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

Elaboration of a biotic index of pollution using macroinvertebrates for the monitoring of Lake Nokoué in Benin

A study on the relationships between the physicochemical parameters and of the macroinvertebrates of the Lake Nokoué was carried out for the purpose of developing a biotic index of pollution. A total of 96 stations were prospected twice during the flooding and the dry seasons from September 2004 to February 2006. At each station, seven physicochemical parameters were measured and macroinvertebrates were collected. Canonical analyses of correspondence were used to show the relations between the parameters of the environment and the macroinvertebrates. A self-organizing map (SOM) of Kohonen allows the categorization of the studied stations into four groups according to different degrees of pollution. Rough scores were allotted to each taxon according to its abundance in the various groups of stations determined by the SOM for each campaign. A synthesis of the data obtained from the four field surveys allows the assignment of a score to each taxon according to its abundance in the different groups of stations. A biotic index was developed and used for the evaluation of the level of pollution of the stations studied. It then emerged that the borders of the lake present a «poor quality» of water; however, during the dry season there is slight improvement.© 2015 International Formulae Group. All rights reserved.Keywords: Biotic index, pollution, invertebrates, lagoons, Benin, West Afric

Analyse Et Illustration De La Valeur Indicatrice Des Espèces Macrobenthiques Du Delta De l’Ouémé Au Bénin

In this work, it was matter of determining the species characteristics of the delta of the Oueme through the illustration of their indicative value. Sampling was carried out in eight heterogeneous stations covering the periods of flood and low water. The various indices including that of biserial correlation IndVal (Indicator Value Index) and the cover sites of groups were used as the basis of analysis. The results showed that the selected significant indicative species are highly correlated and have a preference for stations full of organic and mineralized matter. Also, taxa have a marked preference for the flood season (21 taxa) than low water (5 taxa). Most characteristic taxa highlighted by this procedure should be useful to assess changes in quality of the plants studied. Most taxa characteristics highlighted by this procedure should be useful to assess changes in quality of the plants studied

Effet de la Densité de Mise en Charge sur la Croissance de la Palourde Amiantis umbonella Élevée sur les Sites de Douda et Obock (Djibouti)

La palourde Amiantis umbonella présente dans les zones intertidales sablonneuses/vaseuses en Asie constitue une source de protéines bon marché de ces régions. Malgré ces potentialités économiques, elle demeure peu étudiée à Djibouti où elle est fait l’objet d’une production. Cette étude a pour but d’étudier l’effet de la densité d’élevage sur la croissance de la palourde Amiantis umbonella. Les expériences ont été conduites sur les sites de Douda avec des densités de 50 individu/m2 et de 100 individu/m2 et Obock avec 50 individu/m2. La taille et le poids des spécimens ont été mesurés toutes les deux semaines, pendant 6 mois de mars à aout 2018. La température moyenne était de 36°C.  Les paramètres de croissance des palourdes ont été estimés avec l’équation de Von Bertalanffy. A la densité de 50 individus/m2, les constantes de croissance K étaient de 0,13 cm/mois et 0,15 cm/mois respectivement à Douda et Obock tandis qu’elle était de 0,11cm/mois pour une densité de 100 individus/m2à Douda. Ainsi, il ressort que la taille commerciale (40 mm) a été obtenue plutôt après 8 semaines à Douda à la densité 50 individus/m2 et Obock contre 14 semaines d’élevage à la densité de 100 individus/m2à Douda. Ces résultats révèlent une amélioration de la croissance de la palourde Amiantis umbonella à la  densité de 50 individus/m2 dans les  conditions d’élevage à Douda et Obock.    The clam Amiantis umbonella found in sandy/muddy intertidal zones in Asia constitutes a cheap source of protein in these regions. Despite its economic potential, it remains little studied in Djibouti where it is produced. This study aims to investigate the effect of stocking density on the growth of the clam Amiantis umbonella. The experiments were conducted at the sites of Douda with densities of 50 individuals/m2 and 100 individuals/m2 and Obock with 50 individuals/m2. The size and weight of the specimens were measured every two weeks, during 6 months from March to August 2018. The average temperature was 36°C. Clam growth parameters were estimated with the Von Bertalanffy equation. At a density of 50 individuals/m2, the growth constants K were 0.13 cm/month and 0.15 cm/month respectively in Douda and Obock while it was 0.11cm/month for a density of 100 individuals/m2 in Douda. Thus, it appears that the commercial size (40 mm) was obtained after 8 weeks in Douda at a density of 50 individuals/m2 and Obock against 14 weeks of rearing at a density of 100 individuals/m2 in Douda. These results reveal an improvement of the growth of the clam Amiantis umbonella at the density of 50 individuals/m2 under the rearing conditions in Douda and Obock.&nbsp

