水産養殖研究開発ジャーナル

概要

Red Tilapia Broodstocks and Larval Production Under Different Water Salinities Without Acclimation

Ghada R Sallam, Walied A Fayed, Mohamed A El-Absawy, Hadir A Ali and Zeinab A El-Greisy

The direct transfer of fish to marine water without acclimation is considered critical on survival rate of fish. Florida red Tilapia, Oreochromis sp., was introduced to four salinity levels (9‰, 18‰, 24‰ and 36‰) and a control freshwater treatment in pre-spawning period to investigate the tolerance of the offspring to direct transfer to marine water without acclimation. Fish were stocked at a rate of 25/m3 with initial body weight of 29.4 ± 0.12 g for six weeks as acclimation period. Broodstocks after acclimation were then stocked at 5/m3 and fed to satiation with 25% crude protein commercial diet for 24 weeks as spawning period. Offsprings survival and growth were compared for their tolerance to three salinity levels (9‰, 18‰ and 36‰) in indoor concrete tanks with stocking density of 1000/m3, and fed on 30% crude protein (470 kcal ME/100 g) diet for 8 weeks. The results implied that best growth for broodstocks was observed with (36‰) and no significant difference in survival. However, the least number of fry/kg were produced from broodstocks reared in 36‰ salinity, and the highest was observed with 18‰. Consequently, fry delivered from broodstocks reared in high salinity level (36‰) tolerated high salinity levels (18‰ and 36‰) with high survival rate (90% and 92%) respectively, and with highest growth rate. This study highlights the importance of rearing Florida red tilapia broodstocks in saltwater in order to have offspring tolerable to marine environment.