First estimates of growth, mortality and recruitment parameters of Macrobrachium macrobrachion Herklots, 1851 in the Cross River estuary, Nigeria

The growth, mortality and recruitment parameters of the brackish-river prawn, Macrobrachium macrobrachion, in the Cross River Estuary, Nigeria, were estimated based on 12 monthly length-frequency samples (October 1991-September 1992). The estimated growth parameters were: L sub( infinity ) = 12.93 cm total length, K = 1.79 per year, C = 0.5, WP = 0.5 of year or 1st July, R sub(n) = 0.259. Total mortality (Z) was estimated at 10.6 per year, while natural mortality (M) was 3.36 per year and fishing mortality (F) was 7.24 per year. This gave an exploitation rate (E) of 0.68, indicating heavy fishing pressure on the stock. The yield-per-recruit analysis suggested that the exploitation rate of the fishery is well beyond the level giving optimum yields. Further research effort to ascertain these findings was recommended, to provide the basis for advancing management options for the fishery.