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This study aims to improve the understanding of algal community's dynamics in response to different environmental factors in two dam ponds (Mokolo and Mopa) in the city of Bertoua (East-Cameroon). Physicochemical and biological analyzes were carried out monthly by direct sampling at the surface and using Van Dorn bottle at 1 m depth. The organisms were collected using transparent glass vials of about 500 ml and fixed with 2.5 ml of a lugol solution, then analyzed using the Utermôhl method. Physicochemical analyzes show low transparency (<75 cm) of the ponds despite their shallow depth (≤150 cm), high levels of dissolved oxygen (>60%), BOD 5 (>30 mg/L) and chlorophyll "a" (>30 µg/L). These data made it possible to categorize the Mokolo and Mopa ponds as hypereutrophic with nitrogen as the limiting factor for eutrophication. Biological data show quite diversified ponds with 138 species identified in Mokolo Pond and strongly dominated by Diatoms with 2951 ind. representing 46% of the total abundance. In Mopa Pond, 147 species were identified, mainly represented by Chlorophyceae with 3629 ind. representing 52% of the total abundance. Azpeitia africana (Mokolo) and Eresmophaera gigas (Mopa) were the most represented taxa during the study. This study will have deduced that the structure and dynamics of algal communities are under the control of different factors or processes that interact simultaneously, namely ascending factors or bottom-up corresponding to nutrient resources and sunlight and descending factors or top-down that are exerted by grazing and active physiological substances produced by other algae that are known to influence phytoplankton.

Dans de nombreux pays en voie de développement, 80% des captures de poissons sont fumés ou séchés afin de limiter les dégâts. Les insectes constituent un problème récurrent du poisson fumé stocké causant des grandes pertes économiques. Le but de l’étude réalisée dans quatre campements (Djeela, Nemeyong I, Malene I, Ndengué) de la boucle nord de la Réserve de Biosphère du Dja (RBD), était de déterminer la diversité des insectes ravageurs des poissons fumés stockés et leurs dégâts. Dans chaque campement, 25 outils de stockage des poissons fumés ont été inspectés, puis caractérisés et les espèces de poissons fumés identifiées. Lors de cette prospection, des collections de 8 espèces de poissons fumés ont été ramenées et mises en observation au laboratoire. Les insectes émergés des collections ont été dénombrés et identifiés et les dégâts évalués. Il ressort de cette étude que 31 espèces ichtyologiques appartenant à 12 familles sont fumées. Les Cichlidae (35,4%), les Clariidae (20,1%) et les Cyprinidae (10,3%) sont les familles les plus représentées. Oreochromis niloticus, Clarias gariepinus, Clariallabes manyangae sont les espèces les plus fumées. Les claies sont les outils de stockage les plus utilisés (46,66%). Excepté C. gariepinus infesté à 80%, les autres collections sont toutes infestées. Dermestes maculatus, Necrobia rufipes (Coléoptères) et Calliphora sp (Diptères) sont les insectes ravageurs des poissons fumés stockés. D. maculatus est le Coléoptère le plus préjudiciable aux stocks de poissons fumés avec 786 individus (99,49%) et 173,8 g de farine de forage. Les Insectes sont les principaux ravageurs des poissons fumés dans la RBD. C. gariepinus, C. manyangae et M. moorii sont les poissons fumés les plus attaquées. Les claies sont les outils de stockage les plus répandues.Mots clés : poissons fumés, structure de stockage, insectes ravageurs, dégâts, Réserve de Biosphère du Dja. English Title: Insect pests of smoked fishes during storage and damages done in the north loop of the Dja Biosphere Reserve (East-Cameroon) In many developing countries, 80% of fish catches are smoked or dried to limit losses. Insects are a recurring problem of stored smoked fishes causing great economic losses. The purpose of the study carried out in four camps (Djeela, Nemeyong I, Malene I, Ndengué) of the north loop of the Dja Biosphere Reserve (DBR), was to determine the diversity of insect pests of stored smoked fishes and their damages. In each camp, 25 smoked fish storage tools were inspected, then characterized, and the smoked fish species identified. During this survey, collections of 8 species of smoked fishes were brought back and put under observation in the laboratory. The insects emerged from the collections were enumerated and identified and the damage assessed. This study shows that 31 fish species belonging to 12 families are smoked. Cichlids (35.4%), Clariidae (20.1%) and Cyprinidae (10.3%) are the most common families. Oreochromis niloticus, Clarias gariepinus, Clariallabes manyangae are the most smoked species. Racks are the most used storage tools (46.66%). With the exception of C. gariepinus infested at 80%, the other collections are all infested. Dermestes maculatus, Necrobia rufipes (Coleopterans) andCalliphora sp (Dipterans) are the insect pests of the stored smocked fishes. D. maculatus is the more prejudicial Coleopteran to the storage of smoked fishes with 786 individuals (99.49%) and 173.8 g of drilling flour. Insects are the main pests of smocked fishes in the DBR. C. gariepinus, C. manyangae and M. moorii are the most attacked species. Racks are the most common storage tools.Keywords: Smoked fish, storage structure, insect pests, damages, Dja Biosphere Reserve.

The impact of land use changes on watercourses is poorly documented in Cameroon. Therefore, this study examines the effects of agriculture and urbanization on water quality, the structure and functional organization of macroinvertebrates of streams in the coastal zone of Cameroon. Nine sampling stations including three per catchment area with different land occupations (agricultural, urban and forest) were selected. Benthic macroinvertebrates were sampled monthly from February to July 2018 and the physicochemical variables were measured simultaneously. The urban and agricultural streams showed highly polluted waters with high nutrient and suspended matter content, whereas the forest stream waters are moderately polluted. In addition, the hierarchical ascending classification indicated a proximity in water quality between the agricultural and forest streams for which the main physicochemical variables did not vary significantly. With regards to macroinvertebrates, the forest watercourse is characterized by the proliferation of pollution-sensitive taxa, high diversity indices and complex trophic structuring, indicating its good ecological status. In contrast the urban watercourse, heavily polluted is characterized by low diversity indices reflecting a simplification of the structure of stands dominated by the pollution-tolerant collector-gatherer stands. The majority of biological indices and functional feeding groups were not significantly different between the agricultural and forest streams, sug