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Diseases are among the major constraints to sustainable aquaculture. Fish pathogens include bacteria responsible for devastating effects on the fish health and even that of consumers. In Cameroon, there is a dearth of quantitative data related to fish diseases and the economic impact. An epidemiological survey was carried out from April 22 to May 23, 2021 during a first epizootic of the enteric red plague in the fishes Oreochromis niloticus and Cyprinus carpio reared in ponds in the Monatélé Subdivision of the Centre Region of Cameroon. The objective was to assess clinical disorders and mortality rate, associated risk factors and economic losses in semi-intensive farms due to red plague in Cameroon. So, the standard epidemiological procedures were used to assess the mortality rates before and after antibiotic (Oxytetracyclin) treatment of the disease. Results showed that clinical signs recorded within three months of observing included lateral recumbency, breathing difficulties (dyspnea) and wide opening of mouths of affected fish. The overall mortality rate of 7.74% (294 dead fishes out of 3800) was recorded. The mortality rate was significantly higher (p < 0.001) in polyculture pond (11.33%) compared to monoculture pond (4.70%). Cyprinus carpio was significantly more affected than Oreochromis niloticus. The mortality rate was higher (p < 0.01) in younger fishes than older ones and was sex independent. The therapy was more effective in monoculture pond than in polyculture pond and in Oreochromis niloticus compared to Cyprinus carpio. Females were more sensitive to antibiotic treatment than males. The direct financial loss was $420.50. This study revealed that the main risk factors of the red plague disease were farming practice, species, age and size of fish. Rigorous epidemiological surveillance of fish diseases was suggested for improved productivity of fish farms in Cameroon. Vol. 9, No. 3, December 2022: 323-335

In order to contribute to the increase of table fish production in the world in general and particularly in Cameroon through an optimal valorization of local by-products, the zootechnical performance of Clarias gariepinus fry was evaluated in concrete tanks according to the replacement levels of soya bean meal by water hyacinth flour (Eichhornia crassipes). For this purpose, a trial was conducted at the Logbaba Intensive Aquaculture Pilot Unit (LN: 4°02’ and 4°34’; LE: 9°41’ and 9°18’). A total of 240 Clarias gariepinus fry of initial mean weight 5 ± 0.22 g were divided into 12 batches of 20 fry each into 0.5 m3 baits in concrete tanks in a completely randomized device. These fries were fed for 56 days. The feed rations consisted of 4 iso-protein feeds with 47% protein. Either T0+ (positive proof) an imported food (Coppens), T0- (Negative proof) local food without soya bean meal and two other experimental foods whose soya bean meal has been replaced at 5% (T5) and 10% (T10) by Eichhornia crassipes flour. The results obtained showed that the highest survival rate (98.33% ± 2.88%) was recorded with the imported feed T0+ and lower (93.33% ± 2.76%) with the food containing 5% water hyacinth powder. The final mean weight and daily weight gain were significantly (P < 0.05) higher (26.08 ± 1.25 g and 1.49 ± 0.08 g/d respectively) with the T0+ diet and lower with the T1 local food (11, 92 ± 0, 90; 48 ± 0,06 g/d respectively). The average daily gain was comparable between the T5 and T10 diets (0.67 ± 0.14 g/d; 0.93 ± 0.12 g/d respectively). The specific growth rate (P < 0.05) and consumption index (P < 0.05) were significantly higher (2.87 % ± 0.08% g/d and 0.34 ± 0.04 respectively) compared to treatments containing 5% (T5) and 10% (T10) of water hyacinth powder (1.83 ± 0.24 g/d; 2.24 ± 0.17% g/d) and 1.08 ± 0.31; 0.66 ± 0.14) respectively. Thus, water hyacinth flour can be used to replace the soya bean meal as a protein source in the diet of Clarias gariepinus fry for optimal growth.

