Oceanographic net for horizontal or oblique towsin CalCOFI design
Based on the design of California Cooperative Oceanic Fisheries Investigations (CalCOFI), the Ring Trawl Net today is the standard non-opening/ non-closing plankton net for quantitative sampling of larger volumes of water during horizontal or oblique tows. The 100 cm diameter stainless steel ring, equipped with a 4 meter long net bag should be operated in conjunction with a 22 kg V-Fin depressor to create negative lift at the instrument. For easy retrieval the sample is concentrated inside a removable plastic net bucket with side window (covered with sieve gauze). A Mechanical Flow Meter can be fixed in the net to measure the filtered water volume.
Remark:
The conventional operational setup of the Ring Trawl Net follows the traditional standard methodology of the California Cooperative Oceanic Fisheries Investigations (CalCOFI) program where samples are obtained by lowering the net to a set depth and towing it obliquely at a 45° angle to the surface at a constant speed. However, the net may also be used for horizontal and flat-angled oblique tows. For these applications simply remove the mounting bar for the depressor from the net ring and shackle the steel rope of the depressor into the end eye of the winch rope.
