In September of 1963 a 55-foot fin whale was killed off the coast of Oregon that showed signs of being irradiated by waste products that traveled from Hanford down the Columbia River and into the Pacific Ocean. Samples of most of the whale's organs and part of the stomach contents were reduced to ash and sent to Oregon State University's department of oceanography for further examination. The whales flesh was found to be emitting gamma rays from radioactive elements. This was mostly coming from Zinc-65, a radioactive byproduct of plutonium production which can be distinguished from ordinary inert zinc. Researchers felt the levels were low and did not present a health hazard.

References

http://www.hanfordchallenge.org/hanfords-history/the-hanford-x-files/#whale