Males with limited sperm reserves should allocate sperm efficiently during the reproductive season to maximize their reproductive success. The efficiency would depend on the temporal distribution of mating opportunities with females of high reproductive quality because male reproductive success is determined by number and reproductive quality of mates. I examined whether the sperm allocation strategy of stone crab males with limited sperm reserves is determined by the temporal distribution of good mating opportunities.

First, to examine how sperm number per ejaculate depends on female quality and future mating opportunities, I artificially controlled female size or timing of mating within a reproductive season and skewed the sex ratio towards females in laboratory experiments. Second, I investigated the temporal distribution of good mating opportunities for males in a natural population.

In conclusion, the temporal distribution of mating opportunities with good females during a reproductive season would be one of factors determining the pattern of their sperm allocation, and the temporal change in mate quality, one of the factors varying with phase of reproductive season, should be considered when predicting sperm allocation strategies.