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Changes in filtering efficiency of plankton nets due to clogging under tow
Smith, P.E.; Counts, R.C.; Clutter, R.I. (1968). Changes in filtering efficiency of plankton nets due to clogging under tow. J. Cons. - Cons. Perm. Int. Explor. Mer 32(2): 232-248. hdl.handle.net/10.1093/icesjms/32.2.232
In: Journal du Conseil - Conseil Permanent International pour l'Exploration de la Mer. Conseil Permanent International pour l'Exploration de la Mer: Copenhague. ISSN 0902-3232, more

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Keyword
    Marine

Authors  Top 
  • Smith, P.E.
  • Counts, R.C.
  • Clutter, R.I.

Abstract
    The problem of clogging is inherent in sampling plankton and this paper reports a study of clogging rates in tests of design variables of plankton nets, such as mesh size, filtering area, and net form. Telemetering flow meters were used to determine the effects of these variables on the rate of clogging of pairs of plankton nets under tow in waters of different clarity. Metering of flow is necessary for evaluating clogging. A water clarity measurement is not useful for predicting clogging rate and the gross appearance of the net after the tow is not necessarily a reliable indicator of whether clogging has lowered filtration efficiency during the tow. Fine mesh nets with comparable mesh aperture area filter as well initially as do nets with larger apertures but clog much more rapidly. Compared to silk with mesh apertures 0.550 mm wide, nylon with apertures 0.333 mm, 0.201 mm and 0.101 mm wide clog 3, 5 and 35 times as rapidly. In the cylinder-cone nets of 0.333 mm nylon mesh, the volume filtered at more than 85% efficiency was increased six-fold by doubling the filtering area. An equation describing the relation of the ratio of filtering area to mouth area for 0.333 mm nylon is: Formula where R is the ratio of filtering area to mouth area, V is the volume to be filtered and A is the mouth area of the net. The cylinder and cylinder-cone nets were superior in sustained filtration efficiency to cone-shaped nets. We attribute this advantage to the oscillations of the cylindrically placed mesh which tend to clean the mesh at a higher rate. An example is given of the method by which a new net was designed to lessen the probability of clogging.

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