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Nile tilapia, Oreochromis niloticus females were fed three commercial diets (20, 25 and 30% crude protein) in 200 m3 earthen ponds fertilized with compost at rate of 25 kg/pond/week to evaluate their growth performance, seed production and survival rate of produced fry throughout winter season. Average initial body weight of females (19.30±1.05g) and males (23.45±2.1g) were stocked separately with density of 1000 fish/pond, and fed to satiation twice daily for 120 days as a pre-spawning period. Both sexes were then transferred to concrete ponds in hothouses with a ratio (6:2 females: male) per tank. During spawning period, broodstocks were fed a diet (25% crude protein) at 1% of their live body weight for 90 days. Last batch of produced fry were nursed in concrete tanks in hothouses, and fed on 30% crude protein diet for 45 days. Fry from each treatment was then transferred to wintering ponds, stocked at 500 fry/m3, and fed twice daily tosatiation for 120 days. Results indicated that final body weight, gain and average daily gain of broodstocks increased significantly (P<0.05) with increasing dietary protein level in fertilized ponds. Feed conversion rate and protein efficiency ratio improved, but insignificantly with increasing dietary protein level and with adding fertilizers. However,number of progeny increased significantly (P<0.05) by increasing protein level in fertilized ponds. Correspondingly, initial and final body weight of the offspring was significantly (P<0.05) triggered with increasing protein level and fertilizers. Also, feed conversion rate of fry improved significantly (P<0.05) with increasing dietary protein level and fertilized treatments. Moreover, survival of fry increased significantly (P<0.05) with fertilization treatments and increasing protein level. Therefore, the study highlights that by feeding O. niloticus broodstocks diets containing 25% crude protein supplemented with compost fertilizers during pre-spawning period, could be sufficient to trigger the production of viable fry that might tolerate low winter season temperatures.

mediterranean aquaculture journal /mediterranean aquaculture journal

Influence of Protein Levels and Pond Fertilization during Broodstock Pre-Spawning Period on the Tolerance of Nile Tilapia, Oreochromis niloticus, Fry to Winter Season Temperature