Great White Sharks Live for 70 Years or More
Great white sharks (Carcharodon carcharias) live for about 70 years or more, according to a latest study.
Scientists at NOAA's Northeast Fisheries Science Center (NEFSC) and the Woods Hole Oceanographic Institution (WHOI) used radiocarbon dating technique to estimate the age of four adult male and four adult female white sharks. All the eight specimens were caught between 1967 and 2010 in the Northwest Atlantic Ocean.
The study not only shows that great whites can live for as long as humans, but also reveals a flaw in current methods used to estimate shark age.
Disbanding the Growth Band Pairs
Previously, researchers used growth band pairs- "alternating opaque and translucent band pairs deposited in sequence in their vertebrae "- to estimate sharks' age. These bands are somewhat similar to tree-rings that are deposited annually. However, many biologists are still unsure whether the growth rings in the sharks are added uniformly each year.
"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," said Lisa Natanson, a fisheries biologist in the Apex Predators Program at NOAA's Northeast Fisheries Science Center (NEFSC).
Previous research on shark specimens from Pacific and Indian Oceans had shown that none of the samples were older than 23 years of age.
Bomb radiocarbon dating
Nuclear testing and eventual release of discrete radioactive particle around the world during the 1950s and '60s has given a kind of "time stamp" to all living tissues. Many researchers study the levels of carbon-14 in tissue samples to determine its age.
In the current study, too, researchers looked at radioactive carbon level in shark vertebrate and compared it with a reference table that charts the amount of carbon-14 taken up by marine organisms.
Radiocarbon dating showed that the oldest male shark in the study was 73 years old and the female was 40 years old. Other male sharks in the group were 9 to 44 years old.
The study is published in the journal PLOS One.