New catfish species for the development of fish culture in Africa.

Besides Clarias gariepinus introduced in aquaculture in the early 1970s, other African catfishes (Siluroidei) have been studied for their potential in aquaculture for about 15 years. These belong to the genus Chrysichthys (Claroteidae) and Heterobranchus (Clariidae) investigated in Ivory Coast, Nigeria and Benin, and mainly in the context of a brackish water aquaculture in lagoon or estuaries. It is in the Ivory Coast in the early eighties that reproduction in captivity of Chrysichthys nigrodigitatus, and then of Heterobranchus longifilis, was obtained for the first time as a result of research carried out within the Ivorian Oceanologic Research Center (CRO) in Abidjan. Nowadays, the breeding cycles of both species has been achieved and extension towards the production sector has been initiated. Production of C. nigrodigitatus is mainly monospecific? intensive or semi-intensive, in lagoon enclosures (Ivory Coast) or in brackish-water ponds (Nigeria). In Ivory Coast, its culture became significant since 1990 with an annual production of 200-300 tons. The biology of H. longifilis is similar to that of C. gariepinus, but the former presents the advantage of a faster growth. The commercial production of this species is now beginning in Ivory Coast. intensive rearing of H. longifilis in lagoon enclosures appears as an appropriate option, but promising results have also been obtained in freshwater ponds. Based on the Ivorian experience, H. longifilis aquaculture development projects are currently carried out in Niger and Cameroon. The recent literature reports also culture trials with H. bidorsalis in Nigeria. Intergeneric hybrids between H. longifilis or H. bidorsalis and C. gariepinus have been produced in South Africa, Ivory Coast and Nigeria. However, the real advantage of using the hybrids instead of the parental species for aquaculture remains to be demonstrated. The results obtained so far show that the culture of C. nigrodigitatus and H. longifilis constitutes now a possibility of diversification, and even an alternative to the use of C. gariepinus, for African aquaculture. A synthesis of existing data on the biology and culture of these species is presented.