Growth and food consumption of milkfish (Chanos chanos) during dry and wet seasons

Abstract

This study was conducted to evaluate the quality of the food consumed by the fish, to estimate the food consumption of the fish in the natural environment during the wet and dry seasons, and to determine the relationship between the growth and food intake. The milkfish fingerlings with the average weights of 4.0 g (wet season) and 9.0 g (dry season) were stocked @ 700 ha^-1 in three 1000 sq. m brackishwater ponds. The unfed fish depended on the natural food alone (natural food treatment), while the fed fish were given the supplemental diets containing either 25 per cent protein and 3031 Kcal energy (natural food plus 25% protein diet) or 36 per cent protein and 3344 Kcal energy (natural food plus 36% protein diet). The food consumption increased linearly with the fish growth. Among the environmental factors measured, the salinity varied greatly between the seasons. The caloric and protein intakes for all the fish were higher during the wet season (average salinity, 22 ppt) than during the dry season (average salinity, 36 ppt). Also, the quality of food in terms of the protein and energy levels and the protein energy to total energy ratio was better in the wet than in the dry season. Based on the estimated contribution of the natural food, the rate for the supplemental feeding ranged from 2 to 4 per cent for the body weight during the wet season and from 1 to 2 per cent during the dry season. The feeding during the dry season, however, appeared to have less effect on the growth. It is recommended that the salinity should be maintained below 36 ppt for effective feeding management.