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 fixed gill net consists of a single piece anchored to the seabed. The corkline where the floats are placed is made of braided polyamide, as is the foot rope that, rather than having plummets distributed singly, is often formed by a lead core covered by a polyamide sleeve.
The mesh size of the net varies according to the target species, the fishing season and the area. The catch takes place by gillnetting, enmeshing or entanglement.
In an attempt to pass through the net, the fish puts its head through one of the mesh spaces in the net as far as its gill cover. Here, the thread of the mesh tightens around it, so that it cannot turn back nor go forward, since the circumference of its body is larger than the space in the mesh, until it becomes trapped.
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 at that point 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.