水産養殖研究開発ジャーナル

概要

Role of Salinity on Growth Performance of Oreochromis niloticus♀ and Oreochromis urolepis urolepis♂ Hybrids

Levinus Leonard Mapenzi and Aviti John Mmochi

Influence of salinity on hybrids descended from O. niloticus♀ and O. urolepis urolepis♂ was investigated for 63 days. A total of 120 fry of 0.29 ± 0.01g were stocked in 1m3 plastic tanks at a density of 10 fish/m3 per tank. The experiment involved three salinity treatments 15, 25 and 35 with fresh water (2 salinity units) as control. The hybrids were fed on a balanced diet of 40% crude protein at 5% body weight twice a day. Water quality parameters were measured once a week. However, results on SGR, average weight gain and survival rate were not significantly affected by salinity (p>0.05). FCR differed significantly among treatments (p<0.05). The 25 Practical Salinity Unit (PSU) showed better growth performance than other treatments. Surprisingly all treatments showed better growth than control. When examined at the end of the study all hybrids were found to be 100% males. Length-weight relationship “b” values and condition factor “K” showed that hybrids had isometric growth, good health and were properly managed. It was concluded that if proper management is followed, the studied hybrids can be good candidates in both intensive and semi intensive mariculture by coastal people. The hybrids can solve the problem of stunted growth, be an alternative to the use of hormones in sex reversal.