POPULATION-DYNAMICS OF THE BIVALVES VENUS-ANTIQUA, TAGELUS-DOMBEII, AND ENSIS-MACHA FROM CHILE AT 36-DEGREES-S

Venus antiqua (King and Broderip, 1832), Tagelus dombeii (Lamarck, 181 8), and Ensis macha (Molina, 1782) are dominant members of the shallow -water, soft-bottom communities of the Chilean coastal zone. The repro duction, growth, mortality, and production of these species were studi ed in a small bay in Chile at 36 degrees S. All of these species had a n annual reproductive cycle with a short spawning season in summer. Th e growth parameters of the von Bertalanffy growth function were: V. an tiqua: L(infinity) = 73.9 mm, K = 0.218/y, t(0) = -0.161/y; T. dombeii : L(infinity) = 88.5 mm, K = 0.232/y, t(0) = -0.658/y; E. macha: L(inf inity) = 189.9 mm, K = 0.210/y, t(0) = -0.578/y. Somatic 1-, gonad pro duction (grams of ash free dry weight per square meter per year) and t he P/(B) over bar-ratio of the population were 22.0, 270.3, and 0.180 (V. antiqua), 7.8, 22.9, and 0.292 (T. dombeii), and 9.7, 98.5, and 0. 222 (E. macha), respectively. Total mortality (Z) and natural mortalit y (M) were 1.084 and 0.275 (V. antiqua), 0.839 and 0.191 (T. dombeii), and 1.089 and 0.216/y (E. macha). Production estimates agree very wel l with data of the same superfamilies taken from the literature.