A trammel net consists of two/three layers of netting with a slack small mesh inner netting between two layers of large mesh netting within which fish will entangle. These nets are strings of single, double or triple netting walls kept more or less vertical by floats on the head rope and mostly by weights on the ground rope. These are occasionally set in strings.
Trammel nets are similar to a gill net but are made up of three layers of netting. In UK waters they are generally set on or close to the seabed to target demersal fish. In some overseas fisheries they may be set in mid water or just below the surface to target pelagic fish.
Trammel nets are most common as stationary gear, but they can also be used drifting. The fish entangle themselves in a pocket of small mesh webbing between the two layers and large meshed walls. Afterwards, the trammel nets are hauled back to the surface for extracting the entangling fish from the netting.
Accessory Equipment Small solid floats, usually made of plastic and either cylindrical or egg-shaped, are attached to the head rope and lead weights are evenly distributed along the ground rope
Environmental Impact
Compared to gill nets, trammel nets sometimes show poorer selectivity because of the tangling characteristics of the three layers of netting compared to the single layer of a gill net. By catch is usually minimised by the skippers knowledge of the grounds and by him shooting his gear where he expects there to be an abundance of the target species with minimum by-catch.
In some areas there can be problems with cetacean by-catch, but in most fisheries the skippers are already aware of this and have adopted the use of acoustic pingers to keep the cetaceans away from the gear.
Seabed contact with trammel nets is limited to very light contact from the footrope and minimal contact from the small anchors at each end. These will penetrate the seabed but will have minimum, if any ploughing effect on the seabed, only moving when the gear is hauled. As the gear is not towed over the seabed there should be very little abrasion.
Occasionally there may be problems with ‘ghost fishing’. This is where the nets are lost and continue fishing for some time after they are lost. There have been attempts to mitigate this by encouraging fishermen to report lost gear so that it can be retrieved at a later date. It has also been found that lost nets will very quickly get entangled with weed and become visible to the fish and eventually sink to the seabed.
Further Information
Trammel nets are similar to a gill net but are made up of three layers of netting. Two outer layers of large mesh with a sheet of fine small mesh sandwiched between them. The inner layer of small mesh netting is hung onto the headline and foot rope much slacker that the outer two layers, it is also made much deeper than the two outside layers. This creates plenty of slack netting that the fish swim into and get tangled in pockets of netting between the two outer layers. Trammel nets are found to be more efficient at catching broad selection of species and size of fish than a gill net.