Many fisheries around the world throw away more fish than they keep. Some of the biggest offenders are shrimp fisheries. In the worst cases, for every pound of shrimp caught, up to six pounds of other species are discarded. And this incidental catch of unwanted or unsellable species, known as "bycatch," doesn't just include fish—turtles, seabirds and other animals also suffer.
Most Fishing Gear Isn't Finicky
Bycatch is often caused by less selective fishing gear like longlines or bottom trawls. Longlines have baited hooks and can extend for 50 miles or more. When cast out and left to "soak," longlines attract anything that swims by, from sharks to sea turtles. Bottom trawls drag nets across the seafloor, catching everything in their paths.
In contrast, gear like hook-and-line fishing can limit bycatch, because fishermen can quickly release unwanted catch from their hooks since lines are generally reeled in soon after a fish takes the bait.
The Effects of Bycatch
Nearly 20 percent of shark species are threatened with extinction, primarily as a result of being caught accidentally on longlines. Bycatch also includes young fish that could rebuild populations if they were allowed to grow and breed.
But It's Not Just Fish
Despite declines in recent years, hundreds of thousands of sea turtles, seabirds and marine mammals, including whales, dolphins and porpoises, die as bycatch. As many as 200,000 loggerhead sea turtles and 50,000 leatherback sea turtles are caught annually. Longline fishing also kills hundreds of thousands of seabirds when they become entangled in driftnets or caught on longline hooks when they dive for bait.
Fishermen Don't Like Bycatch, Either
Fishermen truly don't want to haul in bycatch—it wastes their time and wears out their gear. Boats need to be outfitted with more selective gear to reduce this waste, and to help preserve our oceans. Cost-effective "streamer lines" are dramatically reducing seabird deaths in the Pacific halibut longline fishery.