Tuesday, August 18, 2015

Bluefin Satellite Tag Hunt

Low Fog kisses the Highlands along the Cabot Trail
Place yourself for a moment in the office of a tuna tagging scientist staring at a map with a GPS location of a popped-off mini-PAT satellite tag.  The tag had been attached to a Giant Bluefin Tuna for the past 10 months, and it contains a virtual diary of its movements, behaviours and environments encountered.  The tag is sending a summary of the tuna’s story to a satellite which relays it to your computer.  This summary data is like reading the first and final chapter of a novel and the story line on the back cover.  It’s valuable and you get the highlights and main point of it all, but you feel cheated somehow, especially after you spent weeks travelling and fishing to tag the tuna in the first place. If you can get the tag back, you can download the entire "story".

A lot of tags pop off far from shore, well beyond reach of an inshore vessel’s range.  So what happens when a tag comes to the surface 15 kms from shore?  And 25 kms from the nearest port where you know a local fisher who has a boat at the dock?  You scramble; you email, call and coordinate a recovery as fast as humanly possible…and then you pray, for good weather, calm seas and good visibility.  On Wednesday, this week, such an event happened.  Although I wasn’t the scientist staring at the map of the first GPS location, early Thursday morning...I was the scientist along with a Honours student from Acadia University rushing to the dock to jump on board the ‘Mary Heather’ captained by TAG-A-GIANT’s Captain Lloyd MacInnes based out of Little River, Cape Breton, Nova Scotia.
The search for the tag begins
Finding a tag the size of an egg with a thin black antenna sticking out would be an ok Easter-egg-hunt on land. However, throw in waves, a large area, a GPS location that is hours old, and the fact that the tag is floating with only the antenna peaking out, all of a sudden the easter egg hunt isn't quite as easy. That’s where Seth Newall, a Honours student from Acadia University comes in.  He brought a "tag locator" with him, which picks up the specific frequency of the tag and allows us to home in on the signal.  It’s a lot like playing ‘hot-cold’ as a kid, except you’re still looking for a black, half-submerged tag within 300 to 50 m of the boat.  So with Captain Lloyd at the helm spinning circles and squiggles on his chart display, Seth relaying signal strength of the tag, and myself standing on the cabin roof searching the water, we played that very game.  It was bit foggy, but relatively calm, no breaking waves or chop.  With help texts coming from TAG-A-GIANT’s Robbie Schallert in Texas, we honed our rookie skills using the tag locator.  Seth’s signal strength got stronger as the search continued.  After 3 hours of playing hide-and-seek, I spotted the black egg with antenna sticking straight up, 20 m off the port bow.
“I got it!” I yelled out, “10 o’clock! 60 feet off the port side!”
“I see it!” confirmed Captain Lloyd.
“Seth, grab the dip net while I keep an eye on it!” I instructed.
Captain Lloyd had the boat alongside the tag within seconds.  He wasn’t waiting for a dip net.  He had a deck-brush in hand and was frantically sweeping the tag closer to the boat.  Seth netted our find and with that, we had in hand the day-to-day story of one Bluefin.
Relieved Capt. with the tag

Close up of the Wildlife Computers miniPAT
Steaming back to port, the sun broke through the fog to illuminate the sea’s surface and rocky cliffs onshore, yet the lush green mountain tops of Cape Breton’s Highlands remained covered.  A pod of white-sided dolphins broke the surface and a puffin dove under upon the Mary Heather’s approach.  Some gifts in view while others remained out of sight, a fitting summary to our search’s conclusion.
Acadia Team with the tag safely secured!!

-          Written by Aaron Spares, Acadia University Coastal Ecology Lab