Adult white sharks, also known as great whites, may live far longer than previously thought, according to a new study that used radiocarbon dating to determine age estimates for white sharks in the Northwest Atlantic Ocean.
Sharks are typically aged by counting alternating opaque and translucent band pairs deposited in sequence in their vertebrae. It is unclear whether these band pairs are deposited annually, making it difficult to accurately estimate age or provide estimates for longevity for many shark species.
The goal of the white shark ageing study, published January 8 in PLOS ONE, was to determine the periodicity of band pair deposition in vertebrae of white sharks from the Northwest Atlantic Ocean using radiocarbon dating. Once validated, the band pair counts can provide a method for determining minimum estimates of longevity in white shark populations.
This first successful radiocarbon age-validation study analyzed vertebrae from four male and four female white sharks (Carcharodon carcharias) caught between 1967 and 2010 in the Northwest Atlantic Ocean.
"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 fisheries biologist in the Apex Predators Program at NOAA's Northeast Fisheries Science Center (NEFSC) 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. Deposition rates in vertebrae can change once the sharks reach sexual maturity, resulting in band pairs that are so thin they are unreadable. Age is therefore frequently underestimated. "
Bomb radiocarbon dating is one of the best techniques for age validation in long-lived species like sharks. The technique uses the discrete radiocarbon pulse in the en
|Contact: Shelley Dawicki|
NOAA Northeast Fisheries Science Center