According to a new study published in Frontiers in Marine Science on Wednesday, a decade-long analysis has confirmed that female sharks rule as the largest fish in the ocean – surpassing males reaching an average of 14 meters (almost 46 feet).
Mark Meekan, a fish biologist at the Australian Institute of Marine Science and first author on paper, noted that some whales have even reached up to 18 meters (59 feet).
“It’s absolutely huge – about the size of a flexible bus on a city street,” he said. “But even though they are large, they grow very, very slowly. It is only about 20 cm or 30 cm a year.”
Due to the slow growth rate, the team tracked 54 individual whale sharks over 10 years and recorded more than 1,000 measurements with stereo camcorders.
“It’s basically two cameras mounted on a frame that you push with when you’re underwater,” said Brett Taylor, a biologist at the Australian Institute of Marine Scientist and co-author of the study.
“It works the same way our eyes do – so you can calibrate the two videos and get a very accurate measurement of the shark,” Taylor said.
The team also discovered that the increased size of female whale sharks can be beneficial when it comes to producing offspring. Only one pregnant whale shark has ever been documented, but unlike most sharks that carry between two and 12 young, the whale shark held up to 300.
The discovery may also have consequences for conservation efforts. Whale sharks have been listed as an endangered species since 2016. Due to their long growth rates, whale sharks targeted by fishermen can result in a further population decline for the animals.
“If you are a very slow-growing animal and it takes you 30 years or more to reach maturity, the chances of a disaster hitting before you get a chance to breed are probably quite high,” Meekan said.
“And that’s a real concern for whale sharks.”