Friday, August 18, 2017

'Tis the Season of the Giant Bluefin Pop-Ups!

Summer Recovery Season Begins:

The tuna tagging team from the TRCC put out over 30 pop up satellite archival tags in 2016 on large bluefin tunas built by Wildlife Computers in collaborations that took the team from the waters off California, Canada, Israel and Ireland. These tags are unique instruments  that ride on a giant bluefin tuna externally, and release at a preprogrammed time. The tags float up to the surface and send via radio transmissions to Earth orbiting satellites summaries of position, behavioral diving and environmental data from the sensors on board (depth, temperature, time, light). From these data the scientific team can reconstruct the behavior  of how bluefin tuna use our oceans. TRCC, TAG and affiliate team members are busy this month collecting some of these tags put on over a year ago on Atlantic bluefin in Canada, Ireland, and on Pacific bluefin tuna off the west coast of North America. The team has fanned out this past week to pick up some of the tags on the ocean as they have high resolution data sets archived in the memory. 

First up was the longest ever pop up satellite tag on any tuna in the Atlantic or Pacific. This 13+ month tag and a few others of similar length and archival data quality were on very large Pacific bluefin tuna tag- put out over a year ago on the large Pacific bluefin tuna “ The fish were - about 7 years of age- part of the great bite last July off San Clemente of 200-300 lb fish” Dr. Block said.  These bluefin were caught aboard the F/V Shogun using flying fish as baits, and trolling a kite a long way back. Barbara and the team tagged these fish with the pop up  satellite tag placed on the outside and internal archivals sewn inside the peritoneal cavity. The fish which were approximately 7 years of age (as determined by length measurements) a year ago (last July) are still at large with the internal tags. The bluefin tuna’s  satellite tag  popped up to the south of where we tagged the fish. I was pleased that we were able to keep the tag on this long. Recovering the tags can be challenging as the scientists are looking for a  small 25 gram instrument floating at the surface. Luckily there is w a locator that can “identify” the tag’s radio signature. The team hopes to get out again shortly to potentially recover a few tags in the Pacific.

-Barb Block