The Mystery of the Irish Smooth-Hound Sharks

This almost unknown species of smooth-hound shark has been the object of a deep research carried out by scientists at University College Dublin, and might just take its rightful place as an endangered and in-need-of-protection species.

These sharks grow over a meter in length, can reach 12 kg in weight and swim every summer in the shallow waters of the east Irish coast, but not much was known about them until recently.

All this changed thanks to Dr. Edward Farrell, who recently graduated from UCD School of Biology & Environmental Science, and spent the last four years studying these animals.

He gathered many information, like age, growth, reproduction and identification of the species in the Northeast Atlantic, under the guidance of Dr. Stefano Mariani of the SBES and Dr. Maurice Clarke of the Marine Institute.

“It’s amazing how little was known about this species considering their size and abundance on the east coast,” Farrell said.

“Until recently we weren’t even sure what species we were dealing with but we developed a genetic method which allowed us to confirm that it is the starry smooth-hound which occurs in Irish waters and not the related common smooth-hound.

Once this was established we were able to investigate their life-history.”

The study of this species is also more important as starry smooth-hounds were previously considered to be a very fast growing and early maturing species, so they were not a conservation concern.

After the researchers got to know these sharks a little better, they realized that there was a conservation concern and that these fish needed to be protected or risked becoming extinct.

And the reasons are quite simple: the Irish smooth-hounds grow twice as slowly as it was previously thought, they reproduce only every two years and they mature very late.

“Some of the findings are quite worrying for the species as males don’t mature until they are 4-5 years old and females until they are 6 years old,” said Farrell.

“Females also appear to take two years to complete the reproductive cycle.

“The pups develop inside the female for approximately 12 months before being born after which the female has a resting period of about another year before she is capable of becoming pregnant again.”

This shark species is not valuable in Ireland but on the continent it is, and the landings from French boats are increasing.

They were once numerous in the Mediterranean Sea and Southern European waters, but because of intense fishing over the years, they have become very rare.

In the Irish waters however, they thrive and even if the reasons for this happening are not known, this new research offers the possibility of better conserving this species.

“There are currently no management measures for this species in European waters mainly due to the lack of biological information,” Farrell reminded.

“So our main aim was to gather the necessary data; hopefully this can be used now to ensure their sustainability and prevent a repeat of the overexploitation seen in Mediterranean waters.”

This work is published in the Journal of Fish Biology, AplhaGalileo reports.