Age Of Fish Can Be Determined Through Cold War Era Radiocarbon Traces

Researchers have used traces of C-14 to confirm the ages of Pacific Ocean perch from the Gulf of Alaska, and have proven the method to be important information for fishery stock assessment and management. Alaska Fisheries Science Center researchers plan to apply the method to other fish species.

During the height of the Cold War in the late 1950's to early '70's, the United States, Russia, and other countries exploded enough above-ground nuclear bombs to raise the amount of C-14 in the atmosphere and in the surface layers of the ocean. C-14 has a half-life of 5,730 years. After the increase from the test bombing, C-14 has been decaying slowly in the environment, giving scientists a benchmark level for each year.

Fish ear bones, called otoliths, grow in 'rings' similar to annual growth rings found in trees.

Researchers know the year that the fish was collected, and can count growth rings back to estimate the age of the fish. If the amount of C-14 detected in the first growth ring of the otolith matches up with the expected environmental amount in that year, then the estimated age of the fish is correct.