In 2015, we collected an individual fish that we could detect artificial radioactivity in the fish itself. This contrasts with almost all the other fish we've collected on the order of about 400 fish over those three years where we were unable to actually detect any artificial radionuclides in the individuals. In this particular one, we can detect cesium-137 which is artificial, a man made radio nuclide, and so we decided to have a more careful look to see if some of that contamination was related to Fukushima. The way that we do that is to look for cesium-134 and that isotope has a relatively short half life of two years, and if we see cesium-134 in a fish today, we know that it has been affected by Fukushima. When we count for longer, we can see smaller and smaller amounts of radioactivity," said Jay Cullen, professor of the School of Earth and Ocean Sciences with the University of Victoria.
It is important to note that airborne radioactive fallout from the initial explosion and meltdowns at Fukushima in 2011 reached the USA and Canada within days, and circled the globe falling out wherever the currents and precipitation carried it - mostly to places unknown to this day.