The aim of this study was to evaluate the effects of cassava, yam and sweet potato peels on Black Soldier Fly Larvae (BSFL) production. Four different treatments were performed in triplicate in a completely random block consisting of soy bran (TSB), cassava peel (TCP), yam peel (TYP) and sweet potato peel (TPP). A density of 1 larva/g of substrate was used with a uniform ratio of 100 mg/larva/day. Larval growth duration was ten days, and growth monitoring was carried out every 2 days. The daily weight gain (DWG) ranged from 2.19 ± 0.09 g/day (TYP) to 4.53 ± 0.02 g/day (TSB). The production of these BSFL ranged from 43.90 ± 1.87 g/kg of substrate (TYP) to 90.56 ± 0.54 g/kg of substrate (TSB). The degradation rate ranged from 36.00 ± 2.30% (TYP) to 65.00 ± 2.88% (TSB), and the survival rate ranged from 77.66 ± 1.45% (TYP) to 99.00 ± 0.28% (TSB). According to the Z correlation test, there was a strong correlation between the organic matter content of the substrates and the DWG (99.1%). It was also observed that phosphorus content was strongly correlated with DWG (92.9%). Regarding the nutritional quality of the larvae, the protein content varied from 33.51 ± 0.94% (TYP) to 40.64 ± 032% (TSB), and the lipid content varied from 26.24 ± 0.35% (TYP) to 30.44 ± 0.18% (TSB). A significant difference (p < 0.05) between the different treatments depending on the parameters were noticed. This study revealed that cassava, yam and sweet potato peels can be used for BSFL production, but the best growth of BSFL was obtained with the cassava peel substrate that presented also the best degradation rate.

The purpose of this work was to investigate the physical and chemical dynamics of Lake Nokoué for its efficient management. For this purpose, two sampling campaigns per month from five stations (North, South, Central, East and West) were conducted for a period of one year (November 2020 to November 2021). Physic and chemical parameters (temperature, salinity, depth, water transparency, pH, dissolved oxygen and total dissolved solids) were measured and wet substrate samples were collected to study the granulometry. Data analysis revealed that Lake Nokoué is mainly affected by two regimes: flooding and low water. Flooding, which is not directly related to rainfall, did not begin until one month after the major rainy season in June. The sources that contributed to the flooding of Lake Nokoué were the freshwater tributaries coming mainly from the Ouèmé River and the flow of the Sô River from August to November. The inflow of fresh water contributed to the decrease in salinity and transparency of the lake from the east to the south. During the low water period (from December to July), Lake Nokoué is characterized by an increase in salinity and transparency from the south to the northeast due to the massive intrusion of sea water into the lake. The highest dissolved oxygen levels are observed in the south and center (5.92 ± 0.46 mg/L) while it varies greatly in the north and west (Eichhornia crassipes concentration zone) during flooding. The average annual depth of Lake Nokoué was 1.47 ± 0.66 m with an average annual pH of 6.85 ± 0.56.

The export of shrimps to the European Union was one of the mainstays of the Beninese economy. It is an income-generating activity for the populations living along Lake Nokoué. The lack of a fisheries management strategy has caused a drastic decline in shrimp’s production in Lake Nokoué since 2003. To remedy this problem, it is necessary to hypothesize on their spatial-temporal dynamics in the Lake Nokoué-Cotonou channel complex. This is investigated by combining a literature review on their life cycles and habitat suitability with spatial-temporal evolution of salinity obtained from in-situ observations. The literature review reported four (04) potential families of shrimp species whose part of their life cycle is common to the ecology of Lake Nokoué: Penaeidae (Penaeus); Palaemonidae (Macrobrachium); Atyidae (Atya) and Desmocarididae (Desmocaris). The overall results in relation to the life cycle of the shrimp species indicate that adults of the Macrobrachium, Atya species have a favorable environment in Lake Nokoué from August to November and their larvae must remain in the lake from December to June to ensure their survival. The species of the genus Desmocaris, which carry out their entire life cycle in fresh water, can stay in Lake Nokoué from August to November. The species of the genus Penaeus have a favorable environment in Lake Nokoué from December to June but their larvae can only survive in the sea. Species of the genus Caridina (freshwater) and Palaemon (estuary and marine) belonging to the family Palaemonidae can however be found in Lake Nokoué because of their wide distribution on the West African coast although they are not reported in Benin. This research makes it possible to predict the presence or absence of shrimp genera in a lake system, based on their life cycle. Based on the results obtained, we suggest a ban on fishing in Lake Nokoué between December and February and a ban on shrimp fishing in the Cotonou canal for a good management of the shrimp stock in Benin.

The aim of this work was to evaluate the spatial and temporal distribution of shrimp species in the Lake Nokoué-Cotonou Channel complex for an efficient management of the fishery. The results of one year sampling from five stations (North, South, East, Central and West) in the complex revealed the following proportions: Penaeus notialis 73.68%, Macrobrachium macrobrachion 13.81%, Macrobrachium vollenhovenii 5.36%, Penaeus monodon 2.68%, Macrobrachium felicinum 2.20%, Penaeus kerathurus 1.72%, Macrobrachium cf. zariquieyi 0.27%, and Macrobrachium equidens 0.27%. The species M. cf. zariquieyi and M. equidens were never reported from Benin, but are now found in Lake Nokoué. Spatially, Penaeus (Penaeus notialis) are more abundant in the west (Acadja concentration zone), while Macrobrachium (Macrobrachium macrobrachion) are more dominant in the east (near the Ouémé entrance) and north (near the Sô entrance) of the lake. Penaeus are strongly present in the lagoon complex from January to August, while Macrobrachium are more abundant in Lake Nokoué from September to December. Spearman’s correlation analysis revealed that increasing salinity, pH, transparency and total dissolved solids (TDS) positively influenced the abundance of P. notialis, while increasing salinity, pH, transparency, and TDS negatively influenced the abundance of M. macrobrachion at the 5% significance level. For an efficient management of the shrimp fishery, it is desirable that the shrimp fishery in Lake Nokoué, mainly in the Cotonou Channel, which is a very sensitive area for their seasonal migrations, benefits from at least three months of respite per year, from November to January. This period corresponds to the strong migration of juvenile Penaeus towards the lake. This should allow many Penaeus to grow up and breed at least once in their lives, according to the species’ life cycle presented.