Minke whale © Jenny Stark

Marine Mammals and Sharks

In 2021, Scotland celebrates the Year of Coasts and Waters, and COAST celebrates 25 years of the community of Arran’s efforts to protect our seas.

Here we bring you a little bit closer to what lies beneath our waves with a focus on the charismatic and well-loved marine mammals and sharks that call Scotland’s seas home.

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It is pretty much indisputable that the megafauna we find in Scotland’s seas are the things that capture most attention of the general public, and it’s easy to see why. Seals, otter, porpoise, basking shark and many different species of whale and dolphin call our seas home.

Local to Arran, we have a wealth of marine mammals and sharks in our seas. We have a resident population of porpoise – so many in fact that the waters have been deemed “porpoise soup” in the past, and Bottlenose and Common dolphin are both occasional visitors to our waters, as are Minke whales. We’re lucky to have both species of seal – the Harbour and the Grey – as residents all year-round, and basking sharks seasonally visit from June through to October on the search of food. And of course we have Otter, who thrive on the kelp habitats in our seas as they hunt for big fattening Urchins or small crabs and fish to feed upon.

Under the waves, more lies waiting to be discovered. Divers always report sightings of the small-spotted catshark – a timid, bottom-dwelling shark – and we have recordings from drop down cameras of Spurdog in the area too.

Glimpses of any marine mammal or shark are treasured moments in one’s life, as they really are magnificent animals. This month, we’ll share with you fun facts about just a handful of the ones we find here in Scotland, along with ways in which how you can take that extra step to help protected them.

The importance of marine mammals and sharks

The presence and health of marine mammals and sharks can tell us a lot about the state of our seas as they are the top dogs of the marine world. That said, that isn’t really why they are so amazing. These species – of which there are far too many to name check individually – are all super charismatic and just a wonder to encounter.

Basking Shark
The second largest fish in the ocean, and the largest found in Scottish seas. They’re seasonal visitors to Arran, most often reported in August and September. These gentle giants are one of three shark species that feeds entirely on plankton, having specialised structures to filter the plankton from the water as it passes through the creature’s gills. Look out for distinctive “classic” triangular shark fin on a calm day.

Harbour and Grey seals are, on first glance, challenging to distinguish between for the untrained eye. While they look similar the Harbour (also known as the Common) seal has a puppy dog face whereas the grey has a longer head and Roman nose. Both species live for around 30 years and feed on a variety of marine species protected by the South Arran MPA.

Although not true marine mammals, as they rely on a freshwater source to keep their fur salt-free, the Eurasian otters (Lutra lutra) we find on our shores feed on small crabs and shellfish they find on the seabed. These creatures are important as they are recognised as a ‘Keystone Species’, meaning their position in a food chain is crucial in maintaining the ecological health of an area.

Special Species

Are you ready for fun fact overload? What we have discovered in preparing for this month’s feature on was that we could actually have done a year’s worth of promotion just on these species alone, there is just SO much information out there. Here we concentrate on the most common ones seen in Arran’s waters.

– Haul out to digest food and moult
– The latin name for Grey seal is 𝐻𝑎𝑙𝑖𝑐ℎ𝑜𝑒𝑟𝑢𝑠 𝑔𝑟𝑦𝑝𝑢𝑠 which means hook-nosed sea pig!
– Grey seals have parallel nostrils, Harbour seals have V-shaped ones.
– Harbour seal pups can swim within a few hours of birth, grey pups must wait until their white fluffy coat moults.

– Can eat up to 25% of their body weight a day
– Known to eat up to 50 different types of marine species
– Cubs are in the water by the time they are 10 weeks old!

𝐁𝐚𝐬𝐤𝐢𝐧𝐠 𝐒𝐡𝐚𝐫𝐤
– Grow up to 10m and weigh up to 5000kg
– Have hundreds of tiny teeth but do not use them for feeding
– Their throat is only about the size of a human fist
– Estimated to live up to 50 years
– Has the smallest brain to body weight ratio of any shark
– Young are born live, and can be up to 2metres long
– Can breach clear of the water, although this is rare. This behaviour is responsible for the only UK fatality recorded as a basking shark “attack”. The ‘Carradale Incident’ in 1937 reports a breaching shark capsizing a small dinghy, resulting in the death of the three occupants.

