Growth, mortality and yield of Sarotherodon melanotheron melanotheron (Rüppell, 1852) in the Lake Nokoué and Porto-Novo Lagoon complex Benin, West Africa

The study evaluated some population parameters of Sarotherodon melanotheron melanotheron within a lagoon complex in southern Benin: Lake Nokoué and Porto-Novo Lagoon. Data on the total length, total weight, and sex were recorded monthly between January and December 2015 for 1,745 specimens captured by local fishermen. The asymptotic length L∞ was estimated at 24.68 cm. The growth rate K was 0.86. The total, natural, and fishing mortalities were estimated at 2.46, 1.71, and 0.75 y−1, respectively. The size at first sexual maturity was 8.9 and 9.2 cm, respectively, for males andfemales. The size at first capture was estimated at 9.2 cm, which indicates that fish spawn at least once before capture. The current exploitation rate of 0.31 remains below the maximum exploitation rate Emax which was 0.604 but was equal to the exploitation rate retaining 50% of the biomass of the stock (E0.5 = 0.324). This suggests that the stock of S. m. melanotheron is not overexploited in the complex. However, it is recommended that the actual rate of exploitation be kept as it is to ensure a sustainable management of these fish populations

Efficiency of fatty acid-enriched dipteran-based meal on husbandry, digestive activity and immunological responses of Nile tilapia Oreochromis niloticus juveniles

peer reviewedThis study aimed to compare the enrichment capacity of polyunsaturated fatty acids (PUFA) and the long chain polyunsaturated fatty acids (LC-PUFA) of two dipteran species, Hermetia illucens - black soldier fly (BSF) - and a blowfly, Chrysomya putoria (CP), and to test its influence on growth, digestive activities and immune responses of Nile tilapia. Two types of enriched insect larval meal were produced using larvae cultured either on vegetable substrates (VGS) to formulate two diets rich in linolenic acid (ALA) (BSF/VGD and CP/VGD), or on fish offal substrates (FOS), in order to produce two diets rich in ALA and eicosapentaenoic acid (EPA) (BSF/FOD) or in ALA + EPA and docosahexaenoic acid (DHA) (CP/FOD). These four insect-based diets containing only palm oil as a lipid source were compared to a control diet based on fish meal (FM) and fish oil (FO). After 60 days of feeding, ALA or DHA muscle content of fish fed BSF/VGD or CP/FOD diet was comparable to that of the FMFO diet, and all insect diets increased the EPA muscle levels, except for a reduction by the BSF/VGD one. The CP/FOD diet induced similar fish growth, feed efficiency and protein efficiency ratio compared to the control FMFO diet, while a decrease was observed in fish fed other insect diets. Only BSF/VGD led to a decrease in protein and lipid digestibility. CP or BSF larval meal significantly increased alkaline phosphatase activity regardless of fatty acid (FA) enrichment. The expression level of fads2, fads6 and elovl5 was significantly higher in fish fed the BSF/VGD diet compared to fish fed the FMFO diet. FA-enriched insect diets increased some immune variables such as lysozyme, peroxidase and ACH50 values of fish fed CP/FOD, CP/VGD or BSF/VGD diets. Moreover, the expression level of β-defensin-1 and mhcII genes were significantly higher in fish fed the BSF/FOD diet than the FMFO diet. Also, the expression of the pro-inflammatory gene il-1-β was significantly higher in fish fed FMFO diet than in those fed CP/FOD diet, but comparable to fish fed all other diets. No significant effects were observed for the other tested genes. The results showed a better efficiency in LC-PUFA enrichment of the CP larvae compared to BSF ones, resulting in a higher stimulation of the fish nutrient utilization processes and therefore, a higher growth capacity. Nonetheless, all dipteran larval meal stimulated the immune status whatever the insect species or dietary essential fatty acids

Total replacement of fish meal by enriched-fatty acid Hermetia illucens meal did not substantially affect growth parameters or innate immune status and improved whole body biochemical quality of Nile tilapia juveniles

