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January 10, 2014

Great White Sharks Could Live to 70 or Beyond

by VOA News

There’s now another reason to fear the great white shark: They live a lot longer than previously thought, according to a new study by the National Oceanic and Atmospheric Administration’s (NOAA) Fisheries Service.

Using radiocarbon dating techniques, the scientists said they were able to measure the age of sharks from the Northwest Atlantic Ocean, finding that some lived to 70 years-old and beyond. This is the first successful age-validation study, according to NOAA’s announcement. Sharks have usually been aged by counting alternating opaque and translucent band pairs deposited in sequence in their vertebrae, which is not as accurate.

"Ageing sharks has traditionally relied on counting growth band pairs, like tree rings, in vertebrae with the assumption that band pairs are deposited annually and are related to age," said Lisa Natanson, a NOAA fisheries biologist and a co-author of the study. "In many cases, this is true for part or all of a species’ life, but at some point growth rates and age are not necessarily in sync. Growth rates slow as sharks' age … Age is therefore frequently underestimated. "

The oldest female shark aged in the study was found to be 40, while the oldest male was 73, according to NOAA. The other three males tested aged 9, 14 and 44, and the females were 6, 21 and 32.

NOAA said previous aging of great whites in the Pacific and Indian oceans using the band pair technique showed that none of the sharks was over 23. Natanson’s findings show that either sharks in the Northwest Atlantic live longer than those in the Pacific or Indian oceans, or that age has been underestimated in previous studies.

Great whites are listed as a vulnerable species under the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, according to NOAA, and the results of the study could help with conservation efforts.