The Isle of Mull is home to an incredible variety of wildlife along its coastline. This ultimate guide takes you on a journey through tidal pools, sandy flats, and rocky shores, where crabs, gobies, flatfish, and many other fascinating animals thrive. Whether you are exploring at low tide or simply observing from the shore, this guide to shore creatures on the Isle of Mull will help you discover and understand the rich intertidal life of this Scottish island.
Shore Crab
Shore crabs are among the most common inhabitants of Mull’s tidal pools and rocky shores. Their shells range in colour from green to brown, often patterned with mottling or stripes, providing perfect camouflage against rocks and seaweed. They move sideways with remarkable speed and use their claws both to catch food and defend themselves from predators or rivals. Shore crabs are opportunistic feeders, consuming small molluscs, worms, and bits of detritus found in pools. Their presence helps maintain the balance of invertebrate populations along the intertidal zone, making them essential for the local ecosystem. They are particularly noticeable at low tide when the rocks are exposed and they scuttle quickly between hiding spots.
Where to Look: Under rocks and among seaweed in shallow pools at low tide.
Fun Fact: Shore crabs grow by moulting, forming a new exoskeleton beneath the old one before it splits open.
Hermit Crab
Hermit crabs are small, social crustaceans that occupy empty snail shells to protect their soft bodies. As they grow, they must find progressively larger shells and sometimes line up to swap with other hermit crabs in an orderly fashion. They scavenge for algae, decaying matter, and tiny invertebrates, helping to clean the shore and recycle nutrients. Hermit crabs are quick and can retreat completely into their shells when threatened. Their movements are surprisingly fast for their size, and they often appear to be exploring the pools methodically. These crabs play a vital role in the tidal ecosystem, serving as both predator and prey to other shore creatures, and they are especially fascinating to watch at low tide.
Where to Look: Sandy patches near rocks, shallow pools, and under seaweed.
Fun Fact: Hermit crabs carry their homes on their backs, providing protection wherever they go.
Blenny (Rock Blenny)
Blennies are small, elongated fish that inhabit rock pools along the shore. Their large eyes allow them to spot predators and prey effectively, and their slim bodies enable them to slip into tight crevices for protection. Blennies feed on tiny crustaceans, plankton, and small invertebrates, using their quick movements to dart between hiding spots. They can survive briefly out of water by absorbing oxygen through their skin, allowing them to remain in shallow pools when the tide recedes. Blennies are curious and often appear to watch nearby movements, adding to the interest of observing tidal pool ecosystems. Their presence contributes to the dynamic life of Mull’s shores.
Where to Look: Shaded rock pools and under boulders.
Fun Fact: Blennies are often observed following human movements from their hiding spots.
Butterfish
Butterfish are small, flattened fish that live in shallow rock pools and sandy areas along the Isle of Mull’s shore. They are named for their smooth, slippery texture and silvery colour. These fish feed on tiny crustaceans, worms, and other small invertebrates, darting quickly between rocks and seaweed to avoid predators. Butterfish are an important part of the intertidal ecosystem, serving as both predator and prey. Observing them at low tide shows their rapid movements, their ability to hide in crevices, and their crucial role in maintaining balance in tidal pool communities.
Where to Look: Shallow rock pools and sandy patches under seaweed.
Fun Fact: Butterfish are named for their smooth, slippery texture, which helps them escape predators.
Pipefish
Pipefish are slender, elongated fish closely related to seahorses, often camouflaged among kelp fronds and floating seaweed. Male pipefish carry eggs in a specialized brood pouch until they hatch, ensuring the next generation is protected. They feed on small planktonic creatures, using their tube-like mouths to suck in prey. Pipefish rely heavily on camouflage to avoid predators, blending seamlessly into the kelp. Observing them at low tide is challenging because they are small and cryptically coloured, but they play an important role in the intertidal food chain, serving as both predator of plankton and prey for larger fish and crabs.
Where to Look: Kelp beds and floating seaweed near the shore.
Fun Fact: Their tube-like mouths allow them to suck in plankton like a straw.
Sand Eel
Sand eels are slender, elongated fish that burrow vertically into sandy tidal flats to avoid predators. They feed on tiny crustaceans and plankton, and their burrowing behaviour makes them an important food source for larger shore predators such as crabs and fish. Sand eels are quick and elusive, darting in and out of the sand to escape detection. Their ability to bury themselves allows them to survive in exposed sandy areas, even during low tide. Watching sand eels at work provides insight into the hidden activity occurring beneath the sand and the vital ecological role they play in transferring energy up the food chain.
Where to Look: Sandy tidal flats and shallow sand pools at low tide.
Fun Fact: Despite their name, sand eels are true fish, not eels.
Flat Fish (Plaice, Flounder)
Flat fish are small, flattened fish that lie on sandy tidal flats, perfectly camouflaged against the sand. Their eyes are on one side of the body, allowing them to watch for predators while remaining almost invisible. They feed on worms, small crustaceans, and molluscs, darting quickly into the sand when disturbed. Flat fish are highly adaptable and survive in both shallow and slightly deeper sandy areas. Their cryptic colouring provides protection from birds and larger fish. Observing them at low tide is rewarding, as they often move slightly when approached, demonstrating their incredible camouflage abilities and quick reflexes to avoid threats.
Where to Look: Sandy tidal pools and shallow sand flats at low tide.
Fun Fact: Flat fish can slightly change colour to blend with the sand, making them almost invisible.
Sea Scorpion
Sea scorpions are small, bottom-dwelling fish commonly found in rocky pools along the Isle of Mull’s shore. Despite their name, they are not true scorpions but get it from their spiny appearance and predatory habits. They feed on tiny crustaceans, worms, and other small invertebrates, using their camouflaged bodies to blend perfectly with rocks and seaweed. Sea scorpions are fascinating to watch as they remain almost motionless, waiting for prey to come within striking distance, and they play an important role in the intertidal ecosystem by controlling populations of smaller animals.
Where to Look: Under rocks, in shallow rock pools, and among seaweed at low tide.
Fun Fact: Sea scorpions have spiny fins that help them blend into rocky surroundings, making them nearly invisible to predators.
Sea Anemone
Sea anemones are colourful, predatory animals that attach themselves firmly to rocks in tidal pools. Their tentacles are covered with stinging cells, which they use to paralyse small prey such as plankton, shrimps, and tiny molluscs. Sea anemones can contract their tentacles and close up into small, shiny blobs to avoid drying out when the tide is low. They reproduce both sexually and asexually and contribute to the biodiversity of the intertidal zone. Observing anemones at low tide provides insight into their fascinating feeding behaviour and the symbiotic relationships they often share with small shrimp or algae that live among their tentacles.
Where to Look: Calm rock pools and under boulders.
Fun Fact: Tentacles sting tiny prey but are harmless to humans.
Limpet
Limpets are small, cone-shaped molluscs that cling firmly to exposed rocks along the shore. They feed by scraping algae from rock surfaces using a ribbon-like tongue called a radula. Each limpet establishes a “home spot” to which it returns after foraging, often grinding a shallow depression into the rock to fit snugly. Limpets play an important role in controlling algal growth and maintaining ecological balance. Their strong adhesion helps them resist waves and predation. Observing limpets at low tide shows their slow, methodical movement as they graze and return to their home, a behaviour that can continue for many years.
Where to Look: Exposed rocks in mid and low shore areas.
Fun Fact: Over time, limpets grind a small indentation into their rock home.
Periwinkle
Periwinkles are small, spiral-shelled snails that graze on algae growing on rocks and seaweed. They can survive periods out of water by sealing themselves inside their shells using a hard plate called an operculum, which keeps them moist until the tide returns. Periwinkles reproduce by laying eggs on hard surfaces and are a crucial food source for crabs, birds, and fish. They move slowly but methodically, often climbing over seaweed and stones in search of food. Their presence demonstrates the interconnectivity of tidal pools, as they help recycle nutrients and maintain the health of the shore environment, providing stability to the small ecosystem they inhabit.
