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Zooplankton constitutes a sensitive tool for monitoring environmental changes in coastal lagoons; however, the available information on zooplankton communities is not sufficient to optimize their rational management. The relationships between zooplankton distribution and environmental factors were studied in a tropical lagoon to test whether the indicator properties of zooplankton assemblages could be used to monitor water quality, in a context of expected eutrophication provoked by an increasing anthropogenic activity. Twenty-one (21) stations were sampled monthly from January to December 2004. The community was composed of 65 taxa including Copepoda, Rotifera, and Cladocera. Copepoda was the most abundant group (81% of total numbers). The main zooplankton species were Oithona brevicornis, Acartia clausi, and Brachionus plicatilis. The highest zooplankton abundance (171-175 ind. l -1 ) was recorded during the long, dry season (February-April) and the lowest (40-45 ind. l -1 ) during the rainy and the flood periods (June-July). At a spatial level, the lowest abundance was observed in the estuarine zone. During the dry seasons (December-April and AugustSeptember), marine zooplankton taxa were abundant near the channel of Grand-Lahou, and brackish water taxa dominated in the other sites. Multivariate analyses (Co-inertia) showed that the composition of zooplanktonic communities and their spatio-temporal variations were mainly controlled by salinity variations closely linked to the climatic and hydrological context. The role of the trophic state on zooplankton communities could not be clearly evidenced. Our results and a comparison with previous studies in the neighboring, highly polluted Ebrié Lagoon suggest that the ratio between Oithona and Acartia abundance could be used as biological indicator for the water quality.

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Twenty-two sites were monitored in the Lower Sassandra River Basin (Côte d'Ivoire, West Africa) to examine patterns in fish species assemblage structure along environmental gradients. Hierarchical clustering of the species presence-absence data identified four types of assemblages corresponding to the man-made Lake Buyo, the main channel, and the two major tributaries. Canonical Correspondence Analysis (CCA) indicated that canopy closure, leaves-wood, aquatic plants, temperature, width, total dissolved solids and depth were the environmental factors most strongly correlated with variation in the fish assemblages. Five species: Papyrocranus afer, Micralestes elongatus, Parailia pellucida, Tilapia busumana and T. mariae were reported from the basin for the first time. The investigation of the variation in species richness led to the assessment of a major anthropogenic disturbance induced by a palm oil factory. In conjunction with the fact that the Sassandra River hosts an endemic species, Synodontis koensis, it was concluded that this basin is of high conservation priority.

Length frequency data collected from artisanal fisheries in Lake Ayame´I (Coˆte dÕIvoire) from August 2004 to 2005 were analysed with FISAT ISAT software using the ELEFAN LEFAN package to estimate the population parameters of 11 fish species. Asymptotic values for total length (L¥) ranged from 20.5 cm for Brycinus imberi to 78 cm for Mormyrops anguilloides. Growth rates (k) varied from 0.24 year )1 for Chrysichthys nigrodigitatus to 0.57 year )1 for Hemichromis fasciatus. The growth performance estimates were close to the values found by others authors and reported in FishBase 2008. Fishing mortality (F) and exploitation rate (E) were found to be below optimum levels of exploitation for most fish species. Recruitment was noted as year-round and bimodal for most studied populations. The data sets were limited in most cases, thus this study provides preliminary population parameters only, but for species for which information is scarce. For application in stock assessment, the growth parameters and especially the natural mortality data require further confirmation.

Bahou, L., Koné, T., N'Douba, V., N'Guessan, K. J., Kouamélan, E. P., and Gouli, G. B. 2007. Food composition and feeding habits of little tunny (Euthynnus alletteratus) in continental shelf waters of Côte d'Ivoire (West Africa). – ICES Journal of Marine Science, 64: 1044–1052. The stomach contents of 170 little tunny, Euthynnus alletteratus, sampled between June 2003 and December 2004 were examined. Fish size ranged from 27 to 81 cm fork length, and all fish were caught in gillnets deployed over the continental shelf off Côte d'Ivoire (West Africa). The type and quantity of prey ingested changed seasonally. Outside the major upwelling period the diet was more varied. Overall, fish were the dominant prey of all sizes of little tunny, far exceeding crustaceans, of which shrimps and prawns were commonest but were not found in the stomachs of juveniles (<42 cm FL) or larger adults (≥53 cm FL). Little tunny are carnivorous fish that feed opportunistically. A relationship was found between the size of the prey and the size of the predator.