Monday, November 2, 2015

A 20-Step Guide to Tagging Giant Atlantic bluefin

There’s a long list of things that have to go right to tag a giant bluefin tuna.  Here’s an abbreviated version.

To tag a giant bluefin tuna you have to:
1.) Obtain research permits, program and prepare the electronic tags, and pack a lot of gear (don't forget anything!!!).

2.) Travel to a remote corner of Nova Scotia.

Autumn colors on Cape Breton Island, Nova Scotia. photo: E. Estess
3.) Wait, and wait, and wait for the weather to clear up. We were only able to fish 7 days out of 3 weeks this October due to weather!

4.)  Make sure your tagging boat motor is working.

5.) Find and catch large mackerel for bait.

6.) Search for a school of bluefin tuna (this can take hours/days).

Diving gannets and busting bluefin. photo: E. Estess
7.) Get a bluefin to bite the bait. Bluefin are notoriously picky about what they will bite. Last week we had a school of giant bluefin jumping through our mackerel baits without a single hookup!

A bluefin nails the bait! photo: E. Estess
8.)  Make sure the circle hook sets in the corner of the tuna’s mouth.

9.) Fight the fish to the stern without pulling so hard that you break the straining monofilament or bend the small metal hook.

Lloyd MacInnes and Dennis Cameron work together to angle in a
large bluefin for the tagging team. photo: E. Estess
10.) Guide the head of the tuna to the back door of the tagging boat. This is one of the hardest steps as the tuna can easily shake its head and pull the hook, particularly when the seas are rough.

11.) Use 5 people to pull the (up to 1,600lb) animal through the back door of the tagging boat onto a padded surgical mat.

12.) Place a hose into the tuna’s mouth to irrigate the gills with oxygen rich seawater and place fabric over the animal’s eye to reduce stress.

An eye cover and irrigation hose help keep the bluefin calm
and safe on deck.  Photo: R. Schallert
13.)  Remove the hook from the corner of the mouth.

14.)  Measure the length of the fish. This length measurement can be converted to an estimate of the fish’s weight at a later time.

15.)  Insert sterilized titanium darts into precise locations along the tuna’s back to anchor acoustic and satellite tags securely to the fish.  If done correctly, the acoustic tags will last for up to 5 years and the satellite tags will automatically detach from the animal after 1 year. Note: All tagging and handling procedures are conducted under the strictest animal care protocols.

Dr. Steve Wilson places a satellite tag into the dorsal muscle of a
large Atlantic bluefin. Photo: E. Estess
16.)  Insert a conventional/spaghetti tag with the phone numbers to call in case the fish is recaptured by a commercial fisherman.

17.)  Take a small (pencil eraser-sized) clip of the tuna’s fin to use for DNA sequencing.  This will allow us to understand if the animal is from the eastern or western Atlantic population of bluefin.

18.)  Lift and rotate the surgical mat to point the tuna’s head out the door (easier said than done!).

The Tag-A-Giant team lifts a giant bluefin to release it back into
the Gulf of St. Lawrence. Photo: R. Schallert
19.)  Guide the tuna out the door and watch it kick away into the deep blue of the Gulf of St. Lawrence.

20.)  Exchange high 5’s with the team!

The weeks of preparation and decades of expertise between the fishermen and researchers paid off and we were able to tag and release two giant bluefin on this trip. Our past results have shown that a majority of these tunas swim south from the foraging grounds in Nova Scotia to the Gulf of Mexico to spawn, and a small percentage swim across the Atlantic into the Mediterranean Sea for lesser-known reasons.  Only through long-term tagging studies like this will we be able to understand tuna migration and life history in order to effectively model population sizes for stock assessment and sustainable management of this species. 

Follow this link to the recent publication of our 8-years of tagging effort in Nova Scotia: