Induce spawning and larval reading of gilthead sea bream (sparus aurata)collected from fish farms, egypt
El-Absawy, M. El-G.
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Sparus aurata females in captivity were injected with human chorionic gonadotropin hormone (HCG), pituitary extraction and both them during the spawning season. First hormonal treatment was applied as cumulative doses required for successful ovulation ranged from 4500 to 7500 IU\fish, the maximum fertilization percent was 71. The ovulation period under the influence of this treatment extended up to 14 days. In the second experiment, the total dose requirement for successful ovulation ranged from 2 to 4 pituitary extractions. Fish and the maximum fertilization percent recorded was 81, while the longest ovulation period obtained was 15 days. In the third experiment the total doses required for successful ovulation ranged from 2 pituitary extractions and 4500 IU to 3 pituitary extraction and 7500 IU/fish. The maximum fertilization percent recorded was 88, while the ovulation period was extended up to 23 days. The combined treatment gave the highest value of fertilization percent and the longest ovulation period. Moreover, the results from the combined treatment showed the highest value of hatching percent of 83.5 when compared to those of HCG was 70.5 % or pituitary extraction was 80%. The maximum ovulation and fertilization percent was recorded at temperature ranging between 10 and 16°C. The survival percent of Sparus auratus larvae up to 10 days old after hatching were greatly affected by both temperature and photoperiod. The proper temperature ranged between 17 – 22 °C recording the highest survival percent 29 at natural photoperiod (8 h. light), while it increased to35% under continues illumination. The larvae starts feeding with rotifer at third day old were measured 0.2 mm. At 11th day old the post larvae measure 3.1 mm. and being reared to accept next feeding regime represented by Artemia nauplii.