Thursday, September 21, 2017

Two for One Tag Retrieval

Sitting in the office at Acadia University in Wolfville Nova Scotia, TAG scientists in California emailed that a MiniPAT pop-up satellite archival tag, that had been previously outfitted on a bluefin tuna, recently popped up just 5km offshore of Cape Breton in the Gulf of St. Lawrence. When this tag popped up it transmitted some of the data it had recorded since being placed on the tuna, but by retrieving the tag a whole suite of archived data – basically a complete record of the tuna’s activity since being tagged – could be collected. So with this tag popping up so close to the coast, retrieving it was worth a shot!

Once popped up, these tags begin to transmit their location to satellites which then pass the information along to the scientists who own the tags. With the location data coming in from the tag, going out to get it sounds easy enough, but in reality, spotting a tiny black ball with an antenna on top just floating along in the open ocean is no easy task.

With winds high on Friday and starting back up again Sunday, Saturday was our only opportunity of getting calm enough waters to have a chance at spotting the tag before it got caught in the current and was swept too far off shore for retrieval.

Friday afternoon, Dr. Aaron Spares, part of the coastal ecology lab at Acadia University, and I, a Master’s student, packed up and began the trip to Margaree Harbour in Cape Breton to meet John Lauchlin, the captain of ‘Keepin’ Tradition’. We arrived late Friday night and after a quick trip to the wharf it was right to bed to rest our eyes and prepare for an early morning start. Just before sunrise we set out to the last transmitted location which was about 5km off of Cheticamp Island. We could not have picked a better day; the waters were flat calm as the sun rose over the highlands and as we got closer to our location our eyes were peeled and ready to spot that tag.

Sunrise over the Cape Breton Highlands
Once at the last known tag location, we turned on the tag locator, which can pick up the transmissions from the tag and help us narrow in on the exact location. The tag locator measures the distance between you and the tag and uses a scale from 0 to 237 to tell you how close you are, with 0 being the farthest and 237 the closest. It’s like a big game of hot and cold and based on the numbers that the locator gives you, you choose which direction to head.

We received our first transmission from the tag as soon as we turned on the locator. With Aaron and I both relatively new with this equipment, as soon as we received a transmission we decided to start corkscrewing around that location to narrow in on the tag. After about an hour of this, with no head way, we realized that the range of tag reception must be larger than we first thought and we might be much farther away than expected. We decided to take the path of strongest reception and drive until we got significantly higher numbers. Reaching what we assumed to be a much stronger signal we began to slow down and narrow our search again only to run into the same problem. After another hour or so, we still weren’t any closer. As this point, a little bit frustrated, we chose the path of the last strong signal and headed in that direction until we got to almost max signal strength before we slowed down. By some luck – or our captain’s expert navigation skills – it seemed like once we picked a direction, that he basically drove directly to the tag!

Tag in the water
Upon reaching 237 (the strongest signal on the tag locator) we slowed right down and there it was, bobbing along just a few meters from the starboard side. Aaron noticed it about a second before I did and as we both kept an eye on it John pulled the boat right up beside it, grabbed the dip net, and just like that, we had the tag! After hours of what seemed like aimless and frustrating searching, it was all smiles, mixed feelings of excitement and relief, aboard the ‘Keepin’ Tradition’. 

John Lauchlin and Danni Harper happy to have found the tag
With the work done, Aaron and I sat on the bow as we steamed back to the wharf. The perfect weather seemed to bring everyone out on that beautiful Saturday morning. With a couple fin whales off the stern, a pod of pilot whales off the starboard side, and grey seals playing off the bow. It really was the perfect day on the water and Aaron and I took in every last bit of it before we had to make our way back on land.

Having finished up earlier than expected, we decided to stop in at Port Hood to visit some long time TAG team members en-route back to Acadia. Upon arriving at the wharf, Dennis Cameron, the fisherman who assists with tuna tagging, informed us of some exciting news. There were a couple of fishermen on their way back in with a tuna that was outfitted with a satellite tag! We couldn’t believe it, what were the chances, two tags in one day! And for me, having never seen a Bluefin tuna in real life, I was pretty excited.

As news of the tagged tuna spread, the wharf got busy, and so did Dennis who was in scattered communications with TAG’s Barb Block and Robbie Schallert in California about what to do about the tag and what samples to get from the tuna.
Tags on the tuna

Once the tuna arrived at the docks it was brought up and sure enough, securely attached beside the dorsal fins were a pop-up satellite tag and an acoustic tag. Everyone on the wharf was so interested in the tags and it was a great experience to share with them what the tags were, how they worked, and what information the scientists were getting from them.

Fisherman checking out the satellite tag
The tags and tethers were taken off the tuna and then it was into the ice house to be dressed. Dennis collected a variety of samples (muscle, liver, and ear bones called otoliths) that will provide great information coupled with the tracking data from the tags.

With the fish on ice, the excitement died down and Aaron and I parted ways with the crew in Port Hood to continue our scenic drive through Nova Scotia from the Cape Breton Highlands back to Acadia University.  

-Danni Harper

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