Baby sharks being born earlier and weaker as oceans warm

Baby sharks will struggle to survive in warmer oceans, scientists have warned.

Researchers studied the development of baby epaulette sharks, a species found only on the Great Barrier Reef that reproduces by laying eggs.

The study from scientists at Australian James Cook University, published in Scientific Reports, examined shark eggs in water as warm as 31C to measure their growth and development.

Lead author Carolyn Wheeler said: “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.”

Once hatched, the baby sharks were smaller and needed to eat almost immediately, making their early survival more difficult.

Sharks do not care for their eggs once laid, so they need to survive unprotected for up to four months.

Water around the Great Barrier Reef will reach average temperatures of 31C during summers by the end of the century, the authors said.

The epaulette shark is widely considered to be among the more resilient species, raising concerns for other animals that are more sensitive to temperature change and ocean acidification.

Sharks are apex predators, meaning they sit at the top of the food chain, so their decline can have ramifications for the ecosystems they usually help to regulate.

A previous study of the US coastal Atlantic Ocean found that when shark numbers decline it can have knock-on effects for species lower down the food chain, such as molluscs, because their predators are greater in numbers.

Wheeler added: “The study presents a worrying future given that sharks are already threatened.

“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.”

Last year, scientists warned that the Great Barrier Reef is losing its ability to recover because of rising water temperatures.

Bleaching events in 2016 and 2017 and last year have affected different parts of the reef, and overall coral numbers had fallen by more than half in just 20 years.

The coral reefs provide important habitats for other marine life, and when they die it impacts the wider marine biodiversity of the area.

Source: Read Full Article