Caractérisation De La Pêche Au Lac Kivu

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

Ecological status of a West African lagoon complex under anthropogenic pressure, Toho-Todougba complex, Benin

Management and preservation of aquatic environments are essential for their productivity and the maintenance of aquatic life. This study aims to characterize the trophic state of Toho-Todougba lagoon complex which has been subject for several years, to an intense fish production in cages. For this purpose, physico-chemical parameters were measured from June 2019 to May 2020 as well as chlorophyll-α, phosphorus and nitrogen. The trophic characterization indices were calculated basedo n Carlson (1977), Burns and Bryers (2000), Neverova-Dziopak and Kowalewski (2018), Primpas et al. (2010) and CCME-WQI (2001). It appears that the temperature (29°C), dissolved oxygen (3.19 mg.L-1 to 4.33 mg.L-1) and pH (6.66 to 7.31) are those characteristic of tropical lake environments. The production parameters revealed that the chlorophyll-α concentration varies from 0.19 to 37 mg.L-1 (stations and months combined). The concentration of phosphorus ranged from 0.02 to 0.42 mg.L-1 while nitrogen varied from 1.91 to 4.03 mg.L-1. Only nitrogen is not in critical proportion for the ecosystem. It should be noted that with the exception of the Carlson index, all other indices revealed that the ecosystem is in a state of advanced eutrophication with a tendency to hyper-trophication according to the eutrophication index of Primpas et al. (2010). Consequently, Toho-Todougba lagoon complex is eutrophic and requires adequate measures for its restoration despite its good health revealed by the physico-chemical parameters

Migración de pescadores artesanales en la pesquería de pequeños peces pelágicos en África occidental: tendencias actuales y desarrollo

This study sought to present the evolutions and new trends of migrant fishing targeting small pelagics in West Africa from fishing to consumption stage. The work involved the characterization of migrant fishers targeting small pelagics in West Africa (country of origin, fishing gear and target species), modalities of access to resources, estimation of their catches and finally the assessment of the impact in the host countries. This work was useful to analyse changes in terms of the actors involved, the volumes and values of catches, and forms of valorisation and marketing of products from the migrant sectors over the period 2008-2018. Overall, the quantities of pelagic fish caught by migrant fishermen were increasing. The production of small pelagic by migrant fisheries has almost doubled over a decade, from an estimated of 180,000 t over the period 2008-2012, to a current estimated production of almost 324,500 t. More than 50% of this production was sold on the market in fresh or frozen form. More than 75,000 t (22%) and 94,000 t (28%) were destined for artisanal and industrial processing, respectively. Migrant fisheries thus supply more to industrial processing than to artisanal processing. Indeed, migrant fisheries have contributed over the last ten years to the emergence of fishmeal factories in West Africa. However, despite their significant evolution in terms of catch volumes and values, migrant fisheries still operate outside of legislative frameworks and without being explicitly accounted for in national statistics. Moreover, conflicts are increasingly important given the current tensions and issues surrounding the exploitation of small pelagic fish in West Africa. This work recommends the development of a common management plan for migrant fishers in the countries of the Sub-Regional Fisheries Commission (SRFC) and the West Central Gulf of Guinea Fisheries Committees (WCGC).Este estudio buscó presentar las evoluciones y las nuevas tendencias de la pesca migratoria dirigida a los pequeños peces pelágicos en África occidental desde los caladeros de pesca hasta los centros de consumo. El trabajo consistió en caracterizar a los pescadores migrantes que se dirigen a estas pesquerías en África Occidental (país de origen, artes de pesca y especies objetivo), presentando las modalidades de acceso a los recursos, estimando sus capturas y evaluando el impacto en los países anfitriones. Este trabajo permitió analizar los cambios en cuanto a los actores involucrados, los volúmenes y valores de las capturas, así como las formas de valorización y comercialización de los productos de los sectores migrantes durante el período 2008-2018. En general, las cantidades de peces pelágicos capturados por los pescadores migrantes están aumentando. La producción de las pesquerías migratorias de estos pequeños peces pelágicos casi se ha duplicado en una década, desde un promedio de 180.000 t durante el período 2008-2012, a una producción promedio actual de casi 324.500 t. Más de 50% de esta producción se vende en el mercado en forma fresca o congelada. Más de 75.000 t (23%) y 94.000 t (28%) se destinaron al procesamiento artesanal e industrial, respectivamente. Así, las pesquerías migratorias suministran más al procesamiento industrial que al procesamiento artesanal. Consecuentemente, las pesquerías migratorias han contribuido en los últimos diez años al surgimiento de fábricas de harina de pescado en África Occidental. Además, su contribución a las economías locales es cada vez más importante. Sin embargo, a pesar de su importante evolución en términos de volúmenes y valores de captura, las pesquerías migratorias todavía operan fuera de los marcos legislativos y no son contabilizadas explícitamente en las estadísticas nacionales. Además, los conflictos son cada vez más profundos dadas las tensiones actuales y los problemas que rodean la explotación de pequeños peces pelágicos en África occidental. Este trabajo recomienda el desarrollo de un plan de gestión común para los pescadores migrantes en los países de la Comisión Subregional de Pesca (SRFC) y los Comités de Pesca del Golfo de Guinea Centro-Occidental (WCGC)

