Northwest Fisheries Science Center

Bycatch reduction devices

Bycatch is the portion of a commercial fishing catch, including non-target fish and invertebrates, that are caught unintentionally or through accidental interactions with mammals, seabirds and sea turtles. It is of particular concern to resource managers when bycatch includes species that are overfished, threatened, or endangered.

Bycatch is an issue of great interest to the fishing industry and resource managers, especially since many of the fisheries have converted to a catch-share management system. Catch share programs cap the number of fish individual fisherman can catch and requires observers to be onboard each fishing vessel to note the catch numbers and weight of both targeted fish and bycatch.

NWFSC has recently tested a new excluder device that shows promise to significantly reduce the incidental bycatch of Pacific halibut from commercial bottom trawl fishermen. The development of this device is part of a series of bycatch reduction projects conducted through a collaboration between NOAA Fisheries and the Pacific States Marine Fisheries Commission.

How do bycatch reduction devices work?

The flexible sorting grid excluder for halibut uses two vertical sorting panels that sort fish by size as they progress back toward the codend. The concept to the design is that fish smaller than the grid openings will pass through and be retained, where fish greater than the grid openings — such as the halibut — will be excluded from the net via an exit ramp. In a recent series of tests off the Washington coast, commercial fishermen using this device were able to reduce the number of halibut taken as bycatch by 57 percent, while retaining 84 percent of the targeted groundfishes--a significant number that may be improved by further research.

NWFSC scientists have also developed bycatch reduction devices for the Pacific whiting industry aimed at reducing Chinook salmon bycatch. In this work, the device used an open escape window to allow strong-swimming Chinook salmon to escape through the open window, while weak-swimming Pacific hake were able to pass through to the codend.

We have also worked with Oregon Department of Fish and Wildlife to help the Oregon pink shrimp industry reduce habitat impacts and bycatch of eulachon, a small threatened species in the smelt family, by modifying components of the trawl net. We are continuing to work with shrimpers, developing new proposals to further decrease the bycatch of eulachon as well as juvenile rockfish.