42 
PACIFIC SCIENCE, Vol. XX, January 1966 
try to maintain a wire angle of 45°. Generally 
a maximum depth of 300 m was desired, but 
actual depths range from 203 to 401 m for 
hauls listed in Tables 1 and 2. At some stations 
identified in Table 1, the hauls were made to 
a desired maximum depth of 140 m (actual 
depths from 126 to 145 m); in each of these 
cases the zooplankton volume for a haul to 300 
m was estimated as explained in Appendix I 
from the volume obtained, and the estimate 
(only) was listed and used in the analysis. 
Measurement of standing crop was expressed 
as milliliters of displacement volume of the 
catch of small organisms (i.e., excluding or- 
ganisms >5 cm in length or >5 ml in volume) 
per 10 3 m 3 of water strained. This was regarded 
as a very imperfect estimate of standing crop of 
herbivores, because the net catches many pri- 
mary carnivores but not all herbivores. An at- 
tempt to minimize these difficulties for some of 
the zooplankton data is described below (see 
section on Copepods). 
Most of the zooplankton measurements in 
Tables 1 and 2 have been published previously 
(see , references in section on Chlorophyll a, 
above); other observations, namely those for 
Table 1, B, are from Griffiths (MS). 
Micronekton 
Micronekton, which consists of active animals 
about 1 to 10 cm long, was collected with the 
large net and towing routine described by Black- 
burn and associates (1962:31-32). In brief, an 
oblique haul was made between 90 m (on the 
average; actual depths ranged from 72 to 115 
m) and the sea surface, from a ship steaming 
at about 5 knots, with a large open subpyramidal 
net of uniform mesh aperture about 5.5 mm by 
2.5 mm. Watery planktonic organisms were dis- 
carded from the catch, which was then sorted 
into its fish, cephalopod, and crustacean com- 
ponents; displacement volumes of these com- 
ponents were measured. The volume of water 
strained was estimated from the mouth-area of 
the net (2.3 m 2 ), the distance steamed during 
the haul, and a filtration coefficient of 0.757. The 
coefficient was measured in the way described 
by Blackburn and associates (1962); a subse- 
quent experiment yielded a similar value, 0.738. 
Measurements of standing crop were ex- 
pressed in ml/ 10 3 m 3 of water strained. For the 
purpose of this study only the fish and cephalo- 
pod components (combined) are considered. 
These may be regarded, in the main, as primary 
carnivores, but the Crustacea are probably a mix- 
ture of herbivores, primary carnivores, detritus 
feeders, and omnivores; it is probable that some 
fish and cephalopods avoid the net. The author 
is responsible for these data in Table 1, none 
of which have been published previously in their 
present form. 
Copepods 
Measurements of standing crop of copepods 
from the zooplankton are available for two 
cruises, for which it was thought to be particu- 
larly important to have a better measurement of 
herbivore standing crop than that given by zoo- 
plankton. Even this measurement is imperfect, 
because some herbivores are excluded and some 
copepods are probably carnivorous. The data are 
from R. C. Griffiths (unpublished). They were 
obtained by a volumetric method, which is es- 
sentially that of Yentsch and Hebard (1957) 
with minor refinements (Griffiths and Fee, 
MS), and are expressed in ml/10 3 m 3 of water 
strained. The manual sorting of copepods from 
the zooplankton is so time-consuming that no 
attempt was made to provide similar data for 
all cruises. 
The copepod volumes are all much lower 
than the corresponding volumes of zooplankton 
(Table 1, A and B); they average 4.3% of the 
zooplankton and none is higher than 12%, al- 
though a figure of a much higher order was in- 
dicated by gross inspection of most of the 
unsorted zooplankton samples. This is clearly an 
effect of the different volumetric method which 
was used for the copepods; interstitial water is 
far more efficiently removed by this method than 
by the ordinary filtration method which was 
employed for the unsorted zooplankton. Possibly 
it is also an effect, due to shrinkage in formalin, 
of the later date at which the copepod measure- 
ments were made. 
The volumes of zooplankton and carnivorous 
micronekton may not be precisely comparable 
either, although both were measured by the same 
(ordinary filtration) method at about the same 