𝐁𝐨𝐭𝐭𝐥𝐞𝐧𝐨𝐬𝐞 𝐃𝐨𝐥𝐩𝐡𝐢𝐧
– Have a brain-to-body size proportion second only to humans
– Scotland’s bottlenose dolphin are bigger and fatter than populations further south
– Attack and kill their smaller cousins, the harbour porpoise, for fun
– Each individual has a unique whistle that functions like a name. Dolphin that haven’t seen each other in 20 years recognise each other by this whistle.

This is some rare footage of Harbour porpoise underwater. This was taken immediately after a dive, when divers were de-kitting on the boat. The motor was off and all was still when all of a sudden we heard a “puff” and porpoise surfaced right next to the boat. Slowly we lowered the gopro into the water as the creatures were passing by the boat.

Encounters this close with porpoise are incredibly rare, as they are naturally very shy animals who speed off in the opposite direction to any sort of unnatural noise – you usually just see their low backs and small dorsal fins arching through the water. The Harbour porpoise is the smallest cetacean, and the only porpoise to be found in European waters. Calves are born half the length of the female, and the female swims on her side when the calf is suckling to allow it to breathe more easily.

The word porpoise derives from a Medieval Latin word, porcopiscus; a compound of porcus meaning ‘pig’ and piscus meaning ‘fish’. This, and the pig-snort type breath they take at the water’s surface, is why porpoise are sometimes nicknamed the “puffing pig”.

Human Benefits

Many coastal communities livelihoods are supported by healthy populations of marine mammals and sharks. Marine tourism accounts for 14% of all of Scotland’s tourism, and a large proportion of this is attributed to marine wildlife excursions, tours and photography.

As top predators, marine mammals and sharks are vulnerable to any impacts on the marine food web, meaning the presence and health of these species can tell us a lot about the state of our seas. Mounting evidence demonstrates that restoring populations of marine megafauna can help buffer marine ecosystems from destabilising stresses like CO2 emissions and global climate change as these large animals have the ability to sequester carbon in their bodies.

It is further important for humans to protect these large charismatic animals as they facilitate nutrient transfer through the entire water column, both as they feed at depth and surface to breathe, and as they migrate from high latitude areas to low latitudes. This movement increases overall productivity of the oceans, having a bottom-up effect that eventually benefits fish, birds and other marine mega fauna creating rich, diverse seas.

Threats to marine mammals and sharks

Historically, hunting was the biggest threat faced by marine mammals and sharks in our seas.
Up until as recently as the 1990’s, Basking shark were hunted in the Firth of Clyde for their oil-rich livers. Historic fisheries data shows a decline of between 50-90% of basking shark in Scottish waters and, due to their slow growing nature and the fact they produce only a small number of young in a lifetime, this dramatic population decline will take a long time to recover.

Marine tourism, although great for local communities, must be responsible else it threatens many of the charismatic species we set out to find in the first place. For example, if you see a seal hauled out – and trust us, on Arran you most likely will! – it is so important you do not disturb them. These creatures haul out to do essential things like digest their food and to moult. If they are disturbed, they’ll drop back into the water which can have dire consequences in the middle of a moult. Our suggestion? Invest in a good pair of binoculars and watch from a distance and that way you’ll see much more natural behaviour.

If you’re visiting an area that affords the opportunity to get out onto the sea to observe these creatures in their natural environment then we suggest choosing a provider who is part of the WiSe Scheme – the UK’s national scheme for minimising disturbance to marine wildlife. All these operators are fully accredited and trained to responsibly interact with some of Scotland’s most amazing species.

