Zooplankton — Bary 
21 
needed to produce a T-S-P diagram from 
which the distribution of the species group 
can be related to the hydrological conditions. 
Second, and the more important, is that in 
the majority of instances, those species which 
were taken in daylight occurred in similar condi- 
tions of temperature and salinity to the same 
species taken at night. In other words, when a 
species was collected in day and night tows, 
it occurred almost only in the environmental 
conditions which were acceptable. This is re- 
flected in the cohesion of the species’ distri- 
butions in each of the groups in the T-S-P 
diagrams. Therefore, day tows serve to sup- 
plement night tows from a distributional 
point of view in the diagrams, and it is be- 
lieved that data from both may justifiably be 
used in their construction. It has been found 
preferable to base interpretations of distribu- 
tional relationships on the species’ groups be- 
cause diurnal migration may be affecting 
detail. To guard against the possible adverse 
effects which might accrue, it would be de- 
sirable to occupy future stations at compar- 
able times, and preferably at night. 
In T-S-P diagrams planktonic groups, or 
species, are shown independently of their 
times of capture. Therefore, occurrences of 
either individual species, or groups of species, 
can be directly related only to the environ- 
mental conditions in which they were cap- 
tured, and to the species’ composition at 
other stations. The species, and through them, 
the species’ groups, will react to environ- 
mental changes (if of sufficient magnitude), 
but when these occur is not important in the 
T-S-P diagram. It is possible, therefore, to 
utilise asynoptically collected data in the 
T-S-P diagram. When species or groups of 
species are considered in relation to the geo- 
graphic distribution of the water properties 
then it becomes essential that as near synoptic 
series as possible are utilised. Nevertheless, it 
is believed that even for the T-S-P diagram, 
the nearer the approach is to synoptically 
made collections (as, for example. Series 4 to 
6), the more reliable will be interpretations 
from the diagrams. 
Pickford (1952: 209) has plotted the occur- 
rences of Vampyroteuthis infernalis in relation 
to density as well as salinity and temperature. 
She quotes a suggestion that the distribution 
of this species is determined by its being 
‘'passively caught in a layer of constant 
density. ...” Because of this suggestion, 
densities are plotted in Figures 3 and 10. It 
appears from Figure 10, however, that species 
may occur over a wide range of densities. It 
would appear, therefore, that this factor has 
little if any control over the distribution of 
surface zooplankton in the area of sampling. 
WATERS INFLUENCING SOUTHERN AND 
EASTERN New Zealand 
The surface waters are described as being of 
subtropical origin in the northern half and of 
subantarctic origin in the southern half of 
eastern New Zealand (Deacon, 1937; Garner, 
1954). To the west, and lying north of an ill- 
defined subtropical convergence zone (Gar- 
ner, loc. cit.) is Tasman Sea water. It is 
believed to move in an east-going drift to- 
wards New Zealand (Deacon, loc. cit.). On 
approaching the west coast of South Island 
the bulk of the water seems to be deflected 
northwards while some is thought to move 
southward and penetrate towards Foveaux 
Strait and Stewart Island (Deacon, Garner). 
Fig. 3. T-S diagram of surface waters, southern and eastern New Zealand. Stations at which plankton was 
collected are differentiated from those where only salinities and temperatures were taken. Stippled arrows indicate 
the direction of water movements within the diagram, as deduced from the distribution of properties and the 
form of the water envelope (and as later confirmed by the plankton distribution). An underlined station number, 
e.g., 212, indicates a night tow; an overlined station number, e.g., 216, indicates a station occupied at dawn or 
dusk. An unmarked station is one occupied in daylight. 
NOTE: The shape of this diagram superficially resembles that of the area in which samples were taken, but it 
is not a reproduction of the geographic area in another form. 
