There was a reunion of sorts at the Wedgeport Tuna Tournament and Festival this year when an Atlantic bluefin tuna that was tagged and released with a pop-up satellite archival tag by the Fin Seeker in waters off Port Mouton in October, 2012 was landed by the Claw Patrol on the last fishing day of the tournament.
For Dr. Molly Lutcavage, director and founder of the Large Pelagics Research Center in Massachusetts, it was the highlight of this year’s tuna weigh-in.
Dr. Molly, as she’s called by everyone, has been working with Canadian fishing partners in the South West Nova Tuna Association since 2003 tagging and releasing the giant bluefin with electronic tagging. “We come up here every year and go fishing with them usually in September and October. My students have come up here to work with real fishermen. We call it cooperative research,” said Dr. Molly in an interview.
“The electronic tags are designed to stay on the fish for hopefully one-year recording depths, temperatures and light ambient levels,” said Dr. Molly.
Programmed to stay on one year and then release, “the tether holding the tag stays in the fish, the tag pops up to the surface like an EPIRB and transfers the data. We get it as email as the data rolls in. Over two weeks it comes in and we can tell from that, we can reconstruct what happened to the fish for the year the tag was on so we get the whole migration route of the fish.”
Dr. Molly has also been doing ecological testing on the bluefin landed by southwestern Nova Scotia tuna fishermen. She has been involved in tuna research since 1993, when fishermen in New England said “what we see out there doesn’t match with what the federal government is assessing as the state of bluefin and nobody believes us, so in 1993 they came to the New England Aquarium and asked the right whale group if they could help them document how many fish they were seeing in schools at the surface in the Gulf of Maine. That’s when we started the program,” she noted.
“And we learned very, very quickly what the fishermen said with regards to the number of fish was very accurate and from then on we realized we better do a lot more scientific work because the scientific understanding is not what it should be. What we’ve learned over the years from working with fishermen and putting the satellite tags on the fish has completely upended the assumptions about what Bluefin do in the Atlantic,” said Dr. Molly.
“I think together over the last 17 years we were able to show the biological assumptions that are used for the basis of management are incorrect and it was the work done here and in the Gulf of Maine by the satellite tagging and the sampling of the gonads and the guts that we were able to see some of the understanding of what Bluefin might be doing.”
The old understanding was there were two separate stocks, two spawning grounds and the amount of mixing between the two stocks was very, very low in the Atlantic, said Dr. Molly.
“Over time the electronic tag data has shown that can’t be accurate because not only have we predicted and found the spawning grounds that are outside the Gulf of Mexico, we’ve shown that the majority of spawning fish are not spawning in the only assumed spawning grounds. We think the majority of spawning fish are spawning in the Atlantic and that means that biomass of reproductive fish has not been included in thinking about the spawning stock biomass.
“The second thing is from one-year to two-year-old fish both in simple tag and electronic tag is they are crossing the Atlantic as early as the first or second year of life and continue to cross the Atlantic throughout their lifespan so the idea that there is little mixing and they go back to the same place to spawn all the time we think is contradicted by new science understands.”