Effet de la Densité de Mise en Charge sur la Croissance de la Palourde Amiantis umbonella Élevée sur les Sites de Douda et Obock (Djibouti)

La palourde Amiantis umbonella présente dans les zones intertidales sablonneuses/vaseuses en Asie constitue une source de protéines bon marché de ces régions. Malgré ces potentialités économiques, elle demeure peu étudiée à Djibouti où elle est fait l’objet d’une production. Cette étude a pour but d’étudier l’effet de la densité d’élevage sur la croissance de la palourde Amiantis umbonella. Les expériences ont été conduites sur les sites de Douda avec des densités de 50 individu/m2 et de 100 individu/m2 et Obock avec 50 individu/m2. La taille et le poids des spécimens ont été mesurés toutes les deux semaines, pendant 6 mois de mars à aout 2018. La température moyenne était de 36°C.  Les paramètres de croissance des palourdes ont été estimés avec l’équation de Von Bertalanffy. A la densité de 50 individus/m2, les constantes de croissance K étaient de 0,13 cm/mois et 0,15 cm/mois respectivement à Douda et Obock tandis qu’elle était de 0,11cm/mois pour une densité de 100 individus/m2à Douda. Ainsi, il ressort que la taille commerciale (40 mm) a été obtenue plutôt après 8 semaines à Douda à la densité 50 individus/m2 et Obock contre 14 semaines d’élevage à la densité de 100 individus/m2à Douda. Ces résultats révèlent une amélioration de la croissance de la palourde Amiantis umbonella à la  densité de 50 individus/m2 dans les  conditions d’élevage à Douda et Obock.    The clam Amiantis umbonella found in sandy/muddy intertidal zones in Asia constitutes a cheap source of protein in these regions. Despite its economic potential, it remains little studied in Djibouti where it is produced. This study aims to investigate the effect of stocking density on the growth of the clam Amiantis umbonella. The experiments were conducted at the sites of Douda with densities of 50 individuals/m2 and 100 individuals/m2 and Obock with 50 individuals/m2. The size and weight of the specimens were measured every two weeks, during 6 months from March to August 2018. The average temperature was 36°C. Clam growth parameters were estimated with the Von Bertalanffy equation. At a density of 50 individuals/m2, the growth constants K were 0.13 cm/month and 0.15 cm/month respectively in Douda and Obock while it was 0.11cm/month for a density of 100 individuals/m2 in Douda. Thus, it appears that the commercial size (40 mm) was obtained after 8 weeks in Douda at a density of 50 individuals/m2 and Obock against 14 weeks of rearing at a density of 100 individuals/m2 in Douda. These results reveal an improvement of the growth of the clam Amiantis umbonella at the density of 50 individuals/m2 under the rearing conditions in Douda and Obock.&nbsp

Exploitation Patterns of Anchovies (Engraulis encrasicolus) by Marine Artisanal Fisheries in Togo (West Africa)

