Fishermen sometimes catch animals they do not want, cannot sell, or are not allowed to keep. This is what we know as bycatch.
Bycatch can be classified into various categories, including finfish and non-finfish species, live or dead release, rare-event or frequent occurrence, and in the case of finfish, whether retained and sold for human consumption or discarded. Bycatch that can be retained and legally sold in the market is referred to as “incidental catch.”
In the U.S., fishermen are required by law to reduce bycatch to meet limits set by the Endangered Species Act and the Marine Mammal Protection Act, both of which regulate the fishery to reduce bycatch of protected species, including marine mammals, sea turtles, and seabirds. The domestic swordfish fleet is also regulated by the Magnuson-Stevens Fisheries Conservation and Management Act, which includes a requirement that: “Conservation and management measures shall, to the extent practicable, (a) minimize bycatch and (b) to the extent bycatch cannot be avoided, minimize the mortality of such bycatch.”
Specific to the California swordfish drift gillnet fishery, bycatch of marine mammals and sea turtles has been greatly reduced and the rate of compliance among fishermen regarding regulations pertaining to the Marine Mammal Protection Act conservation requirements appears to be high (Carretta and Barlow 2011; Geijer and Read 2013; Carretta et. al. 2017).