APPARENTLY IT TAKES TIME TO GROW TO BE THE WORLD’S BIGGEST FISH. A new study of whale shark size and age has indicated that gargantuan fishes can live to the ripe old age of 130 years.
Marine biologists at the U.K.-based Maldives Whale Shark Research Programme and Florida’s Nova Southeastern University analyzed a decade’s worth of repetitive, non-invasive underwater measurements of whale sharks in the Maldives to understand whale shark age and growth details.
Previous studies had relied on counting growth rings – analogous to counting tree rings – to make such estimates.
THEY ALWAYS COME BACK
The research team could compare sizes and estimate growth parameters of the same free-swimming whale sharks (Rhincodon typus) because the sharks return to the same areas every year or so, in this case the Maldives’ South Ari Atoll.
It turns out that the spot patterns on whale sharks are like fingerprints – unique to each one, meaning the researchers could keep track of who was who and monitoring their growth.
Using physical tape measures as well as laser and camera measurements, the scientists gathered data on 186 encounters with 44 sharks over a period of 10 years. They then analyzed their data with a mathematical model that took into account older estimates of whale shark growth.
WHALE SHARK SIZE AND AGE
To state the obvious, it was already known that whale sharks are big. The researchers found:
- Whale sharks can grow as large as 61.7 feet on average – nearly 17 feet longer than a school bus.
- They can live as 130 years, which gives them time to do so.
- They calculated that male sharks matured at 25 years old but weren’t able to make an estimate of female whale shark longevity – there were too few females in the data.
AN INFORMED ESTIMATEThe paper was published in the journal Marine and Freshwater Research. Its authors emphasize that the study is a model, though – that is, an informed estimate. They haven’t directly confirmed a 130-year-old whale shark.
But these measurements are the best that scientists have at this stage, said Dr. Mahmood Shivji, director of NSU’s Guy Harvey Research Institute and a co-author.
“A more thorough grasp of age and growth parameters will lead to better estimates of the ability of whale shark populations to recover from overexploitation and is vital for effective management plans,” the scientists write.
PRINCIPAL SOURCES: “Novel Approach Studies Whale Shark Ages the Best Way – While They Are Swimming,” Nova Southeastern University News Room; “Whale Sharks Can Live 130 Years, New Study Estimates,” Ryan F. Mandelbaum, Gizmodo; “Comparing length-measurement methods and estimating growth parameters of free-swimming whale sharks (Rhincodon typus) near the South Ari Atoll, Maldives,” Marine and Freshwater Research.