Assessment of Maximum Sustainable Yield and Optimum Fishing Effort for the Nile Tilapia (Oreochromis niloticus L.) in Lake Chamo, Ethiopia
Abstract
The study was conducted to estimate the maximum sustainable yield (MSY) and optimum level of fishing effort for Nile tilapia (Oreochromis niloticus) stock in Lake Chamo, Ethiopia. Data were collected from eight major landing sites of Lake Chamo for three days in a week for ten months (February to November, 2018). The total length, sample weight and total weight of O. niloticus caught by the fishermen and the fishing effort were the basic information collected from these sites. Totally, 7,570 O. niloticus samples were collected in 120 days. The FiSAT software was used to determine von Bertalanffy growth and mortality parameters. Jones length based cohort analysis model and length-based Thompson and Bell yield prediction models were employed to estimate the maximum sustainable yield. The estimated growth parameters; asymptotic length that the fish attains at an older age(L∞) and growth constant(k)of O. niloticus were 55 cm and 0.37 yr-1, respectively. Overall about 11 million O. niloticus populations were estimated to exist in the lake. The estimated current annual yield was 290.1 tons per year for O. niloticus fisheries of the lake. However, the predicted value of MSY was 313 tons per year obtained at fMSY of 136,249 nets. The length at first maturity (L50) was 39.6 and out of the total annual catch 93.1% were below their respective size of maturity. Thus, the current yield reduction might be due to growth overfishing with reduced mesh sizes. As reported in the earlier studies and according to the finding of this investigation, the catch and yield of Lake Chamo is in the state of reduction through year. Unless the lake is properly managed, the future yields of Lake Chamo will be declining that may lead the resources depletion. Co-management practices, using the recommended mesh size and level of effort (number of nets) should be considered for the sustainability of the resources.References
Ayenew, T., and Legesse, D. (2007). The changing face of the Ethiopian rift lakes and their environs: Call of the time. Lakes& Reservoirs: Research & Management, 12, 149–165. composition data (with notes on VPA and cohort analysis). FAO, fisheries technical Paper, 256: 118 p.
Bekele, S. (2006).Abaya-Chamo lakes physical and water resources characteristics, including scenarios and impacts. International Water Management Institute.
Belay A., and Wood, R.B. (1982). Limnological aspects of an algal bloom in Gamo Goffa administrative region of Ethiopia in 1978.SINET: Ethiop. J. Sci. 5:1–19.
Cushing, D.H. (1982). Climate and fisheries. Academic Press, ISBN 0- 12-199720-0. Lond Lewis and Morris (1986 on).
Dadebo, E., Ingemar, A., and Gunnel, A. (2005). Maturation, sex ratio and fecundity of the Nile perch Lates niloticus (L.) (Pisces: Centropomidae) in Lake Chamo, Faculty of Science, Addis Ababa University, Ethiopia. Ethiop. J. Sci., 28(2):151–160, 2005.
Dejene, Z. (2008). Impact of fisheries and water quality changes on the management of Lake Chamo, Ethiopia. M.Sc. Thesis Addis Ababa University, 7-50.
Doubleday (1976).Environmental fluctuations and fisheries management. ICNAF Sel. Pap.1:141- 150.
FAO (1999).The state of world fisheries and aquaculture 2000. Rome.
FAO (2003).Fishery and aquaculture country profiles. Ethiopia (2003).Country profile fact sheets. FAO Fisheries and Aquaculture Department [online]. Rome. Updated 1 January 2003. [Cited 13 July 2015]. http://www.fao.org/fishery/facp/ETH/en
Gulland, J.A. (1971). The fish resources of the Ocean. Fishing News (Books), West By fleet, 255 pp.
Israel D.C, and Banzon, C.P. (2000). Over fishing in the Philippine Marine Fisheries Sector. International Development Research Centre, Ottawa, Canada.
Jones, R. (1984). Assessing the effects of changes in exploitation patterns using length.
LFDP, (1997). Lake management plans. Lake fisheries development project, phase II, Working Paper 23. 2nd ed. Ministry of Agriculture, Addis Ababa.
MacLean, J.A., and Evans, D.O (1981). The stock concept, discreteness of fish stocks and fisheries management. Canadian Journal of Fisheries and Aquatic Sciences, 38(12): 1889-1898.
Pauly, D. (1980). On the interrelationships between natural mortality, growth parameters and mean environmental temperature in 175 fish stocks. Journal of conservation, CIEM, 39(2): 175-192.
Pauly, D. (1987). Theory and Practice of Over fishing: A Southeast Asian Perspective. Indo-Pacific fishery commission symposium on the exploitation & management of Marine fishery resources in Southeast Asia, IPFC/87, Symp/IV/WP 1.
Pauly, D.G. (1979).Estimation of mortality and growth parameters from the length frequency of a catch. Rapp. P. –V. Reun. CIEM, 175: 167-169.
Schnute, J. (1987). A general fishery model for a size- structured fish population. Canadian Journal of Fisheries and Aquatic Science, 44 (5): 924-940.
Sparre P, Venema, SC. (1992). Introduction to tropical fish stock assessment. Part 1.Manual. FAO Fisheries Technical.; 306(1):376. Technical Paper, 256: 118 p.
Teferi, Y. (1997). The condition factor, feeding and reproductive biology of Oreochromis niloticus Linn. (Pisces: Cichlidae) in Lake Chamo, Ethiopia. M.Sc. thesis. School of Graduate Studies, Addis Ababa University, Addis Ababa, 79 Pp.
Tekle-Giorgis, Y. Berihun, A., and Dadebo, E. (2017).Assessment of sustainable yield and optimum fishing effort for the tilapia (Oreochromis niloticus L. 1758) stock of Lake Hawassa, Ethiopia.
Tesfaye, G., and Wolff, M. (2014). The state of inland fisheries in Ethiopia: A synopsis with updated estimates of potential yield. Eco-hydrology and Hydrobiol. 14: 200–219.
Thopson, W.F, and Bell, F.H. (1934). Biological statistics of the pacific halibut fishery. Effects of changes in intensity upon total yield and yield per unit of gear. Report of the international fisheries (pacific halibut) commission, (8):49p.
Tudorancea, C., and Taylor, W. D. (Eds.). (2002). Ethiopian rift valley lakes (p. 289). Leiden: Backhuys Publishers.
Ward, A., and Wakayo, T. (2013). Final Technical Report: Provision of Technical Assistance to review and improve the catch and effort data recording system (CEDRS) and deliver basic training in stock assessment in Ethiopia.159 pp.
Wetherall, J.A., Polovina, J.J., and Ralston, S. (1987). Estimating growth and mortality in steady-state fish stock from length-frequency data. Proceedings ICLARM Conference, 13:53-74.
Yilma, A., and Geheb K. (2003). Wetlands of Ethiopia. Proceedings of a seminar on the resources and status of Ethiopia's Wetlands.
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