Gillnets - Cetacean Bycatch Resource Center

Mesh fishing nets are used in many different ways around the world. Larger fish are caught by their gill covers when they encounter the net and retreat, leading to the name "gillnet". Depending on how big the holes are, a gillnet can catch larger fish while allowing smaller fish to pass through. For example, Oregon fishermen use a specific mesh size that allows them to catch salmon while allowing smaller steelhead trout to escape.

Large nets for salmon and other fisheries are stored on a reel on the back of a boat which helps unwind the net into the water without tangling. This kind of net can be set at different depths between pairs of anchored buoys. Gillnets are generally retrieved after anywhere between 6 hours to a few days of soak time. Learn more about pingers.

People in coastal communities often set small gillnets close to shore, while commercial operations set larger nets in deeper waters. Though a gillnet may be only 3m deep, it can stretch for 50 to 200m. Groups of nets can be tied together and extend from 300 to 3000m.

Set nets are attached to the bottom and held open with weights at depth and floats along the top. In contrast, drift nets are released by a boat and allowed to drift with the current. In some cases the boat remains attached and will drift with the net to avoid losing it.

A drift net that escapes will continue fishing, and without anyone to retrieve the catch, the net will continue to trap fish and marine life long after it has been abandoned. For this reason, large drift nets have been banned in the European Union, the Baltic Sea, and other areas of international waters.

Kinds of gillnets

Set net, anchored or set gillnet - nets are anchored in one place
Bottom gillnet - nets are anchored along the seafloor
Midwater gillnet - nets are anchored off the bottom, in water column
Drift net, drift gillnet - nets without an anchor
Tangle net - net with smaller mesh that catches fish by teeth rather than gills. Improved survival allows fishermen to keep hatchery salmon and release wild salmon.
Trammel net - two or three layers of netting, including a middle layer with smaller mesh. Often used at or near the bottom.

Targeted fish

anglerfish, barracuda, dogfish, flying fish, hake, halibut, herring, mackerel, monkfish, pilchards, sprats, salmon, shad, sharks, shrimp, smelt, sturgeon, swordfish, tuna, white sea bass, white shrimp, yellowtail, and many other species

Gillnet Bycatch

Gillnets sometimes catch cetaceans along with the fish, including bottlenose dolphins, common dolphins, white-sided dolphins, dall porpoises, harbor porpoises, sperm whales and beaked whales, to list only a few. Bycatch in gillnets may be the single greatest threat to porpoise and dolphin populations worldwide (Jefferson and Curry 1994, Kraus et al. 1997). The vaquita, a tiny porpoise in Mexico's Gulf of California, is currently on the brink of extinction due to being caught in the gillnet fisheries for sharks and totoaba (Jefferson and Curry 1994, W. Perrin personal communication).

Extensive effort has been made to modify gillnets to either reflect or produce sounds in order to warn cetaceans away from the net, with varying success. Recent experimental studies of acoustic deterrents known as "pingers" show reduced bycatch for certain fisheries (Barlow et al. 2003, Kraus et al. 1997), though some scientists caution that pingers are not a panacea.

Other regulations sometimes limit the soak time and mesh size of gillnets in order to reduce bycatch. Brief time area closures in the Gulf of Maine yielded equivocal results (Murray et al. 2000) In the state of California (USA) and around the Banks Peninsula (New Zealand), specific areas have been closed to gillnet fishing seasonally or permanently in order to reduce marine mammal bycatch (Dawson 1991).

[ Sources ]




		Fishing Gear: Gillnet \| Longline \| Purse Seine \| Trawl \| Sources Gillnet Mesh fishing nets are used in many different ways around the world. Larger fish are caught by their gill covers when they encounter the net and retreat, leading to the name "gillnet". Depending on how big the holes are, a gillnet can catch larger fish while allowing smaller fish to pass through. For example, Oregon fishermen use a specific mesh size that allows them to catch salmon while allowing smaller steelhead trout to escape. Large nets for salmon and other fisheries are stored on a reel on the back of a boat which helps unwind the net into the water without tangling. This kind of net can be set at different depths between pairs of anchored buoys. Gillnets are generally retrieved after anywhere between 6 hours to a few days of soak time. Learn more about pingers. People in coastal communities often set small gillnets close to shore, while commercial operations set larger nets in deeper waters. Though a gillnet may be only 3m deep, it can stretch for 50 to 200m. Groups of nets can be tied together and extend from 300 to 3000m. Set nets are attached to the bottom and held open with weights at depth and floats along the top. In contrast, drift nets are released by a boat and allowed to drift with the current. In some cases the boat remains attached and will drift with the net to avoid losing it. A drift net that escapes will continue fishing, and without anyone to retrieve the catch, the net will continue to trap fish and marine life long after it has been abandoned. For this reason, large drift nets have been banned in the European Union, the Baltic Sea, and other areas of international waters. Kinds of gillnets Set net, anchored or set gillnet - nets are anchored in one place Bottom gillnet - nets are anchored along the seafloor Midwater gillnet - nets are anchored off the bottom, in water column Drift net, drift gillnet - nets without an anchor Tangle net - net with smaller mesh that catches fish by teeth rather than gills. Improved survival allows fishermen to keep hatchery salmon and release wild salmon. Trammel net - two or three layers of netting, including a middle layer with smaller mesh. Often used at or near the bottom. Targeted fish anglerfish, barracuda, dogfish, flying fish, hake, halibut, herring, mackerel, monkfish, pilchards, sprats, salmon, shad, sharks, shrimp, smelt, sturgeon, swordfish, tuna, white sea bass, white shrimp, yellowtail, and many other species Gillnet Bycatch Gillnets sometimes catch cetaceans along with the fish, including bottlenose dolphins, common dolphins, white-sided dolphins, dall porpoises, harbor porpoises, sperm whales and beaked whales, to list only a few. Bycatch in gillnets may be the single greatest threat to porpoise and dolphin populations worldwide (Jefferson and Curry 1994, Kraus et al. 1997). The vaquita, a tiny porpoise in Mexico's Gulf of California, is currently on the brink of extinction due to being caught in the gillnet fisheries for sharks and totoaba (Jefferson and Curry 1994, W. Perrin personal communication). Extensive effort has been made to modify gillnets to either reflect or produce sounds in order to warn cetaceans away from the net, with varying success. Recent experimental studies of acoustic deterrents known as "pingers" show reduced bycatch for certain fisheries (Barlow et al. 2003, Kraus et al. 1997), though some scientists caution that pingers are not a panacea. Other regulations sometimes limit the soak time and mesh size of gillnets in order to reduce bycatch. Brief time area closures in the Gulf of Maine yielded equivocal results (Murray et al. 2000) In the state of California (USA) and around the Banks Peninsula (New Zealand), specific areas have been closed to gillnet fishing seasonally or permanently in order to reduce marine mammal bycatch (Dawson 1991). [ Sources ] See also: "Pingers: Warning cetaceans away from the nets"

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