Few marine animals capture the briny deep’s mystery and fragility as well the bluefin tuna.

Bluefin tuna can grow up to three meters in length and over a thousand pounds in weight. They are the Michael Phelps of ocean swimmers, with bodies perfectly contoured for long distance swimming – they can even pull their dorsal fins in to reduce drag. They’re not the fastest (that award goes to the Sailfish, closely followed by the Marlin), but they usually fall somewhere in the top five fastest fish.

Bluefin tuna are cruisers. Pacific bluefin spawn off the coast of Japan and the young fish migrate over six thousand nautical miles to the eastern Pacific. Some tuna make this trip in as few as 21 days. Bluefin tuna return to their natal waters to breed and spawn once more. Atlantic bluefin model a similar pattern, traveling between the Mediterranean and the Gulf of Mexico.

But bluefin tuna are severely over fished because they are highly coveted for sushi. Bluefin is one of the most tender, flavorful fish available. A single bluefin can sell for $100,000 at fish markets in Japan. They’re caught nearly everywhere they swim, and often before they reach maturity and can reproduce to replenish the population.

Creating a fishing policy or conservation plan for the bluefin tuna is difficult because no one knows exactly where they swim. This is where the Tag-A-Giant program comes in. A joint project between Stanford University and the Monterey Bay Aquarium, Tag-A-Giant attaches small tags that will signal the fish’s location back to researchers. The researchers have focused most closely on bluefin tuna, but have also followed billfishes and a couple of shark species.

You can follow the Tag-A-Giant team as they capture tuna and attach the tags at their blog.

Bonus fun tuna fact: Bluefin tuna are ectotherms, meaning that like most fist, their body temperature fluctuates with the temperature of the water. But where many people would call ectotherms cold-blooded, bluefin tuna are warm-blooded. They can heat their core body temperature to about ten degrees fahrenheit above the surrounding water. Keeping their blood and muscles warm allows them to work more efficiently, helping the tuna to cruise through a trans-ocean journey like it’s no big deal.