The fish diversity of the Adamawa lakes is among the most undocumented in Northern Cameroon. Faced with this lack of knowledge, an inventory of ichthyofauna and habitats characterization was conducted in nine lakes. Seven lakes (Assom, Gegouba, Massote, Mbalang, Ngaoundaba, Piou and Tizong) are located in the Sanaga Basin and two (Bini and Dang) are located in the Lake Chad Basin. In order to assess the composition and variation in fish assemblage, eight sampling campaigns were carried out seasonally between 2017 and 2018; they revealed 26 species of fish distributed in 6 orders, 9 families and 16 genera. Communities in Lakes Assom (13 species) and Bini (9 species) were the most diverse. Omnivorous (42.3%) and spawners in open water or on substrates of sand, gravel, rock or plants (69.2%) were the most represented. Nonmetric multidimensional scaling, analysis of similarities (ANOSIM), and similarity percentage analysis (SIMPER) revealed that fish species composition differed significantly among lakes. Canonical correspondence analysis (CCA) identified temperature, pH, TDS, and conductivity as variables explaining the most variation in fish species. The presence of four endemic species in the Sanaga Basin in lakes Assom, Gegouba, Massote and Piou, shows that these lakes stand out as hotspots for conservation due to the uniqueness of their ichthyofauna.

The presence of numerous crater lakes in the Cameroon Volcanic Line offers an exceptional opportunity to study the influence of habitat on the evolution of cichlids. We examined the characteristics of three lake populations of Hemichromis camerounensis, all located on the Adamawa plateau in northern Cameroon. In total, 31 morphometric characters were examined of 277 fish specimens caught in two lakes with an outlet (Dang and Bini) and in a lake without an outlet (Tizong). Length-weight relationships and condition factors were estimated for each population. The physico-chemical parameters of the water were measured. Lake Tizong differed significantly from the other two lakes by its higher values of pH, conductivity and TDS. The length/depth and height/width ratios of different parts of the body and the total number of gill rakers on the first gill arch were significantly reduced in the population of Tizong, which was also characterized by small size individuals. The length-weight relationship was positively allometric for the populations of Bini and Dang but negatively allometric for the population of Lake Tizong. The condition factor of the fish was very low in Tizong. The morphological differences observed between the three populations should be taken into account in any systematic study that includes H. camerounensis populations from the studied zone.

L’anthropisation intensive du bassin de la Sanaga impose une accélération des recherches sur la biodiversité et la conservation de ses ressources aquatiques. Dans ce contexte, l’ichtyofaune d’un segment du fleuve Djerem a été étudiée en vue d’identifier les déterminants environnementaux de sa distribution et de sa conservation. Trois stations situées respectivement en amont de la retenue d’eau de Mbakaou, au milieu de ce réservoir et en aval dans le Parc National du Mbam et Djérem (PNMD) ont été retenues pour ce travail. A la suite de l’échantillonnage par pêche d’avril à octobre 2015, l’étude taxonomique des poissons et de leurs habitats a révélé la présence de 44 espèces appartenant à 28 genres et à 13 familles. L’ichtyofaune du PNMD s’est montrée la plus diversifiée (33 espèces), dépourvue d’espèces invasives, avec une prédominance d’invertivores (50,3%) et de pondeurs sur substrats divers (60,9%). Celle du réservoir de Mbakaou a été la moins diversifiée (12 espèces), avec quatre espèces introduites devenues invasives et une prédominance d’herbivores / détritivores (65,9%). Onze espèces endémiques ont suscité un intérêt pour d’éventuels programmes de conservation des poissons dans le PNMD à cause de leurs habitats restreints et sensibles tandis que 13 autres, toujours endémiques et connues du bassin de la Sanaga, n’ont pas été retrouvées dans la zone étudiée.Mots clés : Sanaga supérieur, poissons, espèces endémiques, espèces invasives, habitats, gestion.   English Title: Diversity of the Djerem River ichthyofauna: impact of Mbakaou regulation dam and challenges for fish conservation in the Mbam and Djerem National Park (Cameroun)The intensive anthropization of the Sanaga river basin requires to accelerate research on biodiversity and conservation of its aquatic resources. In this context, the ichthyofauna of a part of the Djerem River has been studied with the aim to know its diversity and identify environmental factors that determine its distribution and conservation. Three stations were sampled from April to October 2015, they were located respectively upstream of the Mbakaou water reservoir, in the Mbakaou reservoir and downstream in the Mbam et Djerem National Park (PNMD). The Fish inventory followed by a taxonomic study and that of their habitats revealed the presence of 44 species belonging to 28 genera and 13 families. The ichthyofauna of PNMD with highest specific richness (33 species) was also devoid of invasive species, with a predominance of invertivorous (50,3%) and substratum egg-scatters (60,9%). The ichtyofauna of the reservoir with lowest specific richness (12 species) contained also four alien species, with a predominance of herbivores / detritivores (65,9%). 11 endemic species were concerned by the possible fish conservation programs in the PNMD due to their restricted and sensitive habitats while 13 other endemic species known from the Sanaga River basin were wanted in the study area.Keywords: Upper Sanaga, fish, endemic species, invasive species, habitats, management