Gillnets are passive nets: in other words, they capture fish as they swim along, but are themselves fixed with respect to the water or the bottom. They can be cast individually (single panel), but are more usually employed as a series of panels linked together to form a “stesa”(“tesure”, in French). The size and number of panels in a “stesa” depends on a number of factors, such as the area to be fished, the species targeted, the size of fishing boat, the number of crew members, etc. This artisanal fishing technique is strictly seasonal and coastal; scientific analysis over recent years has shown that when gillnets are used in compliance with local regulations, they are highly selective and have a low environmental impact. Three types of gillnets are used in Friuli Venezia Giulia: the so-called imbrocco, tremaglio and set gillnets. Imbrocco nets. These nets have a single 50-metre nylon mesh panel, ranging from 1.50 to 3 metres in height. Various types of imbrocco nets are used in the gulf and in the lagoons: barracuda, with a 34-40mm mesh for pandora, striped seabream, gilt-head bream and sea bass; menaide, with 10-14mm mesh, used to catch blue fish in summer, when trawling is forbidden (these were common in the 1920s before being replaced by the saccaleva, a type of lift net); cagnolere, with 60-80mm mesh, used by fishermen in Grado and Marano to catch dogfish in spring and summer; squaineri, similar to the previous nets but used in winter near river mouths to catch turbot, ray and angelshark. Tremaglio nets (also known as passelere). These nets are the most commonly used in the Region and are one of the many different kinds of gillnet. They consist of three long rectangular mesh panels attached at the top to a float line and at the bottom to a weight line. From whichever direction the fish comes, it first passes the outer panel (“serbera”), with wide mesh (60-120 mm), then comes into contact with the second panel (with a 35-50 mm mesh), shaped like a sort of funnel, and as it tries to escape, it gets drawn tighter and tighter into the net. This type of net is usually anchored to the bottom and is used throughout the year and at all depths to catch a variety of bottom-dwelling species, such as flounder, sole and mantis shrimp. Fixed gillnets. Distinguished by their high panels, sometimes as high as 20 metres, and fine, 12-20 mm mesh, these nets are anchored to the bottom perpendicularly to the Trieste coast to catch cuttlefish, squid and shad.