Révision systématique du genre Microthrissa Boulenger, 1902 des eaux douces africaines (Pisces, Clupeidae)

Le genre #Microthrissa a été révisé à partir de caractères morphologiques et ostéologiques de 461 exemplaires, y compris les spécimens types de toutes les espèces nominales. Le genre #Poecilothrissa est synonyme du genre #Microthrissa, au sein duquel il a été reconnu comme un sous-genre distinct. Cinq espèces valides ont été retenues. Deux espèces nominales ont été mises en synonymie. Enfin, #Microthrissa normanae a été rapporté au genre #Pellonula, et mis en synonymie avec #P. leonensis. (Résumé d'auteur

Activite Photosynthetique Du Phytoplancton Dans Le Barrage Hydroelectrique D\'ayame I (Côte D\'ivoire)

L\'activité photosynthétique du phytoplancton du barrage hydroélectrique d\'Ayamé I a été suivie au cours de six campagnes de mesures sur deux stations (Bakro, Ayamé) afin d\'évaluer son évolution spatio-temporelle et d\'identifier les variables qui la contrôlent. Les mesures de la productivité photosynthétique du phytoplancton ont été effectuées dans la couche euphotique (0-3 m). Les résultats montrent une variabilité temporelle de l\'activité photosynthétique dans les deux stations du lac. Les productivités phytoplanctoniques sont maximales à Bakro et à Ayamé en début de saison des pluies (respectivement 0,35 et 0,81 mg.C.m-2.j-1) et minimales en saison sèche (respectivement 0,18 et 0,43 mg.C.m-2.j-1). Les productivités phytoplanctoniques ont été positivement corrélées aux nitrates (r > 0,8 ; p 0,6 ; p < 0,05), ce qui souligne l\'importance des nutriments dans la productivité du phytoplancton.Photosynthetic activity of phytoplankton in the hydroelectric reservoir of Ayamé I was studied during 6 data acquisition campaigns at two stations (Bakro, Ayamé). The main objective was to monitor spatial and temporal changes in phytoplankton productivity and identifiy potential variables responsible for the changes. Phytoplankton photosynthetic activity was determined in the euphotic layers (0-3m) of the lake. Results show changes in photosynthetic activity with time in the two stations. Maximum concentrations of carbon assimilation were observed during the begining of the rainy season (0.35 and 0.81 mg.C.m-2.j-1 ) and minimum activity during the dry season (0.18 and 0.43 mg.C.m-2.j-1) at Bakro and Ayamé, respectively. The phytoplankton productivities correlated with nitrate (r > 0.8 ; p 0.6 ; p < 0.05) which underscores the importance of nutrients in phytoplankton productivity. Keywords: Activité photosynthétique, phytoplancton, barrage hydroélectrique, Côte d'Ivoire.Agronomie Africaine Vol. 19 (1) 2007: pp. 63-7

Macroinvertebrates communities of a coastal lagoon in southern Benin, West Africa

The macroinvertebrate, assemblage investigated were collected in eight seasonal samplings from July 2007 through June 2009. A total of 4,179 individual macroinvertebrates were gathered, comprising 182 taxa belonging to 25 orders and 114 families. The most predominant groups were Molluscs and Crustacean which make up 71.11% of the taxonomic richness observed. Annelids and Insects were the second most predominant. This restricted biodiversity is based on a limited number of species such as Tympanotonus fuscatus radula, Pachymelania aurita, Neritina glabrata, Corbula sp., Clibanarius spp., Grandidierella africana, Nereis sp. and Chironomus sp.. Site typology based on environmental parameters reveals five assemblages in which no significant difference exists. The community is controlled by a salinity gradient but is also probably affected by hydrologic factors and human economic activities.Keywords: Macroinvertebrates, communities, distribution, abundance, diversity, lagoo

Production de Oreochromis niloticus avec des aliments à base de sousproduits agricoles

