Are Bonita fish big
Tuna (Thunnus spp.)
|habitat||both near the coast and in the open sea in water depths of up to 1,000 meters|
|Geographical distribution||Tuna live in all oceans far from the poles|
|Endangerment status||IUCN: Southern bluefin tuna (Thunnus maccoyii) "critically endangered"; Yellowfin tuna (Thunnus albacares) "endangered" and bigeye tuna (Thunnus obesus) "endangered", white tuna or germon (Thunnus alalunga) and bluefin tuna (Thunnus thynnus) are also listed, but are not yet assigned to a risk category due to insufficient data.|
|Stock size||worldwide tuna stocks have declined by up to 90 percent in recent years, and the trend is continuing to decline|
Sought-after food fish
Tuna are closely related to bonitos and mackerel and belong to the mackerel family (Scrombridae) and thus to the perch-like order (Perciformes) with approximately 10,000 species.
Tuna are extremely fast: over short distances they can reach 80 kilometers per hour. They reach such high speeds thanks to their strong, spindle-shaped body. Between the second dorsal and anal fin, a row of so-called flippers extends up and down to the caudal stalk, usually 5 to 12 pairs. They help avoid vortices during very fast swimming. A bone ring around the large eyes is another special feature of the tuna.
The bluefin tuna or bluefin tuna is the largest tuna with a length of up to five meters. It weighs between 130 and over 600 kilograms, but animals of this caliber are rarely found today.
Tuna are widely migrating schooling fish. They cover thousands of kilometers in the seas every year. Bluefin tuna that were tagged in the Bahamas were caught off the coast of Norway and the Brazilian coast.
The bluefin tuna occurs in all seas, but has only two permanent spawning grounds - in the Gulf of Mexico and in the Mediterranean. The western Atlantic bluefin tuna meet off Mexico between April and June, the eastern Atlantic between June and August in the Mediterranean. Female tuna fish can produce an average of 500,000 eggs that float just below the surface of the water. Old and large female tuna are said to be able to produce up to ten million eggs per spawning season. The larvae hatch after only three days with a size of three millimeters. After a month, the small tuna are already around 3.5 centimeters tall.
When hunting, tuna play at their enormous swimming speed. They prefer to eat mackerel. Their larvae feed on amphipods, other fish larvae and microorganisms. The fry also eat small organisms.
The bluefin tuna is currently one of the most expensive fish in the world: a specimen weighing 200 kilograms was paid for at the Tokyo fish market of $ 175,000. The economically most interesting species are bigeye tuna, yellowfin tuna, bonito and albacore tuna. Their main fishing regions are the Indian Ocean and the Pacific.
With ever larger ships and more powerful fishing techniques, fishing fleets are chasing after the fish. The purse seine is a very efficient, but also unselective principle: First, the shoal is circled with the net, then the net is pulled together at the lower end and the prey is already in the trap - but not only the shoal of tuna. Above all, dolphins, sharks, manta rays, the very endangered sea turtles and countless other marine animals are killed as bycatch.
Worldwide tuna stocks have declined by up to 90 percent in recent years. Only a few adult animals end up in the world's luxury markets for a lot of money. Mostly they are so-called “farmed fish” - behind them are actually wild tuna that were caught young and then fattened on the high seas. And which are not added to the already excessive catch quotas when they are caught.
For the Mediterranean, the WWF is therefore calling for a moratorium that prohibits the development of further such wild tuna farms until solutions at national and international level are in sight. This is what it takes
- a fishing ban for industrial fisheries during the spawning season,
- Monitoring programs for fishing and so-called tuna fattening,
- Obligatory observers on board all tuna vessels and in the fattening farms as well
- better regulation of the fishery for small and medium-sized schooling fish that feed tuna.
Finally, overfishing of wild tuna stocks must be stopped urgently.
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