Growth performances and gonadal development of golden rabbitfish, Siganus guttatus fed with two types of floating diets in sea cages

Abstract

A feeding trial was designed to evaluate the effects of utilizing floating pellets on the growth performances, feed utilization and gonadal maturation of the golden rabbitfish, Siganus guttatus. The treatments were two kinds of commercial floating pellet containing different crude protein (CP) levels which were 26% (FD1) and 33% (FD2). The tested diets were fed to golden rabbitfish. Golden rabbitfish with initial body weight of 239.7±4.8 g were stocked into six sea cages with size of 2x2x2 m3 with density of 50 fishes/cage. The feeding trial lasted for 120 days with results showed that the growth performances of weight gain and specific growth rate were significantly higher (P<0.05) in fish fed FD2 diet (55.0±3.7% and 0.37±0.02 %/d) compared to those fed with FD1 diet (41.7±1.6 and 0.29±0.01%/d), respectively. Both female and male fishes had developed gonad at the end of feeding trial. The gonadosomatic index (GSI) for spermatid significantly higher (<0.05) in fish fed FD2 (4.8±0.6%) than FD1 group (3.4±0.3%). Similarly, the GSI for oocyte of fish fed FD2 diet (8.9±1.0%) was significantly higher than the group fed FD1 diet (4.2±0.5%). The FD2 diet produced higher protein content in the whole body and fillet. In contrast, lipid content of whole body and fillet of fish fed FD1 diet was higher than FD2 diet. As conclusion, better growth performances and gonadal development was found in fish fed FD2 diet, a floating diet containing approximately 33% CP.