Variability in life history characters of the Chilean oyster Tiostrea chilensis (Philippi, 1845)

Differences in some life history characters of the Chilean oyster, Tiostrea chilensis, were examined for three populations in the northern North Island of New Zealand. Previous studies of oyster populations in the South Island have predicted that populations at lower latitudes would produce smaller-sized larvae and substantial numbers of planktonic larvae. For only one northern population was there some evidence of the release of planktonic larvae. However, larvae from all three northern study populations were smaller in size than reported for all other locations, both in New Zealand and Chile. This was because of a trend for larval size to vary inversely with sea water temperature. The results of this study indicate that life history characters of this species can vary greatly at both the individual and population level. Furthermore, this variability does not always conform to commonly proffered life history principles which assert that planktonic development and small larvae become more common at low latitudes.