New research is using the latest electronic fish tags, capable of reporting via satellite, to understand the migration patterns of Pacific bluefin tuna.
Researchers at Auckland University's South Pacific Centre for Marine Science at Leigh Marine Laboratory are using pop-up satellite archival tags (PSAT) to collect information about the movements, diving patterns and temperature preferences of Pacific bluefin tuna.
The tag collects and stores data for eight to 12 months and then automatically releases from the fish and floats to the surface, where it can transmit summary information via satellite to the researchers.
There are three species of bluefin tuna worldwide, two in the Pacific Ocean and one in the Atlantic. The two species found in New Zealand are referred to as Southern bluefin and Pacific bluefin.
A world-class recreational fishery has been established for the Pacific bluefin, which grows up to 350kg, off the West Coast of the South Island.
All bluefin tuna species are considered highly migratory, moving through numerous international waters throughout the year. It is thought that Pacific bluefin probably migrate to New Zealand to feed before departing for the tropics to breed.
"Bluefin tuna are being caught on rod and reel while feeding behind hoki trawlers during August and September," said Professor John Montgomery.
"This project, in collaboration with Stanford University and Blue Water Marine Research in Northland, aims to gather data which are essential for coordinated international fisheries management programmes.
"Unless we understand how these fish live, and where they move, it's close to impossible to effectively manage these highly migratory species."
The satellite tags are roughly the size and shape of a hand held microphone and can sometimes be found washed up on beaches, or on tuna caught by fishing boats. Each tag collects data every 10 seconds for up to a year.
Contact information is printed on the tag, and anyone finding tags should return them to ensure the data is collected, for a cash reward.