How to Catch a Fish

Modern methods are more efficient than ever--and more destructive.

Dredging

How does it work?
Fishermen drag a heavy frame with an attached mesh bag—called a dredge—along the seafloor to catch bottom-dwelling shellfish. Some dredges have metal “teeth” along the base of the frame that act like a rake. As the gear is dragged along the seafloor, it stirs up shellfish, which flow into the bag. Water, sand or mud pass through the mesh. The durable bag is made of metal rings to withstand being dragged along the seafloor.

To catch what?
Scallops, clams, oysters and other shellfish that live on the seafloor or burrow into mud or sand.

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Environmental impact
Dredging damages the seafloor and results in unintentional catch.

  • Dredges cause significant habitat damage when dragged along gravel and rocky bottoms. Dredges also smooth out sandy and muddy bottom habitats, removing or smothering a variety of animal and plant life.
  • Fish, sponges and other marine life unintentionally caught as bycatch are unlikely to survive under the weight of the heavy bag.

Harpooning

How does it work?
Harpooning is a traditional method for catching large fish—and it’s still used today by skilled fishermen. When a harpooner spots a fish, he or she thrusts or shoots a long aluminum or wooden harpoon into the animal and hauls it aboard.

To catch what?
Open ocean swimmers--large, pelagic predators such as bluefin tuna and swordfish.

Environmental impact
Harpooning is an environmentally responsible fishing method. Bycatch of unwanted marine life is not a concern because harpoon fishermen visually identify the species and size of the targeted fish before killing it.


Hook and Lining

How does it work?
Hook-and-line fishermen use a pole (rod) and fishing line with one to several hooks. Handliners don’t use a pole—they simply hold a line in their hand. To attract fish, hook and liners use artificial lures or bait, “jigging” or jerking the line to simulate the motion of smaller fish. Sometimes they toss baitfish into the water to start a feeding frenzy among the fish. The catch is hauled in manually or with a mechanized reel.

To catch what?
A variety of fish, ranging from open ocean swimmers, like tuna and mahi mahi, to bottom dwellers, like cod.

Environmental impact
Hook and lining is an environmentally responsible fishing method. Fishermen can quickly release unwanted catch from their hooks since lines are reeled in soon after a fish takes the bait.


Longlining

How does it work?
Longliners attract fish with a central fishing line that ranges from one to more than 50 miles (80 km) long. This central line is strung with smaller lines of baited hooks, which dangle at spaced intervals. After leaving the line to “soak” for a time to attract fish, longliners return to haul in their catch.

To catch what?
Different species at different depths. Pelagic longliners hang their hooks near the sea surface to catch open ocean fish, such as tuna and swordfish. Demersal—or “bottom”—longliners float their hooks just off the seafloor to catch fish that live on or near the bottom, such as cod or halibut.

Environmental impact
Pelagic longlining can accidentally kill sea turtles and seabirds.

  • The baited hooks of pelagic longlines attract a variety of open ocean swimmers, such as endangered sea turtles, sharks and other fish, resulting in wasteful bycatch.
  • As the line is deployed into the water, seabirds dive for the bait and are ensnared on the hooks and drown.
  • By sinking their longlines deeper, U.S. fishermen avoid the migratory paths of sea turtles. Other innovations to reduce bycatch include the use of “circle” hooks to ease the release and survivability of unwanted species and the deployment of longlines through a chute to reduce seabird interactions.


Purse Seining

How does it work?
A purse seine is a large wall of netting that encircles a school of fish. Fishermen pull the bottom of the netting closed (like a drawstring purse), herding the fish into the center. Purse seiners either haul the net aboard or bring it alongside the boat to scoop out the fish with smaller nets.

To catch what?
Primarily schooling fish, such as sardines, or fish that gather to spawn, like squid. The most popular fish caught by purse seines are tuna used for canning.

Environmental impact
Purse seining for tuna results in large amounts of unintended catch

  • To locate schools of tuna, fishermen look for schools of dolphins (tunas often travel below dolphins) or set out floating objects (logs or rafts) to attract fish in the open ocean.
  • The net encircles the school of tuna, but also catches the dolphins and a variety of other species, including sharks, sea turtles and juvenile fish.
  • In response to public outcry over the deaths of hundreds of thousands of dolphins, innovations have been developed to release dolphins alive—but dolphin populations have yet to recover. Scientists believe this may be due to the stress of the chase and frequent capture.


Traps and Pots

How does it work?
Traps and pots are submerged wire or wood cages that attract fish and hold them alive until fishermen return to haul in the gear. Traps and pots may or may not be baited, and they usually lie on the bottom—either singly or in a row. A rope runs from the trap or pot to a buoy floating at the surface, so fishermen can locate their gear.

To catch what?
Traps and pots catch bottom-dwellers, such as lobsters, crabs and shrimp. They're also used to catch bottom-dwelling fish, such as sablefish or Pacific rockfish.

Environmental impact
Environmentally responsible, for the most part. There are some problems, though.

  • Baited traps may attract juveniles or unintended species. However, these animals can either escape through specially designed vents or be released alive once the trap is hauled aboard.
  • Traps may damage seafloor habitats when large ocean swells and tides bounce the gear around. Hauling in a row of traps may also drag the cages along the seafloor, causing damage.
  • Marine mammals can become entangled in the lines connecting the traps to the buoys.


Trawling/Dragging

How does it work?
Trawlers tow a cone-shaped net behind a boat. They tow midwater trawl nets at various depths, ranging from just below the surface to just off the seafloor. They drag bottom trawl nets along the seafloor. Trawlers can add chains to the mouth of a net to stir fish like shrimp and flounder up off the seafloor and into the net. They can also add heavy tires—called “rockhoppers”—to help the net roll over rough, rocky seafloor areas without getting snagged.

To catch what?
Different animals at different depths. Midwater trawlers catch faster-swimming schooling fish such as sardines. Bottom trawlers catch fish that live on or near the seafloor, such as cod, flounder and shrimp.

Environmental impact
Trawl nets catch everything in their path and can damage the seafloor.

  • Pelagic trawlers often accidentally catch endangered sea turtles, juvenile fish and other unwanted species, resulting in a significant amount of bycatch.
  • Trawlers (such as U.S. shrimpers) can reduce bycatch by adding turtle excluder devices and bycatch reduction devices to their nets, which allow sea turtles and unwanted fish to escape.
  • Dragging nets along the seafloor can damage or destroy fish habitat [Glossary] . Bottom trawlers can minimize habitat damage by avoiding rocky or coral habitats and ceasing the use of rockhopper gear.


Trolling

How does it work?
Trolling is a hook-and-line method that tows fishing lines behind or alongside a boat. Fishermen use a variety of lures and baits to “troll” for different fish at different depths.

To catch what?
Trollers catch fish that will follow a moving lure or bait Trollers catch fish that will follow a moving lure or bait, such as salmon, mahi mahi and albacore tuna.

Environmental impact
Trolling is an environmentally responsible fishing method Fishermen can quickly release unwanted catch from their hooks since lines are reeled in soon after a fish takes the bait.

Source: Monterey Bay Aquarium

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