N. Mashaii - National Research Center of Saline Water Aquatics, Iranian Fisheries Science Research Institute, Agricultural Research, Education and Extension Organization, Bafq, Yazd, Iran
F. Rajabipour - National Research Center of Saline Water Aquatics, Iranian Fisheries Science Research Institute, Agricultural Research, Education and Extension Organization, Bafq, Yazd, Iran

Better management of tilapia hatcheries depends on effective factors on spawning and is affected by different factors. Nile tilapia Oreochromis niloticus were held at a water salinity of ۱۱.۵ppt, a temperature of ۲۷±۰.۵°C. Fish were fed a ۴۰% protein food. Absolute fecundity varied between ۵۰ and ۲۶۰۰ (mean ۸۵۳±۲۵) eggs per clutch. Relative fecundity varied from ۰.۲۹ to ۶.۸ (mean ۲.۷۷±۰.۱۳) eggs/g of female. Mean of wet weight of egg clutches was ۴.۹۸±۰.۳۱g during the study period, increasing with size of female (p<۰.۰۵). Mean wet weight of each egg was ۰.۰۰۶۲±۰.۰۰۰۱g. Diameter of the eggs varied between ۱.۸ to ۳.۵mm and its mean was ۲.۵۸±۰.۰۰۹mm increasing with average length and weight of spawners. The impact of sex ratio, stocking density, photoperiod, water salinity and replacement period on spawning performance of Oreochromis niloticus were investigated. Sex ratios ۱:۱, ۱:۴ and ۱:۷ (Male: Female), stocking densities ۲, ۳.۵ and ۵ fish/m۳, photoperiods ۶:۱۸, ۱۲:۱۲ and ۱۸:۶ (Light: Dark) hours, water salinities ۰, ۴, ۸ and ۱۲ ppt, also ۱۰- and ۱۵-days replacement of breeders were studied. Fecundity, breeder and egg per day, spawning intervals, egg diameter and weight were investigated. Results showed stocking density ۵ fish/m۳, photoperiod ۱۲:۱۲ h, ۸ ppt water salinity and ۱۰ days replacement had better performance.

Nile tilapia, Breeding, Brackish water, Iran