Identification and characterization of some fish breeding areas in Lake Kivu, Bukavu Basin

Abstract

The majority of Lake Kivu’s fish species inhabit the littoral zone, which is regrettably a target of overfishing. In the present study, four bays (Lwacigoli, Nyakadaka, Cigezi and Kwamuzungu) were selected in the northern part of the Bukavu basin, between Birava isthmus, the Gombo and Ibinja islands, in order to evaluate their potential as fish breeding areas. The physico-chemical parameters of the water were measured by using the Hanna HI 9829 multiparameter probe and the Secchi disk was used for water Transparency. Experimental fishing sessions were carried from September to November 2022 using a beach seine net of 350 m long, 6 m wide and 5 mm in mesh size, between 6 pm and 5 am. Sample processing and data analysis continued in the laboratory. These sites were characterized on the basis of ecological variables including the nature of the bottom, the vegetation on the littoral zone, the flora, and the anthropogenic activities. Thus, in addition to the physico-chemistry of the water being conducive to fish breeding activity, the bottom of Lwacigoli bay is characterised by a rocky substrate, that of Nyakadaka by a rocky, gravelly and muddy substrate, those of Cigezi and Kwamuzungu are more dominated by mud, clay, some rocks and detritus, with some vegetation cover on the coastal part. More fingerlings were found at Kwamuzungu (611), followed by Nyakadaka and relatively lesser at Cigezi and Lwacigoli (400-465). In the four bays explored, the predominant size classes for Limnothrissa miodon and Lamprichthys tanganicanus are those between 50 - 80 mm and between 40 - 60 mm for Haplochromis spp. Therefore, sexual maturity stages I and II of the fishes represent 63.5% of specimens and those in stages III, IV and V represent 36.5%. According to the increasing fishing pressure in Lake Kivu, linked with the excessive use of fishing-gear and practices that threaten the survival of the fish species, identification and description of spawning areas should be continued in order to better protect its ichthyofauna. Fishing regulations are also essential for the sustainable management of the Lake Kivu.