Oceans are becoming too warm for sharks to survive in, study finds
A new study has found that warming oceans are causing sharks to be born smaller and undernourished. (Courtesy ARC Centre of Excellence for Coral Reef Studies/E. Moothart)
TORONTO -- A new study has found that warming oceans are causing sharks to be born smaller and undernourished, making it difficult for them to survive.
The study, conducted by researchers at the ARC Centre of Excellence for Coral Reef Studies at Australia's James Cook University, found that as climate change continues to warm the world’s oceans, baby sharks are emerging from their egg cases sooner, causing them to be weak and exhausted.
"The hotter the conditions, the faster everything happened, which could be a problem for the sharks. 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," lead author and PhD candidate Carolyn Wheeler said in a press release.
The findings, published Tuesday in peer-reviewed journal Scientific Reports, looked at the impact of increased water temperatures on the growth, development and physiological performance of epaulette sharks up to 31 C.
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According to the study, epaulette sharks are an egg-laying species found only on the Great Barrier Reef. The researchers studied the sharks as embryos and later as hatchlings.
The study found that the hatchlings were not only smaller, but had to feed almost immediately as they lacked "significant energy."
Co-author and associate professor Jodie Rummer explained in the release that this makes it difficult for the species to survive as the epaulette sharks don't care for their eggs after they are laid. She said this means a shark egg has to survive "unprotected for up to four months" on its own.
Rummer said that rising ocean temperatures are a "major concern for the future of all sharks," including egg-laying and live-bearing species.
"The epaulette shark is known for its resilience to change, even to ocean acidification. So, if this species can't cope with warming waters then how will other, less tolerant species fare?" Rummer said.
Rummer added that the waters of the Great Barrier Reef will “likely” experience average temperatures "close to or even in excess of" 31 C by the end of the century.
The study suggests that sharks will be born, or hatch, into environments that are already at the warmest temperature they can tolerate, decreasing their chance of survival.
Wheeler says the findings are worrisome given that shark species are "already threatened" across the globe.
According to the study, sharks are "slow growing" creatures that don't reproduce as often as other fishes, adding to their decline.
"Sharks are important predators that keep ocean ecosystems healthy. Without predators, whole ecosystems can collapse, which is why we need to keep studying and protecting these creatures," Wheeler said in the release.
Rummer added that future ocean ecosystems "depend [on] us taking urgent action to limit climate change" to protect sharks and other aquatic species.