Pelagic fish, including sardines and anchovies (Order Clupeiformes), are the most common species taken by artisanal marine fisheries along the Togolese coast. We investigated fisher involvement as well as fish captures over a period of 10 years, particularly of the European anchovy (Engraulis encrasicolus). Our results indicate that 60% of fishers operated from the Lomé fishing harbour, most fishers being Ghanaians working seasonally in Togo. 63.7% of all the fishers used canoes with outboards, a higher percentage compared to the previous decades. Seven fishing gear type were identified, with bottom gillnet and surface gillnet being the most commonly used. However, in the most important fishing camp in the country in terms of fish production (Lomé fishing harbour), all fishers used shark nets. Overall, fisheries catches did not change significantly across years, but anchovy fishing effort and catch per unit of effort (CPUE) declined over the study period, suggesting some depletion of the species stocks on the Togolese coast and a demotivation of fishers.

Effect of high temperatures on sex ratio and differential expression analysis (RNA-seq) of sex-determining genes in <i>Oreochromis niloticus</i> from different river basins in Benin

peer reviewedAbstract The high temperature sex reversal process leading to functional phenotypic masculinization during development has been widely described in Nile tilapia (Oreochromis niloticus) under laboratory or aquaculture conditions and in the wild. In this study, we selected five wild populations of O. niloticus from different river basins in Benin and produced twenty full-sib families of mixed-sex (XY and XX) by natural reproduction. Progenies were exposed to room temperature or high (36.5°C) temperatures between 10 and 30 days post-fertilization (dpf). In control groups, we observed sex ratios from 40 to 60% males as expected, except for 3 families from the Gobé region which showed a bias towards males. High temperature treatment significantly increased male rates in each family up to 88%. Transcriptome analysis was performed by RNA-sequencing (RNA-seq) on brains and gonads from control and treated batches of six families at 15 dpf and 40 dpf. Analysis of differentially expressed genes, differentially spliced genes, and correlations with sex reversal was performed. In 40 dpf gonads, genes involved in sex determination such as dmrt1, cyp11c1, amh, cyp19a1b, ara, and dax1 were upregulated. In 15 dpf brains, a negative correlation was found between the expression of cyp19a1b and the reversal rate, while at 40 dpf a negative correlation was found between the expression of foxl2, cyp11c1, and sf1 and positive correlation was found between dmrt1 expression and reversal rate. Ontology analysis of the genes affected by high temperatures revealed that male sex differentiation processes, primary male sexual characteristics, autophagy, and cilium organization were affected. Based on these results, we conclude that sex reversal by high temperature treatment leads to similar modifications of the transcriptomes in the gonads and brains in offspring of different natural populations of Nile tilapia, which thus may activate a common cascade of reactions inducing sex reversal in progenies

Growth, mortality and yield of Sarotherodon melanotheron melanotheron (Rüppell, 1852) in the Lake Nokoué and Porto-Novo Lagoon complex Benin, West Africa

The study evaluated some population parameters of Sarotherodon melanotheron melanotheron within a lagoon complex in southern Benin: Lake Nokoué and Porto-Novo Lagoon. Data on the total length, total weight, and sex were recorded monthly between January and December 2015 for 1,745 specimens captured by local fishermen. The asymptotic length L∞ was estimated at 24.68 cm. The growth rate K was 0.86. The total, natural, and fishing mortalities were estimated at 2.46, 1.71, and 0.75 y−1, respectively. The size at first sexual maturity was 8.9 and 9.2 cm, respectively, for males andfemales. The size at first capture was estimated at 9.2 cm, which indicates that fish spawn at least once before capture. The current exploitation rate of 0.31 remains below the maximum exploitation rate Emax which was 0.604 but was equal to the exploitation rate retaining 50% of the biomass of the stock (E0.5 = 0.324). This suggests that the stock of S. m. melanotheron is not overexploited in the complex. However, it is recommended that the actual rate of exploitation be kept as it is to ensure a sustainable management of these fish populations

