Zooplankton associations off otago peninsula, south‐eastern New Zealand, related to different water masses

Distinctly different water masses are to be found near the sea surface within 40 km of the coast off Otago Peninsula, south‐eastern New Zealand (45° 50’ S, 170° 45’ E). Although the hydrological regime is complex in this area, the three water masses have a stable relationship to one another: neritic water close to shore, then modified Subtropical Water, and Subantarctic Water off shore. Quantitative zooplankton samples from the upper 150 m were taken from a four‐station, 50‐km latitudinal transect at monthly intervals over 15 months, October 1966‐December 1967. Data were analysed by group‐average sorting methods into a hierarchical classification of 37 components, identified to species where practicable. Each species group was clearly associated with particular stations and from this hydrological affinities were deduced. The classification recognised a primary division between “neritic” and “oceanic” groups of zooplankton, each of which contained further subdivisions. “Neritic” zooplankton contained “coastal” and “shelf” subgroups; “oceanic” plankton contained “transitional” and “subantarctic” subgroups. Zooplankton from Otago waters had hydrological affinities which were consistent with their wider distributions. Presence of subtropical zooplankton in Otago waters helps to resolve confusing differences between various interpretations of surface circulation in the southern Tasman Sea.