Annual pattern of brooding in populations of Chilean oysters, Tiostrea chilensis, (Philippi, 1845) from northern New Zealand

The annual pattern of brooding in two populations of adult Chilean oysters, Tiostrea chilensis, in northern New Zealand, was examined. Both populations were brooding larvae throughout the year, with less brooding activity in winter and increased larval production around spring and early summer. Despite the extended brooding season, the proportion of individuals brooding during peak periods remained high. Larger broods of larvae appeared to be associated with periods of raised brooding activity and lower water temperatures. In both populations, there were no differences in the size of oysters brooding at different times of the year. Overall, the annual pattern of brooding in both populations was markedly different from previous reports for this species in other regions. These differences tend to confirm the role of water temperature as the most important environmental factor regulating the annual pattern of reproduction in this oyster species. This conclusion has important implications for the hatchery production of larvae for aquaculture.