Growth and mortality, recruitment and yield of the fresh-water shrimp, Macrobrachium vo Èllenhovenii, Herklots 1851 (Crustacea, Palaemonidae) in the Fahe reservoir, Co Ãte d'Ivoire, West Africa Lawrence Etim a,b,* , Yacouba Sankare c a Faculty of Agriculture, Fisheries and Aquaculture Department, University of Uyo, Uyo, Nigeria b Alfred Wegener Institute for Polar and Marine Research, Box 120161, D-27515 Bremerhaven, Germany c Centre de Researches Oceanologiques, 29 Rue des Perches, BPV 18 Abidjan, Ivory Coast Accepted 28 June 1998 Abstract We studied the growth, mortality rates and recruitment pattern of an exploited fresh-water shrimp (Macrobrachium vo Èllenhovenii) population in the Fahe reservoir of the San-Pedro River, Co Ãte d'Ivoire using 12 consecutive months (January to December 1995) length±frequency samples and FISAT software (which incorporates both the ELEFAN and LSFA programs). A ®t of the seasonalized von Bertalanffy growth equation to the length±frequency data gave the following results: L 1 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 coef®cient Z3.69 year 1 through the seasonalized length-converted catch curve procedure. The instantaneous natural mortality coef®cient M was 1.97 year 1 while the instantaneous ®shing mortality coef®cient was 1.72 year 1 . An exploitation rate E of 0.47 implies that the stock is almost optimally exploited. The results of our yield-per- recruit analysis lend further credence to this assertion. The distribution 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 arbitrary one-year scale. The results also show that there is one recruitment in a year. # 1998 Elsevier Science B.V. All rights reserved. Keywords: Macrobrachium vo Èllenhovenii; Fresh water shrimps population dynamics; Growth; Mortality rates; Recruitment; Co Ãte d'Ivoire 1. Introduction Macrobrachium species occur throughout the West African region. Many workers have studied their ecology, biology and ®sheries. Georges (1971) reported on the catch statistics and general biology of the shrimp in St. Paul River, Liberia and Marioghae (1982, 1990) investigated the ®shery, distribution and salinity tolerance of M. macrobrachion and M. vo Èl- lenhovenii in the Lagos lagoon (Nigeria). He reported that M. macrobrachion constituted about 60% of all shrimp landings and about 83% of all Macrobrachium species catches. Powell (1982) reviewed the systema- tics and ecology of many shrimps and noted Macro- Fisheries Research 38 (1998) 211±223 *Corresponding author. Present address: Faculty of Agriculture, Fisheries and Aquaculture Department, University of Uyo, Uyo, Nigeria. E-mail: root@uniuyo.edu.ng 0165-7836/98/$ ± see front matter # 1998 Elsevier Science B.V. All rights reserved. PII: S0165-7836(98)00161-1