Des alevins de Oreochromis niloticus (0,7 ± 0,06 g) ont été nourris dans seize étangs avec quatre aliments dont trois aliments tests (A1, A2 et A3) formulés uniquement à base de sous-produits agricoles. La composition de ces aliments tests est la suivante : A1 (tourteaux de soja, de coton, sons de maïs et de mil) ; A2 (tourteaux de soja, de coton, sons de maïs et de riz) et A3 (tourteaux de soja, de coton, sons de mil et de riz). Le quatrième (At), contenant de la farine de poisson, est un produit industriel et a servi de témoin. Deux densités de mise en charge (10 et 13 ind./m2 ) ont été appliquées pour chaque traitement alimentaire. Chaque densité d\'élevage a été répliquée une fois. Après 120 jours d\'élevage, tous les poissons ont atteint au moins 25 g (poids seuil de sexage). Les meilleures performances zootechniques sont obtenues avec l\'aliment A1, suivi de l\'aliment A2. Les poids moyens finaux observés aux densités 10 et 13 ind./m2 sont de 54,69 ± 7,76 et 46,77 ± 5,87 g (A1), 46,32 ± 6,71 et 41,23 ± 5,32 g (A2) ; 40,90 ± 7,64 et 37,31 ± 5,73 g (A3) puis de 41,72 ± 6,57 et 37,45 ± 5,84 g (At). Les quotients nutritifs respectifs correspondants sont de 1,13 ; 1,30 ; 1,87 et 1,72 (10 ind. /m2), puis de 1,40 ; 1,63 ; 1,74 et 1,80 (13 ind. /m2). Les aliments A1 et A2 permettent un niveau de production supérieur à celui du témoin. Comparés au témoin, des taux de réduction respectifs de 30 % et d\'environ 14 à 37% des coûts des aliments tests et de production des fingerling ont été obtenus..Alevins of Oreochromis niloticus (0.7 ± 0,06 g) were fed with three test diets (A1, A2 and A3) formulated using agricultural by-products and a commercial one containing fish meal (control diet = At). The composition of these test diets is: A1 (oilcakes of soy, of cotton, bran of corn and of millet); A2 (oilcakes of soy, of cotton, bran of corn and of rice) and A3 (oilcakes of soy, of cotton, bran of millet and of rice). Two stocking densities (10 and 13 ind. / m2) were applied for each experimental diet. At the end of 120 days of rearing, all experimental fish reached more than 25g (doorstep weight for manual sexing). Diets A1 and A2 displayed the better growth and food utilization performances. Final mean weight of fish at stocking densities 10 and 13 ind. / m2 respectively, ranged from 54.69 ± 7.76 to 46.77 ± 5.87 g (A1), 46.32 ± 6.71 to 41.23 ± 5.32 g (A2); 40.90 ± 7.64 to 37.31 ± 5.73 g (A3) and 41.72 ± 6.57 to 37.45 ± 5.84 g (At). The corresponding food conversion rates were 1.13; 1.30; 1.87 and 1.72 (10 ind. /m2), then 1.40; 1.63; 1.74 and 1.80 (13 ind. /m2). Test diets A1 and A2 produced more yield than the control one. Relatively to the assessment economic aspect, test diets reduce the diet cost and fingerlings production cost, respectively of rate about 30 % and 14 to 37 %, compared to that of the control diet. Keywords: Oreochromis niloticus, feeding, agricultural by-products, production, Côte d\'Ivoire.Sciences & Nature Vol. 5 (1) 2008: pp. 89-9

Structure Demographique D’un Labeo Africain, Labeo coubie Rüppel, 1832 (Pisces: Cyprinidae), Dans Le Lac De Barrage De Taabo (Bassin Du Bandama, Côte D’ivoire)

