The seasonal accumulation of cadmium, copper, lead, mercury and zinc was determined in sediments, water, and black-chinned tilapia (Sarotherodon melanotheron; muscle, brain, kidney and liver tissues) collected monthly from Biétri Bay. The mean water concentration of metals (in mg L(-1)) ranged from 0.01 to 0.30 (mercury), 0.02-0.26 (cadmium), 2.40-4.80 (lead), 9.05-9.68 (copper), and 12.05-19.87 (zinc). The seasonal variations showed a significant difference in the levels of mercury, cadmium and lead among season. The highest mercury (0.30 ± 0.02 μg L(-1)), cadmium (0.26 ± 0.02 mg L(-1)) and lead (4.80 ± 1.03 mg L(-1)) levels were observed during dry season, while the lowest levels (0.21 ± 0.01, 0.02 ± 0.01 and 2.40 ± 0.02 mg L(-1), respectively mercury, cadmium and lead) were measured during rainy season. The average cadmium (0.58 ± 0.36 mg L(-1)), copper (42.15 ± 19.40 mg L(-1)), lead (58.47 ± 38.10 mg kg(-1)), mercury (0.79 ± 0.47 μg kg(-1)) and zinc (187.58 ± 76.99 mg kg(-1)) concentrations determined in Biétri Bay sediments showed a similar trend as in water. The seasonal variations of mercury, cadmium and lead in tissues revealed that these metals were higher concentrated during dry and swelling seasons. The levels of zinc and copper followed by lead were higher in the tissues. The order of tissues metals concentrations was: kidney > liver > brain > muscle.

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Objectives:The interest of this study is double. Firstly, these results allow for the characterisation of species assemblages, to identify their spatial distribution boundaries. Secondly, these findings are relevant to define spatial or ecosystem units in order to provide background for fisheries management. Methodology and Results: Samples were collected and studied at a grid of three zones during the cruise of investigation on board the Oceanographic Vessel ITAF DEME in March 2012. Forty-seven taxa belonging to four orders (Cephalopoda, Malacostraca, Chondrichtyes and Osteichtyes) were selected for analysis. Spatial differences in fish structure were analysed through different multivariate routines from PRIMER including between-matrix analysis of similarities (ANOSIM), species contributions to similarity/dissimilarity (SIMPER), non-metric multidimensional scaling (MDS) and group average cluster analysis. Typical or abundant species from those zones included fishes from the families Sparidae, Haemulidae, Carangidae. The most abundant species were Ariomma bondi (Ariommidae), Selene dorsalis (Carangidae), Brachydeuterus auritus and Pomadasys incisus (Haemulidae), Pagellus bellottii (Sparidae). The species Sardinella maderensis, Brachydeuterus auritus, Trachurus trecae and Selene dorsalis had the highest frequencies of occurrence. Conclusion and application: The distribution of the species halieutics is not uniform along the coast of Côte d'Ivoire. This study pointed to the fish resources of Côte d'Ivoire's Exclusive Economic Zone. These results will be used by the fishermen and for the development of adequate measures to prevent the loss of aquatic biodiversity.

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