This study was focused on the description of fishing gears on Lake Kivu. Data were collected from March 2012 to February 2014 in Goma, Bukavu, and Kibuye fishing stations. The study findings indicate that gill nets, beach seine, lift net, trammel net composed of two panels of small and larger meshes (mosquito net attached to lift net parts), mosquito net, longline, single line, pots, and cast net were identified as fishing gears used on Lake Kivu. Longline was more selective (2 species) in terms of species selection. The lift net presented the best catch (19.4 ± 11 kg), while the trammel net showed the highest CPUE (7.9 ± 6.1 kg/h). The large dimensions of gears and the long netting duration characterized gillnets (1023.2 ± 620.1 m2 ) and longline (10.3 ± 4.6 hours) respectively. Cast-nets (20mm) showed the largest mesh size, while mosquito nets (1 ± 0.3 mm) were the smallest.

In Nile tilapia Oreochromis niloticus, phenotypic males and females with different sexual genotypes (XX, XY, YY) have particular behavioral and physiological traits. Compared to natural XX females and XY males, XY and YY females and XX males expressed higher level of aggressiveness that could be related to higher levels of 17β-estradiol and 11-ketotestosterone, respectively. Our results suggest that the presence of a Y chromosome increases aggressiveness in females. However, since the same relationship between aggressiveness and the Y chromosome is not observed in males, we can hypothesize that the differences in aggressiveness are not directly dependent on the genotype but on the sex reversal procedures applied on young fry during their sexual differentiation to produce these breeders. These hormonal treatments could have permanently modified the development of the brain and consequently influenced the behavior of adults independently of their genotype. In both hypotheses (genotype or sex reversal influence), the causes of behavioral modifications have to be searched in an early modification of the brain sexual differentiation.

No abstract

Haplochromis pharyngalis and Haplochromis petronius, two endemic cichlids from the Lake Edward system (Uganda, Democratic Republic of the Congo), are very similar in general morphology but have been reported to differ in pharyngeal jaw morphology and distribution. This study analysed 51 morphometrics and various qualitative characteristics of 48 specimens from different localities. The morphological traits of both species strongly overlap, and differences in the pharyngeal jaw morphology correspond to a geographic morphocline. We conclude that all specimens belong to one valid species, H. pharyngalis, and consider H. petronius to be a synonym.

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.