Where to Look: Rocks, seaweed, and crevices.
Fun Fact: The operculum acts like a door, keeping them moist until the tide returns.
Dog Whelk
Dog whelks are predatory snails that feed mainly on mussels and barnacles, using their radula to bore holes into shells. Their spiraled, tough shells protect them from predators, and they can live for several years in rock pools. Dog whelks are slow-moving but efficient hunters, often waiting patiently to feed. They play an important role in controlling populations of other molluscs, helping to maintain balance in tidal pool ecosystems. Observing dog whelks at low tide reveals their methodical feeding behaviour and how they use chemical cues to locate prey, making them fascinating subjects for anyone interested in intertidal life.
Where to Look: Mussel beds, rocky pools, and lower shore rocks.
Fun Fact: Dog whelks were historically used to produce purple dye.
Whelk
Whelks are predatory sea snails commonly found in tidal pools and on rocky shores around the Isle of Mull. They feed mainly on mussels, limpets, and other small molluscs, using their strong, coiled shells for protection. Whelks have a radula, a ribbon-like tongue with tiny teeth, which they use to bore holes into prey shells. They move slowly but methodically, often hiding under rocks or seaweed during low tide. Whelks are an important predator in the intertidal ecosystem, helping maintain the balance of mollusc populations along the shore.
Where to Look: Rocky tidal pools, under stones, and among seaweed at low tide.
Fun Fact: Whelks can drill through the shells of mussels and limpets to reach the soft flesh inside.
Mussel
Mussels are bivalve molluscs that attach to rocks, piers, and kelp using strong byssus threads. They filter plankton and tiny particles from seawater, playing a crucial role in cleaning the water and supporting other intertidal species. Mussels often form dense clusters called beds, which provide shelter for small crabs, shrimps, and other creatures. These molluscs are resilient, able to survive fluctuating tides and salinity levels. Observing mussel beds at low tide shows the abundance of life they support, highlighting the complexity of intertidal ecosystems. Mussels are a key food source for gulls, starfish, and crabs, demonstrating their importance in the tidal food chain.
Where to Look: Sheltered rocks, piers, and kelp-covered areas.
Fun Fact: Mussels are vital in creating habitat for other intertidal species.
Barnacle
Barnacles are crustaceans that permanently attach to rocks, pier posts, and boulders. They feed by extending feathery appendages called cirri into the water to catch plankton when submerged. Barnacles reproduce by releasing eggs and sperm into the surrounding water. Their dense colonies create microhabitats for other small intertidal organisms. Barnacles are incredibly strong and can withstand pounding waves, making them a resilient feature of the shore. Observing barnacles at low tide demonstrates their fascinating feeding behaviour and the way they interact with other organisms, showing how even tiny creatures play a role in shaping the intertidal ecosystem.
Where to Look: Mid-shore rocks and pier posts.
Fun Fact: Barnacle glue is one of the strongest natural adhesives known.
Sea Urchin
Sea urchins are spiny, spherical molluscs that graze on algae and contribute to controlling algal growth in tidal pools. They use their sharp spines for protection against predators and move slowly using tiny tube feet on their undersides. Sea urchins can live for several years and are an important part of the intertidal ecosystem, affecting the distribution of algae and creating microhabitats for smaller organisms. Observing sea urchins at low tide reveals their deliberate movements as they feed and interact with their environment. They are especially interesting because of their unique anatomy, including a mouth structure called Aristotle’s lantern that scrapes food from rocks.
Where to Look: Rock pools and under kelp.
Fun Fact: Their mouth, called Aristotle’s lantern, has five teeth for scraping algae.
