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DISTANCE TO TRAWL GEAR CALCULATOR:
A Submarine Cable Protection A Tool To Estimate The Distance Of Trawl Fishing Gear From The Trawl Vessel BY SCOTT McMULLEN
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he Oregon Fishermen’s Cable Committee, Inc. (OFCC) offers to those involved in submarine cable protection a tool to estimate the distance of trawl fishing gear from the trawl vessel. This could be useful in determining the likelihood of a trawl vessel’s gear being snagged on a cable. The OFCC and many of the OFCC member company’s network operations centers (NOCs) use this tool in training scenarios and if a trawler calls in to a cable company “hotline” to report that they are snagged in the vicinity of an OFCC submarine cable. The chief purpose of the calculator is to be able to determine if the vessel’s gear is sufficiently distant from the subsea cable to conclude the cable is not at risk. In a normal training scenario, or in an actual hotline call from a trawler, the NOC operator takes the name of the skipper, vessel and call-back information. They then ask the skipper to provide the Latitude/Longitude and water depth of the vessel to determine the trawl vessel’s proximity to the subsea cable. The vessel is then plotted on an electronic chart plotter with submarine cables overlaid. The NOC operator then follows with questions on the trawler’s direction of travel, weather conditions and the following questions about the fishing gear:
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SUBMARINE TELECOMS MAGAZINE
• Type of trawler (i.e. double rig shrimp trawl, midwater trawl or bottom trawl) • Length of main trawl wire (warps) out (from the vessel to the trawl doors) • Length of sweeps, also known as mudgear • Length of bridles (between the sweeps and the wings of the net) To use the calculator, NOC personnel use information provided by the vessel to fill input cells in the MS Excel© spreadsheet with information on the fishing gear and the water depth. The calculator, which is based on Pythagorean’s theorem, estimates the distance to the trawl doors and net by assuming a Right triangle exists between the vessel, the seafloor below the vessel and the seafloor at the trawl doors. A formula using this equation was taught to fishermen taking classes at the North Sea Centre in Hirtshals, Denmark in the 1980’s. In the Pythagorean equation, a² + b² = c², c represents the hypotenuse, while a and b represent the other two sides of the right triangle. When the length of any two sides are known, the length of the third side can be calculated.