The Effects of Rabbitfish Existence in Polyculture System and Feed Type against the Growth Performance of Bigeye Trevally in Floating Net Cage

The objective of this research is to investigate the effects of rabbitfish (Siganus canaliculatus) existence in polyculture system and feed type against the growth performance of bigeye trevally (Caranx sexfasciatus) in floating net cage. Study on polyculture of bigeye trevally and rabbitfish and monoculture of bigeye trevally in the cage were conducted at the coastal of South Bolaang Mongondow, North Sulawesi, Indonesia in 2018. The experiment was designed with three treatments for bigeye trevally, namely: monoculture of bigeye trevally fed with fresh trash fish + corn oil 4% (Treatment A), polyculture of bigeye trevally and rabbitfish fed with fresh trash fish + corn oil 4% (Treatment B), polyculture of bigeye trevally and rabbitfish fed only fresh trash fish (Treatment C); On the other hand, 2 treatments for rabbitfish, namely: polyculture of rabbitfish and bigeye trevally which are fed with only carp pellets + fresh trash fish (1:1) (Treatment D) and polyculture of rabbitfish and bigeye trevally which are fed with carp pellets + fresh trash fish (1:1) + corn oil 4% (Treatment E). Each treatment consisted of 3 replications. The results show that the daily growth rates of bigeye trevally from treatment A, B, and C are 0.67%, 1% and 0.68% of body weight per day, while the daily growth rates of rabbitfish from treatment D and E are 0.56% and 0.81% of body weight per day, respectively. Feed conversion ratios of bigeye trevally from treatment A, B and C are 6.69, 4.86 and 6, while feed conversion ratios of rabbitfish from treatment D and E are 4.57 and 4.16, respectively. Rabbitfish existence in polyculture system and feed type gave a faster growth of bigeye trevally in the cage compared to the absence of both.