Seasonal effects on the nutritive value of the natural food of three omnivorous fish (Oreochromis niloticus,Sarotherodon galilaeus,Citharinus citharus) in Batamani Pond (Mali, West Africa)

Abstract

Key-words: omnivorous fish, natural food, nutritive value, climate, Batamani Pond, MaliThe chemical composition of the stomach contents and the digestibility of organic matter, proteins and energy of three planktivorous fish species (Oreochromis niloticus, Sarotherodon galilaeus and Citharinus citharus) were studied in Batamani Pond (Mali, West Africa) during the dry and wet seasons. The diet contents of O. niloticus and S. galilaeus presented high levels of organic matter and proteins during the wet season (ashfree dry weight (AFDW): 753 mg·g −1 dw and 703 mg·g −1 dw, protein contents: 479 mg·g −1 AFDW and 449 mg·g −1 AFDW, respectively). In the dry season, the chemical composition of the food was characterized by high proportions of inorganic material (73% and 68% for O. niloticus and S. galilaeus, respectively). The chemical composition of the food of C. citharus was characterized by low seasonal variation. The levels of AFDW (396-461 mg·g −1 dw) and proteins (65-86 mg·g −1 AFDW) in its diet were generally low, reflecting a high proportion of mineral content. During the wet season, the digestibility of AFDW (52% and 58%), total amino acids (68% and 76%) and energy (63% and 56%) increased significantly for O. niloticus and S. galilaeus, respectively. Nutrient and energy digestibility for C. citharus showed no significant seasonal variations (AFDW: 36-45%; total amino acids: 57-64%; energy: 31-39%). The marked seasonal character of the pond, in terms of both hydrology and trophic conditions, had a low impact on the availability and quality of nutritive resources for the two tilapia species O. niloticus and S. galilaeus, while C. citharus appears to have the capacity to adapt its regime to the available food quality, whatever the season.

Seasonal effects of the water quality in ponds on nutritive potential and digestibility of tilapia Oreochromis niloticus in natural feeding condition (Mali, West Africa)

“…This is confirmed by the low digestibility of organic matter (32-37%) and amino-acids (40-50%). The values are comparable to those observed in the batamani pond (Ble and Arfi, 2009) and for the same species in other Ethiopian lakes (Getachew, 1987(Getachew, , 1993.…”

“…Similar results on the abiotic parameters were shown in pond of Batamani, a shallow pond in the Inner Niger Delta of Mali. Hydrobiological characteristics of this pond were subject to a very marked seasonal influence (Blé and Arfi, 2009). In the lake Ziway of Ethiopia, Getachew and Abebe (1992) found that the low organic matter content of water was related to the low primary productivity due to turbidity caused by runoff during the rainy season.…”

“…The field of DEMESSO, like most of reservoir in Mali (West Africa) is located in the sudanian climate zone subject to a marked seasonal alternation (Arfi, 2003;Blé and Arfi, 2009). This climate features a dry season between October to April and a wet season between May to September.…”

“…Several studies have described the impact of environmental conditions on the quality of the fish diet (McQueen et al, 1986;Tadesse, 1999;Figueredo and Giani, 2005;Blé and Arfi, 2009). In the ponds of DEMESSO, the food ingested by the fish is characterized by a significant amount of indigestible materials (75%).…”