Thank you for your question about the potential impacts to US west coast fisheries from the release of radioactive isotopes from the Fukushima Dai-ichi into the ocean. Two Cesium (Cs) isotopes were released from Fukushima, one which decays quickly (Cs137) and when detected means that the radioactivity can be traced back to Fukushima. The other isotope decays more slowly (Cs134) and is found at background levels in the environment from nuclear testing in the 1950's and 1960's.
It is true that these two radioactive isotopes (Cesium-137 and Cesium-134) released from the Fukushima reactors have been detected in offshore waters near the US West Coast. However, to put that into perspective, the highest measured nearshore samples on the West Coast are more than 1000 times lower than the US Government safety limits for drinking water (7,400 Bq/m3), and well below limits for direct exposure while swimming or boating.
Researchers in Canada found extremely low levels of radioactive Cesium in salmon during initial testing of 20 fish caught in rivers in BC and Yukon Territory, but are not concerned about health impacts and have no plans to close any fisheries. You would need to eat between 2000-3000 pounds of king salmon at that concentration to recieve the same radiation dose you would get during a single cross country flight. More recent testing on over 400 salmon samples from the same area has not detected any radioactivity.
OSU researchers also found trace amounts of radioactivity in albacore tuna caught off Oregon, but you would have to consume 700,000 pounds of fish just to match the average person's annual exposure to radiation in everyday life from cosmic rays, the air, the ground, x-rays and other sources.
There is evidence that radioactive materials are still being released from the Fukushima reactors in very low levels, and US researchers are continuing to monitor the radioactivity off West Coast waters. Ken Buesseler, one of the leading researchers on radioactive ocean chemistry said, “Levels today off Japan are thousands of times lower than during the peak releases in 2011. That said, finding values that are still elevated off Fukushima confirms that there is continued release from the plant."
Overall though, there is very little concern that radiation levels will pose a threat to human health on the US West Coast, and you can continue to eat wild caught fish with confidence.
I have included a few links below in case you would like more information. Please feel free to get back in touch if you would like more clarification or have additional questions on this topic.
There are a few good resources to look for the most recent testing information on the West Coast of Canada and the US:
This website has information about current testing of water and biological organisms in Canada.
This website has current test results for water samples. You can look for 2017 samples, highlighted in Red on the map. For example, a sample was taken at in the surf at Pacific City, OR on January 4th, 2017. They could not detect the Fukushima radioactive isotope (Cesium 134), and the Cesium isotope found from other sources (Cesium 137) was detected at 2.8 Bq/m3, a level more than 2,500 times lower than the US action level for drinking water (7,400 Bq/m3)