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The Anambra and Imo River basins are richly endowed with fishery resources. The use of unconventional fishing methods, such as local poisonous herbs and chemicals and various explosives, threatens to destroy their aquatic resources. Some control measures to be taken are suggested in the following areas: education, patrols, cooperatives and legislation.
Comparative methods are presented which allow for quick and relatively reliable growth parameter estimates when growth data are not at hand. One of these methods involves the use of a newly developed "auximetric grid." An empirical equation for the estimation of natural mortality of any fish stock, given a set of growth parameters, is briefly reviewed. The methods are applied to data from the Gulf of Thailand trawl fishery, and the mortality caused by this fishery is estimated.
The following parameter values are derived for a West Kalimantan (West Borneo) stock of the threadfin bream, Nemipterus marginatus : L infinity = 24.5 cm (L.T.), W infinity = 210 g, K = 0.42, t = -0.41 and M = 1.73. Yield-per-recruit for N. marginatus are presented. Catch per hour of N. marginatus is very low, even in the area of highest density ( approximately equals 3.5 kg/h at 45 m depth). Single-species exploitation of a stock of the type represented by N.