Greenland shark

Researchers dated the eye-lens tissue of 28 female sharks and concluded that these animals live at least 272 years. The largest shark they studied was probably around 390 years old, and females seem to reach breeding age near 150.

Ages come from radiocarbon dating, not direct counting. The oldest shark's age fell between 272 and 512 years with 95% confidence.

Context

The Greenland shark (Somniosus microcephalus) lives in the cold, deep waters of the North Atlantic and Arctic. It is a slow swimmer, cruising at roughly one kilometre an hour, and it grows very slowly, which is part of why it lives so long.

Sharks have no bones or growth rings that can be counted, so age is hard to measure. In the 2016 study cited here, researchers used radiocarbon dating on the eye lens, whose core forms before birth and does not renew. Matching carbon levels to known changes in the atmosphere gave age estimates, and that is why the oldest shark has such a wide range, between 272 and 512 years. The honest summary is that it lives for centuries, and the exact age of any one animal is uncertain.

The meat is toxic if eaten fresh because of the chemicals the shark carries in its tissues. In Iceland it is made safe by long fermenting and drying into a traditional dish called hákarl, which is famous for its strong smell.