Fishing with gill net tools is the type of fishing that requires the most experience, with regard to the behaviour of the species that can be fished in the different seasons. This fishing is performed by fishermen who have a profound "culture" of the sea. The quantity of catches made depends on this culture of theirs.
The combined trammel-gillnet brings together the advantages of the gill net with those of the trammel net. In fact, it is formed by a gill net in the upper part and a trammel net in the lower part. With this solution, it is able to catch species found close to the seabed and also pelagic species (cuttlefish, soles, mantis prawns, mullets, white breams, etc.). Among the gill nets, this tool is the least used, despite remaining part of the tradition and in common use in some territories. The catch takes place by gillnetting, enmeshing, entanglement or sacking-up.
The fish, in an attempt to pass through the net, puts its head through the meshed net as far as its gill cover (1).
Here, the thread of the mesh tightens around it, so that it cannot turn back nor go forward (2), since the circumference of its body is larger than the size of the space in the mesh, until it becomes trapped (3).
The fish squeezes into the mesh and is able to go beyond its gill cover, but it becomes trapped in the area of its first dorsal fin, since the circumference in that area of its body is larger than that of the mesh, thus preventing the fish from moving forward.
The fish is too large for the size of the mesh to permit either of the two capture methods described above, but it has several particular protuberances (antennae, bodily unevenness, spines) which, by getting entangled in the netting, make it possible to capture it. The movements of the prey, as it tries to free itself, end up facilitating its entanglement in the netting, where it becomes trapped.
The fish that encounters this net and attempts to pass through it, squeezes through the external larger-meshed net and finds itself before the abundant smaller-meshed net on the inside. Intent on passing through it, the fish advances in the opposite direction from the one he came from, dragging some of the internal meshed net with him into the piece of meshed net located on the opposite side, thus forming a sack inside which he becomes trapped.