The study was designed to evaluate the effects of total remplacement of fish meal (FM) and fish oil (FO) by vegetable oil and black soldier fly (BSF) larval meal enriched with fatty acids (FAs) in Nile tilapia juveniles. Fish were fed a FMFO control diet compared to a non-FA-enriched BSF diet (BSF/T0) and diets enriched in linolenic acid-ALA (BSF/T1) or in eicosapentanoic acid-EPA (BSF/T2). After 59 days, the BSF diets did not affect growth except for a decrease by the BSF/T1 diet. However, protein utilization and digestibility were reduced by all the BSF diets. FA-enriched diets did not improve the digestive enzyme activities or immune parameters, while lysozyme and ACH50 values were increased by the BSF/T0 diet. Levels of polyunsaturated FAs in the whole body of fish fed ALA or EPA-enriched BSF diets were comparable to those of FMFO controls. The results demonstrate that BSF meal can totally replace FM without substantially effect on growth or innate immune status. The decrease in fish carcass FA quality induced by the BSF meal can be prevented by a well defined protocol for PUFA enrichment. Nonetheless, investigation of the long-term effects of the BSF meal use during the ongrowing phase is still needed

Facteurs déterminants de la volonté des petits pêcheurs d'adopter la cogestion des droits de propriété dans le complexe lagunaire du lac Nokoué et de Porto-Novo au sud-est du Bénin.

peer reviewedThe estuarian and lagoon areas of southeast Benin are atypical lake territories where private property rights are hereditary from endogenous legal tradition. People live in stilt dwellings and are exclusively dedicated to free-to-access fishing. Consequently, an increasing number of fishers with low respect for the State’s general rules for sustainable fishing contribute to legal pluralism and the tragedy of the commons. Co-management of small-scale fisheries has been advocated to offer various benefits, including improved socio-ecological integration, shared sustainable livelihoods, and adherence to biodiversity objectives. This study aims to assess the factors that influence the willingness of small-scale fishers to adopt property rights co-management options in southeast Benin. The data were collected using the discrete choice experiment method. The results show that 44% of fishers are willing to adopt property rights co-management options. This willingness is determined by their involvement in the co-management committee, access to a subsidy and livelihood diversification options. These fishers are the oldest in the sample and primarily owners of Acadja, a traditional fishing tool made of bush and tree branches planted in the lake. Institutional agreements for co-management establishment, such as subsidies to support small-scale fishers’ livelihood diversification and capacity-building, must be set up to achieve co-management goals.14. Life below wate

First record of the globally invasive crab, Charybdis hellerii (A. Milne-Edwards, 1867), in Benin, with notes on its taxonomy (Crustacea, Decapoda, Brachyura, Portunidae)

Dessouassi, Comlan Eugène, Lalèyè, Philippe A., 'Udekem, Cédric (2019): First record of the globally invasive crab, Charybdis hellerii (A. Milne-Edwards, 1867), in Benin, with notes on its taxonomy (Crustacea, Decapoda, Brachyura, Portunidae). Zootaxa 4576 (2): 201-238, DOI: 10.11646/zootaxa.4576.2.

FIGURE 18 in First record of the globally invasive crab, Charybdis hellerii (A. Milne-Edwards, 1867), in Benin, with notes on its taxonomy (Crustacea, Decapoda, Brachyura, Portunidae)

FIGURE 18. Location of the study area, showing fishing sectors

Population parameters and exploitation rate of Sarotherodon galilaeus galilaeus (Cichlidae) in Lakes Doukon and Togbadji, Benin

Growth, mortality, recruitment and relative yield per recruit of Sarotherodon galilaeus galilaeus from Lakes Doukon and Togbadji were studied. Data on total length, total weight and sex were recorded on a monthly basis between January and December 2013 for S. g. galilaeus captured by local fishers. The estimated asymptotic lengths L∞ were 26.2 and 23.6 cm for Lakes Doukon and Togbadji, respectively, while the growth rate K was 0.73 in Lake Doukon and 0.87 in Lake Togbadji. Estimates of fishing mortality, 0.27 and 0.47 y−1 for Doukon and Togbadji, respectively, were low relative to natural mortality, 1.51 and 1.74 y−1, respectively. Sizes at first sexual maturity were 12.8 and 13.2 cm for females and males, respectively, in Lake Doukon, and 11.5 and 12.4 cm for females and males, respectively, in Lake Togbadji. The size at first capture was estimated at 13.3 and 12.7 cm for Lakes Doukon and Togbadji, respectively, which, in the light of the size at maturity estimates, indicates that fish spawn at least once before capture. The current exploitation rates of 0.15 for Lake Doukon and 0.21 for Lake Togbadji suggest that their stocks of S. g. galilaeus are not overexploited in either lake

