Techniques

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How do Fishermen catch fish? What techniques do they use? These are techniques that are used by fishermen in the US.

Trawl: Trawl boats tow a funnel shaped net behind their boat to catch fish either along the bottom of the ocean (bottom trawler) or midway through the water column (midwater trawl). Shrimp, sablefish, rockfish, flounder, and sole are some of the fish caught by this method. Some trawls have devices attached to them (such as Turtle Excluder Devices in the shrimp fisheries) to release fish or animals that are not targeted and may have gotten accidentally caught in the trawl net. (See illustration.)

Dredging: Fishermen drag a heavy frame with an attached mesh bag—the 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. The frame is connected to a towing cable and dragged along the sandy floor. This stirs up shellfish, which flow into the bag. Water, sand or mud pass through the mesh. Other variations include hydraulic or jet dredges, which use pressurized water to stir up deep burrowing clams, and suction dredges, which use pump driven suctions to suck the shellfish up a pipe to the boat. Oysters, scallops, and clams are some of the fish that are caught by this method.

Trap or Pot: Fishermen build traps (sometimes also called pots) to catch specific fish or shellfish. Traps have funnel opening to allow the targeted species to enter, and often another opening to let non-targeted species out. The traps are baited and weighted and dropped in different areas and left for a few days to let fish and crustaceans wonder into them. The traps, which are marked by buoys, are collected and the fishermen go through the traps looking for fish or crustaceans that they are targeting that fit size and sex requirements. Typically lobsters and crabs are caught by this method, although fish species are also caught. Fish weirs also fall into this category. For a weir, brush and twine are permanently attached to the sea floor. Two fences direct fish to swim voluntarily into successive enclosures known as the heart, pound, and pocket. (See illustration.)

Seine: Purse seines are walls of netting used to encircle entire schools of fish at or near the surface. A drawstring cable is threaded through the bottom of the net. When the cable has pulled the netting tight, enclosing the fish in a pouch, the catch is hauled on board with a dip net. Sometimes, a motor skiff sets off from the fishing boat and quickly deploys the net around a school of fish. There are different kinds of seines, most notably the purse seine and lampara. Sardines, tuna, and squid are caught this way.

Handline (aka vertical gear): This is fishing with a line that is handheld, or rod and reel, sometimes with more than one hook. Jigging can also fall into this category. To jig you set the line with baited hooks or lures, and continually jerk the line, either by hand or with a jigging machine. Tuna, mahi mahi, salmon, and cod are some species that are harvested this way.

Longline: Longlines use baited hooks on offshoots of a single main line to catch fish at any depth. The main 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. The line can be anchored at the bottom in areas too rough for trawling, or set adrift, suspended by floats. 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. (See illustration.)

Troll: Trolling is a hook and line method that involves fishing lines towed behind a moving boat. Salmon and Albacore Tuna are among the fish harvested this way. (See illustration.)

Gillnet: A gillnet is a wall of netting set in a straight line, equipped with weights at the bottom and with floats at the top. Fish swim through the netting and are entangled when their gills are caught in the webbing. The size of the gillnet’s mesh determines what size fish it will harvest. Larger mesh allows smaller fish to swim though, and smaller mesh prevents larger fish from entering at all. Drift netting is the act of allowing the net to drift freely. Set gillnets are anchored to the bottom of the ocean and typically retrieved 24 hours or less after the set. Fish are usually alive when retrieved and are of top-quality when delivered to market.(See illustration.)

Divers: A person dives down into the ocean to hand select targeted species. Urchin is primarily harvested this way. (See illustration.)

Harpoon: Harpoons are thrown by hand or shot by mounted guns and have are tipped with a barb which is attached to a long line with a buoy at the end. The line is free of the boat and fish are followed with the assistance of the buoy until they tire and can be hauled aboard. Larger, pelagic fish are harvested this way, such as Swordfish and Bluefin tuna.

Hand Rake: Hand held rakes are used by individual harvesters who rake up the ocean floor at low tide to hand collect shellfish. Clams and mussels are primarily harvested this way.