Ocean Column: What Cetacean Strandings Reveal About Our Seas

Along the UK’s coastlines, rising numbers of washed up whales, dolphins and porpoises are sending a stark message about the health of our oceans. What do these strandings mean, and how can we help?

A mother and baby sperm whale. Credit: Gabriel Barathieu/wikimedia

A new study analysing three decades of data from the Scottish Marine Animal Stranding Scheme (SMASS) has revealed a steady rise in cetacean strandings since the early 1900’s. Strandings of baleen whales and common dolphins had soared, while deep-diving and pelagic species are so increasing. The number of young animals washing ashore is also rising, a sign of the growing environmental pressure on Scottish marine life.

This trend is not confined to the UK. Across the world, researchers are reporting similar increases in strandings, from North America to Oceania. Studies link these events to climate-driven changes in ocean currents, prey distribution, and human disturbance. In many regions, strandings are becoming important early warnings systems for ocean health crises.

Cetaceans

Cetaceans are the group of marine mammals that include whales, dolphins, and porpoises. Although they live entirely in the ocean, they breathe air, give birth to live young and feed their calves with milk – just like land mammals.

There are two main types of cetacean: baleen whales, such as humpbacks and minkes, which filter tiny creatures like krill from the water, and toothed whales, which include dolphins and porpoises that hunt fish and squid using sound to find their prey. Because they live for many years and feed high up the food chain, changes in their health and numbers often reflect what is happening in the wider ocean.

What is a stranding?

A stranding happens when one or more of these animals becomes trapped in shallow water or wash up on shore, either alive or dead. This can occur for many reasons: storms, illness, disorientation, or loud underwater noises that interfere with navigation. Sometimes a single animal strands, while other times whole pods come ashore together.

Cetacean strandings provide a vital scientific record of ocean change. As apex predators and long-lived mammals, they accumulate the effects of pollution, prey shifts, and human disturbance. Each beached animal reveals patterns in population health, mortality, and ecosystem stress – signals that might otherwise remain invisible beneath the waves.

A stranded humpback whale. Credit: Salko de Wolf/wikimedia

What's driving this trend?

Several factors contribute to the rise in cetacean strandings, some natural causes such as disease outbreaks, storm events, or navigational errors. But many pressures are deeply tied to human activity.

One of the most significant pressures is bycatch: the accidental entanglement of sealife in fishing gear. A recent study monitoring nearly 20,000 static net hauls in UK waters found clear patterns in when and where bycatch occurs, highlighting that harbour porpoises and common dolphins remain at high risk.

Another invisible threat is noise pollution. Naval sonar, seismic surveys, and dense shipping traffic create an underwater wall of sound that can confuse or even disorient whales, disrupting navigation or communication. For deep-diving species like beaked whales, who are already sensitive to sound, these disturbances can be fatal.

Chemical pollution adds another layer of stress. Despite bans on many persistent organic pollutants, UK cetaceans still carry levels that exceed safe limits, affecting their immune and reproductive health. As climate change drives heavier rainfall and coastal erosion, legacy pollutants (hazardous substances that remain in the environment long after their production or release) may be re-released into the sea, compounding the risks.

 

Then comes the broader reshaping of our seas, ultimately driven by climate change. As waters warm, prey species are shifting northward to cooler seas, leaving young dolphins and porpoises in Southern nurseries without enough food.

Beyond these drivers, ship strikes, marine debris ingestion, and plastic entanglement continue to take a toll. These pressures do not act in isolation, they build upon each other, making survival even more difficult. Each stranded calf on the sand is more than an isolated loss; it is a warning that the ocean is in distress far beyond where it lies.

Why do cetaceans matter?

Cetaceans are vital engineers of the marine ecosystem. Whales help circulate nutrients, fertilise plankton (the foundation of marine food webs) and even influence carbon storage in the ocean helping to regulate the local climate. Their health is closely linked to the health of the planet itself.

 

Dolphins and porpoises regulate prey populations and support ecological balance across coastal and open-sea habitats. Strandings represent not only the loss of individuals, but a disruption to ecosystem processes that keep our oceans healthy.

A pod of dolphins. Credit: Shaain Ibrahim on Unsplash

The role of public reporting 

Yet, there is hope. The SMASS dataset itself exists thanks to decades of public vigilance. Strandings in the UK are largely reported by people like you and me — walkers, fishers, surfers, birdwatchers. Each phone call or online record feeds into a growing knowledge base that helps scientists identify patterns, guide conservation priorities, and lobby for stronger protections. Citizen science, in this way, becomes an act of guardianship.

If you ever come across a stranded whale, dolphin or porpoise, the most crucial step is to report it. In Scotland, contact the SMASS hotline; elsewhere in the UK, networks such as the Cetacean Strandings Investigation Programme (CSIP) coordinate responses. Never approach or touch the animal, but do take photos, note the location, and pass details on. It may feel small, but your report could add to a dataset that shapes the future of conservation.

A signal we cannot ignore

Rising strandings across the globe reflect more than chance events; they are indicators of cumulative human pressures and ecological instability. Addressing them requires coordinated action: reducing bycatch through modified fishing practices, regulating underwater noise, controlling pollutants, and tackling the impacts of climate change on marine ecosystems.

 

Cetaceans are not only wonderful species but also vital components of ocean. Their strandings serve as a visible warning of the challenges facing our seas — and a call to act on behalf of the ecosystems on which both they, and we, depend on.

About the Author:

Katie-Mae White is a biology student with research interests in animal behaviour, climate science, and marine ecosystems. When not studying, they can often be found travelling the UK coastline with their family, watching for seabirds and cetaceans alike. LinkedIn.