Longline fishing

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Longline fishing

The longline fishing is a type of fishing in the industrially operated deep-sea fishing . In this case, secondary lines with many bait hooks are laid out on a main line made of plastic (also called the base line or mother line). Long lines can be up to 130 kilometers long and have more than 20,000 bait hooks. However, the number of baits and the length of the line vary greatly.

Mackerel or squid are used as bait . From South America , for example Peru , it is known that dolphin meat is also used as bait in the shark longline fishery. Target fish species are black hake , various types of tuna , cod , swordfish , halibut , mahi-mahi (dolphin fish), sharks and other, mostly valuable, food fish species.

The advantages of this method of fishing is the low compared to fish with nets damage to the target fish, and that the seabed is not damaged or destroyed, as for example in the use of bottom trawls or beam trawls is the case.

Longline fishing is particularly widespread in the waters of the southern hemisphere (South America, Africa, Australia, Antarctica / Southern Ocean), but is also used in the North Sea to catch cod and in the Baltic Sea for cod and eel and in the Mediterranean .

Longline fishing techniques

Basically, a distinction is made between two different types of use, pelagic longline fishing and demersal longline fishing.

Pelagic longline fishing

In pelagic or semi- pelagic longline fishing, fishing vessels deploy the lines at or near the surface of the water and let them drift (no anchoring). Radio transmitters on buoys enable the fishing cutter to find and retrieve the fishing gear later. This method is mainly used to fish large species of tuna or swordfish .

Demersal longline fishing

Here, the longlines are sunk on the seabed and anchored horizontally to it. The technique, also known as bottom fishing , was introduced in 1988/89 to catch black hake and other fish species living near or on the seabed and has since become widespread. It is fished at depths of 500 to 2500 meters with lines over 5 kilometers long and equipped with up to 5000 bait hooks.

criticism

While longline fishing was initially seen as an effective and selective fishing technique , it is now heavily criticized for its high bycatch rates . According to the Food and Agriculture Organization of the United Nations (FAO) in 2005, the average bycatch rate was around 20 percent of the total catch. Numerous nature conservation organizations consider them to be one of the greatest threats to non-target fish species such as sharks and rays as well as to sea ​​birds such as various species of albatross (especially in the Southern Ocean) and frigate birds as well as sea ​​turtles . Added to this is the now severe overfishing of target fish species such as black hake or bluefin tuna (Mediterranean), particularly by pirate fishermen operating illegally .

Sea birds

The baits placed near the surface of the water while the lines are being set attract sea birds in search of food. They get caught and are drowned when the line drops. BirdLife International estimates that one dead albatross must be expected for every 2500 hooks . With an estimated 200 million hooks being placed each year, all 21 albatross species are now endangered or acutely threatened with extinction . The Amsterdam albatross , of which just over 100 specimens still exist, is almost extinct. Environmental organizations estimate that 300,000 seabirds, including 100,000 albatrosses, are killed annually in longline fishing in all the world's oceans.

The Save the Albatrosses campaign was launched back in 1997 and in 2001 the Convention for the Protection of Albatrosses and Petrels of the Bonn Convention for the Protection of Migratory Species was signed by various states. The Agreement on the Conservation of Albatrosses and Petrels (ACAP) , however, only came into force on February 1, 2004.

Sharks and rays

Sharks are both targeted and, like rays, killed as accidental bycatch. According to a study by WWF from July 2007, seven million sharks and rays per year as bycatch in the longline fishery for tuna, swordfish and hake in the south-east Atlantic alone (around 5.5 million blue sharks and around 1.1 million of the threatened mako sharks ). However, the number of unreported cases is high because of illegal fishing. The longline fishery alone is said to be threatened with extinction today about 20 percent of all shark species. Another threat to the sharks comes from shark finning , i.e. catching the sharks to cut off their fins, which is also carried out with the longline.

Sea turtles

Leatherback turtles , loggerhead turtles and hawksbill turtles are particularly endangered by longline fishing. Estimates of annual losses vary widely. In the Mediterranean, the annual bycatch rate is said to be around 20,000 loggerhead turtles, and between 250,000 and 400,000 worldwide. The animals die of injuries caused by the hooks or drown because they can no longer free themselves from the hooks.

