Aquacultural techniques for floating cage are unknown in Benin that limited the agricultural policies to increase the fish production. This study aims to clarify that situation. Indeed, a questionnaire has been developed and computed in KoBocollect application. The survey's team is 19 fish farmers. The survey took place in the first quarter of 2019 and concerns technical data. Descriptive statistics were presented and PCA was used for statistical analysis. It was concluded that 89.47% of the fish farmers are men and only 03.30% are aquacultural technicians. In addition, it is noticed that 604 cages are operating on the lagoon with 78.95% of the fish farmers who are owners of 01 to 24 cages and 05.26% own more than 100 cages. The most produced fish species is tilapia (78%). Furthermore, 63.16% of the farmer feed their fish twice per day while 26.32% feed three times per day. Tilapia yield varies between 836 kg and 1,220.22 kg compared to Clarias yield which ranges from 825 kg to 850 kg. The simple rate of return is 1.52 and 1.77 for tilapia and Clarias respectively. Density, feeding frequency, year of experience, number of cages and production cycle time influences yield.
The present study aim to estimate the ratio of aquaculture in the phosphorus and nitrogen concentrations determined in the Toho - Todougba lagoons. For this purpose, the two lagoons were subdivided into 7 stations for the determination of phosphorus and nitrogen concentrations in the water column. Production data from 2017 to 2019 were collected from the Direction of the Ficheries Production and from the literature. Data for 2020 were collected directly from fish farmers. Annual tilapia production was estimated by year and the amounts of phosphorus and nitrogen released from aquaculture are deduced based on the ratio of Montanhini Neto & Ostrensky (2013). The concentration of each of these nutrients was estimated by station and compared to the concentration determined by laboratory analysis of the water. This methodology shows that the amount of phosphorus and nitrogen released to the environment varies from 0.49 mg/L to 0.18 mg/L for phosphorus and from 1.53 mg/L to 0.58 mg/L for nitrogen. The lowest values are obtained in 2020 and differ significantly from the other years (p <0.05). The quantity of phosphorus discharged is higher at the high production stations (Tonon 0.20 mg/L and Lokohoue 0.11 mg/L). Some of this is stored in the sediment. The nitrogen generated by aquaculture is significantly lower than the average determined in water (p <0.05). However, the concentration determined is still related to the amount of organic matter released due to aquaculture. Although aquaculture is not the only source of nutrient release to water, strategies for aquaculture with less nutrient release should be determined.
This study aimed to compare the growth performance and economic profitability of rearing Oreochromis niloticus in floating cages using three feeding strategies (5 days a week, 6 days a week, and 7 days a week) coupled with three stocking densities (20, 40, and 60 fish·m−3). Male monosex fish measuring 6.44 ± 0.18 cm and weighing 3.42 ± 0.7 g were used. The controls were weighed every 15 days from the 35th day of rearing until 185 days to assess zootechnical parameters. BioMar feed (Efico Cromis 832F) was used during the study, and the feed ration was adjusted for each treatment every 2 weeks. At the end of the study, the average weights varied from 293.09 g to 468.41 g for the conditions of 40 fish·m−3 with a 5/7-day diet and 20 fish·m−3 with a 7/7-day diet, respectively. The yield per m2 values were between 7.11 kg and 23.17 kg, respectively. On the other hand, the economic profitability was better with the condition of 40 fish.m−3 with daily feeding. These results suggest that in the Toho-Todougba lagoon complex, a stocking density between 40 and 60 fish·m−3 coupled with daily feeding (three times a day) promotes the optimization of fish production and profitability of fish farming.
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