Loranthaceae are epiphytic hemiparasitic plants causing a lot of damage to cultivated or spontaneous woody species, but these parasitic plants are also used to treat a wide spectrum of diseases traditionally. It is with a view to searching for new sources of bioactive compounds that the present study was conducted with the aim of exploring the endophytic mycoflora of the haustoria of Phragmanthera capitata. The isolation of the endophytic fungi of P. capitata was done on a PDA (Potato Dextrose Agar) medium. The identification was on the basis of macroscopic and microscopic observations using identification keys. The mass culture of the isolated fungi was made on a solid medium based on rice and the extraction with ethyl acetate. 20 endophytic fungi belonging to 7 genera and 2 unidentified species were isolated from P. capitata: Aspergillus, Trichoderma, Penicillium, Cladosporium, Aureobasidium, Mucor and Fusarium. Flavonoids, tannins, anthocyanins and coumarins were detected in all extracts of these endophytic fungi. The endophytic fungi associated with this plant would also be a potential source of bioactive compounds and the exploration of medicinal plants, and habitats of endophytes would be an advantageous path for the discovery of new species of endophytes and new bioactive secondary metabolites.

This study aimed to provide relevant knowledge about the dynamics of the hydrological parameters in the river-estuary continuum of the Wouri-Nkam river estuary for a sustainable management program. The hydrological parameters were recorded in eleven stations spanned out on the basis of population density and human activities. Water quality parameters (Temperature, salinity, dissolved oxygen, pH, Total dissolved solutes, Redox potential and conductivity) were collected in subsurface water using a multiple parameter. Surface currents and morphometric (depth and width) parameters were recorded using a drifter, sonar depth and GPS. The field measurements took placed between 18/05/2019 to 08/09/2020 and were divided into six (06) cruises. The data were later subjected to an analysis of variance (ANOVA) and Principle Component Analysis using XLSTAT 2017 (2.7 version) software. Results obtained revealed that, the water quality parameters were spatially more stable notsignficant at (df = 9, p 0.05) with a relatively low temperature (25.5°C - 27°C) during the wet period. The limit of the frontal zone extended to S5 (Bonalokan, 8.25 km from S1) during the snapshot of the dry period, spring phase and flood tide conditions. Inversely, during wet period, this extension reduced to S1 (Bridge) and relatively increases slightly to S3 (Bonangang) during the neap phase and ebb tides of this season. This result revealed a change in the axial gradient of about eight (08) and four (04) kilometers during the seasonal and tidal scales (lunar and diurnal periods) respectively. These changes were also accompanied by changes in the water quality signatures, that may affect the fishery distribution and compositions. However, futures studies to buttress the results of this investigation should focus on longer time series sampling methods and model developments.

The recently constructed Besseke’s flood drain is always filled with water due to individual or combined effect of the tide, urbanization drainage, underground plumes and precipitations runoffs. This study focused on the analysis of small scales dynamics inferred from short term tidal measurements to mitigate the daily flooding in the Besseke’s flood drain. The methodology used is based on field measurements observation. The sampling of water level was conducted during two (02) different tidal regimes in May 2019. The volume of brackish water moving in and out of the Besseke’s flood drain was calculated using the formula of O’Brien. The results showed that Spring conditions had greater amplitudes than Neap tide conditions. During Spring tides, the tidal prism that passed in the midsection of the Besseke’s flood drain (S4) was 3.5 × 101 m3. This means that only a negligible amount of the incoming brackish water reaches the Besseke’s flood drain, amplifies and causes the daily flooding. The unexpected stronger amplitudes and dynamics observed in S4 could be due to its sub estuary nature. Furthermore, the percentage composition of water in this section, showed that the fraction of brackish water changes from 85.7% during Spring tide to 77.8% in the Neap tide conditions. The overall spatial evolution revealed that, the trend in tidal prism (during Spring conditions) was (S0) > (S2) > (S1) > (S3) > (S4) with corresponding values of 2.1 × 104, 1.3 ×104, 1.0 × 104, 2.5 × 102 and 3.5 × 101 m3 respectively. Finally, Tidal prism and Cross-sectional area showed a perfect correlation (r2 = 0.96). The best fitted Cross-sectional area-Tidal prism relationship was obtained in S3 (Market) during Spring tide condition.

