Survival and Growth Rates of Tilapia zillii and Oreochromis urolepis urolepis in Full Strength Sea Water for Mariculture Development
The potential for Tilapia zillii and Oreochromis urolepis urolepis culture in marine waters was evaluated by determination of their survival and growth rates in full strength sea water (FSSW) at 35‰. Fingerlings were collected from Pangani River by using seine nets and reared in 1m3 concrete ponds where acclimatization was done by raising the salinity by 2 ‰ to 35 ‰. For salinity control, the fingerlings were also reared into 0 ‰ salinity. Fingerlings were fed twice daily using commercial fish feeds (white Rose floating type), initially at a rate of 5% of their total body weight (TBW) and two weeks later at 10% of their TBW. The growth rate (weight and length) was recorded once a week except for handling control fingerlings which were recorded at the beginning and the end of the experiment. The average weight gain (g/week), percentage weight gain (%/week) and specific growth rate (SGR, %/day) in freshwater (FW) and full strength sea water (FSSW) at 35‰ (in bracket) for T. zillii were found to be 1.01 (1.69), 10.35 (8.43) and 1.37(1.13) and for O. urolepis urolepis 0.57(2.10), 23.57 (5.17) and 2.9 (0.71), respectively. There was no significance difference (p > 0.05) in SGR between the two species in FSSW. The survival rates in FW and FSSW (in bracket) for T. zillii and O. urolepis urolepis were 89% (96%) and100% (100%), respectively. This study shows that if managed well T. zillii and O. urolepis urolepis can survive and grow in FSSW.
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