Longline, purse seine, pole and line and troll fishing gears are employed in pelagic tuna and billfish fisheries. However, there is very little bycatch associated with pole and line fishing and there are very few commercial vessels trolling for tuna. For these reasons, the BMIS focuses on longline and purse seine fishing gear.
Longline bycatch includes marine mammals, sea turtles, sharks and rays, and seabirds and is in general higher than for purse seine fisheries. Seabirds are the only BMIS bycatch group unlikely to be caught in purse seine operations.