Pair trawlers operate both midwater and bottom trawls. Scallops are most commonly harvested using scallop dredges or bottom trawls. The false catshark is an infrequent bycatch of longlines and bottom trawls. Bycatch happens most commonly with the use of gillnets, longlines, or bottom trawls. Commercial techniques for catching wild shrimp include otter trawls, seines and shrimp baiting. Otter trawlers deploy one or more parallel trawls kept apart horizontally using otter boards. It is susceptible to incidental capture by commercial bottom trawls, gillnets, or line gear. European anchovies are caught with purse seines, lamparas, trawls and beach seines. These trawls can be towed in midwater or along the bottom. The crew used a variety of dredges and trawls to collect biological samples. They also become stuck in traps, pots, trawls, and dredges. Freshwater stingrays are often caught by hook-and-line and as bycatch in trawls. Some are killed accidentally by fishing trawls and nets intended for catching sharks. A fishing trawler is a commercial fishing vessel designed to operate fishing trawls. They are typically caught with nets, trawls, and harpoons.