The current emphasis of schistosomiasis control is placed on preventive chemotherapy using praziquantel. However, reinfection may occur rapidly in the absence of complementary interventions. Recent studies from Senegal suggest that predatory prawns might feed on intermediate host snails and thus impact on schistosomiasis transmission. We designed a study with four repeated cross-sectional surveys pertaining to prawns and snails, coupled with a single cross-sectional parasitological survey among humans. We assessed for potential associations between the presence/density of prawns and snails and correlation with Schistosoma infection in a composite sample of school-aged children and adults. The study was carried out between October 2015 and December 2016 in 24 villages located near the Agnéby and Mé coastal river systems in south-eastern Côte d'Ivoire. At each site, snails and prawns were collected, and in each village, 150 individuals were subjected to stool and urine examination for the diagnosis of Schistosoma mansoni and S. haematobium. We found peaks of relative abundance of intermediate host snails in the villages of the Agnéby River system, while predatory prawns were predominantly recorded in the Mé River system. A negative association was observed between intermediate host snail densities and riverine prawns; however, no pattern was found between this trend in the predator–prey relationship and the prevalence of human schistosomiasis.

The general aim of this study is to update the inventory of the fish species and to specify distribution patterns in the Nero River ichthyofauna in order to establish some basis for the conservation of these fish communities and their habitat. From February 2009 to January 2010, thirty-three sites were sampled monthly with gill nets and a backpack electrofisher, and environmental variables were recorded. Overall, 46 species included in 33 genuses, 24 families and 9 orders were collected. Eleven families and 30 species were the first records for the Nero River. Including all species previously listed in the literature, the number of species presently known in the Nero River and its tributaries is revised to 59. Four families, Alestidae (21%), Schilbeidae (19%), Cyprinidae (17%) and Cichlidae (16%) that made up 73% of the total number of the catches, were the most dominant. The most dominant numerical species were Schilbe mandibularis and Brycinus longipinnis. Fish species and sampling sites along with eight environmental variables were ordinated with canonical correspondence analysis (CCA) coupled to the Monte Carlo test. Ecological status based on fish assemblage according to environmental variables and anthropogenic pressures showed that miss dead wood leaves and roots, electrical conductivity, total dissolved solids, mud, nitrite, basin width, dissolved oxygen and pH, were the primary factors influencing fish distribution. The environmental tolerance index (ETI), ecological tolerance (tk ) and optima (uk ) values of 10 species to 8 different environmental variables were analyzed. Six species (Hemichromis fasciatus, Epiplatys chaperi, Barbus ablabes, B. longipinnis, Hemichromis bimaculatus and Chromidotilapia guntheri) have high ETI and a cosmopolitan distribution in the Nero River. In the tributaries of the middle course, high concentrations of nitrite in the water, added to the presence of a lot of tolerant species in the ichthyofauna are indications of disturbance of these areas. Subsequent recommendations were formulated for efficient restoration and conservation management of this River.

The food and feeding habits of Cardisoma armatum Herklots, 1851 was investigated in Ehotile Islands National Park from January to December 2018. A total of 355 cardiac stomachs were examined, and the diet studied according to size, sex, and seasons. The relationship between the length of the intestine (Li) and carapace (Lc) was found to be log Li = –0.3203 + 1.0064 × log Lc. The relative importance of food (RIF) showed that C. armatum has an omnivorous diet with insectivorous tendency. Macrophytes, insects, crustaceans, molluscs, fishes, and oligochaete worms were the major feed. Macrophytes (RIF 64.17%) was the main prey, insects (RIF33.6%) a secondary prey, while molluscs (RIF 1.26%), crustaceans (RIF 0.7), fishes (RIF 0.14%), and oligochaetes (RIF 0.13%) were incidental prey. Macrophytes and insects were respectively the primary (RIF 59.35% and 57.79%) and secondary (RIF 37.51% and 39.33%) prey consumed by juveniles (Lc ˂ 64.44 mm) and adults (Lc ≥ 64.44 mm). There was a significantly different diet between males and females (P ˃ 0.05), between rainy and dry seasons (P ˃ 0.05) and a similar diet composition between juveniles (P ˂ 0.05) and adults (P ˂ 0.05).

The feeding habits of Hippopotamyrus pictus and Cyphomyrus psittacus were investigated to determine the trophic relationships in the both species. The stomach contents of 97 Hippopotamyrus pictus and 72 Cyphomyrus psittacus were collected during 4 sampling periods from April 2010 and November 2012 in Bagoe River of Côte d'Ivoire. Vacuity Index of Hippopotamyrus pictus and Cyphomyrus psittacus showed 13.4% and 22.22% of stomachs respectively. Food items were identified to the minimum taxon possible. The importance of the different prey types was assessed using the index of preponderance for both species. The results indicated that the composition of the prey ingested varied with species. Hippopotamyrus pictus consumed 23 prey items and Cyphomyrus psittacus consumed 17 prey items with 16 items shared by both species. The Chironomidae was principal prey of the 2 species. Hydroptilidae was the secondary prey of Cyphomyrus psittacus. In this fact, the diet of Hippopotamyrus pictus varied with size fish and seasonally. The Syrphidae was secondary prey of juvenile and Macrophytes was secondary prey of adults. In wet season, Hippopotamyrus pictus fed exclusively of Insects. Insects and Macrophytes were more important during dry season. In terms of the diversity of items, the Shannon index was higher at Hippopotamyrus pictus than Cyphomyrus psittacus. Schoener coefficient values (α = 0.99) indicated the high overlap.