Sharks are diverse cartilaginous fish that have navigated Earth’s oceans for hundreds of millions of years. They inhabit various marine environments, from shallow coastal waters to the deep abyss. A fascinating aspect of these predators is their wide range of lifespans, which is a complex area of study.
Typical Lifespan Ranges
Shark longevity varies significantly, from a few decades to over a century. Smaller, more active species typically have shorter lifespans due to faster growth rates and higher metabolic demands. For instance, the shortfin mako shark lives about 30 years. Coastal species like spinner and blacktip sharks often live 10 to 12 years.
Conversely, larger shark species tend to live considerably longer. The great white shark can live up to 70 years or more, maturing slowly. Whale sharks, the largest fish, are estimated to live between 70 and 100 years, reflecting their slower growth and massive size.
The Oldest Sharks
The Greenland shark (Somniosus microcephalus) holds the record for the longest known lifespan among all vertebrates. These sharks, over 6 meters (20 feet) long, inhabit the frigid, deep waters of the North Atlantic and Arctic Oceans. They can live for at least 272 years, with some estimates suggesting over 500 years.
One study estimated a 5-meter female Greenland shark to be 392 years old, with a potential range of 272 to 512 years. This longevity is linked to their slow growth rate, less than 1 centimeter (0.4 inches) per year, and late sexual maturity, around 150 years of age.
How Scientists Determine Age
Scientists employ several methods to determine a shark’s age. A common technique analyzes growth rings on their vertebrae, similar to counting tree rings. These rings, composed of calcium carbonate, are deposited annually, providing a record of growth. However, rings may become less distinct in older sharks.
For exceptionally long-lived species like the Greenland shark, radiocarbon dating of the eye lens nucleus is used. The eye lens core contains proteins formed before birth, retaining a chemical signature of atmospheric radiocarbon levels, including the “bomb pulse” from nuclear tests. This technique estimates the age of these ancient creatures, though it provides estimates rather than exact ages.
What Affects Shark Longevity
Multiple biological and environmental factors influence shark longevity. A primary factor is metabolic rate; species with slower metabolisms generally live longer. This is evident in the Greenland shark, whose stable metabolism allows for extended longevity.
Habitat also plays a role, with sharks in colder, deeper waters often living longer due to slower growth rates and reduced metabolic activity. Size is another element, as larger sharks typically grow more slowly and live longer. Other contributing factors include genetic adaptations, diet, and reproductive strategies like late maturity and fewer offspring.