Alimentación de la vieira patagónica Zygochlamys patagonica (King y Broderip, 1832) en el banco Reclutas (39ºS-55ºW) durante un período anual
Zygochlamys patagonica is distributed in the Atlantic Ocean from 35 degree S to Tierra del Fuego (Argentina), and in the Pacific Ocean, up to 42 degree S, between 40 and 200 m depth. There are 9 beds in the Argentinian Sea. Scallops are suspensivore organisms, feeding on detritus and phytoplankton. The aims of this thesis are to make a quali-quantitative study of the diet of the Patagonian scallop, to detect seasonal changes in diet and to link these results with oceanographic conditions and with the growth pattern. Gut contents of 180 scallops were analyzed from samples (n=30) taken in June, August, October and November 1996, and February and March 1997. This procedure was tested statistically. Twelve species of diatoms and resting stages, five species of dinoflagellates and two different forms of cysts, two species of silicoflagellates, prasinoficeans and a number of organisms and rests grouped as miscellanea were found in gut contents of Patagonian scallop. The dimensions of particules varied between 19 and 170 mu m (mainly 25-60 mu m). Total number of particles varied significantly during different months (mean: between 300 and 800 particles/gut), while maximum values were found in November. Diatoms were always the main group followed principally by dinoflagellates. The main diatom species was Paraliasulcata, except in February when Thalassiosira spp. predominate. It is possible that processes of sedimentation or phytoplankton "rain" to the bottom occur during spring in Reclutas bed, allowed by the oceanographic conditions (thermocline in formation), originating an increment in food supply after the phytoplankton bloom. The period of maximum food ingested totally agrees with the period of maximum somatic (muscle) growth, registered in this species by other authors.