A “living fossil” fish can live for an impressively long time — perhaps for up to a century, according to a new study. The coelacanth was thought to have a life span of around 20 years, but new estimates suggest it is a centenarian of the ocean, alongside sharks. French researchers studied marks on the scales of museum specimens — much like tree rings tell the age of trees. They believe the fish reproduces only in late middle age and can be pregnant for as long as five years. Slow-growing fish that produce few young are particularly vulnerable to extinction pressures, such as climate change and overfishing.