Title : Diets of Mormyridae (Teleostei: Osteoglossiformes) in two rivers of Congo Basin (Boumba and Kadei) in Eastern Cameroon
Abstract:
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 Mormyridae, 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. The collection of different fish samples took place monthly from December 2018 to May 2019 on the landing stages of Boumba and Kadei rivers independently of the fishing gear (dormant gillnets, cast nets, hooks and creels) used by the fishermen. The Captured fish were identified using specific keys, then were labeled, photographed, measured (total and standard lengths), weighed and dissected in order to remove their stomachs and intestine which were preserved in tubes containing alcohol at 70%. These stomachs and intestine were then emptied separately 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 22 specimens of Mormyridae, divided into seven genera and 10 species were collected at Boumba compared to a total of 87 specimens divided into 11 genera and 24 species at Kadei. The qualitative analysis of stomach and intestine contents reveals that, independently of the seasons, the diet of Mormyridae of Boumba and Kadei oscillates around three food categories: macroinvertebrates, macrophytes, and other various particles; however the most represented food item in the diet of Mormyridae are macroinvertebrates, which still identifiable until the intestine level.
The Mormyridae are highly prized by the local population due to their taste and their fairly large body mass, thus depending on their strong preference for animal food origin, the Mormyridae have good aquaculture potential. This is for example the case of C. tamadua which has a good ability to exploit the different invertebrates present in its living environment; it can easily adapt to feeding by Diptera larvae in pond. It is also the case of M. anguilloides which due to its fish-eating predatory nature, could be tested in aquaculture to regulate the populations of very fertile and invasive species (Oreochromis nilitucus etc.) Furthermore, the success of these species in ponds must also take into account the physicochemical parameters of the water suitable for the proper development of each of them.
However, the forest of the Congo Basin is home to numerous insects (macroinvertebrates) which are important source of food for the ichthyofauna of his different rivers. Consequently, deforestation would negatively impact certain taxa of fish such as the Mormyridae which depend on them and would inevitably lead to their loss
