Standing on the shores of Mounts Bay on a clear, calm day, it might be hard to imagine just how much vibrant marine wildlife is darting around below the surface of the sea.
But did you know Mounts Bay is a biodiversity hotspot? The bay plays host to some of the UK’s most remarkable marine wildlife – from porpoises, dolphins and seals to a variety of seabirds that regularly traverse the ocean through the different seasons. And it’s all right on our doorstep.
The good news is that, if you’re patient, you might just catch sight of a dolphin’s fin, or spot a grey seal lounging on the rocks. So, to help you understand what you’re looking for, we caught up with Hannah from Marine Discovery, an ethical wildlife watching business based in Penzance.
Whether you’re a seasoned wildlife watcher or simply enjoying a stroll along the prom, here are six of the marine stars you might spot in our waters.
Harbour Porpoise
Sighted most commonly through late summer and early autumn, the harbour porpoise is the UK’s smallest cetacean (measuring around 1.5m), and is often mistaken for a dolphin.
The key difference is that the harbour porpoise is an all-purpose predator, with specially-adapted teeth, which means they can hunt on a variety of fish – including larger species in relation to their own size. Earlier in the season, they might feed deep down on bottom-dwelling fish, while, in the summer, they take on dolphin-like behaviour by group herding fish into bait balls.
As an apex predator that relies on an abundance of fish stock and clean waters, their presence is a key indicator of a healthy marine ecosystem. However, while the porpoise is still the most commonly-cited cetacean nationwide, pollution and coastal development, as well as bycatch via commercial netting, have really affected numbers.
Grey Seals
Grey seals are one of the rarest seal species, and around 40% of the world’s population is based right here in the UK and Ireland. If you haven’t spotted them already, these pinnipeds are mostly grey in colour, with females generally sporting some darker markings.
Cornwall is as far south as they breed, and there are a number of haul-out spots across the Cornish coast where they can be spotted – particularly during more temperamental weather. Through the breeding season, which can start as early as August, you might see them with fluffy white pups, which will generally stay with them for around three weeks before heading off on their own adventures.
With climate change and a more unstable climate, coastal erosion can have a massive impact on the safety of seals (especially when hauled out under cliffs). The breeding season also seems to be starting earlier – having previously started in autumn – making them more vulnerable to harassment and disturbance from a higher volume of beach visitors in the summer months.
Risso’s Dolphins
With their striking pale scars and bulbous heads, Risso’s dolphins are one of the more unusual residents of Mounts Bay – but numbers do seem to be increasing, and it’s no longer rare to see them in the summer months. These large dolphins, reaching up to four metres in length, are sometimes mistaken for orcas (but aren’t as big) thanks to their tall fins.
While a mysterious species, the team at Marine Discovery have been doing lots of work on individual IDs, seeing which dolphins return to Mounts Bay each year. Their continued presence could be down to a healthy area of seagrass outside Newlyn, where the species can feast on cuttlefish that breed there.
Unlike other dolphins, Risso’s dolphins are far more vulnerable to disturbance. As a deep-diving species, they’re incredibly sensitive to sound, and struggle with engine sounds in the water. Often resting just under the surface, they can also be easy victims of collisions, meaning they need plenty of space.
Common Dolphins
Unlike the more reserved porpoises, common dolphins could be considered the life of the party – often, the species you see bow-riding alongside boats. Their vibrant markings with creamy patterns along their sides make them easy to identify, even from a distance, and they can grow to around 2.5m.
Highly sociable and energetic, they usually travel in tight-knit pods, using one another to hunt by rounding up fish (like mackerel or even anchovies) into bait balls. Mounts Bay is an ideal place to see them, particularly in late summer and early autumn when fish shoals attract them closer to shore.
Like Risso’s dolphins, common dolphins can also be vulnerable to collision and disturbance, particularly when feeding, instead of engaging with the boats around them.
Manx Shearwater
Not all of Mounts Bay’s marine wildlife is underwater, and we’re lucky to have some incredible bird species – including The Manx shearwater.
This species (whose scientific name is Puffinus Puffinus!) can be seen nesting on islands around the UK, including on the Isles of Scilly, which means it’s not unusual to spot them in Mounts Bay through the summer months. They can be identified by their straight, slim wings, which are black above and white underneath.
These birds will nest underground, often sharing sites with puffins, and will migrate as far as South America during the winter, following the trade winds. While particularly vulnerable to rats, elimination efforts mean we’re now seeing a good breeding success, improving the numbers seen around the UK coast.
Bluefin Tuna
Once scarce in British waters, bluefin tuna have made a spectacular comeback in recent years, after intense over-exploitation through the 1950s left this species on the brink of extinction. Since protections were introduced in 2008, numbers have bounced back and fishermen can now catch them with a special license.
Here in Cornwall, the first sightings in Cornwall were not until 2015, but, today, they’re becoming a more common sight. These enormous fish, which can weigh over 200kg and reach speeds of up to 40mph, can be spotted around Mounts Bay from August onwards.
In fact, when feeding, these fish can make the ocean look like it’s almost ‘boiling’, as they round smaller fish up to the surface. A great example of how protections can help the sea bounce back!
Protecting our marine life for the future
The marine life in Mounts Bay is magical, and needs our protection. As climate change, pollution, and human activity continue to put pressure on marine ecosystems, the wildlife of Mounts Bay faces increasing threats, but we can do something about it.
With the help of businesses like Marine Discovery, who are charting data for what species are and aren’t in the bay, and working closely with partners like Natural England and University of Exeter, work is already being done to build a picture of what’s happening on our doorstep.
And films like Sir David Attenborough’s latest documentary, Ocean with David Attenborough, are now exposing the impact of destructive fishing practices like bottom trawling on our marine habitats, showing how important it is to change the way we fish commercially.
But our own actions can make a difference, too. By watching wildlife responsibly, calling for more protections, and educating ourselves, we can build a better future for our marine ecosystems.
Here are some things you can do to help right now:
- Reduce (or completely eliminate) your seafood consumption
- If you do eat fish, choose hand line-caught, truly sustainable seafood
- Reduce single-use plastic and take part in beach cleans
- Observe marine wildlife from a respectful distance
- Support local conservation groups and citizen science efforts
Want to know more about the amazing wildlife in our bay? Head out on a tour with Marine Discovery to see it for yourself, or join the Mounts Bay Marine Group to do something active for the marine wildlife.
All images credited to Marine Discovery Penzance, with thanks to Hannah for her help pulling this article together.
