Browsing by Author "Gebru, Shibabaw"

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    Fish Diversity and Production in Tekeze Reservoir, Tekeze Basin, Ethiopia
    (Addis Ababa University, 2020-11-15) Gebru, Shibabaw; Getahun, Abebe (Professor); Teferi, Mekonnen (PhD)
    Ethiopia has several freshwater systems from where plenty of aquatic foods could be produced. However, due to poor management practices, the contribution of the fishery to the country’s economy is by far little. Tekeze Reservoir has potential in fish production, but little or no detailed and documented scientific information is available about the fish biology and fishing activities. Consequently, the fishery of the reservoir is poorly understood and its sustainability is unpredictable. Therefore, this study aimed to contribute to the management of the reservoir fishery by providing scientific information for sustainable utilization of the aquatic resources. Data was collected using various methods over a period of two years and analyzed using various statistical tools and methods. Fifteen fish species were identified in the present study. The index of relative importance (%IRI) of the key species in the reservoir includes Oreochromis niloticus, (35.5%), Bagrus docmak (22.6%), Labeobarbus intermedius (20.5%), Labeo niloticus (10.6%) and Labeo forskalii (10.2%). However, Clarias gariepinus, Labeobarbus nedgia, Raiamas senegalensis, Labeobarbus crassibarbis, Hetrobranchus longifilis, Garra dembeensis, Bagrus bajad, Labeobarbus bynni, Labeo cylindricus and Labeobarbus beso constitute below 1% of the total catch. The river mouth habitats contributed the most catch composition, while the pelagic habitats contributed the least. Length-weight relationship of O. niloticus, L. intermedius and B. docmak were best expressed by the equations TW = 0.014TL3.054 (r2 = 0.9743, P = 0.0001), TW = 0.0196SL2.9493 (r2 = 0.9609, P < 0.0001) and TW = 0.0098SL3.0819 (r2 = 0.9678, P < 0.0001), respectively. The overall mean condition factor was found to be 1.44±0.01 for O. niloticus, 1.88±0.02 for L. intermedius and 0.94±0.01 for B. docmak. The feeding habit of O. niloticus, L. intermedius and B. docmak indicated that both plant and animal origin food items were consumed by the species. However, phytoplankton for O. niloticus, detritus for L. intermedius, fish and fish remains for B. docmak were the most important food types. Although the proportion was different, the studied fish species consumed all food items in all seasons of the study period. In some size classes of O. niloticus and B. docmak, complete ontogenic shifts were observed, but all food items in different proportions were ingested by L. intermedius. The overall sex ratio (female: male) of O. niloticus and B. docmak was significantly deviated from the hypothetical distribution of 1:1(P iv < 0.001). However, the sex ratio of L. intermedius did not significantly deviated. Size (TL) at first maturity of O. niloticus was 24.2 cm for females and 24.87 cm for males. The size at maturity for L. intermedius and B. docmak (SL) were 20.84 and 27.42 cm for females and 22.05 and 26.79 cm for males, respectively. The mean absolute fecundity of the species was 1,513, 4,788 and 92,321 eggs for O. niloticus, L. intermedius and B. docmak, respectively. The studied species had extended spawning period, from July to October with peak spawning in August for O. niloticus and B. docmak and in September for L. intermedius. Labeobarbus intermedius preferred riverine habitats while O. niloticus and B. docmak prefer the littoral habitat for breeding. The catch per unit effort of the fishery ranged from 15.98 kg/boat/day to 3.26 kg/boat/day. The extent of immature fish harvesting by the commercial catch indicated that O. niloticus (33.32%), L. intermedius (37.72%) and B. docmak (42.17%) were caught before they attain their first sexual maturity. A total of 48 fishery associations with 3,174 members were distributed in the reservoir. The average age of the fishers was close to 30 and about 94% of them were males. The majority (67%) of the fishers were full-timers with the average fishing experience of 4 years and 64% of them had taken formal education. Gillnets and longlines were the commonly used fishing gears and operated for 24 hours in the reservoir. Addis Ababa and Mekelle were the major market destinations for filleted fish, but Shire and Humera towns were for the gutted and sun-dried fishes. The fishery contributed to the rural communities as source of nutrition and food security, employment opportunity and source of income. However, due to poor management practices, illegal fishing activities and overexploitation of the resources, the fish production and fishery business have declined. Therefore, to sustain the production and productivity as well as the socio-economic contribution of the reservoir fishery, the federal government and the two regional states such as Tigray and Amhara Regional States should take a responsibility to address the major problems that cause the depletion of the stock in the reservoir.