Managing the tropical inland fish stocks when resources are depleted: The case of Oguta Lake Distichodontidae fishery in Nigeria

Abstract

The Distichodus fishery of Lake Oguta (family: Distichodontidae) in Southeastern Nigeria is biologically and economically overfished. The peculiar nature of the fishery as a common property natural resource with no exclusive use right and which yields no economic rent is largely  responsible. The surplus production model was used in assessing the maximum sustainable yield (MSY) between January 2003 to December 2005. Von Bertalanffy growth parameters were L∞ = 83.3cm, k = 0.30cm year^-1 and t = 0.420 year. Estimate of total mortality (Z), natural mortality (M) and fishing mortality (F) coefficients gave 0.530 year^-1 , 0.152 and 0.378 year^-1 respectively. Rate of exploitation (E) was 0. 710, implying that exploitation is beyond the optimum. The maximum sustainable yields (MSY) estimate of 3.30t km^2-1 computed for the fishery suggests that the stock has been depleted. However, the fishery can still support a maximum yield of l .25t km^2-1 above the present level, subject to a maximum applicable (reduced) fishing effort of 6 nights of fishing with standard gear. Decreasing the fishing effort by 21 % and 46 % of its present level will hopefully return the fishery to its maximum sustainable yield (MSY) and the maximum economic yield (MEY) respectively, while restricting the  minimum size limit of exploitable specimens to about 24.0cm total length will help the stock to recuperate. The implications of the present state of the fishery and the management options for resource conservation and sustainability are discussed.

KEY WORDS: Inland fish Stock Depletion, Management, Distichodontidae, Oguta Lake