2020 Volume 49 Pages 121-132
We investigated the reproductive traits and population structure of a Petrolisthes japonicus population through monthly sampling for one year on an intertidal cobble and boulder shore on the Boso Peninsula, Japan. The main reproductive season lasted for four months, from June to September. The sex ratios were approximately 0.5. Newly recruited juveniles were found mainly from August to October, and three age groups were detected using body size histograms. The growth curves of both sexes were significantly different, and males grew larger than females. Our analyses suggest that females and males in the 0+age group begin to breed in the year after hatching and that a relatively large proportion of 0+aged individuals die during the end of or after the reproductive season. A relatively small proportion of 0+aged individuals survive even after the reproductive season and breed in the next year as the 1+age group; then, individuals that reach the 2+age group likely die by the end of summer. Consequently, the longevity of P. japonicus is estimated to be 1–2 years.
