Comparative study of algal community in African sharptooth catfish (Clarias gariepinus, Burchell 1822) and Nile tilapia (Oreochromis niloticus, Linnaeus 1758) farming ponds

In subsistence and small‐scale fish farming, algae are an important food source for fish. Therefore, understanding their distribution and diversity in fish ponds is essential. This study aimed at characterising algae species in African sharptooth catfish (Clarias gariepinus) and Nile tilapia (Oreochromis niloticus) farming ponds and their contribution to these species’ diet. Water samples were collected from different points of the farming pond: in rearing pond, evacuation canal of each species and decantation pond. Samples were also collected from fish stomachs and intestines. Afterwards, they were analysed with a photonic microscope for species identification using standard identification keys. The highest species richness (S) and Shannon index (H) were observed in fish rearing ponds (S = 73, H = 2.98–3.84) and the lowest in fish stomachs and intestines (S = 41, H = 1.88‐3.07). Jaccard's similarity index, ranging from 0.17 to 0.55, shows a high specific diversity of alga in the different sampling points. During the experimental period, water physicochemical parameters were within the optimum growth for algae and fish species. Since some algae species recorded are consumed by both fish species, this study recommends to select and cultivate them for fish food production. In the fish farming station, algae specific richness varies according to the water collection point (rearing pond, evacuation canal and decantation pond). Algae contribute differentially to fish diets: biomass is mostly used by Nile Tilapia (herbivorous) than African catfish (omnivorous). The diversity and important presence of families such as Scenedesmaceae, Desmidiaceae, Euglenidae and Zygnemataceae in fish guts are related to their presence in the collection areas.