Whale shark girls surpass boys to become the world’s biggest fish

A decade-long study of iconic fish before plateauing at an average adult length of about eight or nine meters, male whale sharks have been found to develop quickly. Female whale sharks grow more slowly, but eventually overtake the male, reaching an average adult length of about 14 m.

The fish biologist of the Australian Institute of Marine Science who led the research, Drs. Mark Maken stated that the length of the whale shark has been reported to be 18 meters.

“It’s absolutely huge – about the size of a bandy bus on a city street,” he said. “But even though they are big, they are growing very slowly. It is only about 20 cm or 30 cm a year. ”

Corresponding author Dr. Mark Maken talks about his research on whale sharks. Sincerely: AIMS

In conducting the research, the scientists visited the Ninglu Reef in Western Australia for 11 seasons between 2009 and 2019. They tracked 54 whale sharks as they grew – made possible by a unique ‘fingerprint’ of spots on each whale shark that could be used to identify them. Individual fish.

AIMS Marine Scientist Dr. Brett Taylor said the team recorded more than 1000 whale shark measurements using stereo-video cameras.

“It’s basically two cameras installed on a frame that you push when you go underwater,” he said. “It works the same way our eyes do – so you can calibrate two video recordings and get very accurate measurements of sharks.”

Measuring whale shark

Measuring whale shark. Credit: Andre Reruca / AIMS

The study also included data on whale sharks in aquaria.

Dr. Mecken said that this is the first evidence that male and female whale sharks differ.

For women, there are huge benefits to growing up, she said. “Only one pregnant whale shark was found, and there were 300 young inside it,” Dr. Meekan said.

“This is a remarkable number, most sharks will only be somewhere between two and a dozen. So these giant females are probably getting larger due to the need to carry lots of puppies. ”

Whale shark rincodon typus

The whale shark (Rhincodon typus) is the largest fish species in the world. Sincerely: Andre Reruca / AIMS

Whale sharks are the maritime symbol of Western Australia, and swimming with the iconic fish in Ninglu Reef boosts the local economy by $ 24 million per year.

But he was listed as endangered in 2016.

Dr. Meken said the discovery has huge implications for conservation, with whale sharks being threatened by targeted fishing and shipwreck attacks.

“If you are a very slow-moving animal and it takes you 30 years or more to attain maturity, then the chances of disaster before you have a chance to breed are very high.” “And this is a real concern for whale sharks.”

Dr. Meken said the discovery also explains why whale shark crowds in the tropics are made up almost entirely of young men.

“They gather to take advantage of an abundance of food so that they can maintain their rapid growth rate,” he said.

Dr. Taylor said that whales go against everything previously thought by scientists in the development of the shark plateau.

He said, “What this letter actually wrote about the evolution of whale sharks has been rewritten.”


Reference: Mark G. Meekan, Brett M. Taylor, Emily Lester, Louisiana c. Ferreira, Ana M.M. Siqueira, Alistair DM Dove, Matthew J. “Whale shark’s asymmetric growth reveals sex-specific life-history strategies” by Burt, Alex. Espinall, Kim Brooks and Michelle Thames, 16 September 2020, Frontiers in Marine Science.
DOI: 10.3389 / fmars.2020.575683

Dr. Meekan and Dr. Taylor is based in Perth, Western Australia.

This research was published today in the journal Frontiers in Marine Science.