Efficiency of fatty acid-enriched dipteran-based meal on husbandry, digestive activity and immunological responses of Nile tilapia Oreochromis niloticus juveniles

peer reviewedThis study aimed to compare the enrichment capacity of polyunsaturated fatty acids (PUFA) and the long chain polyunsaturated fatty acids (LC-PUFA) of two dipteran species, Hermetia illucens - black soldier fly (BSF) - and a blowfly, Chrysomya putoria (CP), and to test its influence on growth, digestive activities and immune responses of Nile tilapia. Two types of enriched insect larval meal were produced using larvae cultured either on vegetable substrates (VGS) to formulate two diets rich in linolenic acid (ALA) (BSF/VGD and CP/VGD), or on fish offal substrates (FOS), in order to produce two diets rich in ALA and eicosapentaenoic acid (EPA) (BSF/FOD) or in ALA + EPA and docosahexaenoic acid (DHA) (CP/FOD). These four insect-based diets containing only palm oil as a lipid source were compared to a control diet based on fish meal (FM) and fish oil (FO). After 60 days of feeding, ALA or DHA muscle content of fish fed BSF/VGD or CP/FOD diet was comparable to that of the FMFO diet, and all insect diets increased the EPA muscle levels, except for a reduction by the BSF/VGD one. The CP/FOD diet induced similar fish growth, feed efficiency and protein efficiency ratio compared to the control FMFO diet, while a decrease was observed in fish fed other insect diets. Only BSF/VGD led to a decrease in protein and lipid digestibility. CP or BSF larval meal significantly increased alkaline phosphatase activity regardless of fatty acid (FA) enrichment. The expression level of fads2, fads6 and elovl5 was significantly higher in fish fed the BSF/VGD diet compared to fish fed the FMFO diet. FA-enriched insect diets increased some immune variables such as lysozyme, peroxidase and ACH50 values of fish fed CP/FOD, CP/VGD or BSF/VGD diets. Moreover, the expression level of β-defensin-1 and mhcII genes were significantly higher in fish fed the BSF/FOD diet than the FMFO diet. Also, the expression of the pro-inflammatory gene il-1-β was significantly higher in fish fed FMFO diet than in those fed CP/FOD diet, but comparable to fish fed all other diets. No significant effects were observed for the other tested genes. The results showed a better efficiency in LC-PUFA enrichment of the CP larvae compared to BSF ones, resulting in a higher stimulation of the fish nutrient utilization processes and therefore, a higher growth capacity. Nonetheless, all dipteran larval meal stimulated the immune status whatever the insect species or dietary essential fatty acids

Total replacement of fish meal by enriched-fatty acid Hermetia illucens meal did not substantially affect growth parameters or innate immune status and improved whole body biochemical quality of Nile tilapia juveniles

The study was designed to evaluate the effects of total remplacement of fish meal (FM) and fish oil (FO) by vegetable oil and black soldier fly (BSF) larval meal enriched with fatty acids (FAs) in Nile tilapia juveniles. Fish were fed a FMFO control diet compared to a non-FA-enriched BSF diet (BSF/T0) and diets enriched in linolenic acid-ALA (BSF/T1) or in eicosapentanoic acid-EPA (BSF/T2). After 59 days, the BSF diets did not affect growth except for a decrease by the BSF/T1 diet. However, protein utilization and digestibility were reduced by all the BSF diets. FA-enriched diets did not improve the digestive enzyme activities or immune parameters, while lysozyme and ACH50 values were increased by the BSF/T0 diet. Levels of polyunsaturated FAs in the whole body of fish fed ALA or EPA-enriched BSF diets were comparable to those of FMFO controls. The results demonstrate that BSF meal can totally replace FM without substantially effect on growth or innate immune status. The decrease in fish carcass FA quality induced by the BSF meal can be prevented by a well defined protocol for PUFA enrichment. Nonetheless, investigation of the long-term effects of the BSF meal use during the ongrowing phase is still needed