Impact of human activities on fish communities in the aquatic systems of the ivorian coastal zone andestablishment of a biotic integrity index (IIB)

The main objective of this study is the establishment of a Biotic Integrity Index (IIB) based on fish by considering 5 coastal basins of Côte d'Ivoire. Samplings were made between 1999 and 2001, in 109 stations using an electrofisher Smith Root model 12 POW Back pack Electrofisher and in 56 stations using 15 mesh vacuum nets of 8, 10, 12, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80 and 90 mm. The results indicated that the ichthyological populating of all the basins was composed of 57 species and 01 hybrid. Stomach analysis revealed four trophic guilds distributed among omnivores, piscivores, phytophages, and insectivores. On the basis of fish populations and trophic guilds, six metrics have been selected for the calculation of IIB. This is the Shannon-Weaver Diversity Index, percentages of omnivorous species and species of the family Cyprinidae and piscivorous species, total biomass by species and total number of species. The average value of the IIB calculated for all five basins is 2.48. The maximum and minimum values are respectively 4.33 and 1. Five integrity classes ranging from 0 to 4 have been identified. Classes are unequally distributed. Class 3 is the best distributed in the coastal zone. The study area is moderately disturbed. Three types of human activities were identified for a sample of 72 sites. This is agriculture, the layout and use of various chemicals. The combination of these 3 types of activities is responsible for the major disturbances of the aquatic system.