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Commercial Fisheries News
Volume 36 Number 4
December 2008
Bluefin tag returns continue to surprise
DURHAM, NH – While fishermen were helping to place tags on juvenile bluefin and raise money for the Large Pelagics Research Center (LPRC) during the Tag-a-Tiny Tournament this summer, data were pouring into the center from tags deployed in 2007.
“Our tagging results continue to show that some giant bluefin of similar sizes, tagged in specific areas, have diverse migration patterns but return with amazing specificity to the same feeding grounds the following season,” said LPRC Director Molly Lutcavage.
These observations suggest that bluefin that don’t travel into the Gulf of Mexico to reproduce do one of three things – they spawn somewhere else, don’t spawn every year, or follow a combination of those two patterns, she said.
“Our research findings from tagging and sampling continue to challenge the paradigm that western-origin fish only spawn in the Gulf of Mexico and at ages 10-12 years,” Lutcavage said.
“Maturity research conducted in our lab strongly supports the view that these bluefin are fully mature,” she continued. “When, where, and how often bluefin spawn is one of the remaining frontiers for research, and we’re working with an international team of experts to resolve this important puzzle.”
Juveniles
In August and September 2007, LPRC bluefin tag team members worked with Eric Stewart on the Tammy Rose and Ed Murray Jr. on the Cookie Too to place a total of 37 tags on juvenile fish off Chatham, MA.
Five were implanted archival tags manufactured by Lotek Inc. and 32 were X-Tag PSATs from Microwave Telemetry Inc.
PSAT stands for pop-off satellite archival tags. The devices record swimming depth, external temperature, and ambient light level data that researchers use in geolocation calculations.
The data in the implanted Lotek devices are recovered when the fish is caught and the tag is returned to researchers. PSATs, on the other hand, are programmed to “pop off” the fish after a certain amount of time and then transmit their data by satellite to researchers.
X-Tag PSATs are considered the next generation of archival pop-up tags because of their smaller physical size, lighter weight, stronger tether attachment point, and high data transmission capabilities.
According to the manufacturer, the X-Tag can transmit 15,000 individual messages over 20-plus days, which is 50% more than the original PSAT. When combined with a “satellite-in-view” device that tells the tag to transmit data only when a satellite is overhead, thus saving the battery, the transmission capacity can be more than doubled.
Most of the juvenile fish tagged were 40"-60" curved fork length. Six of the X-Tags were programmed for short-term attachment, while 26 were programmed to pop off after 12 months. Tag data were coming in fast and furious this fall.
Giants
In light of the shift in distribution of giant bluefin to the north in recent years, LPRC staffers worked with John Neilson of Canada’s Department of Fisheries and Oceans (DFO) St. Andrews Biological Station in New Brunswick to place a total of 10 tags on the big fish last year.
With the help of the Southwest Nova Tuna Association, LPRC’s Walt Golet deployed eight tags on the Northern Edge of Georges Bank in August 2007 aboard the High Rider and Fin Seeker. The fishermen involved were Timmy Nickerson, Chris Mallone, Joel Jacquard, and Camille Jacquard, and the size of the bluefin ranged between 400 pounds and 800 pounds.
Two more fish were tagged in August and September last year off Malpeque, Prince Edward Island with the help of fishermen Cookie Murray and Ewen Clark aboard the Pura Vida. The taggers were Anthony Mendillo and Paul Murray. The longliner Eagle Eye II, captained by John Caldwell and Scott Drabinowicz, deployed three tags.
Although fewer giants were tagged than in previous years, the data collected over the summer were generally similar to those obtained from giants tagged in 2005 and 2006, Lutcavage said.
“A few entered the Gulf of Mexico, while one made a trans-Atlantic trip to the east Atlantic and returned to the Scotian shelf this summer,” she said. “Another tag reported in mid-February east of the Azores. Most of the remaining fish traveled to the Carolinas, the Gulf Stream, or the Caribbean region before returning to the northwest.”
Lutcavage observed that the trans-Atlantic trips were on the same trajectory as the tag returns from the early days of the program from 1997 to 2000 when she and her team tagged large giants in the Great South Channel area. Those PSAT tags were only able to report their pop-off location.
Next steps
While disappointed that they were left with an inventory of 25 tags from 2007, the LPRC team has been putting them to good use this year.
Although the National Marine Fisheries Service declined to fund the center for the 2008-2009 fiscal year, putting its future in serious doubt, Canada’s DFO provided financial support to subsidize charters, allowing the LPRC to continue the joint US-Canada tagging program.
Golet and the Southwest Nova Tuna Association team deployed 18 tags on giants as of Aug. 14 on the Northern Edge aboard the Fin Seeker, while the center’s Tag-a-Tiny team deployed 27 X-Tags and three implanted archival tags from the Tammy Rose.
Sean Smith of the DFO was able to deploy 10 satellite tags supplied by the LPRC on giants off the corner of the Grand Banks in August via the Oran II, a wooden-hulled 59-footer skippered by Gus Reyno that sails out of Sambro, Nova Scotia. Ewen Clark and Ed Murray Jr. deployed five PSAT tags in the Gulf of St. Lawrence on 800-1,100-pound fish. And participating Tag-a-Tiny Tournament fishermen tagged approximately 200 juveniles with conventional tags.
In September, Lutcavage and Tom Weber of the University of New Hampshire Center for Coastal and Ocean Mapping sailed out of Gloucester on the Lily, captained by Billy “Hollywood” Muniz, with a multibeam sonar system on board.
The team, aided by spotter pilot George Purmont, tested the feasibility of using the system for direct assessment of schools of juvenile bluefin tuna. The pilot study, funded by the Northeast Consortium with sonar supplied by DFO expert Gary Melvin, showed the researchers that they could image bluefin schools and estimate their biomass.
“Multibeam sonar is an exciting new tool in our arsenal for gathering better information on bluefin abundance and behavior,” Lutcavage said.
Lutcavage presented the results of the 2006-2007 tagging effort at an International Council for the Exploration of the Sea scientific conference in Halifax Sept. 22-26 and also spoke at the Northeast Regional Tagging Symposium on Oct. 17.
For more information on the Large Pelagics Research Center, its tagging programs, and suggestions on how to help support the center, go to the LPRC web site at <www.largepelagics.unh.edu>.
Lorelei Stevens
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