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

Growth, productivity and potential for exploitation of the clam Tawera gayi from shallow waters (3 to 5 m) of Ushuaia Bay, Beagle Channel were investigated. Mean abundance and biomass in the study area were 1091 ± 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? = 28.03 mm, K = 0.288 y^1, t0 = -0.34 (r^2 = 0.83). Annual production of the population was estimated to be 120.45 g SFWM m^-2 y^-1, corresponding to a P/B ratio of 0.134 y^-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

A New Generic Placement for “Calliostoma” Blakei Clench & Aguayo, 1938 (Gastropoda: Trochoidea)

“Calliostoma” blakei Clench & Aguayo, 1938, described from Río Negro Province, Argentina, appears in the literature either under the genera Calliostoma, Photinula (Calliostomatidae) or as a member of the Umboniinae (Trochidae). The study of live-collected specimens allows to revise its generic placement.The species is characterized by a bipectinate ctenidium with short afferent membrane, isolated appendices in the left side of the neck, and the rachidian and the first lateral teeth reduced to their base. This set of characters, not present in any other trochoid, leads us to propose the new genus Carolesia for this species.Fil: Güller, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Zelaya, Diego Gabriel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin