Abstract

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 11.5ppt, a temperature of 27±0.5°C. Fish were fed a 40% protein food. Absolute fecundity varied between 50 and 2600 (mean 853±25) eggs per clutch. Relative fecundity varied from 0.29 to 6.8 (mean 2.77±0.13) eggs/g of female. Mean of wet weight of egg clutches was 4.98±0.31g during the study period, increasing with size of female (p<0.05). Mean wet weight of each egg was 0.0062±0.0001g. Diameter of the eggs varied between 1.8 to 3.5mm and its mean was 2.58±0.009mm 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 1:1, 1:4 and 1:7 (Male: Female), stocking densities 2, 3.5 and 5 fish/m3, photoperiods 6:18, 12:12 and 18:6 (Light: Dark) hours, water salinities 0, 4, 8 and 12 ppt, also 10- and 15-days replacement of breeders were studied. Fecundity, breeder and egg per day, spawning intervals, egg diameter and weight were investigated. Results showed stocking density 5 fish/m3, photoperiod 12:12 h, 8 ppt water salinity and 10 days replacement had better performance.

Keywords: Nile tilapia, Breeding, Brackish water, Iran