Male body size, female preference and male-male competition in croaking gouramis Trichopsis vittata

摘要

This study examined the role of the male body size in the female sexual preference and male-male competition among croaking gouramis ( Trichopsis vittata Cuvier, 1831). Two studies were conducted; in the first males were matched in size, and in the second males of different sizes were placed together. The results showed that male body size did not affect sexual preference among female croaking gouramis. Regarding the male-male competition study, large males won more fights than small ones. Fighting durations between size-matched fish were longer than those between size-mismatched fish. A comparison of different agonistic behaviours of the fish under both treatments showed that sound producing, biting and total agonistic behaviours were found more frequently among the size-matched fish. Further observations of the large and small fish in the size-mismatched group also revealed that large males performed more chasing and less escaping than small ones. These results indicate that sexual size dimorphism in croaking gourami (in which the male is larger than the female), is associated with male-male competition, not with female preference