The world’s oldest fish species is the Greenland shark. They are described as the oceans’ oldest fish. They can take 150 years to reach sexual maturity and live for up to 4 centuries (400 years) and perhaps longer. In 2016, researchers used radiocarbon dating to determine the ages of 28 Greenland sharks. They estimated that one female was about 400 years old.
In August 2019, the BBC asked whether the oldest fresh water fish ever found was a bigmouth buffalo at 112 years old. In total 5 bigmouth buffalo were over 100 years old with one hitting the 112-years-of-age freshwater fish record.
The Greenland shark is truly remarkable. To wait 150 years before you can mate and produce offspring is equally remarkable. The Greenland shark is also the longest lived vertebrate by at least a hundred years. They grow about 1 cm a year. Scientists worked out a way to judge their age. They used dead Greenland sharks. Most of them had been accidentally killed in trawling nets. They used radiocarbon dating using the shark’s eye lenses. They looked at high amounts of carbon-14 which is a heavy isotope left behind by nuclear bomb testing in the mid-1950s. They could then date when they were born. They then used this as a starting point for a growth curve having established that Greenland sharks are 42 cm long at birth. They also used a technique to calculate the ages of sediments. They correlated radiocarbon dates to the shark’s length.
The oldest shark was aged at 392 years plus or minus 120 years. Their study was published in Science. The bowhead whale is the next oldest vertebrate at 211 years of age. Although whales are not classified as fish but as warm-blooded mammals. Sharks are are a special type of fish. The body is made out of cartilage instead of bones like other fish.
I conclude, therefore, that the oldest fish species in the world is the Greenland shark.
More about the Greenland shark
I feel the need to write a bit more about the Greenland shark as they are so extraordinary. I’ve relied upon Wikipedia. They are also known as the grey shark or gurry shark. They are in the family known as “sleeper sharks” (Somniosidae). They are found in the waters of the North Atlantic Ocean and Arctic Ocean. They are one of the largest shark species. They feed on a wide variety of available foods, being described as “generalist feeders”.
In Iceland, the shark is eaten as a delicacy but it’s flesh is toxic because of high concentrations of trimethylamine N-oxide in its tissues. They can grow to 21 feet in length and 2,200 pounds in weight. It is possible that they can be even bigger at 24 feet in length and weighing more than 3,100 pounds. Unusually, males are typically smaller than females.
They have 48-52 teeth in the upper jaw. They are thin and pointed without serrations. When feeding they use a rolling motion of their jaws. The upper jaw teeth act as an anchor while the lower jaw cuts out massive chunks of their prey. They are an apex predator. There prey is mostly fish but they have been seen hunting seals in Canada. They also prey upon skates, eels, sharks, herring, cod, rosefish, sculpins and flounder to name some. Polar bears, moose and reindeer have also been found inside the guts of Greenland sharks.
They move relatively slowly and often hunt prey that is asleep. They are camouflaged and therefore can approach prey undetected. When close they create a section that draws in the prey by opening their large buccal cavity.
Because of their incredibly slow growth rate and long life they are particularly vulnerable to the possibility of extinction in the wild. They are susceptible to overfishing. There is concern about the sustainability of the species. They are fished. The Inuit from the Canadian Eastern Arctic and Greenland regard this animal is a spirit animal helping shamans.
Postscript: it’s reported that an 81-year-old tropical reef fish living off the coast of Western Australia is the oldest known to science. The fish was caught at Rowley Shoals about 180 miles west of Broome. It was 2 decades older than the previous recordholder, a Caribbean rockfish. In this instance it appears that marine scientists determined the age of the fish by studying their ear bones which have an annual growth band. They can be counted like tree rings. The 81-year-old fish was caught in 2016 therefore was born in 1935.