Browsing by Author "Mmbaga, Twalibu Kithakeni"

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    The effects of exploitation on habitat, reproductive potential and assessment of knowledge for management of sea cucumbers (echinodermata: holothuria scabra and h. nobilis) in Tanzania
    (University of Dar es Salaam, 2017) Mmbaga, Twalibu Kithakeni
    While the impacts of high exploitation on fish populations and aquatic ecosystems are well documented for commercial and small-scale fishing particularly in the marine environment, such impacts on the fishery of sea cucumbers have not received as much attention. The current thesis examines the impacts of exploitation on sea cucumbers’ basic ecological, biological, fishery, and knowledge of management aspects by focusing on Holothuria scabra and H. nobilis. The study sites selected are associated with different exploitation intensities and pronounced selective exploitation along the coast of Tanzania. The impacts range from effects on the habitats (diminished natural ecological parameters, habitat modifications, and habitat disturbance), exploited population (size, structure, and reproductive potential), changes in fishery characteristics (gear, and fishing methods), to lack of biological knowledge for management. The main findings of the study are that, fishers of sea cucumbers fall under four categories, namely collectors, processors, middlemen and exporters. Middlemen are either fishers of sea cucumbers or rich non-fishers/dealers. Sea cucumbers fishing, associated activities and mismatch between stakeholders and knowledge have led to a decline in habitat quality, species abundance, and reproductive potential. The study further showed that fishery characteristics and knowledge for management of fishers are affected. In conclusion, management options (closed areas, closed season) for sustainable sea cucumber fisheries and areas for future research are outlined, with an emphasis on co-operation from all stakeholders in terms of knowledge, experience and actions (indigenous knowledge and experience, scientists and government help) to ensure livelihood success. It is recommended that stakeholders in the management processes should include government, exporters, marine and fishery researchers, grant/funding agents, leaders and fisheries extension officers.
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    Some aspects of the fishery, ecology and the reproductive biology of Holothuria Scabra (Jaeger, 1935) along the coast of Dar es Salaam.
    (University of Dar es Salaam, 2002) Mmbaga, Twalibu Kithakeni
    More than 10 commercial sea cucumber species were recorded at three landing sites along the coast of Dar es Salaam. The most important were Holothuria scabra, Thelonata ananas, Thelonata anax, Bohadschia vitiensis, Holothuria nobilis, Actinopyga milliaris, Actinopyga mauritiana, Stichopus chloronotus, Stichopus hermanii and Holothuria edulis. Other sea cucumbers of low value are known by their local names as "Ulimbo, Kipilipili, Tambi, Sumu, Shapedi, Kibuta and Maua". H. scabra showed considerably higher abundance in Buyuni compared to Mjimwema and Kunduchi, (Fr = 19.44, P<0.0001). There was significant difference in abundance between the three sites (P<0.001). Investigation on the level of exploitation showed significant difference between all study sites. There were temporal variations of H. scabra abundance at the three sites. The catch was generally high during March, April, July, November and December. H. scabra at Buyuni was found to prefer tidal pools located in sea grasses and algae (Fr = 32.5, P<0.0001). Small gastropods, detritus, debris of red algae and fresh pieces of polychaetes were observed and unidentified animal parts mixed with sediments were noted in the gut content. Length frequency distribution of H. scabra showed dominance of young individuals ranging between 7-16 cm. The multiple comparison of size frequency of H. scabra between Kunduchi and Mjimwema showed significant difference (P > 0.05) while that of Mjimwema and Buyuni was highly significant (P < 0.001). Studies on the reproductive biology of H. scabra showed that the length at first maturity is 16.8 cm and they breed throughout the year with two spawning peaks (August - September and December - January). The statistics from the Fishery Division of Ministry of Natural Resources and Tourism showed some discrepancy with those of FAO and a survey of local markets revealed declining size, quality and quantity in Dar es Salaam. Further studies on ecology of developmental stages and future consideration in the conservation and management for holothurians are recommended.