Patterns of pair formation in protandrous anemonefishes,Amphiprion clarkii, A. frenatus andA. perideraion, on coral reefs of Okinawa, Japan

Synopsis

At Sesoko Island, stocks of anemonefishes were observed for 2 years in a 350 m × 150 m area where host sea anemones were sparse. About 40% of the pairs separated, mostly due to typhoon attacks or displacement. Widowed mates remained and acquired new mates on the same sea anemone, except for one case. New mates were immigrant adults inAmphiprion clarkii and A.frenatus, but resident juveniles inA. perideraion. A. clarkii andA. frenatus moved between sea anemones and sometimes displaced smaller consexuals, butA. perideraion rarely moved. The difference in mobility among the 3 species was related to the mean difference in standard length between the largest juveniles in breeding groups and the minimum size of breeding males in each species, and that between breeding males and the minimum size of breeding females. InA. perideraion both of these differences were small, so pairs could be formed quickly by residents after mate loss. On the contrary, inA. clarkii andA. frenatus, either or both differences were large and it would take a longer time to form a pair after mate loss. Differences in mobility affected the patterns of pair formation, and then the size composition of members in breeding groups.