A big-eye tuna caught on a long line. In long line fishing, the fish may remain captured for many hours, or even days.

A big-eye tuna caught on a long line.
In long line fishing, fish may remain captured for many hours, or even days.
Credit: © Greenpeace / Jeremy Sutton-Hibbert

Animal welfare impact on captured fish

Long line fishing, or long lining, is a commercial fishing method that uses hundreds, or even thousands, of baited hooks hanging from a single line which may be 50-100 km long. Unlike the other hook and line fishing methods discussed, the duration of capture for long line fishing is very long. Fish caught on long lines are landed hours, or days, later when the gear is hauled up.

Hooking is stressful to fish (see rod and line fishing) and can lead to severe exhaustion. It can also result in severe injury (see trolling). As with all forms of hook and line fishing, sometimes fish are gaffed (i.e. impaled on a hook) to bring them abroad.

In this method of fishing, it is common for live fish to be used as bait. A semi-automatic machine impales the live fish on hooks as the line is played out. The use of live bait hugely adds to the suffering caused in this fishing method, as do long capture periods. One hooked, the fish may themselves be subsequently attacked by predators and may be dead when landed.

Environmental impact

Long lines kill sea birds, sea turtles and sharks, as well as non target fish, which are attracted by the bait. Sea birds like albatross get hooked when the lines are near the surface. The birds are then dragged under water and drowned. Bird bycatch can be reduced by measures such as bird-scaring devices and weighting the lines to make them sink more quickly. US fishermen can avoid the migratory paths of sea turtles by sinking their long lines deeper.

Large numbers of bycatch fish are reportedly caught and thrown back dead. Long line fishing catches more sharks as bycatch than any other fishing method on the high seas.

As discussed for rod and line fishing, levels of hooking injury, and the survival chances of released bycatch fish, are affected by the type/size of the hook/bait and the method by which the hook is removed.

Measures to reduce suffering in long line fishing

The following measures, combined with humane slaughter immediately the fish is landed, would improve the welfare of fish caught in long line fishing:

Reducing the suffering in long line fishing:

Reduce suffering of bait fish

  • Avoid the use of live bait fish
  • Avoid the use of bait fish generally (use artificial baits or off cuts instead)

Reduce the duration of capture

  • Reduce the time between setting and retrieving the lines (fair-fish limits capture duration to 5 minutes for fish caught by hook)

Reduce the numbers of bycatch animals

  • Use hooks and baits that reduce bycatch
  • Close fisheries when necessary to reduce high levels of bycatch
  • Use measures shown to reduce bycatch e.g. sinking lines to avoid seabird bycatch

Reduce death rates in bycatch fish

  • Avoid fishing in warm-water weather when fish are likely to be particularly stressed

Reduce stress and injury during capture

  • Use hooks than cause less injury e.g. circle hooks, barbless circle hooks
  • Avoid fishing from depths greater than 20m (for fish with swim bladders)

Reduce stress and injury during landing

  • Handle fish carefully when landing prior to humane slaughter (or release as bycatch)
  • Minimise time spent out of water
  • Remove hooks after fish is humanely slaughtered or stunned, rather than before
  • Carefully remove hooks from fish to be released
  • Avoid gaffing fish

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