In the Mediterranean and the Eastern Atlantic, the period 26 May to 1 July marks the season where large vessels (purse seiners), are allowed to fish for bluefin tuna. Trapping in the Mediterranean starts in February and ends in July.
Longlining, as the name suggests, involves long fishing lines which can be as long as 100 kilometres. Attached to them are shorter lines with baited hook tied at fixed intervals. Longlines can be set at different depths to catch different species. Pelagic longline is where the lines are set near the surface of the water to catch open water fish such as bluefin tuna, yellowfin tuna and swordfish. Bycatch is a major environmental issue in the longline fishery, especially impacting billfish, sea turtles, pelagic sharks, and seabirds. Also there are concerns about the baitfish* fisheries for the bait that is needed to catch the fish using hooks; these can be substantial and are largely unmonitored and unmanaged.
Hook and line is one of the best methods of fishing with regards to sustainability. This can involve one person and a rod, or alternatively using a basic winch with a line of hooks. The hook and line fishing method has little impact on the surrounding environment and the catch can be selective. For example, any fish too small, or not the right species can be placed back into the water, with limited harm. Problems with large-volume, yet unmanaged baitfish* fisheries are also associated with pole and line fisheries. *See general coverage on tuna baitfisheries: Gillett, R. E. (2012). Global study of the management of baitfisheries that support pole-and-line tuna fishing SPC Fisheries Newsletter #139 - September/December 2012
Purse seine nets are used as walls to encircle fish. After the fish are surrounded, the bottom end of the purse seine net is pulled up and closed to form a bag that traps the fish. Schooling fish such as sardine, salmon and yellowfin tuna are caught by this method. Can be unselective, particularly if used alongside Fish Aggregating Devices (FADs), where sharks, rays, turtles, dolphins and juvenile tuna can be caught.
The almadraba traps are big nets anchored or held by pegs, open on the surface and provided with different systems to direct and trap the fish. They are usually divided into different chambers, which have nets at the bottom. The fishing season for the pasotype of almadraba traps takes place in spring and ends at the beginning of summer, and for the “return” type almadrabas, it begins at the end of summer and ends in autumn. All almadraba traps currently belong to the pasotype, because the quota is reached within the first few months. Currently the almadraba season begins in February and ends in July. The crew for the almadraba is made up of 40-45 people hired during this period.