Written by Nancy King
A bluefin tuna weighing more than 500 kilograms caught off the coast of Port Hood, Canada, last week was the 1,000th fish to be fitted with a tracking tag that will help collect data intended to improve the health of the species.
The tuna was caught and released Oct. 20 in the
The field team was led by Mike Stokesbury of
“There is no fish more majestic, more capable of traveling than the giant bluefin tuna, and it’s a huge mystery where it goes,†said Barbara Block, the
The TAG team began tagging bluefin tuna in 1996 off of
The work is supported by the Tag-A-Giant and Monterey Bay Aquarium foundations and the Department of Fisheries and Oceans. Each external satellite tag costs $3,500, while internal tags, built by Canadian company Lotek Inc., are $1,300.
In the field, fish are caught using rod and reel and brought aboard the fishing vessel. Tags record data including sunrise and sunset, pressure or depth, water temperature and body temperature. To date, 33 tuna have been tagged off of Port Hood and Block said they are the largest fish to be tagged.
Bluefin tuna is the most lucrative and in-demand fish in the world and the species is now under threat, Block said. While conservation efforts are underway in North America, overfishing in
“The data that we’re putting on the table from the tags help better understand how the North American waters, the tuna that are caught, relate to the tuna in the European waters,†she said.
Fishermen who catch a tagged tuna can return the device for a reward.
“The giant bluefin tuna, for almost all of mankind, we haven’t understood precisely where they go,†Block said. “The advent of electronic tags such as the pop-up satellite tag we’re putting out in Cape Breton right now allow us to follow the fish while it’s submerged ... we do just what ancient mariners were doing to figure out the position, we look at the sunrise and sunset.â€
Block describes the fishermen who work with the team as her heroes.
“They are some of the most remarkable men I’ve ever met and worked with, and the situation we’re working under out there is challenging, but they’ve made it easy ... it’s not easy to do our work out there, it’s rough weather, it’s been difficult for us, we’ve been up here for three years, and they make it easy,†she said.
The tagging data helps identify how populations of bluefin tuna use the
Data from the tagged fish has revealed that bluefin tuna routinely swim across the Atlantic, with fish tagged off the coast of North
One of the internal tags which has been recovered recorded data for almost five years.
“It’s amazing that a tag can ride in a fish, record its every move and then get recaptured up to 10 years later ... you learn everything the tuna did, where it went, did it cross the ocean, did it go over to the other side and things like that,†Block said.
Of the 1,000 tags deployed since 1996, about half have been recovered or reported back, documenting more than 21,000 days of tuna behavior.
Tagging a giant bluefin caught off of Port Hood
