Just how do you study Atlantic bluefin tuna? They travel huge distances and spend a lot of their adult life in the remote and wild North Atlantic Ocean - not the easiest place to visit!
We have recently collected important information that helps us understand where tuna travel in the Mediterranean Sea. Click here to join us on the Med tuna trail.
Tracking bluefin tuna in the Mediterranean Sea
Update from the field
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30 May 2009
Persistence is the key to tagging success
We are again on board. During this last day’s expedition we will try to fish bluefin by trawling lures. The day before one of the boats fished a medium-sized albacore with this method so we will try our best. We cross our fingers!
More information
Tracking bluefin tuna in the Mediterranean Sea
One way to track the migrations of bluefin tuna is to attach tags and then hope that these will be retrieved by fishermen at some point.
Early tagging studies revealed just how far Atlantic bluefin tuna travel. For example, tuna tagged in the Bahamas were caught off the coast of Brazil, as well as off the coast of Norway.
Enter satellites and electronic tags
New technology has allowed more sophisticated studies to be carried out.
Different scientific teams have braved the seas over many years to tag hundreds of bluefin tuna with sophisticated electronic devices. These devices recorded around-the-clock data on the tuna's location, diving depth, body temperature, and surrounding water temperature.
Some devices were “pop-up” satellite tags. At a pre-programmed date, they detached from the tuna and floated to the ocean surface, where they transmitted the data via satellite back to the lab.
Others were permanent “archival” tags, which recorded data over many years. Like early tags, these devices were retrieved by fishers who happened to catch a tagged tuna, and then returned to the scientists.
- Find out more about tuna tagging in the western Atlantic at the Tag-A-Giant Foundation and Large Pelagics Research Center websites.
Rewriting the biology books
Tagging studies have given new insights into Atlantic bluefin tuna biology. A key finding was that up to 30% of the population may cross the Atlantic Ocean. Previously it was thought that only 2-4% of the population made the trip.
Another key finding was that the eastern and western populations are actually quite mixed. For example, juveniles from both populations appear to feed together off the coast of North America, while adults feed together in the Central Atlantic.
Despite their trans-Altantic travels bluefin tunas always swim back home to spawn. So the spawning grounds of the Gulf of Mexico and the Mediterranean Sea are exclusively composed of tuna of purely western and eastern origin respectively.
Management consequences
These new findings have major implications for the way Atlantic bluefin tuna are managed.
Until now the eastern and western populations have been considered almost completely separate and have been managed separately, with different quotas set for each. The problem needs to be addressed of how the fishery should be managed if the two stocks mix without a clear geographical separation.
WWF is grateful for the support of fishermen from Spain's Association of Responsible Recreational Sea Fishing (Confederación Española de Pesca Marítima de Recreo Responsable).
Supported by the Prince Albert II of Monaco Foundation
WWF's “On the Med tuna trail” project benefits from the support of The Prince Albert II of Monaco Foundation.
The support of the Prince Albert II of Monaco Foundation has enabled WWF to tag a number of giant and juvenile bluefin tunas from January 2008 to December 2010. By tagging these bluefin tunas we will gain a better understanding of the species’ migratory paths and contribute new scientific knowledge in this field. This in turn will enable an improvement in the management of this endangered and critical natural resource.
The contents of this webpage are solely the liability of WWF and under no circumstances may be considered as a reflection of the Prince Albert II of Monaco Foundation's position.