Research Unit in Environmental and Evolutionary Biology (URBE), Faculty of Science, University of Namur, Rue de Bruxelles, 61-B-5000 Namur, Belgium
Research Unit in Aquaculture and Aquatic Ecotoxicology (URAEAq), Department of Animal Production, Faculty of Agronomy, University of Parakou, Parakou, Benin
The African catfish Clarias gariepinus is a widespread species in the Beninese cotton basin. In this study, the impacts of exposure to agricultural pesticides endosulfan [Thionex 350 EC (emulsifiable concentrate)] and Tihan 175 O-TEQ (oil toxicity equivalent) on growth, feed utilization and energy budget of C. gariepinus were investigated. Fingerlings (1.58 ± 0.02 g) were exposed to borehole water (control), 0.23 ppb (environmental concentration), 440 ppb (Lethal Concentration 50 %/20, LC50/20) and 880 ppb (LC50/10) of Tihan; and to 11 ppb (LC50/20), 22 ppb (LC50/10) and 29.40 ppb (environmental concentration) of Thionex for 28 days. Fish biomass was assessed weekly and fish samples were taken from different aquaria to determine the specific growth rate (effect on growth), feed efficiency rate and protein efficiency ratio (impact on feed utilization), and the biochemical composition of fish (impact on the energy budget). The results showed that endosulfan environmental concentration induced 100 % of mortality in catfish fingerlings while mortality rate was comparable between control fish and Tihan-treated fish over the 28-day period (p > 0.05). In contrast to survival, the two pesticide types tested induced a marked decrease in growth only during the first 2 weeks of exposure (p < 0.05). The negative impact of endosulfan on growth was associated to a lower feed utilization and protein efficiency compared with control fish or those exposed to Tihan (p < 0.05). The energy reserves were more rapidly exhausted in fish exposed to endosulfan to meet energy demand generated by this chemical stressor.