Instrument: Clarke-Bumpus Sampler

"Clarke and Bumpus designed a small two-messenger zooplankton collection system that could be deployed as multiple units on the wire and had a positive means of opening and closing the mouth of the net. A frame attached at the top and bottom to the towing wire supported a cylindrical tube 12.7 cm in diameter and 16 cm long, to which a net was attached. In the mouth of the tube was a flat plate (like a stove pipe damper plate),which closed off the cylinder when the net was deployed. When the first messenger released a spring-loaded latch, the plate was rotated 90 degrees, opening the net; a second messenger rotated it another 90 degrees to close the net. A flowmeter at the back of the cylinder recorded flow through the net." (Wiebe and Benfield, 2003) The instruments were equipped with No. 2 silk nets (22 strands/cm.) and "oblique" hauls were made at a speed of about 2 knots for periods of 25 to 40 minutes.

References:
CLARKE, G. L., AND D. F. BUMPUS, 1940. The Plankton Sampler-an instrument for quantitative plankton investigations. Linnological Society of America, Special Pub., (No. 5): 1-8.

Wiebe, Peter H. and Mark C. Benfield, 2003. From the Hensen net toward four-dimensional biological oceanography. Progress in Oceanography, 56, pp. 7-136.