Sexual Dimorphism, Allometry, and Size at First Maturity of the Caribbean King Crab,Mithrax spinosissimus, in the Florida Keys

Abstract

The Caribbean King crab Mithrax spinosissimus is the largest brachyuran found in the western Atlantic and it supports subsistence and small commercial fisheries throughout the Caribbean and Gulf of Mexico. Because of its short larval duration and rapid growth, M. spinosissimus is considered a good candidate for aquaculture. Our study documents for the first time the size at sexual maturity, sexual dimorphism, and allometric growth relative to carapace width for certain secondary sexual characters in male and female M. spinosissimus from the Florida Keys, Florida. Using principal component analysis, K-means cluster analysis, and discriminant analysis, we identified 2 major growth phases in the postlarval benthic life of this species (juvenile or prepubertal and adult or pubertal). The typical growth pattern for majoid crabs includes a third, intermediate growth phase that appears absent in M. spinosissimus. The major cheliped of males was larger than that of females and exhibited positive allometric growth to maturity, after which the level of allometry decreased. In females, both chelipeds exhibited positive allometry throughout ontogeny. Abdominal width was negatively allometric throughout ontogeny in males, whereas in females the abdomen exhibited positive allometric growth until reproductive maturity, at which point it became isometric. Logistic regression indicated that the carapace width at first maturity was 45.2 mm in males and 69.7 mm in females. This new information should be taken into account when assessing stocks and setting harvest regulations if this fishery is to be managed sustainably.