The Bay of Bonny, located along the Cameroon coastline, is home to diverse ecosystems. It is under significant pressure from large human activity, but remains very little studied, like much of the Gulf of Guinea. In order to understand its long-term shoreline variations and the role the wave regime plays in the evolution of the coastline, a study was conducted on the basis of optical image archives from Landsat 5 ∕ 7 ∕ 8 and Sentinel-2A/2B satellite missions acquired between October 1986 and May 2020, coupled with daily ERA-Interim wave re-analysis data covering the period from January 1986 to August 2019. Overall, the results show that the evolution of the coast is highly variable in space and time, as indicated by different levels of erosion (30.55 %), and accretion (27.7 %) on the decadal-scale, with the most significant variations occurring in estuarine areas. Nevertheless, 41.75% of the Cameroon shoreline remains stable during the study period. Three main periods (1986–1994; 1995–2005; 2006–2020) during which the coast underwent significant changes a different location were identified, reaching a retreat rate of up to −10 m/year in the northern section during the first period 1986–1994. The annual trend of significant wave heights anomaly along the coast (−5.6 to −4.1 mm/year) with wave height maxima estimated at 1.46 ± 0.65 m, where observed during the summer months (July–August). Monthly shoreline changes are inversely correlated with wave climate in some segments. Eigenvalue orthogonal decomposition analyses (Mode 1, Empirical Orthogonal Function) show that 76.3% of the observed variability would be due to the relatively strong local influence of erosion and accretion. This local influence can be related to wave regime at shorter timescale (monthly to seasonal) and the sediment variability from the source inland to the coast at longer timescale (seasonal to decadal). These observations explain a complex pattern of shoreline changes with an almost continuous retreat shoreline during the period 1986–2013 and a reversal in trend towards accretion during the period 2013–2020. EOF mode 2 explains 23.7% of variability, which can be potentially associated with the synergetic relationship between tidal currents and wave-induced longshore current, tidal currents and possibly pockets of human activity. This is attributed to an overall decrease in the supply of sediment via the coastal transport system that prevails in the Gulf of Guinea.

National audience; Fish culture can be an important food source as well as a way to increase employment and income of rural populations in Africa. In most countries, however, it is not considered to be a full share activity, and, in most cases, the fish culture systems implemented by rural production do not reach their economic viability. In order to promote sustainable fish culture as well as flexible and innovative production systems, it is important that the socio-technical and organizational innovations be codesigned. To study this issue a research program in Western Cameroon developed a project with two fish farming groups organized into Common Initiative Groups. Two theoretical approaches are used: the sociology of translation and sciences - which considers that innovations are socially built and that the role of the research is not only to produce new techniques but to translate the different issues, so as to enrol the actors around a common question; and both action-research and intervention-research developed by sociologists and management researchers. We presented the results of the diagnosis to three groups of farmers gathered by local leaders. During these meetings, we were able to identify the actors concerned, the requests, and the stakes. We will present here the first two phases of what we describe as a Partnership-based Action-Research. The first phase consists of exploring and formalizing how the different actors will commit themselves to work together and to reach an agreement. In the second phase the co-conception of the fish culture innovation is implemented. The main result is the groups (CIG) which were set up. They not only enable the experimental protocols but also build a language, a representation and a common way of working, as a necessary passage point (NPP), essential to any socio-technical and organisational innovation. Another important result is how the experimental protocols helped formalize the ethical framework necessary to work in partnership. In conclusion, it is important for us to learn from the methodological work accomplished - in particular to reflect on the competencies the researchers ought to develop to work with farmers. Researchers act as mediators, facilitators, translators and spokesmen of a hybrid actorresearcher group. The “technical” work is carried out according to a co-defined action plan, generally to solve a problem. The production of action-based scientific knowledge becomes a true task of the research group.