Stranded Sharks | Cetacean Strandings Investigation Programme

Across the UK, many different creatures wash up on our shores. The Cetacean Strandings Investigation Programme (CSIP) is responsible for documenting stranded animals in the UK and retrieves a portion of those that strand for post-mortem examination every year. The main bulk of the project is made up of cetaceans – a group of marine mammals comprised of whales, dolphins and porpoises.

However, many people don’t realise the project also responds to strandings of sharks. Since 2007, the CSIP has recorded the stranding of basking sharks (Cetorhinus maximus) across the UK and more recently secured funding  to expand the research to other large-bodied sharks such as porbeagles (Lamna nasus), angel sharks (Squatina squatina) and blue sharks (Prionace glauca).

WARNING: This blog contains photographs of dead stranded sharks which you may find upsetting

Stranded basking shark in South Uist, Scotland in 2015 (Credit: CSIP-SMASS).

Basking sharks

The basking shark is the largest shark in UK waters and second largest fish in the world, with most adults measuring over 9.5m. Despite the enormity of this species, there is still a lot to learn about their biology and behaviour. Basking sharks are known to aggregate in huge schools, and despite being so big, can breach clear out of the water.

Why these sharks exhibit such behaviours is still not understood, though it has been speculated it may be for mating or feeding purposes. Current research being done by the Scottish Natural Heritage and the University of Exeter is using camera tags to gain a shark’s eye view of such behaviours and may help to understand why and what basking sharks are doing in UK waters.

Basking shark feeding at the surface
Basking sharks get their name from the time they spend feeding and swimming at the top of the water column, seemingly ‘basking’ in the sun and warmer surface waters (© Jidan Chaomian/Flickr CC BY-SA 2.0).

The role of the CSIP is to monitor the location of shark strandings across the UK and use post-mortem analysis to understand the threats which can ultimately lead to their death. In 2009, the Cornish Wildlife Trust Marine Strandings Network (a partner organisation of the CSIP), carried out the first necropsy of a basking shark in England. The shark was a 4.2m male and found to have died from a bacterial infection.

Stranded basking shark in Cornwall in 2009. This animal was found to have died due to a bacterial infection (Credit: Rory Goodall, CWT Marine Strandings Network).

More recently, the team at CSIP were called out to the stranding of a 2.5m juvenile basking shark in Kent. This location was unusual for basking sharks, representing the first documentation of this species stranding in the southern North Sea. Therefore, the team were very keen to retrieve it for post mortem. Updates on the outcome of this stranding will be posted to the CSIP Facebook page if appropriate.

basking 8
Juvenile basking shark washed up in Kent in November 2018. The animal was retrieved by a team from CSIP for post-mortem (Credit: Brian Rumblelow, Dover District Council).

Other sharks of interest

The CSIP team has also had several other large-bodied sharks wash up around the UK this year. In August, a blue shark washed up in north Wales, along with a female angel shark in southwest Wales. Both animals were retrieved for post-mortem examination as part of the newly secured funding.

Angel shark (Squatina squatina)
Stranded angel shark in August 2018 (Credit: Lin Gander and Steve Hart).

Angel sharks have been listed as Critically Endangered on the IUCN Red List since 2006 and it is critical we gain information about the ecology of this species and the threats they face. This makes stranded angel sharks highly valuable for scientists and provides an opportunity to expand our knowledge on the genetics, distribution, population structure and conservation threats of this species.

Blue sharks are one of the most heavily fished sharks on the planet, and as a result are listed as Near Threatened on the IUCN Red List. Blue sharks are often bycatch in long-line fisheries, though as the meat is not sought after, fins are usually taken and the rest of the body discarded back to sea. As top predators, stranded blue sharks are critical for scientists to examine as they are an indicator of the general health of the marine environment. Post-mortems allow the CSIP to monitor cause of death from both human-induced and natural threats to this species.

Blue Shark (Prionace glauca)
Stranded blue shark in August 2018 (Credit: Ben Wray/NRW ).

Get involved in citizen science

If you come across a stranded large-bodied shark then we’d love to hear from you. This project is impossible without help from the public so please call the CSIP hotline on 0800 6520 333 or email and provide us with the following details:

  • Your name and contact number/email
  • Species (if known)
  • Approximate length of the animal
  • Location of the animal (grid reference or longitude/latitude)
  • State of decomposition
  • Degree of accessibility if the animal were to be picked up for post mortem

Photographs are extremely valuable in allowing us to identify the animal correctly so please take pictures from different angles and attach to your email!

You can find out more about the Museum’s role in the Strandings Programme here.

Kate Swindells is a research assistant at NHM, a partner organisation of CSIP. She completed her Masters degree in Wildlife Health & Conservation at the University of Bristol and also has an undergraduate degree in Marine Biology. She joined the museum in January 2018.