Population dynamics of the venerid bivalve Tawera gayi (Hupe, 1854) in the Ushuaia Bay, Beagle Channel

Abstract

Growth, productivity and potential for exploitation of the clam Tawera gayi from shallow waters (3¨C5 m) of Ushuaia Bay, Beagle Channel were investigated. Mean abundance and biomass in the study area were 1091 ¡À 737 ind. m-2 and 901.83 g SFWM m-2 (shell-free wet mass), respectively. Individual growth was described best by the von Bertalanffy growth model with the parameter values H¡Þ= 28.03 mm, K = 0.288 year-1, t 0= 0.34 (r2 = 0.83). Annual production of the population was estimated to be 120.45 g SFWM m-2 year-1, corresponding to a production-to-biomass ratio (P/B) of 0.134 year-1. The single negative exponential mortality model does not fit the population mortality pattern, but predation by gastropods (Xymenopsis muriciformis, Trophon geversianus, Natica sp.) appears to be the major cause of mortality. These highly mobile predators together with the comparatively slow growth and low turnover of T. gayi in Ushuaia Bay limit its potential for sustainable commercial exploitation.