Zooplankton — Bary 
15 
tribute towards an objective determination of 
the indicator species in an area as compara- 
tively little known as that about southern 
New Zealand. Further, the distribution of the 
species in the diagram can be used to confirm 
the distribution of the different waters. Sa- 
linity and temperature changes may take 
place over shorter, or longer distances, but 
may not be readily related to variation in the 
plankton occurrences. In the T-S-P diagram 
both physico-chemical changes in the en- 
vironment, and the response to these of 
planktonic organisms, are demonstrable. 
ACKNOWLEDGEMENTS 
This study has been carried out during my 
service with the New Zealand Defence Scien- 
tific Corps. Facilities have been provided by 
the Zoology Department, Victoria University 
College, Wellington, and the New Zealand 
Oceanographic Institute, D.S.I.R., Welling- 
ton, and I am grateful to Professor L. R. 
Richardson and Mr. J. W. Brodie, respec- 
tively, for these. I am indebted to the Do- 
minion Chemical Laboratory for making the 
necessary salinity determinations. 
Sincere thanks are due to Dr. Keith Sheard, 
C.S.I.R.O., Division of Fisheries & Oceanog- 
raphy, University of Western Australia, Ned- 
lands, W.A.; Mr. K. Radway Allen, Fisheries 
Laboratory, Marine Department, Wellington; 
Dr. R. W. Burling and Mr. D. M. Garner, 
N.Z. Oceanographic Institute; and Dr. M. 
Blackburn, University of Flawaii, Honolulu; 
and Dr. Thomas Austin, U.S. Fish & Wildlife 
Service, Honolulu, Hawaii, for discussions 
and constructive criticism of the technique. 
I am grateful to Mrs. M. Fontaine, c/o 
"Discovery” Investigations, British Museum 
(Natural History), London, for identifying 
Calanus simillimus, and to Dr. Keith Sheard, 
for confirming the identity of Thysanoessa 
gregaria. 
MATERIALS AND METHODS 
The collections of this study were made 
during surveying operations of H.M.N.Z.S. 
"Lachlan” during January, February, and 
March, 1951. Stations were occupied between 
Wellington and the Auckland and Campbell 
islands (Figs. 1, 2), and data are from surface 
samples. Temperatures and salinities have 
been obtained for all stations; in addition, 
temperatures were usually taken at regular 
intervals between stations. Salinities and tem- 
peratures of subtropical water have been in- 
cluded from a cruise between Wellington and 
Auckland via the west coast of North Island 
(small, open circles in Fig. 3 and see pp. 
21-23). 
The temperature and salinity data from the 
above sources have been used to construct 
the T-S diagram (Fig. 3). Ail stations are in- 
cluded. Those for which only physico- 
chemical data are available are differentiated 
from those at which plankton tows were 
made as well. 
Surface plankton collections were made at 
65 of the stations (see Table 4). Hauls were 
of three minutes’ duration, and procedure and 
gear were carefully standardised (Bary, in 
press). Samples have been analysed quantita- 
tively and the order of abundance of the se- 
lected species has been entered on Figures 5 
to 10. The quantitative treatment is of value, 
but its importance is reduced in the present 
study since samples were taken at varying 
times in the 24-hour period (see p. 19). 
A scale of smaller increments thanis usual 
in reporting on quantitative plankton analyses 
has been used in this study. They have been 
adopted because the short hauls frequently 
resulted in only small numbers of organisms 
being captured (see Table 4) . It was necessary 
that occurrences of species in these small 
catches be adequately distinguished in order 
to detect whether there were reactions of spe- 
cies to changed environmental conditions and 
if these might be of ecological value. 
Stations can be grouped conveniently into 
several series, as they were occupied during 
individual cruises (Series 4, 5, 6, and 7) or, 
failing this, in a particular area (Series 1, 2, 
and 3). In general, a series is spread over a 
