Morphometric characteristics of four important fish species from the Rwandan side of Lake Kivu

Inland fisheries are important socio-economic resources for rural communities in Africa. In Rwanda, about two million people directly depend on capture fisheries from Lake Kivu. Sustainable fisheries management requires monitoring of population dynamics that help devise effective intervention strategies. However, the relevant data such as length-length and length-weight relationships do not exist for most of the key species in Lake Kivu. The present study generated morphometric and body weight data for Limnothrissa miodon (n=82), Lamprichthys tanganicanus (n=55), Haplochromis vittatus (n=51) and Haplochromis graueri (n=34) from Lake Kivu. Length-weight relationships (W=aLb) were highly significant for all species (p < 0.0001), high adjusted R2 = 78 to 98% of the variance in weight explained by total length. Negative allometric length-weight relationships were found with regression slope (b) values of 2.7 for Limnothrissa miodon, 2.8 for H. graueri, and 2.8 for L. tanganicanus, and positive (b=3.4) for Haplochromis vittatus. Length-length relationships were highly significant for all species (p ≤ 0.0001), except for the relationship between total and caudal length for L. miodon, and total and caudal peduncle length for L. tanganicanus, both not significant at p > 0.05. The highest R2 was for the relationships between total and standard length for H. vittatus, and total and fork length for L. tanganicanus. No description of length-length relationships exists for these species in literature or in FishBase database. The data generated in the current study will be used to assess changes in fish populations over time.

Impact Socio-économique de l’Introduction du Filet Maillant sur les Conditions de Vie des Communautés Riveraines du lac Kivu : Cas des Pêcheurs et Femmes Marchandes de Limnothrissa Miodon dans la Ville de Bukavu

La pêche au filet maillant joue un rôle considérable dans l’amélioration des conditions de vie des communautés riveraines du lac Kivu. L’introduction de cette technique de pêche au filet maillant est un mécanisme d'emploi et de survie pour au moins dix mille (10.000) personnes dont les pêcheurs, les femmes marchandes et leurs dépendants. Le présent article a pour objectif d'analyser l’impact de l'introduction du filet maillant sur les conditions de vie des communautés riveraines du lac Kivu. La technique documentaire a permis de consulter les études antérieures réalisées sur l’impact de l’introduction du filet maillant sur le lac Kivu au sein des communautés locales. Ainsi, le caractère empirique de l’étude a exigé l’usage de la technique de l’entretien pour collecter les informations d’ordre qualitatif. Le questionnaire administré à 89 enquêtés par la technique indirecte a permis de collecter les informations d’ordre quantitatif que nous avons analysées à l’aide du logiciel statistique pour les sciences sociales (SPSS). Les données qualitatives ont été codées pour la quantification du sens que les enquêtés donnent à l’importance du filet maillant. Ce sont les approches qualitative et quantitative qui ont été utilisées pour analyser l’impact socio-économique de l’introduction du filet maillant sur les conditions de vie des communautés riveraines du lac Kivu. En effet, les résultats obtenus montrent que la première retombée de l’introduction du filet maillant est la création d'emplois, l'augmentation de la production, l’amélioration de la sécurité alimentaire telle qu’affirmé respectivement par 91,01%, 82,2% et 74,15%. L'amélioration des conditions de vie et le renforcement de la cohésion sociale ont été affirmés, respectivement par 93,25% et 77,52% d’enquêtés. Ces affirmations ont été appuyées par le rapport final du projet pêche qui a également aidé les pêcheurs à se constituer en comités de pêcheurs. Du côté des femmes, les marchandes s'organisent en tontine où elles échangent entre elles et cherchent des solutions à leurs différends. Et en dernier lieu, c'est la création de plusieurs marchés de Limnothrissa Miodon qui a été évoquée par 79,77% et qui s'explique par la multiplication des unités de pêche qui sont à la recherche de lieux proches des populations afin d'écouler leurs produits. Toutefois, l’étude a révélé que l’insécurité affirmée par 60,67% d’enquêtés et le travail des enfants affirmé par 92,13% d’enquêtés sont les conséquences néfastes de l’introduction du filet maillant dans le lac Kivu. Gillnet fishing plays a significant role in improving the living conditions of communities bordering Kivu Lake. The introduction of this gillnet fishing technique is a mechanism of employment and survival for at least ten thousand (10,000) people including fishermen, women traders and their dependents. The purpose of this paper is to analyze the impact of the introduction of the gillnet on the living conditions of communities bordering Kivu Lake. The documentary technique made it possible to consult previous studies carried out on the impact of the introduction of the gillnet on Kivu Lake on local communities. Thus, the empirical nature of the study required the use of the interview technique to collect qualitative data. The questionnaire administered to 89 respondents by the indirect technique collected the quantitative information that we analyzed using statistical software for the social sciences (SPSS). Qualitative data was coded to quantify the meaning respondents gave to the importance of the gillnet. Qualitative and quantitative approaches were used to analyze the socio-economic impact of the introduction of the gillnet on the living conditions of communities bordering Kivu Lake. Indeed, the results obtained show that the first impact of the introduction of the gillnet is the creation of jobs, the increase in production, the improvement of food security as affirmed respectively by 91.01%, 82.2% and 74.15%. The improvement of living conditions and the strengthening of social cohesion were affirmed, respectively by 93.25% and 77.52% of respondents. These statements were supported by the final report of the fishing project which also helped fishermen to form fishermen's committees. On the women's side, the merchants organize themselves in a tontine where they exchange ideas with one another and seek solutions to their conflicts. And lastly, it is the creation of several Limnothrissa Miodon markets which was mentioned by 79.77% and which is explained by the multiplication of fishing units which are looking for places close to the populations in order to sell their products. However, the study revealed that insecurity affirmed by 60.67% of respondents and child labor affirmed by 92.13% of respondents are the harmful consequences of the introduction of the gillnet in Kivu Lake.

Reproductive activities of two zooplanktivorous clupeid fish in relation to the seasonal abundance of copepod prey in the northern end of Lake Tanganyika

Reproductive activities of two commercially exploited clupeid fishes (Stolothrissa tanganicae and Limnothrissa miodon) in the northern end of Lake Tanganyika (Bujumbura sub-basin) were investigated during two different years (2004-2005 and 2007-2008). We hypothesized that the timing of largest reproductive investment in these pelagic species coincides with the onset of the rainy season and the highest abundance of copepod prey. For S. tanganicae, the gonadosomatic index (GSI) was significantly higher prior to the onset of the rainy season, and this was observed in both years. For L. miodon, however, this pattern was overall weaker and only statistically significant in 2004-2005. In both species, spawning activities did not seem to be adjusted to provide optimal feeding conditions for the larvae. Instead, investment in reproduction seemed to be related to the availability of copepods in the preceding months. We conclude that the timing of reproductive activities in these clupeids is species-specific, and might be subject to strong year-to-year variation.