Population Dynamics and Life History of the Mangrove Crab Aratus Pisonii (Brachyura, Grapsidae) in a Marine Environment
Abstract:Aratus pisonii commonly inhabits the supralittoral zone of roots, branches and canopy of the red mangrove, Rhizophora mangle. Population dynamics and life history of this crab were studied during a 2-year investigation in a marine environment. Adult crab abundance was estimated with a mark-recapture program at 13 sites. Males attain greater carapace widths (CW) than females. The CW frequency distributions were similar through time, being more symmetrical for females, but strongly skewed to the left for males. Females were significantly more abundant. Sex ratios fluctuated within the year; however, there were no significant differences between years or seasons. A U-shaped sex ratio curve as a function of size was found. A continuously low juvenile abundance was detected throughout the study. Ovigerous females were continuously present in the population during the study. Their percentage fluctuated through time, with the highest value in the last trimester, coinciding with the rainy season. Number of eggs per female increased as a linear function of carapace width, having a mean of 11,577 eggs and extremes of 3,724 and 27,134. No conspicuous crab migrations were observed; marked individuals reappeared consistently at the sites where they had been marked even 5 months after marking. Carapace width and length showed a high isometric correlation for both sexes. Females tend to have a longer intermolting time than males, although the difference is not statistically significant.
Document Type: Research Article
Publication date: 1989-07-01
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