Abstract
Adult mud crabs, Rhithropanopeus harrisii, were held in the laboratory for 14 months at densities of 20 or 40 crabs per 0.5 m2 and at female: male ratios of 2:1, 4:1, and 6:1. Females spawned for 9 months during the calendar year and entered a refractory period from November through January. Field populations in North Carolina spawn for only 5 months of the year. Spawning increased with increasing crab density and female: male ratio. Ovigers were most abundant in habitats containing 40 crabs at a 6:1 sex ratio (8.3 ovigers per week), and were least abundant in habitats containing 20 crabs at a 2:1 ratio (2.8 per week). However, the highest proportion of crabs spawned in habitats containing 20 crabs at a 6:1 sex ratio. Neither density nor sex ratio affected female mortality. Crabs at the lowest sex ratio (2:1) and highest density (40 crabs) produced larvae that survived poorly (45% survival to first crab stage). However, larval viability was good at all other densities and sex ratios. Maintaining crabs at high densities and female: male sex ratios in the laboratory, even during a portion of the nonbreeding season, augmented egg production. These methods can facilitate studies of reproduction and development of R. harrisii.
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