Scotland’s marine environment is vast – from rapid tidal currents flowing over sandy shallows to deep-sea coral reefs growing on seamounts – and the diversity of marine habitats has paved the way for marine organisms to be equally as plentiful and varied. We are spoiled for choice and with such a large range of animals to see, sometimes it can be difficult to decide how best to devote our time.

To help with deciding which animals should be on your ‘must-see’ list, our Living Seas team have identified the ‘Big Five’ that we consider to be Scotland’s most charismatic and rewarding sightings. We are well aware of how opinions may differ – narrowing down to just five was quite a lengthy discussion in our office – and many will question why bottlenose dolphins and puffins are not on the list, but we felt that spotting one of our final five presented a more demanding and rewarding challenge. Other notable absentees are the leatherback turtle and the sunfish, which we all agreed would be incredible to see but the chances of seeing these animals in Scotland’s waters are too low and therefore they didn’t make the cut. We hope you enjoy reading through the list and wish you all the best in ticking them off!

Orca – Orcinus orca

Orca are instantly recognisable. Their large black dorsal fins stand tall out of the water, in some cases close to 2m high, and their distinct monochrome black and white markings clearly distinguish them from other large marine animals. Growing up to nearly 10m in length and living for as long as 90 years, orca are found globally, but some are either permanent residents in Scotland (west coast population) or are annual visitors to our waters (east coast and northern populations).

Orca are social animals that move around in pods – group sizes of up to eight animals have been seen off western Scotland, although much larger pods have been seen in other parts of the world. They are very intelligent and inquisitive predators that feed on many different animals, but predominantly seals. They are also commonly named ‘killer whales’ due to their ability to occasionally kill whales. This has led to the common conception that orca are whales, but they are in fact the largest species of dolphin.

The west Scotland population of orca is small meaning that, despite being permanent residents in Scotland, sightings are rare. Hotspots for orca sightings on the west coast include Skye and the Small Isles. In the summer months, when migratory orca visit Scotland, sightings are common around Shetland, Orkney and off Scotland’s northern coast. There is still a lot we don’t know about orca populations and their movement, so if you see any be sure to report them to Whale and Dolphin Conservation or the Hebridean Whale and Dolphin Trust.

White-tailed sea eagle – Haliaeetus albicilla

The white-tailed sea eagle is the largest bird of prey in the UK. Primarily brown in colour, it has a white head and neck and white tail feathers on adults that clearly distinguish it from other large raptors, such as the golden eagle. White-tailed sea eagles are long-lived birds, the oldest on record being over 32 years old! They mature and begin to breed at around five years old and form monogamous, life-long partners. They are opportunistic feeders, predominantly feeding on fish by flying low over the sea surface before plunging into the water and snatching unsuspecting prey.

Although populations are fairly stable in western Scotland, the white-tailed sea eagle has had a difficult past. Due to persecution from landowners, fishery owners and egg-collectors, the numbers of eagles dramatically declined in the early 20^th century, eventually becoming extinct in the British Isles in 1918. Fortunately, thanks to multiple reintroduction efforts in the 1970’s and 80’s using eagles from Norway, a small but breeding population of white-tailed sea eagles was established on the west coast of Scotland.

Unfortunately, persecution of raptors still exists in Scotland, which can be highly damaging to small populations of birds. If you see evidence of raptor persecution, please report it to the local authorities.

Northern gannet colony – Morus bassanus

Although the sight of a single gannet flying along the coast may not seem like a noteworthy experience, few would say the same when they first set their eyes on a full sized gannet colony. The presence of thousands of breeding birds capable of changing a normally lifeless and grey cliff face into a white-speckled hub of activity can be truly awe inspiring.

Gannets are the UK’s largest seabird and they can be clearly distinguished from other seabirds by their black wingtips and yellow head markings. They are often seen soaring high above the sea looking for shoaling fish, which they catch by plunge-diving into the water from great heights at speeds of up to 100 km/h. The sight of a diving gannet in itself is quite spectacular.

Gannets are migratory birds that breed in large colonies in Scotland, most notably at Bass Rock, St Kilda, and the Northern Isles, from January through to August. Calculating the exact number of breeding pairs is difficult, but it is believed that Scotland is home to about 60% of Europe’s gannet population – Bass Rock alone has an estimated 150,000 breeding pairs that turn the island bright white during the summer months. Although gannet numbers are high, and have been increasing in Scotland, they are still vulnerable to environmental pressures due to the few numbers of sites they breed and feed at.

Basking shark – Cetorhinus maximus

Growing up to 12m in length, the basking shark is the second largest species of fish alive today, beaten only by the whale shark. Although they are big sharks, they feed solely on plankton – microscopic plants and animals that live in the water column. Every spring, basking sharks visit Scottish waters to feed on plankton blooms that occur off the west coast, particularly in the Sea of the Hebrides. Basking sharks can regularly be spotted at or near the surface of the water swimming along with their mouths wide open, filtering the sea water for plankton.

In the past, basking sharks were hunted in Scotland – targeted for the oil in their huge livers (a single liver can weigh up to a tonne!) – reaching a peak in 1947 when a reported 250 sharks were landed. Since 1998, basking sharks have been protected in British waters from targeted fishing, but they still face many threats, primarily collisions with boats and entanglement in fishing gear (both nets and creel lines).

Although they are currently listed as being ‘Vulnerable to extinction’ on the IUCN Red List of Threatened Species, there are regular sightings along the west coast of the UK, in particular around the islands of the Inner Hebrides between April and October. If you see one, be sure to report it to Basking Shark Scotland.

Humpback whale – Megaptera novaeangliae

Weighing up to 36 tonnes and measuring 12-16 m in length, humpback whales are one of the more active species of whales, often giving lucky spectators a show of breaching, lobtailing and flipper-slapping. They can be distinguished by their large, knobbly head and long fins (up to 5m). Humpbacks can be found throughout the World’s oceans, undergoing huge migrations between their cold-water feeding grounds in the polar regions and their warmer breeding grounds in the tropics. They are seasonal visitors to Scottish waters and can occasionally be seen during the summer months, primarily off the coast of the Hebrides.

In recent years, the Hebridean Whale and Dolphin Trust have seen an increase in reported sightings of humpbacks, a promising sign given that the species was once hunted to the brink of extinction in the UK. This species is protected under both UK and EU law, but there is still a high risk of entanglement in fishing ropes and the potential for boat strikes whilst in Scottish waters. Humpback sightings should be reported to Whale and Dolphin Conservation or the Hebridean Whale and Dolphin Trust.

This article was originally published in 2016 as part of National Marine Week