Western Marine Electronics (WESMAR ) claim the new sonars they launched at the Pacific Marine Expo in Seattle last November "offer features never before available".
Each system has a current-speed and direction sensor that detects the direction of the current in the area of the headrope. It says currents at trawl depth are often different in speed and direction from those on the surface. Towing at an angle to the current will skew the net and reduce the effective catch areas. Towing against the current will open the net and enhance fish catch. The readings of speed and direction allow the skipper to adjust vessel GPS speed accordingly, therefore improving fish catching capability and reducing fuel usage, WESMAR said.
WESMAR says the TCS 780 is a forward-looking and net-profiling sonar while the smaller TCS 380 is the same but without the forward-looking capability. Wesmar says these are the first wire trawl sonars capable of directly measuring speed and current direction at trawl depth.
At less than 10 pound in weight it says it believes the TCS 380 is the lightest in the world. By positioning the net ahead of fish that swim with the current, the two models can fill the net much faster, so reducing tow time and fuel consumption.
Dennis Soderberg, WESMAR vice president, says "Operation is with a new hand-held controller, which allows operation anywhere in the wheelhouse. An optional wireless controller adds even more total versatility. Audio catch sensors, when triggered, will sound an alert in the wheelhouse so the operator knows the location of the fish in the net. The equipment can operate up to six sensors, an increase of 50 per cent over earlier gear.
They also provide complete, underwater monitoring of trawl net openings. The result is a constant indication of the bottom, a 360-degree picture of the net mouth (full length of the head rope, wings and footrope), plus fish swimming in or around the net.
Other specification includes: an on-screen clock timing the tow; special viewing options in split screen mode with profile and down sounder. The down sounder and profile work independently, giving constant and independent updates. The down sounder provides a steady view of the net opening, fish and footrope; while the captain can take measurements in the other screen. A level indicator displays the pitch and roll position of the head rope unit and helps survey the affect which the current has on the net. If the current is not in line with the mouth of the net, it will cause the net to lean to one side. A net that is not horizontal will not herd efficiently, losing fish off to one side. As the main wires are adjusted, to align the net to the current, the level indicator will show the correction; self-tuning from the front panel, eliminating the need for sending equipment to the factory for calibration; a proprietary imbedded pressure compensation system; and an advanced digital transmitter-receiver portion.
