DETERMINATE GROWTH IN A PATERNAL MOUTHBROODING FISH WHOSE REPRODUCTIVE SUCCESS IS LIMITED BY BUCCAL CAPACITY

The life history of the paternal mouthbrooding cardinal fish Apogon do ederleini was investigated in the temperate waters of Japan, with part icular reference to its growth and reproductive rate. Both males and f emales almost ceased to grow at age 3 years, although living to 7 year s of age. Their growth pattern, represented by the relative size at se xual maturity to the asymptotic size and the von Bertalanffy growth co efficient, was among the most determinate in ectothermic vertebrates. Brood size just before hatching increased in proportion to the second power of the body size of the brooding male, and correlated more posit ively with the male's than the female's body size, suggesting that it was limited by the male's buccal capacity. The estimated total number of broods hatched in a breeding season showed a weak or no correlation with the body size or age in either sex. Using life-history parameter s based on data of A. doederleini, a simulation model of energy alloca tion without considering sexual interaction revealed that the optimal growth pattern shows an indeterminate growth that differs greatly from the actual growth pattern of A. doederleini. This suggests that there are some brooding constraints to size-advantage of reproductive succe ss in this species. The possible mechanism of such reproductive constr aint is discussed.