Friday, July 1, 2016

Bluefin Tuna Special

Our Pacific bluefin tuna tagging and collecting trip  is out in the Pacific aboard the Shogun a recreational long Range fishing boat we've used annually to do this trip. The objective of the cruise is to electronic tag Pacific bluefin tuna and study their migrations to the spawning grounds in the western Pacific. In addition we hope to collect 15 to 20!bluefin tuna for the TRCC lab to conduct feeding studies.   For tagging we use two types of electronic tags each with their target size of fish and story we hope to tell with the data  One type of electronic tag is a Pop up satellite tag that is programmed to stay on the fish for one year and potentially show us where the largest year classes go after foraging in the eastern Pacific hot spots. This is a hot question in current Pacific bluefin tuna science. The other type of tag is called an archival tag. These tags are programmed to last six years and will provide in depth data in what a bluefin does over the entire period In 10-20 second intervals. That would be immense data and to far we've successfully used these techniques up to three years in the Pacific and five years in the Atlantic. These tags are brand new and when we put them in fish off the shores of North America we hope to see them five to six years from now recaptured. They have the potential to record the daily position, thus the journeys and behavior in high resolution for the entire six years.  They carry three languages  and all say Return for Big reward.bit takes a fisher person to get the tag back. But we know this works to date we have 53 percent returned in the Pacific and about twenty percent in the Atlantic.  It takes a lot of international cooperation but we are hopeful as this type of tagging has given Atlantic and Pacific bluefin tuna researchers the most  detail required to increase our knowledge of when and where tuna spawn a critical question essential to life history and management questions. In addition these tags provide oceanography and behavioral data essential for better understanding the fish. 

Slow Bite but Big Fish😎

Today the first of July l, we got off to great start with the pop up satellite tagging of our first fish which by measurement is the largest fish we ever have tagged on the Shogun. The bluefin tuna was caught by a crew member and measured 177  cm in curved length. We estimate the fish was close to 190-200 lbs. 

We caught the fish using innovative techniques by the Shogun crew and met the challenge of lifting it on board from a swim step and satellite tagging the fish.   If the tag stays on (a problem for these fast moving fish) we hope to get a year of data on where the bluefin tuna go to spawn.  Fish of this size class are very hard to catch as bluefin tuna vision is extraordinary. We were able to catch two more bluefin tuna of a smaller size class well above the size we intend to collect and for our first day we ended with two archival tags and the largest fish ever in twenty years of TRCC tagging. Great start! 

- Barbara Block

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