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Assessment of the Ecological Status and Threats of Welala and Shesher Wetlands, Lake Tana Sub-Basin (Ethiopia)







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    Shesher and Welala FloodplainWetlands (Lake Tana, Ethiopia):Are They Important Breeding Habitats for Clarias gariepinus and theMigratory Labeobarbus Fish Species? 2012
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    This study aims at investigating the spawning migration of the endemic Labeobarbus species and C. gariepinus from Lake Tana, through Ribb River, to Welala and Shesher wetlands. The study was conducted during peak spawning months (July to October, 2010). Fish were collected through overnight gillnet settings. A total of 1725 specimens of the genus Labeobarbus (13 species) and 506 specimens of C. gariepinus were collected. Six species of Labeobarbus formed prespawning aggregation at Ribb Riv er mouth. However, no Labeobarbus species was found to spawn in the two wetlands. More than 90% of the catch in Welala and Shesher wetlands was contributed by C. gariepinus. This implies that these wetlands are ideal spawning and nursery habitats for C. gariepinus but not for the endemic Labeobarbus species. Except L. intermedius, all the six Labeobarbus species (aggregated at Ribb River mouth) and C. gariepinus (spawning at Shesher andWelala wetlands) were temporally segregated.
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    Growth, biomass, and production of two small barbs (Barbus humilis and B. tanapelagius, Cyprinidae) and their role in the food web of Lake Tana (Ethiopia) 2012
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    Growth, biomass and production of two small barbs (Barbus humilis and Barbus tanapelagius) and their role in the food web of Lake Tana were investigated. From length–frequency distribution of trawl monitoring surveys growth coefficient, U0 values were estimated at 3.71–4.17 for B. humilis and 3.70–4.14 for B. tanapelagius, respectively. Values for B. humilis were confirmed in pond experiments. Mean biomass of the small barbs was 13.3 kg fresh wt ha-1, with B. humilis being most abundant in the littoral and sub-littoral zones, whereas B. tanapelagius was most abundant in the sub-littoral and pelagic zones. The two small barbs had a production of 53 kg fresh wt ha-1 year-1. Although their P/B ratios of about 4.0 were relatively high for small cyprinids, both their biomass and production were low in comparison with other small fish taxa in other tropical lakes. Of the zooplankton production only about 29% was consumed by the small barbs. However, they did not utilize calanoid copepods, which were responsible for approximately 57% of the zooplankton production and it is likely that small barb production was food limited during certain periods of the year. Piscivorous labeobarbs consumed about 56% of the small barbs production annually, but additionally, Clarias gariepinus, and many bird species were also preying on them. Therefore, limitation of Barbus production by predation during certain periods in the year cannot be excl uded.
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    Fisheries Development Programme in the Lake Basin Region, Kenya. Report of the Preparatory assistance mission (for the Kenya Lake Victoria Basin fishery development) 1982
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    The Lake Victoria Basin, mostly made of the Western and Nyanza Provinces, covers only 8.4% of Kenya's territory but contains more than 40% of the total population. Land availability is small and rural holdings with a low income and little assets are prevalent. Average fish consumption provides only 68% of the daily fish protein requirements, but it is projected that by the year 2 000, such average fish availability will require a 41 000 t production. The public sector of aquaculture is charact erized by a lack of adequately trained personnel, positive demonstrations and effective extension services. The private sector essentially consists of small rural ponds, numbering about 3 000 or 35% of those recorded ten years ago. Average production is low, the total annual production of farmed fish being estimated to be about 45 t. Four fish farming zones are defined on the basis of prevalent air temperatures. Only the two warmer zones are suitable for tilapia culture. Past failures of fish farming development may be explained by the lack of trained personnel and limited mobility, hampering the technical support. Foreign assistance is actually limited to the World Bank Project and to direct extension work by young volunteers. Short-term and medium-term fish culture development programmes are proposed with the main objective of creating an effective extension service. The Kenyan Lake Victoria capture fishery is briefly reviewed. Its yield was estimated in 1981 to reach close to 46 000 t, most likely near the maximum sustainable yield at least without further major changes in the fish species composition. The Nile perch dominates the catch and the introduced tilapia species have displaced the endemic ones, T. nilotica becoming dominant. The significance of the catch data is doubtful and the actual statistical system should be critically reviewed. A World Bank Project concentrates on the improvement of product quality and reduction of post-harvest losses.

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