As part of a larger research program on the diversity and role of the forest in maintaining the local ichthyofauna of the Congo Basin, a study focused on the diets of Alestidae, a family of many fishes represented in the Boumba and Kadei rivers in eastern Cameroon. Indeed know the diet of savage specie fish can help to make their conservation by aquaculture processes.
106 specimens of Alestidae were captured using dormant gillnets, cast nets, hooks and creels; they were identified using specific determination keys then were labeled, photographed, measured (total and standard lengths), weighed and dissected in order to remove their stomachs which were preserved in tubes containing alcohol at 70%. These stomachs were then emptied and the contents rinsed in Petri dishes, then filtered through a sieve and the retained fractions were sorted, separated, identified, counted and weighed in order to evaluate the rate of food from the riparian forests
A total of 106 stomachs were collected from six species of Alestidae (Alestes macrophthalmus, Brycinus longipinnis, Brycinus macrolepidotus, Brycinus imberi, Hydrocynus vittatus and the Bryconaethiops spp. complex made up of several species grouped into one due to the low abundance of each). Of 63 individuals sampled in Boumba, 89.7% had full stomachs compared to 7.7% empty stomachs while out of 43 individuals sampled in Kadei, 76.1% had full stomachs compared to 14.9% empty stomachs. The emptiness coefficients were 8.33 in A. macrophthalmus in Boumba and 50 in Kadei
Four food categories have been identified in these fish: macroinvertebrates, macrophytes, prey fish and other miscellaneous particles. The frequency of occurrence (Fc) and the preponderance index (Ip), calculated, indicate that Lepidoptera are the very frequent and main prey in the diet of B. longipinnis at Boumba, while at Kadei it is rather Orthoptera and prey fish, respectively in A. macrophthalmus and H. vittatus. Furthermore, it has been observed that the riverside forests provide these prey (leaves, fruits and insects) found in the stomachs of certain species. Thus they mainly contribute to maintaining the balance
The study of the stomach contents of Alestidae in Boumba and Kadei reveals that this family of fish is made up of herbivores, carnivores and omnivores. It is obvious that the forests of the Congo Basin constitute an essential source of food for the ichthyofauna of the rivers they shelter. Consequently, deforestation would negatively impact certain taxa of fish such as the Alestidae which depend on them and would inevitably lead to their loss. The improving knowledge on the feeding ecology of these Alestidae fish can help to take best measure of conservation on those of the IUNC red list.