcatus and Penaeus japonicus were recorded. Distinct shrimp species composition existed between the two estuaries characterised by more abundant F. indicus in the Tana estuary, and more abundant P. semisulcatus in the Sabaki estuary. Bottom trawl fish bycatch species diversity was higher than for artisanal fish catches with a total of 223 and 177 species respectively. Shrimp total biomass and catch rates were significantly higher during the wet Southeast Monsoon (SEM) season than the dry Northeast Monsoon (NEM) season, and decreased as depth increased. On the other hand, trawl bycatch rates were significantly higher in inshore than offshore areas and distinct in composition but less differing between the seasons. Similarity in catch composition was evident between the artisanal catches and bottom trawl bycatches in the inshore areas. This similarity was attributed mainly to seven common and most abundant fish species targeted in artisanal fishery as well as these species made the highest bycatch proportion in the shrimp bottom trawls. Significantly smaller-sized individuals of these seven species occurred in trawl bycatches than in artisanal catches attributed to differences in gear selectivity. Implementation of the present shrimp fishery management plan, and continued monitoring of fish trawl bycatches will be crucial for the effective management of fisheries resources of the estuaries in the bay.

The value of long-term, community-based monitoring of marine turtle nesting: a study in the Lamu archipelago, Kenya

Monitoring of nesting beaches is often the only feasible and low-cost approach for assessing sea turtle populations. We investigated spatio-temporal patterns of sea turtle nesting activity monitored over 17 successive years in the Lamu archipelago, Kenya. Community-based patrols were conducted on 26 stretches of beach clustered in five major locations. A total of 2,021 nests were recorded: 1,971 (97.5%) green turtle Chelonia mydas nests, 31 (1.5%) hawksbill Eretmochelys imbricata nests, 8 (0.4%) olive ridley Lepidochelys olivacea nests and 11 (0.5%) unidentified nests. Nesting occurred year-round, increasing during March–July, when 74% of nests were recorded. A stable trend in mean annual nesting densities was observed in all locations. Mean clutch sizes were 117.7 ± SE 1 eggs (range 20–189) for green turtles, 103 ± SE 6 eggs (range 37–150) for hawksbill turtles, and 103 ± SE 6 eggs (range 80–133) for olive ridley turtles. Curved carapace length for green turtles was 65–125 cm, and mean annual incubation duration was 55.5 ± SE 0.05 days. The mean incubation duration for green turtle nests differed significantly between months and seasons but not locations. The hatching success (pooled data) was 81.3% (n = 1,841) and was higher for in situ nests (81.0 ± SE 1.5%) compared to relocated nests (77.8 ± SE 1.4%). The results highlight the important contribution of community-based monitoring in Kenya to sustaining the sea turtle populations of the Western Indian Ocean region.