Comparison of Specific Ecological Parameters of Nematodes in Six Common Fish Species from the Senegal River and the Gambia River

The Senegal River and the Gambia River share the same sedimentary basin, the same source, and have geographical proximity. This study, conducted over three consecutive years in the Senegal River and the Gambia River, aimed to perform a comparative analysis of the prevalence, abundance, mean intensity, and abundance index of nematodes in six fish species common to both locations: Citharinus citharus, Clarias gariepinus, Chrysichthys maurus, Hydrocynus forskahlii, Mormyrops anguilloides, and Synodontis ocellifer. The inventory of parasitic nematodes in these fish revealed that Chrysichthys maurus hosts the highest diversity of parasitic nematodes, with nine genera identified. Citharinus citharus and Mormyrops anguilloides are each parasitized by only one nematode genus, Cithariniella and Contracaecum, respectively. Except of Spirocamallanus and Camallanus, which were found exclusively in C. maurus, most nematode genera are shared among the different fish hosts. The genus Anisakis exhibits the highest prevalence, with 29.03% in the Senegal River, while Cithariniella shows the highest abundance, mean intensity, and abundance index. Other nematode genera, such as Paracamallanus, Procamallanus, Rhabdochona, Contracaecum, Spirocamallanus, Spinitectus, and Falcaustra, display variable ecological parameters. These nematodes are distributed within the liver and various sections of the digestive tract.