Author:

Keywords:

growth, Orenchromis aureus, heat shock, diploids and triploids, tanks and ponds, feeding regimes, compensatory growth response, Salmo-Gairdneri Richardson, Rainbow-Trout, Oncorhynchus-Mykiss, Salvelinus-Alpinus, Sex Determination, Thyroid-Function, Arctic Charr, Niloticus L, Induction, Fish, 0608 Zoology, 0704 Fisheries Sciences, Fisheries

Abstract:

In this study, triploids of Oreochromis aureus were obtained via the heat-shocking method. Triploid fishes were effectively sterile and predominantly female (80%). Diploid and triploid fishes were reared in tanks or ponds receiving organic manure. In tanks, the survival rate was 65.3% and 60.7% for diploids and triploids, respectively. Triploids, mostly females, grew slower (P < 0.05) than diploids consisting of almost equal number of females and males. In ponds, a significant difference in body weight (P < 0.05) in favour of diploids was also recorded, but both lines grew slower than in tanks. In another tank trial, growth of diploid and triploid females was compared using a normal feeding regime (7 days/week of feeding) or a restricted feeding regime (5 days/week of feeding). A little difference in growth was recorded in favour of triploids under the normal feeding regime. However, a high significant difference (P < 0.001) between diploids (71.8 +/- 5.8 g) and triploids (118.5 +/- 8.9 g) was recorded under the restricted feeding regime. While the diploids under the restricted feeding regime grew slower than diploids under the normal feeding regime, no difference in growth between triploids in the normal and restricted feeding regime was observed. (C) 2001 Elsevier Science B.V. All rights reserved.