GROWTH RATE OF THE SEA URCHIN TRIPNEUSTES GRATILLA ELATENSIS

Abstract

ABSTRACT Growth rates of the sea urchin Tripneustes gratilla elatensis were recorded from two sources: a natural population and in culture, under various diets. T. g. elatensis recruited in the spring, reached an average size of 35 mm horizontal diameter (HD) and a maximum size of 60 mm HD in 150 days. The annual growth rate coefficient, k, of both the Brody-Bertalanffy and Johnson's growth equations for a field population, was 0.87. The fastest-growing individuals, in both equations, showed a growth rate coefficient of 1.46 and 2.89, respectively. The mean growth rate of sea urchins fed the green macroalga Ulva lactuca in culture was higher than that obtained in three other groups: the field population (k = 2.14 and 2.92, respectively for both equations) those in culture fed algal turf (k = 1.46 for the Brody-Bertalanffy equation and 2.05 for Johnson's) and those fed the seagrass Halophila stipulacea (k = 1.40 and 2.05, respectively).