Marine biologist Dan Madigan stood on a dock in San Diego and considered some freshly caught Pacific bluefin tuna. The fish had managed to swim 5,000 miles from their spawning grounds near Japan to California’s shores, only to end up the catch of local fishermen.
It was August 2011, five months since a magnitude 9 earthquake and tsunami had struck in Japan, crippling the Fukushima Daiichi power plant. Madigan couldn’t stop thinking about pictures he’d seen on TV of Japanese emergency crews dumping radioactive water from the failing reactors into the Pacific Ocean.
The graduate student looked at the tuna and wondered: Could they have transported any of that radiation to California?
For most people, the thought of radioactive sushi tuna is nightmarish, but for Madigan it represented an opportunity.
If radiation from Fukushima was detectable, scientists might look for traces of the contamination in all sorts of amazing creatures that make epic journeys across the open seas, from tuna to sharks to turtles to birds. They might learn more about where the animals came from, when they made their journeys, and why.
They might learn how a single, man-made event — the plant failure in Fukushima — could be linked to the lives and fates of animals making homes over half the globe.
Madigan bagged some tuna steaks he had collected from the fishermen, threw them in a cooler and made a mental note to call Nicholas Fisher, a scientist he knew who would be able to tell him whether the tuna had carried radiation from the disaster.
Maybe the fish could still tell their story.
Madigan began thinking about the globe-spanning migrations of marine animals in 2006, during a fishing trip in the open waters off Costa Rica.