Abstract
Spatial distribution, population density, number of ovigerous females, and relative growth of Microphrys bicornutus were studied in an extremely shallow Thalassia complex (Buchuaco- Venezuela). Monthly sampling was undertaken in 5 different biotopes (zones) (July 1988 to December 1990). Zone 3 (coral rubble) was the least populated by M. bicornutus . The highest densities were found in Zones 1 (coral rubble and macro algae) and 4 ( Thalassia and calcareous algae). Crab size ranged between 1.86 and 35.40 mm (carapace length). The largest mean size was found in Zones 2 and 5, and the smallest in Zone 1. The least mean percentage of ovigerous females was found in Zone 3, and the highest in Zone 5. There were strong temporal fluctuations, with the absence of ovigerous females in the first months of each year. The biometric data showed that pre-pubertal males ranged from 1.80 to 24.20 mm carapace length, and post-pubertals from 15.16 to 26.15. Pre-pubertal females ranged from 3.16 to 20.25 and post-pubertals from 8.84 to 21.85. Zone 3 was the most inadequate biotope for M . bicornutus , as it had the lowest density and the least mean percentage of ovigerous females. Zone 4 was the most appropriate biotope. Temporal absence of ovigerous females and the small sizes of the crabs in Buchuaco could be due to extreme environmental conditions.
Highlights
There are numerous publications that deal with the spatial distribution of marine organisms at the community and species levels
Several factors have been given to explain the spatial distribution of crustacean decapods
Thalassia seagrass-beds are found in the abovementioned areas, and in two other localities situated in the Paraguaná Peninsula (Carmona and Conde, 1989)
Summary
There are numerous publications that deal with the spatial distribution of marine organisms at the community and species levels. Several factors have been given to explain the spatial distribution of crustacean decapods. Salinity gradients (Norse and Estevez, 1977; Norse, 1978a, 1978b), content of organic matter and sediment texture (Fransozo et al, 1992; Mantelatto, 2000), degree of exposure to wave action (Murphy and Fonseca, 1995; Martínez Iglesias and García Raso, 1999; Carmona-Suárez, 2000), and moulting stage (Ryer et al, 1990), are considered to be some of the features that could explain the population and community distribution of several decapod species. Thalassia seagrass-beds are found in the abovementioned areas, and in two other localities situated in the Paraguaná Peninsula (Carmona and Conde, 1989). In the State of Falcón, stunted growth and marked seasonal reproduction of several Brachyura have been observed and hypothesized to be correlated to extreme environmental factors (Conde et al, 1989; Conde and Díaz, 1992; Carmona-Suárez, 1992, 2000)
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