Fish exhibit some of the most remarkable examples of extreme longevity among aquatic creatures. The human fascination with enduring existence naturally extends to these inhabitants, prompting questions about which species defy typical aging processes. Their extended lifespans are a result of unique biological adaptations and specific environmental conditions. This article explores the record-holders and the underlying mechanisms that grant them such long lives.
The Greenland Shark
The Greenland shark (Somniosus microcephalus) holds the record as the longest-living vertebrate on Earth, with an estimated lifespan of 272 to over 500 years.
These large sharks typically reach 2.4 to 4.8 meters (8 to 15.7 feet) and weigh up to 400 kg (880 lb). They inhabit the cold, deep waters of the North Atlantic and Arctic Oceans, preferring temperatures between -1.1 and 7.4 °C (30.0–45.3 °F) and depths from 100 to 1,200 meters. This deep-sea environment contributes to their slow metabolism and growth rate, estimated at less than 1 cm (0.4 inches) per year.
Determining the age of Greenland sharks proved challenging because, unlike many other shark species, they lack calcified bones or hard tissues like fin spines or vertebrae that show growth bands. Researchers developed a method using radiocarbon dating of proteins in the sharks’ eye lenses. These proteins form before birth and do not degrade, allowing for age estimation, especially for those born before mid-20th-century nuclear bomb testing.
Greenland sharks reach sexual maturity exceptionally late, around 150 years old for females. This slow reproductive rate, combined with their extreme longevity, makes their populations vulnerable.
Other Ancient Fish Species
While the Greenland shark holds the longevity record, several other fish species are also known for their exceptionally long lives, including deep-sea and freshwater species.
Rougheye Rockfish
The Rougheye Rockfish (Sebastes aleutianus), found in the Pacific Ocean, can live over 205 years. This deep-sea fish inhabits depths of 200 to over 800 meters.
Orange Roughy
The Orange Roughy (Hoplostethus atlanticus), a deep-sea fish, can live for more than 200 years, with some specimens estimated to be over 250 years old. These fish are slow-growing and do not reach sexual maturity until 20 to 40 years old.
Coelacanths
Coelacanths (Latimeria chalumnae and L. menadoensis), often called “living fossils,” were rediscovered in 1938 after being thought extinct. They can live up to 100 years, maturing around 55 years of age.
Sturgeon
Various Sturgeon species (Acipenser genus) also exhibit impressive longevity, with some females living for 80 to 150 years. These ancient fish, found in freshwater and saltwater environments, are slow to reach sexual maturity, often not until 15 to 25 years of age.
How Fish Achieve Longevity
Extended lifespans in many fish species are linked to biological and environmental factors that slow their aging processes.
A primary factor is a slow metabolism, often associated with cold, deep-sea environments. Low temperatures reduce the rate of biological processes, minimizing cellular damage.
Slow growth rates and late sexual maturity are also common traits. Many species grow slowly and do not reproduce until decades or even over a century old. This strategy prioritizes long-term survival.
Certain habitats also offer reduced predation pressure, allowing individuals to survive longer. Deep-sea environments are relatively stable and offer fewer threats. Long-lived fish species may also have enhanced mechanisms for DNA repair and immune system modulation.
Protecting These Long-Lived Species
The extreme longevity and slow life histories of these ancient fish species make them susceptible to environmental changes and human impacts. Their traits, while enabling long lives, also render them vulnerable to population decline.
Species that grow slowly and mature late are sensitive to overfishing. If caught before reproducing multiple times, populations can decline rapidly and take a very long time to recover. The Orange Roughy’s late maturity, for instance, means high fishing pressure can quickly deplete stocks, as they cannot replenish their numbers fast enough.
Beyond overfishing, habitat degradation and climate change pose additional threats. Deep-sea trawling can damage fragile deep-sea ecosystems. Changes in ocean temperature and chemistry can also disrupt their specialized cold-water habitats.
Conservation efforts are important for these species. Protecting habitats, implementing sustainable fishing practices, and reducing bycatch help ensure their survival. Their preservation is important for maintaining marine biodiversity and for the insights they offer into the biology of aging.