Growth and mortality, recruitment and yield of the fresh-water shrimp, Macrobrachium vollenhovenii, Herklots 1851 (Crustacea, Palaemonidae) in the Fahe reservoir, Cote d'Ivoire, West Africa

We studied the growth, mortality rates and recruitment pattern of an exploi ted fresh-water shrimp (Macrobrachium vollenhovenii) population in the Fahe reservoir of the San-Pedro River, Cote d'Ivoire using 12 consecutive month s (January to December 1995) length-frequency samples and FISAT software (w hich incorporates both the ELEFAN and LSFA programs). A fit of the seasonal ized von Bertalanffy growth equation to the length-frequency data gave the following results: L-infinity=18.0 cm total length, K=0.91 year(-1), C=0.92 , WP=0.44 of year (i.e, July), and an R-n value of 0.45, We also estimated the instantaneous total mortality coefficient Z=3.69 year(-1) through the s easonalized length-converted catch curve procedure. The instantaneous natur al mortality coefficient M was 1.97 year(-1) while the instantaneous fishin g mortality coefficient was 1.72 year(-1). An exploitation rate E of 0.47 i mplies that the stock is almost optimally exploited. The results of our yie ld-per-recruit analysis lend further credence to this assertion. The distri bution of juveniles and ovigerous females in the samples show that there is one reproduction peak in August and one recruitment peak from September to November. We back-projected our length-frequency data set on to an arbitra ry one-year scale. The results also show that there is one recruitment in a year. (C) 1998 Elsevier Science B.V. All rights reserved.