A new way to track bigeye tuna

Janet Lathrop at UMassAmherst News & Media Relations: A first-of-its-kind study of bigeye tuna movements in the northwestern Atlantic Ocean led by Molly Lutcavage, director of the Large Pelagics Research Center at the University of Massachusetts Amherst, found among other things that these fish cover a wide geographical range with pronounced north-south movements from Georges Bank to the Brazilian shelf, and they favor a high-use area off Cape Hatteras southwest of Bermuda for foraging.

This NOAA-funded research, which used a new approach to study one of the most important commercial tuna species in the Atlantic, provides the longest available fishery-independent record of bigeye tuna movements to date. Data should help researchers to further characterize habitat use and assess the need for more monitoring in high-catch areas.

...Fisheries oceanographer Lutcavage says, “Although Atlantic bigeye tuna are delivering high prices to the U.S. commercial fleet and are highly sought by recreational fishermen and fishing tournaments, there’s been a surprising lack of scientific research on this species. And in contrast to the Pacific, where tuna fisheries programs have deployed over 400,000 tags over 25 years, the Atlantic lacks the fisheries infrastructure that would increase the odds of reco
vering tags. We have to rely on popup satellite tags that are fishery independent to make sure we get information back from the tuna.”

...Working with pelagic longline vessel captains Scott Drabinowicz and John Caldwell of the FV Eagle Eye II out of Fairhaven, Mass., Lutcavage, with LPRC colleagues Tim Lam and doctoral candidate Ben Galuardi, deployed 21 pop-up satellite archival tags (PSAT) on adult bigeye tuna between 2008 and 2010 in the northwest Atlantic. The sea captains fit tags on fish in good condition and return them to the sea. The PSATs were programmed to record relative light level, temperature and pressure (depth) every two minutes for eight or 12 months.

...Lam explains, “Bigeye tuna dive deeply, like clockwork, at dusk and dawn, making it hard to use light-based geolocation methods to estimate their daily locations. Here, we showcase a new positioning technique to get around the problem of low light levels at depth by using temperature and the bigeyes’ spatial ecology and movements in the western Atlantic. But there’s much more to learn.”

The authors hope their results will inform the International Commission for the Conservation of Atlantic Tuna’s upcoming tagging effort and assist ICCAT scientists as they plan new research to better understand the population....

Pelagic longline vessel Captain Scott Drabinowicz and crew preparing to deploy a tag from the deck of the FV Eagle Eye II. From the UMass Amherst website