EFFECTS OF DENSITY, STARVATION AND SIZE DIFFERENCE ON AGGRESSIVE-BEHAVIOR IN JUVENILE YELLOWTAILS (SERIOLA-QUINQUERADIATA)

The effects of density, starvation and size difference on aggressive b ehaviour in juvenile yellowtails, Seriola quinqueradiata (Temminck and Schlegel), were investigated. When fish were acclimated to densities of 1, 2, 4, 8, and 16 fish L-1, the frequency of aggressive behaviour per fish decreased significantly. Following starvation for 0, 4, 8, 12 and 24 h, the highest aggression was observed at 24 h, while levels o f aggression were equal between 0 and 8 h. According to a pair match t est from one batch among three groups of different size (total length mm: 16.6 +/- 2.0, 21.1 +/- 2.1, and 29.7 +/- 4.9), the highest aggress ion was observed in the group with the largest size difference. Theref ore, in view of the three parameters investigated, aggressive behaviou r in the yellowtail was concluded to be positively starvation- and siz e-dependent, but negatively density-dependent. Synthesizing all releva nt results, including abiotic factors such as the light condition, a p ractical method is presented to reduce mortality caused by aggressive behaviour in yellowtail cultures.