Girl power in the deep blue sea: World’s largest fish are female
WASHINGTON, Sept 16- Male and female whale sharks- filter-feeding marine behemoths- grow at different rates, with females doing so more slowly but getting much larger than the guys, according to research that offers deeper insight into the biology of Earth’s largest fish. Researchers said on Wednesday they had tracked the growth of 54 whale sharks over a 10- year…
By Will Dunham
WASHINGTON, Sept 16 (Reuters) – Male and female whale sharks- filter-feeding marine behemoths – grow at different rates,with females doing so more slowly but getting much larger thanthe guys, according to research that offers deeper insight intothe biology of Earth’s largest fish.
Researchers said on Wednesday they had tracked the growth of54 whale sharks over a 10-year period in the vast Ningaloo Reefoff Australia’s west coast, where hundreds of theseslow-swimming endangered fish migrate annually.
Whale sharks of both sexes were found to have their fastestgrowth as juveniles, about 8-12 inches (20-30 cm) annually.
Overall, males were found to grow slightly more quickly thanfemales, plateauing at around 26 feet (8 meters) long afterreaching sexual maturity at about 30 years old. Femalesplateaued at around 14 meters (46 feet) when they reached sexualmaturity at about age 50.
It is believed whale sharks may live 100-150 years. Thelongest-known whale shark reached about 60 feet (18 meters).
“Whale sharks are remarkable in that females have massivelitters of pups, up to 300 at one time. Being very large isalmost certainly a prerequisite for carrying this many younginside a female’s body,” said Australian Institute of MarineScience marine biologist Mark Meekan, who led the researchpublished the journal Frontiers in Marine Science.
These sharks have a brownish-grayish color on the back andsides with white spots, with a white underside.
“Our study provides the first evidence that male and femalewhale sharks grow at different rates,” Meekan said. “Previously,researchers had to rely on estimates of growth and age extractedfrom the vertebrae of dead sharks that had either stranded onshore or been killed by a fishery. Samples were very limited anddidn’t cover a very wide size range of animals, confoundingattempts to produce reliable estimates of growth patterns.”
They are filter feeders, swimming great distances throughthe world’s tropical oceans to find enough plankton to sustainthemselves.
“Our study has important implications for conservation,”Meekan said. “If it takes many years, 30 or more, for theseanimals to become mature, there are lots of threats such ashunting and ship-strike that they may succumb to before they geta chance to breed, making conservation strategies for theseanimals an urgent task.”
(Reporting by Will Dunham;Editing by Sandra Maler)
