The Trawl Eye is Scanmar’s most advanced sensor and more than 1000 Trawl Eyes have been sold since their introduction in 1990, and we are still alone on the market with such an advanced sensor. The Trawl Eye is suitable for use in bottom trawling as well as pelagic trawling in most fisheries around the world. Many of the species are in fact impossible to see on an echo sounder or sonar, and trawling without a Trawl Eye is like fishing blindfolded.
Because the Trawl Eye, when placed on the headline, is close to where the fish is, it has much better detecting ability than anything corresponding mounted on the vessel. A skipper with experience will therefore easily determine whether it is fish or bait, and if he is fishing for the “right species”, and not wasting time and resources unnecessarily.
More and more of those who do pelagic trawling have begun to use an extra Trawl Eye in the belly, often together with a Flow sensor or an Angle sensor, in order to ensure that what they see in the trawl opening ends up in the back of the bag.
Two different types of Trawl Eye
With the many areas of application and different fisheries, Scanmar was quick to see the need for two variations of the Trawl Eye. The broad beam Trawl Eye was fist introduced to the marked, intended for trawls with low opening and is today largely used for catching white fish. In fishing for shrimp or species that keep close to the seabed, the narrow beam Trawl Eye usually offers the best detection abilities.
Narrow beam Trawl Eye is usually used in pelagic trawling as well.
Bottom trawling
Clear detection of ”Hoki” close to the seabed.
The Trawl Eye gives precise information of the trawl opening and contact with or clearing from the seabed. For bottom trawling you can therefore keep the trawl down on the seabed and avoid that it lifts in areas where essentially all the fish enters, i.e. in the center of the trawl.
Amongst the twin rig trawlers there are currently many that use a Trawl Eye on each trawl to compare the trawl openings, seabed contact and not to mention the catch entrance. When they have more entrance in one trawl they move sideways so that they achieve maximal entrance in both trawls.
To achieve the best possible results it is important that the Trawl Eye is mounted securely tight and directly over the bottom gear. Many trawls have to a greater or lesser extent an overhanging ceiling. With a Trawl Eye on the headline one will in this case not be able to determine whether the trawl presses on or lifts from the seabed. In these cases it would therefore be correct to move the Trawl Eye back onto the top of the trawl so that it will be as close as possible to being right above the bottom gear. By sowing in a suitable bag into the net line with a safety rope up to the headline, the Trawl Eye will be placed precisely and securely every time.
Pelagic fishing
In pelagic trawling, a narrow beam Trawl Eye is the most commonly used both in the trawl opening and in the belly. The application areas are more varied in comparison to bottom trawling. Many use the Trawleye as a headline sensor instead of trawl sonar, or for when the trawl sonar is not working, because of broken cables or other faults. This allows the fishing to continue. Some skip the trawl sonar in certain types of trawling and only use Trawl Eye.
Trawl Eye in the opening: Good entrance - Perfect positioning.
In pelagic fishing when it is important to be as close to the seabed as possible while avoiding landing on the seabed and snagging, the Trawl Eye’s resolution is vital and a trawl sonar does not give sufficient accuracy.
In Iceland we see that skippers use the Trawl Eye on the ground rope when fishing closely to the seabed. They use small range, which provides further increased precision. Additionally the Trawl Eye is programmed with upward view to see the fish that enters.
The skipper, Gisli Runolfsson, on the trawl Bjarni Olafsson, explains it this way: “When fishing close to the seabed I always use Trawl Eye on the ground rope in order to get as close as possible. I program the Trawl Eye to seeing 15 meters up and 15 meters down. On the cable sonar the ground rope is so wide it gives too strong an echo to provide precise information of the distance from the ground rope to the seabed. At the same time the upward view is important in order to see when the herring comes over the ground rope and begins to enter the trawl.”
Trawl Eye in the belly
Trawl Eye in the belly is also an important area of use in pelagic trawling. Placed in a net bag stitched into the center of the net ceiling in the required area of the belly, it shows height, entrance, and where appropriate, distance to the seabed. You can also see if any of the fish escapes outside or under, or, by programming the Trawl Eye to look upwards, over the trawl caused by the fish escaping through the mesh further ahead.
Trawl Eye in the belly: Good entrance but some of the fish escape.
If you do not have the expected opening in the belly, this may be due to poor water flow or simply that the trawl is tangled further ahead (even though everything looks ok on the trawl sonar). As the cod end fills the opening (and water flow) will reduce. In many cases it will be sensible to haul before the bag is completely full and shoot again, instead of continuing to tow for a long period of time for the bag to fill completely.
The entrance into the belly also shows if your trawl is correctly positioned vertically in relation to the fish. In many cases the entrance on the trawl sonar turns out to be bait that does not end up in the back of the trawl. Many also use this sensor to register the size of the fish. Large and small fish can use different time from the opening until appearing in the tunnel.
For many fishermen it is simply unthinkable to tow without a Trawl Eye in the belly.