SYNOPSIS. This paper reviews existing studies on the size of sexual maturity for male Tanner or snow crab (Chionoecetes bairdi), a brachyuran, and the anomuran red king crab (Paralithodes camtschaticus). In this report the term sexual maturity is denned as the ability to reproduce. A variety of indirect and direct methods that have been used to determine maturity are reviewed. Examining the vas deferens for the presence of spermatophores was useful in determining the size at which males first

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... come mature. Breeding experiments in the laboratory demonstrated that most males, from both species, that produced spermatophores could breed with soft-shelled mates. Males of both species can breed at smaller sizes than do females. Morphometric techniques based on reproductive tract weights and chela morphometry overestimated the sizes at which males mature in both species. Previous experiments for Tanner crab, which have internal fertilization, suggest small mature males can fertilize two to five females. Breeding experiments showed recently matured red king crab do not appear to be able to fertilize more than one female per breeding season, while males nearing harvestable size can fertilize more than one female. Breeding experiments and in situ observations of grasping pairs appear to be the most feasible methods for identifying male size at maturity for these species. The value of morphometric estimations for determining when males mature is questionable.