Evaluation of length-weight and length-length relationships of some of the most abundant commercial fishes from the Couffo River basin (Benin, West Africa)

peer reviewedThe Couffo basin is not well known, and neither are its aquatic living resources, such as fish fauna, which are subjected to high exploitation rates. The objectives of this study were to establish length-weight ratios (LWRs) and length-length ratios (LLRs) for the most important species in the catches and those of certain economic value. A total of 12,191 specimens belonging to 40 commercial species of actinopterygian fishes were caught with several fishing gears and methods between February 2018 and March 2021. Allometric coefficient b of the LWRs (BW = a × TLb) ranged from 2.194 for Enteromius callipterus to 3.673 for Protopterus annectens with a mean of 2.902 ± 0.315. The growth of thirteen species was isometric, that of fourteen species was negatively allometric, and that of the remaining thirteen species was positively allometric. Coefficient of determination r2 for the LLRs of 39 of the 40 selected species mentioned above was significant and ranged from 0.781 in Gobionellus occidentalis to 0.997 in Elops senegalensis with a mean value of 0.951 ± 0.049. The results will be useful for further studies on assessments of population dynamics and the sustainable conservation of the already limited fish stocks in the Couffo River basin

Can Insect Meal Replace Fishmeal? A Meta-Analysis of the Effects of Black Soldier Fly on Fish Growth Performances and Nutritional Values

The search for quality alternatives to fishmeal and fish oil in the fish feed industry has occupied many researchers worldwide. The use of black soldier fly meal (BSFM) as a substitute has increased. This study evaluated the effect of this substitution on fish growth and nutritional quality through a meta-analysis of the literature. A list of studies was selected after an exhaustive literature search followed by the extraction of growth and nutritional parameters. Two random-effects models were used to estimate the differences between the experimental parameters and the controls. The results showed significant heterogeneity between studies for all parameters. The sources of heterogeneity between studies were mainly fish species and protein substitution rate. High substitutions can be considered without necessarily worrying about an adverse effect. Financial profitability studies of the fish production chain from BSFM should be carried out to validate or invalidate the economic viability of this substitution

Technical basis for the small-scale production of Black Soldier Fly meal as fish feed in Benin

Producing fish of good quality and at a lower cost is the major objective of fish farmers. In Benin, the feeding of farmed fish is a major predicament. The food composition suffers from the lack of a reliable sources of protein. Hermetia illucens (Diptera: Stratiomyidae) larvae could offer a real solution as they have already been used in several countries in animal production. However, the species is little known in Benin and breeding techniques are ignored by producers. The present study aims at establishing a technical reference for the breeding of this fly in Benin. A larvarium (42 cm x 29 cm x 25 cm) equipped with an automated prepupa harvesting system was manufactured for the rearing of the larvae. A total of 36,000 larvae were used in the trials. Three densities (1 larva/g, 2 larvae/g, 3 larvae/g) have been tested in triplicate in 2kg of chicken feed in order to determine the optimal load density. The experiment lasted 12 days during which growth tests (e.g. weight measures) were conducted. The quantities of fly meal produced from each treatment were evaluated as the total cost of production. Results show that the larvarium designed is suitable for H. illucens larval rearing and that the automatic prepupa harvesting system is efficient. The load density determined as ideal for good larval growth is 2 larvae per gram of chicken feed. With 40 g of 1-week-old larvae, it is possible to produce about 500g of insect meal. The overall production cost came to roughly $ 265, which makes it quite affordable. The proposed rearing system is a high-yield one and is within the reach of any fish farmer or farmer in general. Other types of substrates such as restaurant waste, manure or agricultural co-products could be explored in order to replace the chicken feed.Valorization of organic wastes for insects production for Fish feeding in Beni