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

Patterns of larval settlement were examined in two populations of Chilean oysters, Tiostrea chilensis, in northern New Zealand. Artificial settlement surfaces were used to measure larval settlement rates over 36 mo at one site and 20 mo at the other. Larvae settled at both sites throughout the year, but with distinct peaks beginning in late winter and early spring and often continuing into early summer. This pattern was unlike those found previously in T, chilensis populations at higher latitudes. The annual pattern of larval settlement was closely related to the pattern of oyster brooding over the same period. Overall, the results suggest that colder water temperatures during winter (i.e., below 12°C) are important in synchronizing the annual cycle of larval production and settlement in this oyster species.