Australian researchers find 81-year-old snapper, oldest known tropical reef fish

When it was born, the second world war was several years away, none of the Beatles were alive and there were about five billion fewer people above the waves than today.

An unnamed 81-year-old midnight snapper, caught by the Australian Institute of Marine Science in 2016, has been revealed as the oldest tropical reef fish known to science.

The discovery was made as part of a new study to find out how changing ocean temperatures might affect the biology of these fish, and others like them.

Not far behind the octogenarian snapper among the new discoveries was a 79-year-old red bass caught during a fisheries survey in 1997. Both were caught at Rowley Shoals off north-west Australia.

Related: Why the death of a small, punk-like fish rocked the marine world

Dr Brett Taylor, a fish biologist at the institute who led the study, said he “may have used some colourful language” when he realised the snapper specimen was 20 years older than the previous record for a tropical reef fish – a rockfish from the Caribbean.

“The first thing I did was email my co-authors from Western Australia fisheries ... ‘am I seeing this right?”

Taylor and colleagues aged the fish by examining “one of nature’s gifts to scientists” – small ear bones called otoliths that never stop growing and have visible bands like the rings of a tree.

The study examined the ages of three species – red bass (Lutjanus bohar), midnight snapper (Macolor macularis) and black and white snapper (Macolor niger) – none of which are widely caught commercially. But their close relatives are.

“Snappers make up a large component of commercial fisheries in tropical Australia and they’re also a key target for recreational fishers,” said Dr Stephen Newman, from the WA Department of Primary Industries and Regional Development.

He said long-lived fish were considered more vulnerable to fishing pressure.

As well as the two oldest fish, the research found nine other specimens that were more than 60 years old.

Taylor told the Guardian: “A lot of these snapper species that are commercially harvested are 40, 50 and 60 years old that people are buying. There’s a serious history to some of these.”

Related: The mystery of the shrinking fish: Alaska's salmon are getting smaller

He said he had separately analysed the ocean temperatures in the tropical Indian Ocean where the oldest snapper and red bass were caught.

“We talk about climate change being something in the future, but these 80-year-old fish saw a tremendous uptake of temperature [in the ocean] in their life spans.”

Taylor said the research underscored that as oceans warm, the lifespan and growth rate of fish would change – important information for economies and communities that rely on fishing.

He said: “The main point is to understand how temperature affects growth and the lifespans of these species. By 2100, I don’t think we will have any more 80-year-old midnight snappers.

“These locations will warm to a point that based on current models it will have an impact on their biology.”

The long-lived tropical fish analysed by Taylor and colleagues are a long way from being the oldest fish in the ocean.

That record belongs to the Greenland shark. Analysis of the eyes of these Arctic dwellers has revealed a lifespan as great as 400 years.