La structure d&#233;mographique de Labeo coubie a &#233;t&#233; &#233;tudi&#233;e en vue d&#8217;une gestion rationnelle du stock de poissons dans le lac Taabo. Des &#233;chantillonnages ont &#233;t&#233; effectu&#233;s en juillet, octobre et d&#233;cembre 2006, puis en mars et juin 2007. Les analyses ont port&#233; sur la dynamique spatio-temporelle du sex-ratio, de la structure des tailles, des relations longueur-poids et du coefficient de condition. Le sex-ratio global a &#233;t&#233; en faveur des m&#226;les (1,35 : 1) mais, n&#8217;a pas &#233;t&#233; significativement diff&#233;rent de la valeur d&#8217;&#233;quilibre. La taille moyenne des sp&#233;cimens collect&#233;s en amont du lac (206,18 &#177; 63,55 mm LS) a &#233;t&#233; significativement plus importante (p&lt;0,05) que celle des individus obtenus en aval (179,94 &#177; 56,66 mm LS). De m&#234;me, la taille moyenne enregistr&#233;e pendant les mois de crue (285,28 &#177; 34,69 mm LS) a &#233;t&#233; largement sup&#233;rieure &#224; celle des mois de d&#233;crue (190,14 &#177; 61,13 mm LS), avec une croissance isom&#233;trique &#224; l&#8217;&#233;chelle du lac (b = 2,97). Le coefficient moyen de condition obtenu dans la partie amont (3,59 &#177; 0,39) a &#233;t&#233; plus important (p&lt;0,05) que celui observ&#233; dans la partie aval (2,29 &#177; 0,31).The demographic characteristics of Labeo coubie from lake Taabo was assessed, in order to establish the basis for a rational management of the stock of this fish. Samplings were done at different periods: in July, October and December 2006, and again in March and June 2007. Analyses were concerned with the spatiotemporal dynamics of sex-ratio, size and the structure, as well as length-weight relationships and condition factor of the fish. Results show that overall sex-ratio was in favor of males (1.35 : 1) but, it did not differ significantly from the equilibrium point. The mean size of the fish collected upper stream (206.18 &#177; 63.55 mm SL) was significantly higher than that from downstream (179.94 &#177; 56.66 mm SL) of the lake. Moreover, the mean size recorded during the inflow months (285.28 &#177; 34.69 mm SL) was significantly higher than that recorded during the months of low waters (190.14 &#177; 61.13 mm SL). Fish growth appeared isometric at the scale of the lake (b = 2.97). The average condition factor obtained upstream (3.59 &#177; 0.39), was higher (p&lt;0.05) than that from downstream (2.29 &#177; 0.31).Keywords: Labeo coubie, demographic structure, lake Taabo, C&#244;te d&#8217;Ivoir

Effects of treated agro-industrial effluents on physical and chemical characteristics of the receiving stream Wawa in south-eastern Côte d'Ivoire

In this research we examined the impact of effluents from an agro-industrial plant on River Wawa. Water quality was assessed by monitoring monthly during a year. Eleven parameters were retained: temperature, conductivity, dissolved oxygen, turbidity, pH, chemical oxygen demand, nitrates, nitrites, ammonia, orthophosphates and organic pollution index. Except temperature and ammonia which didn&#8217;t differ among sites, chemical oxygen demand and organic pollution index were significantly (p &lt; 0.00001) higher at reference sites upstream the discharge point of effluents than sites located downstream. On the contrary, values of the other variables were significantly (p &lt; 0.05) higher at sites receiving the effluents. These results certainly support the hypothesis that the rejected effluents have a negative influence on the water quality downstream the discharge point. However, results suggest a decrease of the parameters content at the second site more distant from the discharge point, maybe due to the self-purifier capacity of the receiving stream. Ecological impacts not being all immediate, this wastewater could have a negative impact on the species living in the receiving stream in long term, either by bio-accumulation or by bio-magnification. It would be interesting to undertake complementary studies of bio-accumulation or bio-magnification on fauna.Keywords: Water pollution, industrial wastewater, wastewater discharge, water quality, pollution preventio

Déterminisme des Coassements des Anoures de la ferme piscicole du Parc National du Banco (Côte d\'Ivoire)

Les facteurs déterminant les activités de coassements des anoures de la ferme piscicole du Parc National du Banco ont été étudiés. Une prospection acoustique basée sur l\'enregistrement standardisé des chants des grenouilles, a permis d\'inventorier, pendant quatre cycles nycthéméraux, 14 espèces réparties en 8 genres et 4 familles. La famille des Hyperoliidae avec 7 espèces est la plus diversifiée. Parmi les espèces recensées, une seule (Phrynobatrachus accraensis), a son pic d\'activité à 6 heures. Son rythme d\'activité de chants est influencé par la température de l\'air et l\'intensité lumineuse. Les Bufonidae, Hyperoliidae et Ranidae constituent une communauté aux moeurs nocturnes dont les pics de coassements se situent entre 21 heures et 24 heures. L\'humidité relative de l\'air conditionne leurs comportements. Par ailleurs, la majorité des espèces a une forte activité de coassement en saison de pluies. Nos résultats qui sont parmi les premiers concernant les communautés d\'Anoures du Parc National du Banco, permettront d\'élaborer une stratégie pour leur échantillonnage et leur protection.The factors determining the calling activities of anuran community in the Banco National Park fish farm have been studied. The standard acoustic encounter survey based on listening calling males permitted to inventory 14 species, 8 genera and 4 families, during four circadian cycles. The family of Hyperoliidae is diversified the most (7 species). Only one diurnal species (Phrynobatrachus accraensis) was observed, with a peak of activity at 6 hours. Its daily calling activity is influenced by the temperature of the air and the light intensity. The Bufonidae, Hyperoliidae and Ranidae families are nocturnal community. Their peaks of activity varied between 21 hours and 24 hours. The relative humidity of the air determined the behavior of these families. In addition, most of the species have a strong calling activity during the rainy season. Our results should permit to elaborate a standard method for amphibians survey in the Park. Keywords: Calling activity, Temporal variation, Amphibian, Banco National Park, West Africa.Sciences & Nature Vol. 5 (1) 2008: pp. 71-7

