Fisheries targeting albacore tuna occur all year around.
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.
This fishing method is where one trawl is towed in mid-water between two vessels (also known as pair trawling) to target pelagic fish. The height of the net in the water column can be changed by altering vessel speed and length of wire out. The nets can be very large as big as 240 metres wide and 160 metres deep but the mesh size in the mouth of the trawl are huge sometimes as big as 50 metres long.