Infant sharks that live in the familiar mermaids purses found on most beaches in the UK and throughout the world are more vulnerable to predation because of ocean warming, new research suggests.

According to Daniel Ripley from The University of Manchester, higher temperatures reduce freeze response times which the animals employ to avoid being eaten by predators.

The study by the ecophysiologist is funded by the Biotechnology and Biological Sciences Research Council and The University of Manchesters Knowledge and Innovation hub for Environmental stability

It is published in the Journal of Conservation Physiology today (17 June).

If an embryo employs a freeze response, it stops moving so that predators - including large fish and other sharks - wont detect them.

That explains why being able to elicit a freeze response is key to surviving predation during embryonic development and the longer an embryo can freeze, the better chance it has of not being detected by predators.

In the lab Ripley compared the freeze response time of small spotted catshark embryos - which are 7 to 8cm long - at a water temperature of 15C and a water temperature of 20C.

The 5C temperature rise resulted in a 7-fold decrease in the time the animals froze following a predator simuli, mimicked by gently flicking the egg case

And that could have major consequences for embryonic sharks in a warming world. Being able to freeze is key to avoiding predators and if warming means infant sharks will not be able to freeze as long, it could reduce the number of sharks surviving to adulthood.

Around 45% of shark and ray species lay eggs which grow inside a mermaids purse, which can last for around a year before they hatch

The purses come in various colours, shapes and textures, depending on the species of shark.

Beachcombers often spot the empty shell cases on the beach, though the live egg cases often lie tangled up with sea weed in shallow waters and rockpools.

Continued here:
Ocean warming could hit shark survival - The University of Manchester