This study aimed to assess the impact of the cage fish farming on the water quality in two selected bays of the Bukavu basin, Lake Kivu; from February to December 2021. Physicochemical parameters including pH, Temperature, EC, TDS, Salinity, DO, Transparency were sampled in situ using a COMBO HI 98129 multi-parameter probe, PCE-PHD1 probe and a Black & White Secchi disk; water at different depths was collected with the aid of a Van-Dorn Sampler; nutrients namely PO43−, NH4+, NO2−, SiO2, and Chl_a were analysed using the UV-VIS spectrophotometer. The results revealed that water pH, temperature, TDS, salinity and transparency significantly (p ≤ 0.05) varied between the selected sites. Water at the cage sites contained significantly (p ≤ 0.05) much higher concentrations of PO3 − 4, NH4+, NO2−, SiO2 and Chl_a than in control site. In overall, these results suggest that cage fish farming changed water quality in the selected bays. Therefore, the study recommends that measures should be taken to regulate cage fish farming and related activities and deforestation around Bukavu basin to avoid advert conditions.

This work consisted in physically characterizing the floating cages used for farming Tilapia Nile in four bays of the sub-basin of Bukavu on Lake Kivu. The measurement of several parameters such as the depth of the water column and the distance of the cage taken by D-173 Bricodis decameter. The result shows that there are 218 cages of which 156 are exploited and 62 non-exploited. 76 cages are installed at 50 m and 58 cages are located at 6–49 m of the coast. The fact that the water of Lake Kivu is essentially pelagic pushes the fish farmers to place the cages on the littoral. Local cages are more abundant than those offered by FPI/IITA. 54% of the Oreochromis niloticus fry came from the D.R. Congo and 46% from Rwanda. Anthropogenic activities on a catchment scale cause benthic modification and reduce site characteristics. The diverse origin of fry should be discouraged to avoid new exotic species. Environmental impact studies of this culture on the biology and physicochemical parameters in the bays would help to address the environmental challenges of this culture in the Lake Kivu ecosystem.

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