They grow to over a meter in length, can weigh up to twelve kilos and each summer they swarm into the shallow waters of the Irish east coast. Despite this, the starry smooth-hound has remained Ireland's least well known shark species. However, thanks to researchers at University College Dublin, whose work is now published in the Journal of Fish Biology, this may be about to change.
These are starry smooth-hounds.
Credit: Credit to Edward Farrell
Dr. Edward Farrell, who recently graduated from UCD School of Biology & Environmental Science, spent the last four years studying these unusual sharks. Under the supervision of Dr. Stefano Mariani of the SBES and Dr. Maurice Clarke of the Marine Institute, the PhD project successfully investigated the age, growth, reproduction and identification of the species in the Northeast Atlantic.
"It's amazing how little was known about this species considering their size and abundance on the east coast," said Farrell. "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."
Starry smooth-hounds were previously considered to be a fast growing and early maturing species, meaning they were not a conservation concern. However the results of the four year project have revealed that starry smooth-hounds in Irish waters actually grow twice as slowly as previously estimated and only reproduce every two years rather than annually as is the case in the Mediterranean.
"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."
With such a slow reproductive rate, unregulated commercial fishing could have a serious impact on the species in a short time, as was seen with the spurdog fisheries in the 1980s. Spurdogs were once the most abundant shark species in the Northeast Atlantic however they have been all but wiped out by commercial fisheries and are now listed as critically endangered on the IUCN Redlist.
Starry smooth-hounds are not a valuable commercial species in Ireland but on the continent they are highly sought after and the landings from French boats, currently about 2640 tonnes annually, are increasing. The previous lack of knowledge of their basic life history in the Northeast Atlantic has prevented the development of management and conservation strategies.
Once abundant in the Mediterranean Sea and Southern European waters, years of over fishing have caused their disappearance from much of their former range. In Irish waters though, starry smooth-hounds seem to be increasing in abundance. The reasons for this are unclear but it does offer the unique opportunity to help conserve this enigmatic species.
These findings of the project indicate that starry smooth-hounds are more susceptible to exploitation than previously thought and management measures are needed now to ensure their conservation.
"There are currently no management measures for this species in European waters mainly due to the lack of biological information," says Farrell. "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."
Stefano Mariani believes that it is paramount to protect these sharks in Irish waters. "Smooth-hounds have a very specialized diet: they don't eat fish, they feed on bottom-dwelling shellfish, crunching crabs with their very peculiar molariform teeth. These animals are likely to have a very important role in the trophic web".
Starry smooth-hound sharks are also highly sought-after and respected by anglers, and they certainly provide an additional excitement to our coasts.
"Dublin Bay offers tourists the opportunity to easily observe two species of seals," concluded Mariani. "We should be proud that our coasts also provide beach-goers with a chance of swimming alongside beautiful and harmless sharks. There are not many other places like this in Europe."
For more information and news on the sharks, skates and rays in Irish waters check out the new Irish Elasmobranch Group website: http://www.irishelasmobranchgroup.org
Enduring cold temperatures alters fat cell epigenetics
19.04.2018 | University of Tokyo
Full of hot air and proud of it
18.04.2018 | University of Pittsburgh
Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.
Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...
Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.
The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...
Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.
Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...
In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...
In an article that appears in the journal “Review of Modern Physics”, researchers at the Laboratory for Attosecond Physics (LAP) assess the current state of the field of ultrafast physics and consider its implications for future technologies.
Physicists can now control light in both time and space with hitherto unimagined precision. This is particularly true for the ability to generate ultrashort...
13.04.2018 | Event News
12.04.2018 | Event News
09.04.2018 | Event News
19.04.2018 | Materials Sciences
19.04.2018 | Physics and Astronomy
19.04.2018 | Physics and Astronomy