Like many species and habitats and in our seas, marine mammals and sharks are threatened by over-fishing and unsustainable fishing. Although not necessarily directly targeted by fishing, the over-fishing of their prey species can cause population numbers to diminish, and some creatures end up as by-catch (unwanted catch trapped by commercial fishing) which can, in many instances, be fatal. There is also the issue of entanglement in various types of fishing gear by these large species. Disentangling a Whale of a Problem (@tanglyseas) has done a lot of work into understanding the scale, impacts and potential mitigation of marine animal entanglement in Scottish waters and beyond. In their words “𝐼𝑡 𝑖𝑠 𝑒𝑠𝑡𝑖𝑚𝑎𝑡𝑒𝑑 𝑡ℎ𝑎𝑡 ℎ𝑢𝑛𝑑𝑟𝑒𝑑𝑠 𝑜𝑓 𝑡ℎ𝑜𝑢𝑠𝑎𝑛𝑑𝑠 𝑜𝑓 𝑐𝑒𝑡𝑎𝑐𝑒𝑎𝑛𝑠, 𝑠ℎ𝑎𝑟𝑘𝑠 𝑎𝑛𝑑 𝑡𝑢𝑟𝑡𝑙𝑒𝑠 𝑑𝑖𝑒 𝑒𝑎𝑐ℎ 𝑦𝑒𝑎𝑟 𝑎𝑠 𝑎 𝑟𝑒𝑠𝑢𝑙𝑡 𝑜𝑓 𝑖𝑛𝑡𝑒𝑟𝑎𝑐𝑡𝑖𝑜𝑛𝑠 𝑤𝑖𝑡ℎ 𝑓𝑖𝑠ℎ𝑖𝑛𝑔 𝑔𝑒𝑎𝑟, 𝑤ℎ𝑖𝑐ℎ 𝑐𝑎𝑛 ℎ𝑎𝑣𝑒 𝑑𝑒𝑣𝑎𝑠𝑡𝑎𝑡𝑖𝑛𝑔 𝑤𝑒𝑙𝑓𝑎𝑟𝑒 𝑎𝑛𝑑 𝑐𝑜𝑛𝑠𝑒𝑟𝑣𝑎𝑡𝑖𝑜𝑛 𝑖𝑚𝑝𝑎𝑐𝑡𝑠. 𝑇ℎ𝑒𝑠𝑒 𝑒𝑣𝑒𝑛𝑡𝑠 𝑐𝑎𝑛 𝑎𝑙𝑠𝑜 𝑏𝑒 𝑑𝑖𝑠𝑡𝑟𝑒𝑠𝑠𝑖𝑛𝑔 𝑎𝑛𝑑 𝑝𝑜𝑡𝑒𝑛𝑡𝑖𝑎𝑙𝑙𝑦 𝑑𝑎𝑛𝑔𝑒𝑟𝑜𝑢𝑠 𝑓𝑜𝑟 𝑡ℎ𝑜𝑠𝑒 𝑑𝑖𝑠𝑐𝑜𝑣𝑒𝑟𝑖𝑛𝑔 𝑡ℎ𝑒𝑚, 𝑝𝑎𝑟𝑡𝑖𝑐𝑢𝑙𝑎𝑟𝑙𝑦 𝑤ℎ𝑒𝑛 𝑡ℎ𝑒 𝑎𝑛𝑖𝑚𝑎𝑙 𝑖𝑠 𝑠𝑡𝑖𝑙𝑙 𝑎𝑙𝑖𝑣𝑒, 𝑎𝑛𝑑 ℎ𝑎𝑣𝑒 𝑎 𝑓𝑖𝑛𝑎𝑛𝑐𝑖𝑎𝑙 𝑖𝑚𝑝𝑎𝑐𝑡 𝑜𝑛 𝑖𝑛𝑑𝑖𝑣𝑖𝑑𝑢𝑎𝑙 𝑓𝑖𝑠ℎ𝑒𝑟𝑠 𝑡ℎ𝑟𝑜𝑢𝑔ℎ 𝑙𝑜𝑠𝑡 𝑓𝑖𝑠ℎ𝑖𝑛𝑔 𝑡𝑖𝑚𝑒, 𝑎𝑛𝑑 𝑑𝑎𝑚𝑎𝑔𝑒 𝑜𝑟 𝑙𝑜𝑠𝑠 𝑜𝑓 𝑓𝑖𝑠ℎ𝑖𝑛𝑔 𝑔𝑒𝑎𝑟 𝑎𝑛𝑑 𝑎𝑛𝑦 𝑎𝑠𝑠𝑜𝑐𝑖𝑎𝑡𝑒𝑑 𝑐𝑎𝑡𝑐ℎ.”

