La producción y la biomasa de Chione cancellata un bivalvo abundante en praderas de Thalassia testudinum se estudió desde marzo, 1984 hasta mayo, 1985 en Guaracayal, localidad de la costa sur del Golfo de Cariaco, Venezuela. La población está integrada principalmente por individuos entre 20 y 30 mm de longitud (80%), la cual presentó un bajo reclutamiento. La densidad promedio (45.54 ind m-2) y la biomasa promedio en peso seco de (7.37 g m -2) presentaron variaciones significativas entre los muestreos. Las tasas de crecimiento en individuos marcados en diferentes clases de tallas fueron más altas durante el período comprendido entre el 14-X-1984 al 10-V-1985. Utilizando un método para poblaciones con reproducción continua y clases de edades no separables se obtuvo una producción total de 17.34 g m-2 año-¹ durante el período de estudio. Los máximos valores fueron aportados por los bivalvos entre 20 y 30 mm de longitud y la mayor producción ocurrió entre el 28-II al 27-IV-1985. La tasa anual de renovación (P/B) se estimó en 2.65 año -1 .

Production and biomass of Chione cancellata, an abundant species in Thalassia testudinum sea beds, were studied from March, 1984 to May, 1985 in Guaracayal, Cariaco Gulf, Venezuela. The population distribution ranges were stable. Many individuals were 20-30 mm long (80%) and recruitment was low. The mean density was 45.54 ind m-2 with a mean standing dry weight biomass of 7.37 g m-2, both changed significantly with time. Growth rates in marked bivalves of different size classes was maximum in the period between 14-X-1984 and 10-V-1985. A production of 17.34 g m-2 year-1 was obtained using a method designed to study populations with continuous reproduction and indistinguishable age classes. The greatest production values were obtained for cockles 20 to 30 mm in length. Highest production was between 28-II-1985 and 27-IV-1985. The annual turnover rate (P/B) was 2.65 year-1.

Sexual maturity and other reproductive features of Tivela mactroides collected from Playa Guiria, Carúpano, Sucre State, Venezuela, were studied on the basis of smears and histological sections of gonads. There was continuous sexual cycle, but the development of the visceral mass, in females was less from January to March, 1975. A five steps maturity sexual scale was used to examine the histological sections, indicating that the dominant phase consist of a partial spawning. In total sexes and in intervals (10.1 - 30.0 mm) the ratio does not vary from the proportion 1:1, although the males outnumber the females; the number of females is significantly higher in the larger ones (30,1-45.00 mm).