Fish oils contain polyunsaturated fatty acids that are considered essential for preventing several diseases, some of which have neurological effects that promote growth in children. The overall objective of this study is to extract and characterize the oils in the fresh muscles of Schilbe grenfelli Linné, 1758 fish caught in the Malebo Pool (Congo River) in the Democratic Republic of Congo in order to highlight the nutritional value of the oils present in the muscles of this fish. The oils were extracted using the Soxhlet method and then characterized by thin-layer chromatography. The results obtained show that the muscles of S. grenfelli fish contain essential oils rich in polyunsaturated fatty acids of the omega-3 and 6 group, which allow this fish to be classified as fatty based on the average yield (46.62±2.1%) of oil extracted from its muscles. Analysis of the samples using thin-layer chromatography shows frontal ratios slightly higher than that of synthetic omega tri (0.80 cm). The results obtained show that the fresh muscles of Schilbe grenfelli fish are likely to offer good quality oils that are medically and nutritionally important for the Congolese population. Consumption of this fish meat is likely to contribute to the fight against cardiovascular disease and malnutrition, given the quality of these oils.

The main objective of this study was to assess the level of mercury, cadmium and lead contamination in two species of smoked fish, Protopterus dolloi Boulanger, 1900 and Chanallabes sp, sold in the Baramoto market and widely consumed in the city of Kinshasa in the Democratic Republic of Congo. A total of 60 fish samples (30 for Protopterus dolloi and 30 for Chanallabes sp) were taken and measured using atomic absorption spectrophotometers and molecular absorption spectrophotometers. The results of the toxicological analyses revealed the presence of the three trace elements in the muscles and heads of these two species of fish in varying concentrations. The highest concentrations were found in the Protopterus dolloi species (Hg: 0.79±0.1 µg/L, Cd: 0.41±0.32 µg/L, Pb: 0.33±0.01 µg/L). However, the concentrations found in both species of fish were below the maximum limits of the standard recommended by the WHO (Hg ˂ 10 µg/L; Cd ˂ 0.5 µg/L; Pb ˂ 1 µg/L). Despite the low levels found in the muscles and heads of the fish considered in this study, regular consumption of the flesh of these fish represents a public health hazard for the population of Kinshasa, and exposes consumers to multiple risks. Further studies on the quality of smoked fish should be conducted to ensure food safety for consumers.

In the province of Haut Katanga, the quality of waterways is particularly threatened by mining activities that do not take into account the environmental protection criteria recently introduced through Congolese mining legislation. The objective of this study is to analyze the level of pollution in the water of rivers and Lake Tshangalele, which is rich in fish consumed by local populations in the upper part of the Lufira River basin, near the city of Likasi in the province of Haut Katanga in the Democratic Republic of Congo, in order to assess the level of risk and exposure faced by these aquatic ecosystems and their resources. The concentrations of ten heavy metals (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Se, and Zn) were measured in river and lake water using an inductively coupled plasma optical emission spectrometer (ICP-OES). Water pollution indices based on ETM concentrations were calculated using the weighted arithmetic method. The results obtained show that in terms of contamination levels, As (Kapulande ˃ Kapemba ˃ Lake Tshangalele), Cd (Kapemba ˃ Lufira 2), Co (Kapulande ˃ Panda 2 ˃ Lufira), Cr (Lufira ˃ Kapamba ˃ Kapulande), Cu (Kapulande ˃ Tshangalele), Mn (Kapulande ˃ Panda 2 ˃ Kapemba ˃ Lufira 2 ˃ Tshagalele), Ni (Lufira ˃ Buluo), Pb (Kapulande ˃ CLP ˃ Panda), Se (Kapulande ˃ Panda 3 ˃ Kapemba) and Zinc (Kapulande ˃ Tshangalele) show very high contamination levels with a very significant statistical difference (p < 0.05) compared to WHO standards for drinking water and good ecological quality. Based on the Pollution Load Index (PLI), it can be seen that the water in the Kapulande River (PLI = 31.9) is highly polluted compared to that of the Kapemba (PLI = 9.2), Lufira 2 (PLI = 5), Buluo, and Lufira 1 rivers, with PLI values of 4.7 respectively, followed by Panda 2 (PLI = 3.4) and Lake Tshangalele (PLI = 13.3), compared to the PLI of other rivers where pollution was considered to be low. Taking into account the ecological, social, and economic roles of the Lufira basin, which has been designated a Ramsar Site since 2017, and in view of the chemical and ecotoxicological risks to the aquatic ecosystems surveyed and their resources, as well as to the population exposed to them, appropriate measures must be taken to combat the degradation of these environments.