Effect of diets containing cocoa bean shell and coconut oil cake on the growth of Oreochromis niloticus (LINNE, 1758) in pond

A 180-day feeding trial was conducted at fish farm ‘’Blondey‘’ (Côte d’Ivoire) with Nile tilapia, Oreochromis niloticus (LINNE, 1758) to evaluate the effect of cocoa bean shell and coconut oil cake on its growth. Juvenile tilapia (mean weight of 33.16 ± 2.2 g) was fed with a commercial diet (Ivograin) and two formulated diets twice daily (09.00 h and 15.00 h). The used stocking density was 2 fish/m2. Formulated diets were designated as D1 (cocoa bean shell, corn bran, soybean oil cake and cottonseeds oil cake) and D2 (coconut oil cake, corn bran, soybean oil cake and cottonseeds oil cake). All the tested diets contain around 28% protein and each diet was randomly assigned to triplicate ponds to evaluate growth, feed utilization, body composition and cost benefit. Fish fed diet with D1 gave the highest daily weight gain (1.94 ± 0.30 g/day) and the best feed conversion ratio (2.01). The lowest daily weight gain (1.53 ± 0.32 g/day) and the highest feed conversion ratio (2.47) were recorded for diet D2. Tilapia fed with diet D2 and commercial one (Ivograin) displayed similar growth and feed efficiencies patterns. Lipid accumulation was higher in fish reared with diets D1 and D2 compared to reference diet (Ivograin). Diets D1 and D2 reduce feed costs per unit of weight gain by 34.44 and 19.47%, respectively, compared to commercial diet.Keywords: Oreochromis niloticus, feeding, cocoa bean shell, coconut oil cake, growth, Côte d’Ivoire

Spatial distribution and structure of benthic macroinvertebrates in an artificial reservoir: Taabo Lake (Côte d’Ivoire)

Taabo Lake is facing eutrophication process characterized by a permanent and continuous colonization of its water body by invasive aquatic macrophytes since 1990. Until now, there is limited knowledge of its ecological state. The purpose of this study is to examine the spatial distribution and structure of benthic macroinvertebrates in Taabo Lake. Benthic macroinvertebrates were sampled from July 2006 to June 2007 using an Ekman grab. Four sampling stations were selected on the area of the reservoir along a longitudinal gradient: Sahoua and Ahondo in the upper part; Taabo Cité and Taabo Village in the lower part. Overall, 29 taxa belonging to 17 families, 7 orders and 3 classes were recorded. A total of 4028 individuals were collected. Insecta (53.21%) were most represented, followed by Gasteropoda (36.15%) and Oligochaeta (10.64%). A better knowledge of the ecological traits of species and the identification of indicator taxa will permit to develop a Benthic Quality Index able to monitor the lakes and man-made reservoirs of Côte d’Ivoire.Keywords: Benthic macroinvertebrates, diversity, structure, lake, Côte d’Ivoire

FISH DIVERSITY ALONG THE LONGITUDINAL GRADIENT IN A MAN–MADE LAKE OF WEST AFRICA, TAABO HYDROELECTRIC RESERVOIR, IVORY COAST

Fish assemblage patterns in Taabo Reservoir, a hydroelectric lake of Ivory Coast, were studied and related to the longitudinal gradient (river–dam gradient) composed of riverine, transitional, and lacustrine zones. Data were collected at 5 stations and each one was sampled during 5 surveys. Fish community structure was analysed using alpha and beta diversity indices. In total, 53 fish species were obtained in the whole ecosystem. Total species richness recorded at each ecological zone was 42, 43 and 45 species respectively in the riverine, transitional and lacustrine zones. Alpha diversity did not differed significantly along the longitudinal gradient but reached the highest value (33 species) in the transitional zone and the lowest (18 species) occurred in both the riverine and lacustrine zones. Temporal variability of Alpha diversity according to the hydrological regime of the lake differed with the zone. Beta diversity showed that fish assemblages similarity was higher between the transitional and the riverine zones (βw = 0.43) and lower between the riverine and the lacustrine zones (βw = 0.79)