Larvae of the incubatory oysterTiostrea chilensis(Bivalvia: Ostreidae) in the plankton of central and southern New Zealand

Abstract

Abstract Planktonic larvae of the flat oyster, Tiostrea chilensis (Philippi, 1843), were discovered in Tasman Bay and Golden Bay (central New Zealand) and Foveaux Strait (southern New Zealand). This oyster was previously thought not to have planktonic larvae. The central New Zealand larvae ranged from 394 to 533 μm in length, significantly smaller than those from southern New Zealand which ranged from 448 to 541 μm. By comparison the prodissoconch length of spat indicated these larvae settled between 429 and 537 μm in length in Tasman Bay and Golden Bay, and between 470 and 556 μm in Foveaux Strait. We estimated the total production of larvae as well as the total numbers of planktonic larvae released by oysters in the central and southern areas of New Zealand, the data point to a greater proportion of planktonic larvae being released in the central area. The great majority of T. chilensis larvae appear to be incubated until ready to settle. The ability to release some planktonic larvae should play a considerable part in maintaining gene flow in T. chilensis, enhance dispersal, and could provide a further stabilising factor in the populations and the fisheries of Foveaux Strait and Tasman and Golden Bays.