Age & Growth Program

Bomb Carbon and Fish Ageing

During the height of the Cold War in the late 1950s to early ‘70s, the United States, Russia, and other countries exploded so many nuclear warheads that it significantly raised the amount of C-14 (also known as bomb carbon) in the atmosphere and in the surface layers of the ocean. Because C-14 has a half-life of 5,730 years, its presence remains in earth’s air and oceans for millenniums and serves as a timestamp in fish otoliths.

When using bomb carbon to age fish, we match the increase in C-14 radioactivity found in otoliths with recognized amounts in the atmosphere or in biological structures of known age.

The essence of this age validation method is as follows: if we know the year a fish was collected and have determined the fish’s age in the laboratory (that’s fish ageing), then we know when the otolith core was laid down and, accordingly, how much C-14 activity there should be in that core.

The Age and Growth Program recently completed its first C-14 study on otoliths from Pacific ocean perch caught in the Gulf of Alaska. The results of our study supported the bomb carbon validation theory based on the validity of the ages we read from Pacific ocean perch otoliths.

By Dan Kimura