You can recognize a trawler by the large net reel at the back of the boat. While fishing, the net allows small fish to swim through but keeps larger fish. Trawlers catch groundfish and shrimp. This is the bulk of seafood available to the seafood consumer. Trawling for Groundfish occurs throughout the year, with seasonal distribution affecting availability.
Some people mistakenly believe that all fishing nets capture and kill marine mammals and birds.
Trawl nets move along the ocean floor at great depths. Research has shown that trawling has no effect on marine mammal and bird populations. You can recognize a troller by the long, thin outrigger poles which parallel each other and stand straight up when not in use. Numerous lines containing baited hooks are attached to the outrigger poles and slowly pulled through the water. All ocean salmon are caught by trollers.