A warmer ocean environment as a result of climate change can cause shark pups to be born smaller, exhausted and undernourished into already challenging environments, according to a new study conducted at the New England Aquarium.
Scientists examined the effects of increased temperatures on the growth, development and physiological performance of epaulette sharks, an egg-laying species found only on the Great Barrier Reef. The hatchlings were not only smaller, but they needed to feed almost immediately while lacking significant energy.
“We found that the hotter the conditions, the faster everything happened, which could be a problem for the sharks,” said lead author Carolyn Wheeler, a Ph.D. candidate at the University of Massachusetts Boston and at the ARC Centre of Excellence for Coral Reef Studies at James Cook University. “The embryos grew faster and used their yolk sac quicker, which is their only source of food as they develop in the egg case. This led to them hatching earlier than usual.”
The Aquarium has a successful breeding program for epaulette sharks, allowing the researchers to use some of the eggs to study climate change impacts on a shark species native to the waters of Australia.
“The ocean faces increasing threats from humans, such as the effects of climate change, and it is vital to conduct scientific research to help strengthen the management and protection of those ocean species most negatively impacted and vulnerable,” said Dr. John Mandelman, Vice President and Chief Scientist of the Anderson Cabot Center for Ocean Life at the New England Aquarium. “In this case, we addressed a pressing threat – ocean warming – and the potential impacts on a species that could serve as a model for other egg laying species among sharks and their relatives.”
The waters of the Great Barrier Reef will likely experience summer averages nearing or even exceeding 31°C by the end of the century, according to co-author and Associate Professor Jodie Rummer. Sharks do not care for their eggs after they are laid, meaning a shark egg must be able to survive unprotected for up to four months. The rising ocean temperatures are a major concern for the future of sharks, particularly those that lay eggs.
“The epaulette shark is known for its resilience to change, even to ocean acidification,” said Rummer. “So, if this species can’t cope with warming waters, then how will other, less tolerant species fare?”
Sharks and other species from the Elasmosbrancii family, such as rays and skates, grow extremely slowly, and don’t reproduce as regularly as other fish. The populations of many of these animals are already threatened globally. This study suggests the sharks that are born or hatched in the future will be at a disadvantage, trying to survive in environments that are already at the warmest they can tolerate.
The research was housed at the Aquarium’s Animal Care Center in Quincy, Mass. under the direction of Barbara Bailey, Curator of Husbandry and Sustainability.
For information regarding co-authors and to read the full study, click here.
Photography by E. Moothart.