Growth and spatial distribution of Cassidulus mitis (Echinodermata: Echinoidea) on a sandy beach in Southeastern Brazil |
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Authors: | C A Freire P J P Santos N F Fontoura R A O Magalhães P A Grohmann |
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Institution: | (1) Departamento de Zoologia, Instituto de Biologia, CCS-BI A, Universidade Federal do Rio de Janeiro, Ilha do Fundão, CEP 21941 Rio de Janeiro, RJ, Brazil;(2) Instituto de Biociencias, Pontificia Universidade Católica do Rio Grande do Sul, Avenida Ipiranga 6681, CEP 90620 Porto Alegre, RS, Brazil;(3) Present address: Max-Planck-Institut für Systemphysiologie, Rheinlanddamm 201, W-4600 Dortmund 1, FRG |
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Abstract: | Using a hand dredge, a population of Cassidulus mitis Krau, 1954 was sampled monthly from February 1986 to January 1987 at 15 stations offshore from Vermelha Beach (22°57 18 S; 43°9 48 W), in water depths ranging from 0 to 6 m. The sex ratio indicated a slight numerical dominance of females for adults and a larger numerical female dominance for juveniles. A von Bertalanffy growth curve was estimated as L=71.00 (1-e(-0.390t)), where L=length (mm) and t=time (yr). The instantaneous natural mortality rate (M) was estimated as 0.812. The population occupies a zone parallel to the beach, and displays a spatially aggregated pattern, with higher densities in areas characterized by coarse and very well sorted sand containing low amounts of organic matter. |
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