As I pointed out in April, the FDA is refusing to test fish for radioactivity, even though water currents will eventually bring debris from Fukushima:
The debris mass, which appears as an island from the air, contains cars, trucks, tractors, boats and entire houses floating in the current heading toward the U.S. and Canada, according to ABC News.
The bulk of the debris will likely not be radioactive, as it was presumably washed out to sea during the initial tsunami - before much radioactivity had leaked. But this shows the power of the currents from Japan to the West Coast.
Of course, fish don't necessarily stay still, either. For example, the Telegraph notes that scientists tagged a bluefin tuna and found that it crossed between Japan and the West Coast three times in 600 days: