Investigating the mystery of strandings

Rob Deaville

Every year around 600 cetaceans (whales, dolphins, porpoises) are found stranded around the UK coastline. Our strandings expert Rob Deaville has been helping to investigate these events for the last 18 years.

Sperm whale stranded in Pegwell Bay
Sperm whale stranded in Pegwell Bay, Kent

ZSL is the lead partner in the Defra funded UK Cetacean Strandings Investigation Programme (CSIP), which has been tasked with the investigation of these stranding events around the UK coast since 1990. 

Tonight we’re inviting the public to go behind the scenes at ZSL to witness the primary element of the work of the CSIP. My CSIP colleague Matt Perkins and I will be conducting, in real time, an examination of a harbour porpoise that died shortly after live stranding at Caernarfon in Gwynedd, Wales last August. The lead CSIP scientist, Dr. Paul Jepson, will also be on hand in the ZSL auditorium to provide expert commentary and explanation and we will all take questions on the night from the audience.

Harbour porpoises, like the one we will examine at the CSI of the Sea event tonight, are the most common cetacean species found stranded around the UK coast, reflecting their coastal distribution. But we also find other species, ranging from bottlenose dolphins and killer whales to deep diving species like beaked and sperm whales. In fact, over the last 26 years we’ve recorded strandings of at least 22 individual cetacean species around the UK coast. This is over a quarter of the worlds known species, reflecting the range of marine habitats we have in UK waters. 

Since the projects inception, we’ve collected data on over 13,000 individual cetacean strandings and conducted over 3,600 post-mortem examinations. Whilst it’s always a sad event to see a dead cetacean, by carrying out post-mortem examinations, we hope to be able to determine how the animal died and thus, learn more about the threats these species face in UK waters and specifically, those that may be due to our activities.

We can also gain a great deal of additional information through the course of such research. For example, we can estimate the age of cetaceans by counting the annular growth rings in their teeth, learn what they have been feeding on through examination of their stomach contents and gain a better understanding of their life histories through study of their reproductive organs. So as well as learning more about how they may have died, strandings investigation can reveal a huge amount of detail about how they have lived as well. 

The CSIP team performing a necropsy on a porpoise
The CSIP team performing a necropsy on a porpoise

We’ve also carried out research on a wide range of marine contaminants and their potential impacts, through our collaboration with the Centre for Environment, Fisheries and Aquaculture Science (CEFAS). A paper that we published last year demonstrated that one of the most persistent organic pollutants called polychlorinated biphenyls (PCBs), which have been banned in the EU since the 1980s, are still found at globally significant levels in the blubber of a range of European dolphins and may be responsible for the eventual localized extinction of some populations of killer whales in Europe.

Tonight’s event will use the examination of the harbor porpoise to focus in on the issue of marine pollutants and what we have learnt about this and other anthropogenic threats to cetaceans. 

Although post-mortem examinations can be graphic, we hope the audience in the room and watching online will be able to learn more about the potential drivers of cetacean strandings. Tonight’s event promises to be a unique opportunity to increase public understanding of conservation science and in particular how strandings research can help shine a light on the threats that cetaceans face and inform efforts to improve their long term conservation status.

Although tickets to the CSI of the Sea event have sold out, you can still join us by watching a live stream from 6.30pm.
Find out more about the work of CSIP

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