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A Free‐falling Drop Net for Quantitatively Sampling a Water Column
Author(s) -
Hoagman Walter J.
Publication year - 1977
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/1548-8659(1977)106<140:afdnfq>2.0.co;2
Subject(s) - net (polyhedron) , water column , cylinder , drop (telecommunication) , falling (accident) , environmental science , hydrology (agriculture) , geology , sampling (signal processing) , mechanics , mathematics , geometry , geotechnical engineering , physics , engineering , oceanography , optics , mechanical engineering , medicine , environmental health , detector
A new drop net is described which samples a column of water from surface to bottom. The net is non‐sprung and falls freely to bottom. Surface pontoons release the net as a ring covering 182 m 2 ; the net assumes a cylinder shape closed at the top, and then strains the water column as it descends. On bottom, the net is pursed and retrieved. A parachute effect combined with vertical vectors of downward force keeps the net at full aperture. Field tests with 1.0‐m and 15.2‐m diameter models in depths to 28 m were made in Green Bay, Lake Michigan. Details of net construction and the delivery device employed are provided.