What is the longest-lived fish species?

The longest-lived fish species is the Greenland shark.

Greenland sharks (Somniosus microcephalus) have the longest measured lifespans of any known vertebrate. Radiocarbon dating of proteins in their eye lenses estimated that studied sharks lived for at least 272 years, with the oldest estimate spanning roughly 392 years and potentially reaching 512.

They achieve this extraordinary longevity in the cold, deep waters of the North Atlantic and Arctic Oceans. Their slow metabolism and very slow growth are linked to their near-freezing environment. Greenland sharks swim sluggishly, mature extremely late, and may not reproduce until around 150 years of age.

The answer is sometimes confused with long-lived freshwater fish such as koi, lake sturgeon, or bowfin. Some of those fish can live for many decades, and rougheye rockfish can exceed 200 years, but the Greenland shark remains the record-holder among known fish and vertebrates. Its slow reproduction also makes it especially vulnerable to fishing pressure and accidental capture.