Growth of freshwater

In this paper, we assess the growth performance, survival rate and abiotic factors affecting Etheria elliptica (Mollusca: Bivalvia: Etheriidae), the African freshwater oyster, a species that is widespread in tropical Africa where it is widely harvested for food and as a commodity. We collected wild oysters from the Pendjari River (Benin) and grouped them into small (23.4 ± 5.2 mm) and large (55.8 ± 7.7 mm) size classes. They were reared in cages in the Pendjari River from January to December 2009. Shell height was measured on a monthly basis, and estimated growth parameters were assessed using the von Bertalanffy growth function. Overall, the growth parameter estimates for pooled size classes were K = 0.0718 month−1 and L∞ = 82.2 mm. We estimated the time to reach minimum commercial size T65mm (female sexual maturity size) to be 22 months (1.8 years). Small oysters exhibited a peak in growth rate (2.775 mm month−1) in May, whereas large-sized oysters grew fastest (1.707–2.781 mm month−1) in August–September during the rainy/flood season. Survival of small-sized oysters declined sharply from May (60%) to June (11%) at the onset of the rainy season, six months after the beginning of experiment, while large oysters had higher survival in June (79.2%), which decreased in December (26.4%). Among abiotic factors investigated, water transparency was negatively correlated with the growth increment of small-sized oysters (p < 0.05). E. elliptica is a suitable candidate for culture due to its large maximum size, reasonable growth rate, and wide geographic range

Geographical variation of the structure and population parameters of the freshwater prawn Macrobrachium macrobrachion (Herklots, 1851) in West African coastal hydrosystems: Insights from Benin

Abstract The freshwater prawn Macrobrachium macrobrachion (Herklots, 1851) is widely exploited in the Oueme Delta and the low Mono in Benin. The structure and population parameters of M. macrobrachion were evaluated to provide accurate scientific information for the better exploitation and rational management of freshwater prawn species in these areas. In Oueme Delta (1928 specimens) and low Mono (1045 specimens), 2973 specimens were sampled by artisanal and experimental fishing and analysed. The prawns were caught between January and December 2016. Total length and total weight were taken from each specimen. Global and monthly size–frequency distributions showed that recruitment in both populations takes place from August to October with a peak in September. The population parameters obtained by analysing frequency data with FiSAT II software (FAO‐ICLARM) showed an L∞ = 15.50 cm, K = 0.35 year−1, t0 = −0.56 year in Oueme Delta and L∞ = 15.30 cm, K = 0.45 year−1, t0 = −0.43 year in low Mono. The growth performance index (Φ′) was 1.93 and 2.02 for the Oueme Delta and low Mono populations, respectively. The exploitation rates (Emax and E0.5) suggest that more than half of the M. macrobrachion population was exploited in the two areas. Natural and fishing mortality rates showed that both populations of M. macrobrachion were vulnerable to natural and fishing death. The estimated first capture size (Lc) revealed that the majority of the two populations of M. macrobrachion were captured before they reached the size at first sexual maturity (L50), reflecting fishing pressure on small individuals and growth overfishing in both areas. These results showed that the used fishing gears and the fishing frequencies in both areas did not allow the majority of the prawn to grow and reproduce at least once before being caught

Diversity and seasonal variation of zooplankton of Lake Hlan, Republic of Bénin (West Africa)

Objective: This study is the first assessment of zooplankton community of the Lake Hlan. It aims to assess zooplankton diversity through hydrological season.Methods and Results: It was carried out from May to December 2012. Monthly  plankton harvesting were performed, using plankton net of 30-&gt;m mesh. Three  vertical samplings through the Lake body depth were done at each station and mixed to have a composite sample. Environmental parameters were also assessed at the same time. The zooplankton diversity founded was composed of 45 species (33 rotifers, 6 cladocera and 6 copepods). The community was highly diversified and characteristic of balanced ecosystem. The Shannon diversity index values were ranged between 4.4 bit.ind-1 and 5.1 bit.ind-1. The taxonomic composition and thespecies abundance are affected by the flood coming, when the upstream station is different from the two other at the biological level.Conclusion: The zooplankton community of Lake Hlan has low specific richness, but has very good diversity index across hydrological seasons. Its ecosystem is then lowly affected by anthropological factors. The Lake Hlan currently continues to be a reference ecosystem in ecological status evaluation in Benin republic, since itslocalization has low accessibility.Keywords: Biodiversity; Community structure; Hydrological season; Zooplankton Diversité et variation saisonnière du zooplancton du lac Hlan, République du BéninObjectif: Cette étude est la première évaluation de la communauté zooplanctonique du lac Hlan. Il vise à évaluer la diversité du zooplancton au travers des saisons hydrologiques.Méthodes et résultats: L’étude a été réalisée de Mai à Décembre 2012. Le plancton a été mensuellement échantillonné sur trois stations représentants le plan  horizontal du lac. Un filet à plancton conique de 30 &gt;m de vide de maille a été  utilisé. Un échantillonnage vertical sur toute la colonne du plan d’eau a été réalisé àchaque station. Les paramètres environnementaux ont également relevés. Un total de 45 espèces de zooplancton était identifié (33 rotifères, 6 cladocères et 6  copépodes). La communauté était très bien diversifiée et caractéristique  d'écosystème équilibré. La valeur de l'indice de Shannon a varié entre 4,4 bit.ind-1 et 5,1 bit.ind-1. La composition taxinomique et l'abondance des espèces ont été affectées par la venue de la crue, alors que la station en amont était différente des deux autres au niveau biologique.Conclusion: La communauté zooplanctonique du lac Hlan a une faible richesse  spécifique, mais a un bon indice de diversité à travers les saisons hydrologiques. L’écosystème est alors faiblement affecté par des facteurs anthropologiques. Le lac Hlan continue actuellement d'être un écosystème de référence dans l'évaluation de l'état écologique en république du Bénin, sa localisation étant faiblement accessible.Mots-clés: Biodiversité; Saison hydrologique; Structure d’assemblage; zooplancto