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We analysed the genetic diversity of nine populations of two subspecies of Sarotherodon melanotheron using allozymes in relation to the existence of environmental pressures. The genetic variability of Sarotherodon melanotheron melanotheron in the Ivorian ecosystem (A = 1.23, He = 0.04 and P (95%) = 11.11) was lower than that of Sarotherodon melanotheron heudelotii of the estuaries in Gambia and Saloum (A = 1.68, He = 0.08 and P (95%) = 22.23). The analysis of allelic diversity revealed that the individuals of S. m. melanotheron subspecies from a much polluted environment (lagoon of Grand-Lahou or Ebrié) presented a relatively higher frequency of allele GPI-2 * 80 than those of a less polluted environment (Aby lagoon and Ayamé lake). The allele IDH-2 * 90 was expressed only in the specimens of S. m. heudelotii found in the Saloum estuary, a very saline environment compared to the estuary of Gambia. A deficit of heterozygosis was observed with the tilapia Sarotherodon melanotheron. This study confirmed the possibility of using allozymes as biomarkers and bioindicators of environmental disturbances.

The objective of this study is to evaluate the level of Polycyclic Aromatic Hydrocarbons (PAH) contamination at the Sine-Saloum (Foundiougne, Kaolack and Missirah), Hann Bay and Niayes (1 and 2) sites in Sénégal and genetic ecotoxicology of Sarotherodon melanotheron specimens from these sites.The genes of the specimens were studied by the enzymatic electrophoresis technique. Seven enzymatic systems (ADH, AAT, IDHP, MDH, PGM, GPI and EST) were analyzed. The analysis of the PAHs was carried out by gas chromatography coupled to mass spectrometry (GC-MS). Populations of Sarotherodon melanotheron and sediments used for PAH measurements were sampled in 2009. Chemical characterization of the sampling sites revealed a high concentration of PAHs at Foundiougne and Hann Bay. The high pollution of environment is characterized by PAH napht (Foundiougne (14 378 ng/g) ; Hann Bay (5856 ng/g). The analysis of allelic variability showed the existence of an adaptive polymorphism at the PGM locus in S. melanotheron. The particularly low frequencies of the PGM * 105 allele in populations of disturbed environment (Foundiougne, Kaolack, Hann Bay, Niayes 1 and Niayes 2) suggest its involvement in the response to European Scientific Journal July 2018 edition Vol.14, No.21 ISSN: 1857

1 ABSTRACT The phenotypic characterization of four populations of Oreochromis niloticus (Linnaeus, 1758) from the Haut-Sassandra region was carried out using 147 specimens. Among them, 39 were from the natural environment (Sassandra River) and 108 from three fish farms in the town of Daloa. The body weight, sixteen (16) metric characters and fifteen (15) meristic characters recorded on each individual made it possible to analyze the phenotypic variability of the four populations. Twenty-eight (28) on the 31 morphometric characters studied differentiated populations (P <0.001). Based on these 28 characters, Principal Correspondence Analysis (PCA) and Hierarchical Classification Analysis (HCA) grouped the individuals into two groups, a group consisting of Guessabo and PK 12(Kilometer 12 fish farm located at the end of the city of Daloa) specimens and the other group consisting of APDRACI and Quartier Manioc (two fish farms in the city) individuals. Six morphometric characters (PrAL. IOD. LDF. DAL. AFL and SsL) were the most relevant in the discrimination of these two groups. Discriminant factor analysis (DFA) has also classified these populations into two clusters identical to those of the PCA and the HCA. The brood stocks of PK 12 farm is morphologically identical to specimens of the natural environment (Guessabo). The waters of the PK 12 farm have similar characteristics to the natural environment. The PK 12 farm compared to the others (APDRACI and Quartier Manioc) would be better managed.

Mormyrid fish Feeding habits Guinea Republic Dietary patterns of Brienomyrus brachyistius (Gill, 1862) in Tinguilinta and Kogon rivers were described. Diets composition and feeding strategy were analyzed among hydrosystems based on the stomach content analysis. The diets compositions were similar in the two rivers and essentially composed of insects larvae (Diptera, Coleoptera, Ephemeroptera and Trichoptera) and insects debris. Brienomyrus brachyistius exhibited a generalist feeding strategy with a relatively narrow niche width in the two rivers as there was a trophic specialization by many individuals toward Trichoptera larvae. Apart from insects, seeds and sand were found in many stomach contents. The ontogenetic analysis of diet indicated that there were not size-related changes in the diet of the studied species.