Angling best practices are essential to promote shark survival
University of Exeter
image:
A male porbeagle shark caught off the coast of Scotland
view moreCredit: James Thorburn
Most sharks in UK waters survive catch-and-release fishing when angling best practices are followed, according to a new study.
University of Exeter researchers, working with partners, tagged almost 70 blue, porbeagle and tope sharks caught in recreational fishing in the British Isles, to track their behaviour and survival afterwards.
Fewer than 5% – three sharks, one from each species – died.
“Our results suggest survival rates are high when sharks are caught and released within current best-practice guidelines,” said Francesco Garzon, from the University of Exeter.
Commenting on the sharks that died, Garzon added: “These deaths can’t be definitively attributed to any one aspect of being caught, as the sharks had no external wounds and were energetic when released.
“However, two of them – a porbeagle and a tope shark – were deep hooked and released with hooks in place, to avoid any further injury.”
The data-gathering tags attached to sharks stayed in place for up to 45 days before detaching and transmitting a location, confirming that the shark was alive.
Sixteen of these tags were recovered, allowing much more detailed investigations into the depth and movement of the sharks after they were released.
“Right after release, all three species swam quickly down to deep water – probably to escape and to re-oxygenate their gills,” Garzon said.
“Behaviour after that varied between the different species, but they tended to stay deeper than usual.
“Most individuals appeared to have recovered by 24 hours, although some sharks – especially porbeagles – sometimes took longer.”
Modern shark fishing in the British Isles, as in most of Europe, is almost exclusively a catch-and-release activity, but practices vary. This study provides further evidence of the importance of following best practice handling guidelines when angling.
Despite the popularity of catch-and-release, post-release survival has not been assessed in this way before in European waters and our previous research shows that survival rates are dependent on species and geography.
In Europe, porbeagle sharks are considered “critically endangered” by the IUCN, tope sharks are “vulnerable”, and blue sharks were most recently assessed as “near threatened”.
The sharks in the study were caught during fishing trips from ports in England, Scotland, and the Channel Islands.
The research team included Edinburgh Napier University and the Government of Jersey, with assistance from fishers and skippers, Shark Hub UK, and Centre for Environment, Fisheries and Aquaculture Science, with guidance from the Shark Trust.
Funding came from the European Maritime and Fisheries Fund, Marine Fund Scotland, and Francesco Garzon’s PhD is funded by the NERC GW4+ DTP scheme.
The paper, published in the ICES Journal of Marine Science, is entitled: “Survival and recovery of three shark species in North-East Atlantic recreational fisheries.”
Find out current handling best practice guidelines at:
https://www.sharktrust.org/pages/faqs/category/angling-project
http://www.sharkanglingclubofgreatbritain.org.uk/best-practise
Journal
ICES Journal of Marine Science
Article Title
Survival and recovery of three shark species in North-East Atlantic recreational fisheries
Article Publication Date
3-Nov-2025
Large brains require warm bodies and big
offspring
Body temperature and offspring size influence brain size in all vertebrate groups
Max Planck Institute of Animal Behavior
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Unlike other fishes, many sharks, like this blacktip reef shark, have both large young and live in warm waters. This explains why sharks have brains that overlap in size with those of the warm-blooded vertebrates – birds and mammals.
view moreCredit: Angela Albi
Vertebrates have extremely different brain sizes: even with the same body size, brain size can vary a hundredfold. As a rule, mammals and birds have the largest brains in relation to their body size, followed by sharks and reptiles. Amphibians and most fish, on the other hand, have the smallest brains of all vertebrates.
Why is this the case? In some animal groups, species that live in groups have larger brains than solitary species. They have to cope with rapidly changing social situations and therefore need a more powerful brain. In addition, mammals and birds, which generate their own body heat and therefore have a higher and more stable body temperature, have larger brains than most other vertebrates, whose body temperature is determined by the ambient temperature. But so far we do not have a solid explanation for this difference. Moreover, even within these groups, there are still major differences.
Brain tissue requires a constant amount of energy. Unlike other organs, the brain cannot simply shut down during sleep or periods of hunger. So when the brain grows larger, the organism must find the energy to supply it. According to the “Expensive Brain Hypothesis,” the brain can only grow if it produces the additional energy itself or if it improves the organism's chances of survival so much that it can afford to grow and reproduce more slowly. This explains, for example, why monkey species that do not have to endure periods of hunger and thus energy loss throughout the year have larger brains, and why the brains of sedentary birds are larger than those of migratory birds.
Researchers at the Max Planck Institute for Animal Behavior in Konstanz have investigated whether these correlations apply to all vertebrates. They found that in all vertebrate groups, body temperature has a significant influence on brain size. Species that can keep their bodies constantly warm can usually afford larger brains, as these are more efficient in warm environments. This also holds for so-called cold-blooded species that live in warm waters or specifically select such places. In addition, according to the researchers, the size of the offspring also limits brain size in adulthood. Since the costs of a large brain in relation to weight are particularly high for young animals, it pays to keep the value low at first. Those lineages that manage to both keep their bodies warm and produce large young have the biggest brains for a given body size.
“We humans were lucky to be warm-blooded. In addition, our babies are large and fed for years. This allowed the evolution of largest brain of all vertebrates in relation to weight,” says Professor Carel von Schaik, head of a fellow group at the Max Planck Institute of Animal Behavior.
A constantly high body temperature was therefore a prerequisite for evolution to produce larger brains. However, this ability originally developed for other reasons—presumably, so that mammals could remain active at night and birds could fly longer distances. Only then was the door open for brain growth. In evolution, innovations can therefore have unexpected consequences and open up completely new possibilities.
Unlike other fishes, many sharks, like this blacktip reef shark, have both large young and live in warm waters. This explains why sharks have brains that overlap in size with those of the warm-blooded vertebrates – birds and mammals.
Credit
Imran Razik
Journal
Proceedings of the National Academy of Sciences
Method of Research
Data/statistical analysis
Subject of Research
Animals
Article Title
Parental investment and body temperature explain encephalization in vertebrates
Article Publication Date
3-Nov-2025