Alternatives

Various modifications to the fishing gear can drastically reduce the high bycatch rates in longline fishing. This would make it very easy to avoid bycatching sea birds, as the sea birds usually pounce on the bait when shooting the lines. If the lines are shot through a pipe that is about ten meters deep, albatrosses or frigate birds cannot dive for the bait. Another method is so-called scarecrow leashes , which use colored ribbons to deter the birds. According to the WWF , this method is already mandatory in South Africa , but is not used adequately. Protective measures to reduce bycatches of sea birds were successfully introduced in 1991 by the Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR). The bycatch rate fell by 90 percent, and in 2007, for the second time in a row, there was no albatross bycatch in the Antarctic by the monitored and regulated longline fishery.

In November 2007, the Atlantic Tuna Protection Commission ( ICCAT ) adopted measures against bycatch of seabirds in longline fishing, which apply to the fishing fleets of the EU and 44 other nations in the Atlantic: fishing during the night (low activity rate of seabirds), with Weights weighted suspension lines (baits are out of reach of seabirds) and the use of scarecrow lines . In December 2007, the Western and Central Pacific Fisheries Commission ( WCPFC ), to which the EU and 24 other fishing nations belong, adopted similar measures to prevent bycatch of seabirds in the Pacific. The decisions were largely driven by the Fisheries Division of the United States Weather and Oceanography Agency, NOAA .

The bycatch of sea turtles can be reduced by 90 percent using special round hooks, for example, without less fish being caught.

A magnet attached above the hook scares off sharks and could significantly reduce their bycatch rate.

Setting baited longlines at depths of 100 meters or more when fishing tuna in the tropical East Pacific would minimize the bycatch of sharks and rays as well as that of sea turtles, as these mostly go on hooks above 100 meters, while tuna are caught at depths below 100 meters become. This method is already being tested in US waters by the Fisheries Division of the United States Weather and Oceanography Agency, NOAA .

The environmental organization World Wildlife Fund annually announces a competition in which fishing methods are awarded that reduce or avoid bycatch.

swell

  1. ↑ BirdLife International: What is Longlining? (engl.). BirdLife International, archived from the original on November 1, 2012 ; Retrieved September 26, 2015 .
  2. ↑ Effects of different fishing techniques on the black hake. Lighthouse Foundation, accessed September 26, 2015 .
  3. ↑ Chopped up dolphins as cheap shark bait. Society for the Rescue of Dolphins, accessed on September 26, 2015 .
  4. ↑ Dialogue meeting with fisheries: On the way to reducing bycatch in the German Baltic Sea. Federal Agency for Nature Conservation, archived from the original on September 27, 2015 ; Retrieved September 26, 2015 .
  5. ↑ Fishing techniques. Society for the Rescue of the Delphine eV, accessed on June 26, 2017 .
  6. ↑ eurekalert.org of October 2, 2013: Longline fishery in Costa Rica kills thousands of sea turtles and sharks.
  7. ^ Lighthouse Foundation: Pressure to use the black hake
  8. ↑ Effects of different fishing techniques on the black hake. Lighthouse Foundation, accessed September 26, 2015 .
  9. ^ Save the Albatross. rspb, accessed September 26, 2015 .
  10. ^ Agreement on the Conservation of Albatrosses and Petrels (Eng.). ACAP, accessed September 26, 2015 .
  11. ↑ Millions of sharks die in agony. WWF, accessed September 26, 2015 .
  12. ↑ Definition and assessment of worldwide bycatch in marine fisheries. (PDF) WWF Germany , accessed on September 26, 2015 .
  13. ↑ Fishermen Will Use New Ways to Avoid Snaring Endangered Seabirds. NOAA, archived from the original on September 11, 2015 ; Retrieved September 26, 2015 .
  14. ↑ International Smart Gear Competition. WWF-International, accessed on September 26, 2015 .

literature

  • Peter C. Mayer-Tasch: Sea without fish? Profit and world food. 1st edition Campus Verlag, 2007, ISBN 3-593-38350-0
  • Hans-Peter Rodenberg and Gudrun Pawelke: See in Not. The greatest source of food on the planet: an inventory. 1st edition Marebuchverlag, 2004, ISBN 3-936384-49-5

Web links

Commons : Longline Fishing  - Collection of pictures, videos and audio files