Prudencio T. Agbohessi

Assessment of the health status of wild fish inhabiting a cotton basin heavily impacted by pesticides in Benin (West Africa)

To determine the impact of agricultural pesticides used in cotton cultivation on the health status of fish living in a Beninese cotton basin, we compared the reproductive and hepatic systems of fish sampled from rivers located in both contaminated and pristine conditions. Different types of biomarkers, including biometric indices (a condition factor K, a gonadosomatic index GSI, and a hepatosomatic index HSI), plasma levels of sex steroids (11-ketotestosterone 11-KT, testosterone T and estradiol-17β E2) and the histopathology of the gonads and liver, were investigated for two different trophic levels of the following two fish species: the Guinean tilapia Tilapia guineensis and the African catfish Clarias gariepinus. The fish were captured during both the rainy season (when there is heavy use of pesticides on cotton fields) and the dry season from one site, in Pendjari River (reference site), which is located outside the cotton-producing basin, and from three other sites on the Alibori River within the cotton-producing basin. Comparing fish that were sampled from contaminated (high levels of endosulfan, heptachlor and DDT and metabolites) and reference sites, the results clearly indicated that agricultural pesticides significantly decreased K and GSI while they increased HSI, regardless of the season, species and sex of the fish. These pesticides also induced a decrease in the plasma levels of 11-KT and T and increased those of E2. The histopathology of the testes revealed, in both species, a high rate of testicular oocytes, up to 50% in the African catfish, downstream of the Alibori River, which indicated estrogenic effects from the pesticides. The disruption of male spermatogenesis primarily included necrosis, fibrosis and the presence of foam cells in the lobular lumen. The histopathology of the ovaries revealed high levels of pre-ovulatory follicular atresia, impaired oogenesis, a decrease in the oocyte vitellogenic diameter and other lesions, such as fibrosis, vacuolation and melano-macrophagic centers. The histopathology of the liver revealed the presence of necrosis, hypertrophic hepatocytes, foci of vacuolation, glycogen depletion and hemosiderin. An assessment of the general health of the fish indicated that all of the sampled fish from the polluted sites were in poorer health compared with those from the reference site but that the African catfish appeared much more affected than the Guinean tilapia, regardless of the sex and season. In conclusion, the overall results indicated that agricultural pesticides significantly impair the endocrine regulation of fish living in the Beninese cotton basin and that this would most likely be one of the causes of the severe damage observed in the liver and gonads and the reduced health condition.

Current situation of fish farming in Togo

In Togo, fish farming is faced with several problems which oblige farmers to develop local production techniques that explain the low level of production. To assess the current situation, a survey was conducted to collect information on this activity in 91 Togolese fish farms located in the five regions of the country. The survey has shown the existence of two production systems, namely the extensive majority system (87.91%) practiced in ponds and water reservoirs and the semi intensive system (12.09%) implemented in tanks and ponds. The lack of accurate data has made it difficult to estimate production. Nevertheless, eight fish species are found in these environments in which tilapia ( Oreochromis niloticus ) and the African cat fish ( Clarias gariepinus ) represent 80% of farmed species. Feed, representing over 50% of fish production cost, remains the major constraint on the development of this activity. However, agro-industrial by-product resources were available depending on region and are recoverable for use as fish feed. This is the case for palm kernel meal which was abundant and little studied in Togo. Sociologically, fish farming was more a matter of group (61.54%) than individual (38.46%) activity. The extensive fish farming system deserves to be improved and agro-industrial by-products analyzed and valued for the promotion of fish farming in Togo. Keywords : Fish, food, fish farming infrastructure, agro-industrial by-products, palm kernel meal.

Co-culture Clarias gariepinus-Oreochromis niloticus : quels avantages pour l’amélioration des performances zootechniques et économiques des poissons élevés dans les « whedos » du delta de l’Ouémé au Bénin ?

L’alimentation des poissons est la contrainte majeure pour l’emergence de la pisciculture tropicale. Dans le but d’evaluer l’effet de la co-culture Clarias gariepinus - Oreochromis niloticus sur la croissance de ces deux especes elevees dans les whedos, une experience a ete conduite durant 56 jours dans le village Aize a Ouinhi (Benin). Des alevins de C. gariepinus (6,74 ± 0,27 g) et de O. niloticus (8,11 ± 0,14 g) ont ete places respectivement dans des happas de 1 m 2 (30 alevins / m 2 ) et de 6,25 m 2 (30 alevins / happa), les happas contenant C. gariepinus etant inseres dans les happas contenant O. niloticus . Trois types d’aliments ont ete testes: aliment importe Sckretting (45% de proteines), aliment local (37% de proteines), et aliment mixte (50% aliment local et 50% aliment importe). Seuls les alevins de C. gariepinus ont ete nourris, les alevins de O. niloticus se nourrissant de la production primaire produite par les dejections de C. gariepinus . Les meilleures performances zootechniques et d’utilisation alimentaire ont ete obtenues avec l’aliment mixte suivi de l’aliment importe chez les deux especes. Chez C. gariepinus , le poids moyen final a varie de 20,95 ± 1,12 g a 42,56 ± 2,26 g tandis que chez O. niloticus il a varie de 17,00 ± 1,84 g a 19,63 ± 0,83 g. La presente etude a clairement montre que la co-culture Clarias gariepinus – Oreochromis niloticus avec nourrissage seulement de C. gariepinus est une forme d’elevage de plusieurs especes de poissons a la fois a cout reduit.