Production estimate of Mytella falcata and M. guyanensis in natural beds of Ilha Comprida estuary (São Paulo, Brasil)

Abstract

The purpose of this paper was to estimate the natural stocks of Mytella falcata (D’Orbgny, 1846) and M. guyanensis (Lamarck, 1819) in the Ilha Comprida estuary, and then, to determine the distribution by length class and to quantify the mussels. This survey was conducted from September 2000 to August 2001. The mussel’s beds located between Pedrinhas district and Boguaçu river, in the Ilha Comprida and Iguape counties, were identified. In 13 places where the mussels occurred, a number of 84 samples were collected along 2 transects, completing a total of 1,092 samples. The animals were counted, measured and weighed. The natural beds of M. guyanensis and M. falcata are distinct: these 2 species have their own territory. The bivalves’ density (nº/m²) ranged from 16.6 to 264.4 for M. guyanensis and from 16.8 to 11,036.0 for M. falcata. The density of individuals was heterogeneous in every segment for both species. The maximum length observed was 65 mm for M. guyanensis and 46 mm for M. falcata. The average weight ranged from 2.85 to 4.01 g for M. guyanensis and from 0.10 to 1.79 g for M. falcata. It may be considered that the most appropriate places for extraction are those which presented higher density of animals and also high frequency of individuals with commercial size (> 40 mm for M. guyanensis and > 30 mm for M. falcata). The results of this research shall contribute to a sustainable exploitation plan.