factsheethead_blue.GIF (8610 bytes)


By Kathleen Castro and Erik Williams
bycatch.gif (8188 bytes)

What is it?

Bycatch describes living creatures that are caught unintentionally by fishing gear. Unlike target species—animals specifically targeted for capture—bycatch is unwanted and often unused. Sometimes bycatch may be kept or sold; for example, and angler who catches a legal-sized bluefish while fishing for striped bass may keep the catch to eat at home or to sell, if he has a proper license. Other times, bycatch cannot be used—for example, if it is undersized or a protected species—and must be thrown back. This returned bycatch is called discard.

The problem

Everyone who fishes, whether for a living or recreation, catches bycatch. Unwanted bycatch is usually thrown back into the water; however, handling and exposure sometimes injure the bycatch, which may die after being discarded. Although this discard may serve as food for other species when it is thrown back, it is not recruited into, and does not become a part of, the reproducing population. As a result, discard not only affects the current population, but influences the species' opportunity to replenish itself.

The National Marine Fisheries Service (NMFS), the government agency that manages fisheries, has called bycatch "the problem of the 1990s." Although the extent of the problem has not been satisfactorily determined, three areas of particular concern have been identified by NMFS:

  • User conflicts, which happen when one fishery discards fish that are important to another;
  • Laws, under which animals caught as bycatch are protected by the Endangered Species Act or the Marine Mammal Protection Act;
  • Public regard, through which the public can affect fishing revenues by voicing opinions about the wastefulness of bycatch.

Bycatch in the Northeast

One of the main reasons bycatch is a problem in many fisheries is that different species of animals are found together: this is called a multispecies fishery. It is possible to catch any mix of whiting, flounders, hake, squid, cod, butterfish, or other species on a given day in a given place. Since these fishes attain different sizes when fully grown, it is hard to target only one of them in their shared habitat. However, efforts to adapt fishing gear to specific target species have resulted in more selective fishing. Appropriately, such gear is termed "selective."

Gear problems

Hook and line, and long-line:
Since most fish will bite a hook, it is hard to be selective with this gear. But anglers and commercial fishermen both can make their hooks more selective by using knowledge of fish behavior—for example, choosing bait, jigs, lures, and hook sizes known to catch their target species.

In the Northeast, traps are used for catching lobsters, crabs, whelk, and some finfish. Because traps can attract both nonlegal and nuisance bycatch, they may be constructed in different sizes and shapes to be more selective to the behavior of the target species. Lobster traps must include escape vents to allow for the release of smaller, sublegal animals.

Gill net:
An important fishery in the Northeast and throughout the world, gill net fishing uses a panel of webbing, usually made of clear, monofilament line, that can be set at any depth. Fish can't see the net, so they swim right into it and are caught. Gill net bycatch includes animals that are too large to pass through the webbing.

Bottom trawl:
This is the single most important fishing method in the Northeast, yet it produces the most noticeable bycatch problem. An bottom trawl is a funnel-shaped net that is dragged on the bottom of the sea. Much of the bycatch in an bottom trawl might not survive because it is damaged in the net, brought up from the depths too quickly, or thrown back too late.


Fishermen and scientists have been working for many years to resolve the inefficiency and wastefulness of bycatch. One early response to the problem was the inclusion of escape vents and variably spaced laths, or slats, in traps to allow escape of nontarget species. More recently, educational programs for recreational anglers in catch-and-release fishing have helped minimize harm to fish. And the introduction of the Turtle Excluder Device (TED) in the southern shrimp fishery, and the similarly designed Fish Excluder device—the Nordmore Grate—in the Gulf of Maine fishery, has helped assure the release of nontarget animals from shrimp trawls. Other promising areas of research include the use of sound devices attached to gill nets to ward off dolphins and whales, and new designs of bottom trawls that take into account fish behavior.

As these examples attest, much progress has been made in reducing bycatch. With continued interest and concern, progress will continue, particularly in the following avenues:

Research and Development:
Ongoing research into fish behavior, application of new knowledge to the development and modification of fishing gear, and continued efforts to pinpoint specific bycatch problems should generate practical solutions to this important issue.

The availability of current information about the actual impacts of bycatch, and the progress being made in controlling the problem, should help clarify the issues and encourage cooperation in developing solutions. Conferences and other forums for public discussion enhance prospects for solutions.

Cooperation among the public, the government, academia, environmentalists, and the fishing industry is essential if any proposed bycatch solution is to be effective. Such cooperation has a head start in the collaboration of fishermen, NMFS, and New Hampshire Sea Grant on the use of "pingers"—small acoustical devices—to warn harbor porpoises away from gill nets. In this, as in other responses to bycatch issues, the goal is the same for everyone—fish for the future.

Web site:

FAO Fisheries (Includes State of World's Fisheries and Aquaculture)


Petruny-Parker, M.E., K.M. Castro, M.L. Schwartz, L.G. Skrobe, and B. Somers (eds.) 2003. Proceedings of the new England Bycatch Workshops. Rhode Island Sea Grant, Narragansett, R.I. 52pp. pdf.

Return to Rhode Island Sea Grant Fact Sheets