We investigated spatio-temporal patterns of fish assemblages in four small
coastal rivers in South-East Ivory Coast. The samples were collected
between July 2003 and March 2005 at 8 sampling sites (2 per river: 1
upstream and 1 downstream). A total of 59 fish species belonging to 39
genera, 23 families and 11 orders were captured. Perciforms (30% of the
families and 33% of the species), followed by Siluriforms (22% and
22%), Osteoglossiforms (13% and 17%), Characiforms (9% and
10%) and Pleuronectiforms (9% and 3%) were the most abundant
orders. Among the families sampled, Cichlidae (20% of the species),
Mormyridae (13%), Clariidae (10%), Cyprinidae (10%) and Characidae
(8%) were largely represented. Among the 59 fish species captured, we
identified fifteen marine/brackish species and two introduced species. To
analyse patterns of fish assemblages, we used a non-linear clustering
technique, the self-organizing map (SOM). Using SOM, samples were classified
into 4 clusters, mainly related to the spatial location of the sampling
sites. Except for the distance from the source of the river, environmental
variables (width, depth, current velocity) did not show a clear distribution
gradient on the SOM map. This pattern was explained by the abundance of
estuarine/marine species (i.e. 25% of the species) characterizing the
lower course of the rivers studied. Such a distribution of estuarine/marine
species colonizing the lower and middle course of the rivers was explained
by the absence of dams and contrasts with the patterns observed in more
fragmented rivers of Ivory Coast. Therefore, we suggest that these small
streams should be preserved in order to permit estuarine/marine species to
migrate between streams and the Aby lagoon, thus allowing their large
distribution and their reproduction in favourable habitats. We suggest
particular attention be given to the Soumié River basin which represents
the only preserved stream ecosystem within the Bia River basin.