Interspecific differences in male cannibalistic behavior between two sympatric cardinalfishes (Pisces: Apogonidae)

Abstract

Cannibalistic behavior of a paternal mouthbrooding cardinalfish, Apogon notatus, was examined and compared with that of a sympatric congener, Apogon doederleini. In both species, males sometimes cannibalized their own entire broods, but their postcannibalistic behavior was markedly different. Males of A. doederleini respawned within a few days of cannibalism, usually changing mates, whereas males of A. notatus took several weeks to respawn, less frequently changing mates. This difference was attributed to mate availability for males. The operational sex ratio was female biased in A. doederleini but male biased in A. notatus, suggesting that the former males have higher mate availability and thus opportunities for remating soon after cannibalism. For male apogonids that accept only one clutch at a time, an effective way to compensate for reproductive loss entailed by filial cannibalism is to remate as soon as possible after cannibalism. The higher rate of filial cannibalism by A. doederleini than by A. notatus suggests that this cannibalism is facilitated by high mate availability. In contrast to filial cannibalism, heterocannibalism was more frequent in A. notatus. High population density and gregariousness may be important factors contributing to the frequent occurrence of heterocannibalism.