New research has provided surprising details about the biology of Earth's largest fish, the whale shark. Scientists say that female whale sharks grow more slowly but reach a much larger size than males.
Researchers recently said they had followed the growth of 54 whale sharks over 10 years. The creatures swam in the Ningaloo Reef off of Australia's west coast, where hundreds of the rare fish travel every year.
Whale sharks of both sexes were found to have their fastest growth while young — about 20 to 30 centimeters per year.
Males were found to grow faster than females. They reached around eight meters in length at about 30 years old. At that age, they reach sexual maturity, meaning the fish were able to produce young. Females grew larger than males. Females reached about 14 meters at about age 50, when they reached sexual maturity.
Mark Meekan is a marine biologist at the Australian Institute of Marine Science. He led the research that was published in Frontiers in Marine Science.
Meekan described whale sharks as "remarkable." He noted that females give birth to many young: "up to 300 at one time." For this reason, Meekan said, female sharks probably need to be very large.
"Our study provides the first evidence that male and female whale sharks grow at different rates," Meekan said.
Whale sharks are filter feeders, meaning they take food and nutrients from the water. They swim great distances to find enough to eat.
The longest-known whale shark ever recorded reached a length of about 18 meters. Whale sharks can live for 100 to 150 years.
Meekan suggested the study's findings were important for saving whale sharks. He noted that if it takes 30 or more years for the creatures to reach sexual maturity, "there are lots of threats such as hunting and ship-strike...before they get a chance to breed."
For that reason, Meekan described efforts to save the creatures as "urgent."
I'm John Russell.