324 
December 8, 1949. Casual hauls were also 
made irregularly throughout the year at 
various stations in the southern sector. 
NETS AND HAULS 
Three different plankton nets were used, 
which are hereafter referred to by the diameter 
of their mouth openings: 100 cm., 22 cm., 
and 12.3 cm. 
The 100 cm. net had an overall length of 
about 5 meters. The forward part, 180 cm. in 
length and 100 cm. in diameter, was made of 
fish net of 1.5 cm. stretched mesh, and was 
fastened to the net ring with a 25 cm. strip 
of canvas. The forward part was lined with 
an inner skirt of No. 24 grit gauze (0.81 mm. 
aperture) which was fastened to the canvas 
forward, but was free aft. The middle part of 
the net was 100 cm. in length and 100 cm. in 
diameter. It was made of No. 24 grit gauze 
and was fastened to the forward part with a 
20 cm. strip of canvas. The after part of the 
net was 190 cm. in length and tapered in 
diameter from 100 to 9 cm. It was made of 
No. 40 grit gauze (0.47 mm. aperture) and 
was attached forward to the middle part and 
aft to a 9 cm. detachable net band by small 
strips of canvas. The cod end, 30 cm. in 
length and 9 cm. in diameter, was also made 
of No. 40 grit gauze, and was fastened to the 
net band with a canvas strip. 
The 22 cm. net was a simple conical net 
made of No. 2 Dufour bolting silk (0.35 mm. 
aperture). Its overall length was 50 cm. The 
forward part was fastened to the net ring with 
canvas, and the after end was tied with tape 
rather than having a detachable cod end. 
The 12.3 cm. net was a regular Clarke- 
Bumpus (Clarke and Bumpus, 1940), with a 
closing device (which was not used) and a 
current meter. It was also made of No. 2 
Dufour bolting silk. 
In the four main surveys two nets, the 
100 cm. and either the 22 cm. (Surveys 1, 3, 
and 4) or the 12.3 cm. (Survey 2), were 
hauled simultaneously at slow speed just be- 
low the surface. The large net was towed from 
PACIFIC SCIENCE, Vol. V, October, 1951 
the boom, which was slung out on the star- j 
board side, whereas the small net was towed 
directly astern. Each haul was of exactly 10 
minutes duration. The hauls at each station li 
were made in duplicate, one in one direction |i 
(A) and the other in the opposite direction 'j 
(B) following a reversed course. As nearly as i 
can be determined by timing chips of wood i 
as they passed from bow to stern, the ship’s [ 
speed varied from 1.8 to 2.2 knots. The I 
slower speeds resulted when towing against i 
the wind, and the faster speeds when towing | 
with the wind. 
In the two interim surveys, two identical | 
22 cm. nets were used, one towed just below | 
the surface and the other at a depth. To avoid 
the wash of the ship’s propeller, the towlines 
were fastened to a spar which projected hori- | 
zontally from the port side of the vessel, for- |j 
ward of amidships. The depth, was adjusted j 
by fastening lead weights to the net ring and j 
by varying the length of towline. The depth i 
was estimated by calculation, knowing the 1 
length of line and the angle of stray. The | 
closing Clarke-Bumpus net was not used for | 
hauls at a depth because of the danger of 
snagging on the uneven bottom. Further de- 
tails on haul number, direction, and spacing 
will be given in a later section of this report. 
After each haul, the 100 cm. net was washed 
with sea water from a pressure hose to con- | 
centrate the plankton in the cod end. The 
smaller nets were jerked upward and down- 
ward in the water to accomplish the same 
purpose. The plankton material was then 
transferred to quart jars (100 cm. net) or pint 
jars (22 and 12.3 cm. net), and formalin was 
added for preservation. To prevent contam- 
ination from station to station, the 100 cm. 
net was towed inside-out, with the cod end 
removed, between stations. The smaller nets 
were washed thoroughly in sea water between 
hauls. j 
In a few cases, when an exceptionally large : 
catch was made with the 100 cm. net, a small 
quantity of plankton was lost in attempting ' 
to transfer the material from the cod end to j 