One such incident was shared by Ocean Advocate, @Cal Major just last month when she Paddle-boarded around Scotland as she encountered a dead juvenile humpback that had become entangled on a vertical buoy rope of a creel pot. We agree with Cal when she says “𝐼 𝑠𝑢𝑝𝑝𝑜𝑟𝑡 𝑡ℎ𝑒 𝑐𝑢𝑟𝑟𝑒𝑛𝑡 𝑟𝑒𝑠𝑒𝑎𝑟𝑐ℎ 𝑎𝑛𝑑 𝑡𝑒𝑐ℎ𝑛𝑜𝑙𝑜𝑔𝑦 𝑡𝑜 𝑟𝑒𝑑𝑢𝑐𝑒 𝑡ℎ𝑒 𝑖𝑛𝑐𝑖𝑑𝑒𝑛𝑐𝑒 𝑜𝑓 𝑒𝑛𝑡𝑎𝑛𝑔𝑙𝑒𝑚𝑒𝑛𝑡 – 𝑙𝑜𝑡𝑠 𝑐𝑢𝑟𝑟𝑒𝑛𝑡𝑙𝑦 𝑏𝑒𝑖𝑛𝑔 𝑑𝑜𝑛𝑒 𝑖𝑡 𝑠𝑒𝑒𝑚𝑠….𝑏𝑢𝑡 𝑖𝑡 𝑛𝑒𝑒𝑑𝑠 𝑖𝑛𝑣𝑒𝑠𝑡𝑚𝑒𝑛𝑡 𝑎𝑛𝑑 𝑖𝑡 𝑛𝑒𝑒𝑑𝑠 𝑡𝑜 𝑏𝑒 𝑡𝑎𝑘𝑒𝑛 𝑠𝑒𝑟𝑖𝑜𝑢𝑠𝑙𝑦. 𝑉𝑒𝑟𝑦 𝑑𝑖𝑓𝑓𝑖𝑐𝑢𝑙𝑡 𝑡𝑜 𝑠𝑒𝑒 𝑎 𝑤𝑎𝑦 𝑡𝑜 𝑒𝑛𝑑 𝑖𝑡 𝑎𝑙𝑡𝑜𝑔𝑒𝑡ℎ𝑒𝑟 𝑤𝑖𝑡ℎ𝑜𝑢𝑡 𝑟𝑜𝑝𝑒𝑙𝑒𝑠𝑠 𝑝𝑜𝑡𝑠 – 𝑡𝑒𝑐ℎ𝑛𝑜𝑙𝑜𝑔𝑦 𝑤ℎ𝑖𝑐ℎ 𝑖𝑠𝑛’𝑡 𝑦𝑒𝑡 𝑎𝑣𝑎𝑖𝑙𝑎𝑏𝑙𝑒.” We would also add that effective management of 𝗮𝗹𝗹 fishing methods is required within Scotland’s inshore waters to reduce the likelihood of entanglement and by-catch.

Get involved to help marine mammals and sharks

We all love a marine mammal and shark, and there are plenty of people out there who help protect them as part of their day job. Understanding populations of marine megafauna is the fundamental basis to help protect them.

Sadly, many whales, dolphins, porpoise and seals are found washed up on our coasts across a given year. In Scotland, the Scottish Marine Animal Stranding Scheme (SMASS) leads on collating and investigating reports of [dead] stranded marine animals and, where suitable, they also undertake necropsies (post mortems) of the creature to try to ascertain the cause of death. Specially trained volunteers assist SMASS by taking samples of creatures which help provide insight into diseases, environmental contaminant levels, reproductive patters, diet and other aspects of general health of populations. All this information provides essential baseline data to help detect any future outbreaks of disease, unusual mortality events, anthropogenic stressors or responses to climate change.

It is difficult to designate specific Marine Protected Areas (MPA) for marine mammals and sharks, given they are transient populations that travel great distances to perform different functions such as breeding and feeding. That said, the Scottish Government announced the designation of four new MPAs for minke whale, basking shark and Risso’s dolphin in Scottish waters in 2020. These four areas are recognised as critical habitat for feeding, breeding and calving of many species, including the UK’s first minke whale MPA and the first basking shark MPA in the world. Designation, however, is just the first step and the Government must now make significant steps to actually implement management measures to properly protect the species they are designed to.

Probably unsurprisingly, there are plenty of opportunities for the general public to get involved with helping protect marine mammal and shark species in Scotland.

Both the Cetacean Research and Rescue Unit and Hebridean Whale and Dolphin Trust provide residential experiences, where you spend time with experts in the field helping collect and collate vital evidence that has been instrumental in bringing in MPAs to protect these amazing species.

Staying closer to home and exploring your own coastlines more of your thing? Keep an eye out for Mermaid’s Purses on the beach! Depending on where you are, these may be the eggcases of small-spotted catshark, flapper skate, cuckoo ray or another elasmobranch that lays a distinctive egg case unique to its species. If you’re lucky enough to find a mermaid’s purse (tip: look in the high strandline amongst all the seaweed) the Shark Trust have a great identification guide to help you determine which species it is from. We encourage you to also report your findings as part of the Great Eggcase Hunt – a citizen science project that has been running since 2003 which helps us understand species diversity and presence around our coastlines. If you’re a diver or snorkeller, you can input into this project too as the Shark Trust as keen to receive records of developing eggcases to help pin-point exact locations where sharks and skates are laying.

Cover image: Minke Whale © Jenny Stark