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Zooplankton of Wellington Harbour, New Zealand

Introduction

Introduction

The present Wellington Harbour plankton collecting programme commenced on 2 January 1961, under the direction of Professor L. R. Richardson, assisted by members of the staff and research students from the Department of Zoology, Victoria University of Wellington. Subsequent routine samples were taken at weekly intervals, and these samples revealed a rich plankton fauna in Wellington Harbour. By January, 1964, the present collection consisted of about 250 plankton samples. Several small breaks in the continuity of the record occurred, the longest of these being in March, 1962, when no samples were taken. However, the greater part of the three-year period is covered by four to six samples every month. This plankton programme is continuing.

The fauna discussed in this paper is macroplanktonic. It includes the Coelenterata represented by Hydrozoa and Ctenophora; Chaetognatha of the genus Sagitta; Crustacea including both permanent and temporary planktonic forms; Chordata represented in the Urochordata by the family Salpidae, and in the Vertebrata by the eggs and larvae of various fish. Particular attention has been given to both decapod and stomatopod larvae which form a major component of the plankton. Other groups not mentioned above formed only a small fraction of the total volume of plankton samples, and these have been disregarded.

It was not possible to identify all the taxa to the specific level, as the systematic status of many New Zealand marine organisms has not yet been determined. Many crustacean larvae reared in the laboratory to juveniles still eluded final identification, as juvenile stages frequently lacked the adult characters used in classification.

In the plankton, short period fluctuations of considerable magnitude were observed. In some cases these resulted in the absence of species normally abundant. However, the broad seasonal trends in the Wellington Harbour plankton have emerged with quite startling clarity, and some quantitative work has been done to assist in the description of these trends. In addition a number of relatively common and distinctive species were identified and selected as seasonal indicator species. An annual plankton calendar has been prepared from monthly and seasonal changes in the abundance of these species.

The decapod larval terms "zoea" and "megalopa" are here employed in the sense suggested by D. I. Williamson (1957) and where possible the ambiguous term "post-larva" has been avoided. Non-larval stages following the megalopa have been termed "juvenile stages".