Cannibalism often happens in culture procedure of groupers' fries. They areease eat up each other to increase costs of aquaculture. In order to understandhow cannibalistic behavior effect on groupers, we try to study the effect ofbody length on cannibalistic rate in grouper Epinephelus coioides. The resultwas found that the fish body length less than 6 cm had more tendencies oncannibalism.
Cannibalistic rates of grouper tests less 0.022 were no body lengthdifferences between predator and prey. In different distance experiments of bodylength cannibalistic rate, only one test was zero and the other tests more than0.2 were varied distance between predator's and prey's length. Relationshipbetween body lengths of predator (x) and prey (y) for cannibalistic behaviorwere y=23.65 Ln (x) - 59.99 r=0.912, and no cannibalistic behavior y= 24.71 Ln(x) - 60.54 r=0.926 in body length equation was also calculated.
The relationship of cannibalistic probability predict (p) between predator(x) and prey (y) body length in grouper equation were calculated: , and bodylength unit was mm, e=2.7182. It showed that whether cannibalism happens or notdepended upon the body length of predator and prey.