For zooplankton biomass (displacement volumes), either a "non-closing net" and "modified Clarke-Bumpus" net were used.|
The "non-closing net" was the (1958-1959) standard CalCOFI net, with a mouth diameter of one meter. The main body of the net was made of 30XXX grit gauze (nominally 0.55 mm square mesh) with a rear section and cod-end of 56XXX grit gauze (nominally 0.25 mm square mesh). A flowmeter was mounted in the center of the mouth of each net.
The Clarke-Bumpus net had a mouth diameter of 25 cm. The body of the net was made of 706 Nitex with a 316 Nitex cod-end.