Baby Sharks Enfeebled by Warming Ocean Waters

Image: Wikimedia Commons

by Natasha Lasky, ODP Staff Writer

A new study suggests that baby sharks are being born tiny, tired, and malnourished as a result of rising temperatures in the ocean. Scientists analyzed the effects of warming waters on young epaulette sharks — a small, egg-laying species that lives in the Great Barrier Reef. These researchers examined epaulette shark egg sacs in a lab at the New England Aquarium in Boston, and found that warmer water led to baby sharks being born prematurely and at a developmental disadvantage.

The Experiment: The researchers tested the effects of warming ocean waters on epaulette shark eggs by putting them in water up to 88 degrees Fahrenheit — the predicted summer water temperature for the Great Barrier Reef by the end of the century.

They found that the hotter the conditions, the faster the eggs developed. The study’s lead author, Carolyn Wheeler, a doctoral candidate at the University of Massachusetts and the ARC Center of Excellence for Coral Reef Studies at James Cook University in Australia, said in a statement: “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.”

This meant that hatchlings were smaller and needed to feed almost right after hatching, at the same time that they incurred immense fatigue.

Why This Matters: Smaller sharks tend to lay egg sacs, which are left to hatch and develop without their parents’ involvement. Because of this, egg-laying sharks like epaulette sharks are particularly damaged by the effects of climate change, because their small and malnourished offspring have to fend for themselves in an environment that is too warm for them to thrive.

Moreover, sharks, rays, and skates, grow slowly and reproduce less often than other fishes, leaving their populations already under threat. The epaulette shark is a resilient species — it has adapted to ocean change and acidification. “If this species can’t cope with warming waters then how will other, less tolerant species fare?” Said Co-author Associate Professor Jodie Rummer, also from Coral CoE at JCU.

Sharks are important predators that sustain ocean ecosystems. Without predators, the Great Barrier ecosystem is further jeopardized. What’s more is numerous shark species are closer to extinction than previously thought due to human activity such as shark finning, fishing, pollution. Climate change is affecting mothering of non-egg laying sharks and affecting these keystone species in ways that we still don’t fully understand.

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