Why Thresher Sharks Are Washing Up on UK Beaches
Thresher sharks have been washing up in the UK. Learn why, what it reveals about their plight, and fascinating facts about this vulnerable species.
This year has started on a somber note for thresher shark enthusiasts and conservationists. On New Year’s Day, a thresher shark washed up on Par Sands Beach in Cornwall, causing quite a stir among locals. The cause of death is thought to be sport fishing. This wasn’t an isolated incident—just a few months earlier, another thresher shark had been discovered lifeless on a Devon beach. These rare visitors to UK waters usually stay further out at sea, so seeing them stranded is both unusual and alarming.
Thresher sharks, with their unmistakable whip-like tails, are listed as ‘Vulnerable’ by the International Union for Conservation of Nature (IUCN). While their impressive tails are key to their unique hunting style—used to stun and corral fish—these same tails make them a target for fisheries. Add in slow reproduction rates and habitat loss, and you’ve got a species facing serious challenges.
What Makes Thresher Sharks Special?
Thresher sharks aren’t your typical marine predators. Their long tails, sometimes as long as their bodies, aren’t just for show. They use these tails like whips to stun schools of fish, a strategy that’s as fascinating to scientists as it is effective in the wild. While they’re found in oceans around the world, they’re rarely seen in shallow coastal waters like those in the UK.
Unfortunately, their unique features also put them at risk. Thresher sharks are sought after for their fins, meat, and liver oil. Bycatch—being accidentally caught in nets meant for other species—is another significant threat. Their low reproductive rate doesn’t help; female threshers give birth to just a few pups after a long gestation period, making it hard for populations to bounce back after heavy losses.
Why Thresher Sharks Matter
Sharks play a crucial role in keeping ocean ecosystems healthy, and threshers are no exception. By preying on weaker or overpopulated fish, they help maintain balance in marine food webs. Losing them doesn’t just mean fewer sharks; it could upset entire ecosystems, affecting everything from coral reefs to commercial fisheries.
What Can Be Done?
Conservationists are pushing for better protection for thresher sharks. International agreements like CITES offer some safeguards, but enforcement is tricky, especially in international waters. Stricter fishing regulations and more marine protected areas (MPAs) could help, as could raising awareness about the importance of these sharks.
The deaths of two thresher sharks in UK waters have sparked fresh calls to action. The Cornwall Wildlife Trust has called on commercial and recreational fishers to follow proper guidelines to ensure marine animals accidentally caught are handled and released safely.
They also encourage the public to report any dead animals found on Cornwall’s beaches by contacting the trust’s marine strandings hotline at 0345 201 2626.
In November 2024, a 4-meter (13.1 feet) female common thresher shark was discovered entangled in abandoned fishing gear, often referred to as a “ghost net,” at Clovelly Harbour in Devon. This incident underlines the ongoing dangers of marine debris and highlights the urgent need for more robust conservation measures.
FAQs About Thresher Sharks
Yes, but it’s rare. They’re usually found in deeper, warmer waters but sometimes venture closer to the UK coastline during the summer months.
Not much! Thresher sharks don’t have many natural predators. Occasionally, larger sharks or orcas might go after them, but humans pose the biggest threat through fishing and bycatch.
Your best bet is heading to tropical and subtropical regions. They’re often spotted in places like Malapascua Island in the Philippines or around Indonesia. Seeing them in the UK is very unusual, so if you’re keen on a sighting, tropical waters are the way to go.
Yes, they’re distant cousins! Both are part of the Lamniformes order, which includes mackerel sharks. While they share some traits, their behaviors and ecological roles are quite different.
Totally! Thresher sharks are shy and prefer to keep their distance from humans. They’re not a threat to divers or swimmers and use their tails to hunt fish, not defend themselves.
Facts About Thresher Sharks
Here’s a curated list of intriguing facts about them:
1. Species Variations
There are three recognized species of thresher sharks:
- Common Thresher (Alopias vulpinus): The largest, reaching up to 20 feet (6 meters) in length.
Animalia - Bigeye Thresher (Alopias superciliosus): Notable for its large eyes adapted for low-light hunting.
- Pelagic Thresher (Alopias pelagicus): The smallest, typically around 10 feet (3 meters) long.
2. Hunting Technique
Their hunting strategy involves circling and herding prey into tight groups before striking with their tails to stun them, making capture easier.
3. Breaching Behavior
Thresher sharks are known to leap out of the water, a behavior known as breaching. The reasons for this behavior are not fully understood but may be related to hunting or communication.
4. Reproduction
They are ovoviviparous, meaning eggs develop and hatch inside the mother’s body, and she gives birth to live young. Typically, they have small litters, often of two to four pups.
5. Conservation Status
All three species are listed as vulnerable due to threats like overfishing and bycatch. Their slow reproductive rates make population recovery challenging.
6. Endothermic Ability
Unlike most fish, thresher sharks can maintain a body temperature higher than the surrounding water, aiding in hunting efficiency in varying temperatures.
7. Sensory Adaptations
Bigeye threshers have large eyes adapted for hunting in low-light conditions, allowing them to detect prey in deeper, darker waters.
8. Human Interaction
Thresher sharks are generally not a threat to humans due to their shy nature. However, they are valued in sport fishing for their size and strength.
Most popular destinations for diving with thresher
Malapascua Island, Philippines
- Famous for its reliable sightings of pelagic thresher sharks (Alopias pelagicus).
- Divers often visit Monad Shoal, a cleaning station where thresher sharks are regularly seen at dawn.
- This is the only place in the world where divers are almost guaranteed encounters with thresher sharks.
Indonesia
- Locations like Alor and Komodo occasionally offer sightings of thresher sharks, particularly the pelagic and bigeye species.
- While less predictable than in the Philippines, Indonesia’s biodiversity makes these encounters special.
Azores, Portugal
- The Azores in the Atlantic Ocean is another hotspot for thresher shark sightings, particularly during the warmer months.
- Common threshers (Alopias vulpinus) are more likely to be encountered here.
Baja California, Mexico
- Thresher sharks can sometimes be seen in the deeper waters around Baja.
- Although not as famous as other locations, the region’s pelagic zones offer potential for encounters.
Eastern Pacific (Costa Rica and Galápagos Islands)
- In places like Cocos Island (Costa Rica) and Darwin Island (Galápagos), divers occasionally spot thresher sharks, though sightings are less predictable.
Sri Lanka
- Known for sightings of bigeye thresher sharks (Alopias superciliosus), often seen during pelagic diving expeditions.
These destinations are favored for their biodiversity and the unique opportunity to observe thresher sharks in their natural habitats, often around cleaning stations or during their early morning hunting activities.