Starfish
Starfish are slow-moving predators that use hundreds of tube feet to move along rocks and pry open bivalves like mussels and limpets. They can regenerate lost arms, making them highly resilient. Starfish feed on shellfish by extruding their stomachs over prey and secreting digestive enzymes to absorb nutrients externally. They are an important predator in tidal pools, helping maintain the balance of mollusc populations. Observing starfish at low tide shows their deliberate, methodical movements and fascinating feeding behaviour. They are a classic intertidal species, highlighting the complexity of interactions between predators and prey in the tidal ecosystem.
Where to Look: Rock pools and under boulders.
Fun Fact: Sometimes a single arm can grow into a whole new starfish.
Shrimp
Shrimps are small, transparent crustaceans that dart rapidly among sand and seaweed. They feed on detritus, plankton, and small invertebrates, helping to recycle nutrients in tidal pools. Their nearly invisible bodies make them difficult to spot, but they are abundant and active, contributing significantly to the intertidal food web. Shrimps often hide under rocks and seaweed, emerging to forage or escape predators. Observing shrimps at low tide reveals their quick, agile movements and their interactions with other small creatures. They are important prey for gobies, blennies, and small crabs, demonstrating their integral role in sustaining shore biodiversity.
Where to Look: Sandy pools and under seaweed.
Fun Fact: Their transparency makes them nearly invisible to predators.
Razor Clam
Razor clams are long, narrow bivalves that burrow rapidly into sandy tidal flats. They feed by filtering plankton from the water while buried, playing a key role in maintaining water quality and cycling nutrients. Razor clams can quickly disappear into the sand if disturbed, making them elusive and fascinating to observe at low tide. They are sensitive to tides and water conditions and are often harvested carefully by humans for food. Watching their burrowing behaviour provides insight into the hidden life of sandy shores, highlighting the complex interactions between prey and predator in tidal ecosystems and the adaptations needed for survival in shifting sands.
Where to Look: Sandy tidal flats.
Fun Fact: Razor clams can burrow completely in a few seconds to avoid predators.
Cockle
Cockles are heart-shaped bivalves that live buried in sandy or muddy tidal flats. They filter plankton from the water, contributing to clean water and nutrient cycling. Cockles are an essential food source for birds, crabs, and fish. Their shells provide shelter for small invertebrates, adding to shore biodiversity. At low tide, they can be seen just below the surface, occasionally creating small holes where water seeps in and out. Observing cockles highlights the activity beneath sandy shores, showing how even simple organisms shape their environment and sustain the intertidal ecosystem through feeding and filtering behaviour.
Where to Look: Sandy flats and shallow pools.
Fun Fact: Cockles can burrow quickly into sand to hide from predators.
Lugworm
Lugworms are large, segmented worms that live in U-shaped burrows in sandy tidal flats. They feed by extracting organic material from sand, leaving characteristic coiled casts on the surface. These worms are essential for aerating sediment, recycling nutrients, and supporting other shore species. Their burrowing activity creates microhabitats for tiny invertebrates, contributing to overall biodiversity. Observing lugworms at low tide shows the intricate patterns they create in the sand and provides insight into the hidden life beneath the surface. They are a classic indicator species for healthy sandy shore ecosystems, demonstrating the importance of invertebrates in maintaining shore ecology.
Where to Look: Sandy tidal flats.
Fun Fact: The coiled casts on the sand show where lugworms have been feeding.
Bristle Worm
Bristle worms are segmented, worm-like creatures that live in sand, under rocks, and among seaweed along the Isle of Mull’s shores. Their bodies are covered with tiny bristles, which help them move quickly and deter predators. Bristle worms feed on detritus, small invertebrates, and organic matter, playing an important role in recycling nutrients within tidal pools and sandy areas. They are often active at night or when the tide is low, and can be fascinating to observe as they wriggle through sand and crevices, demonstrating the hidden life that supports intertidal ecosystems.
Where to Look: Under rocks, in sand, and among seaweed in tidal pools.
Fun Fact: The tiny bristles covering their bodies can irritate skin if touched, helping protect them from predators.
Rag Worm
Rag worms are long, segmented worms commonly found in sandy tidal flats and under rocks along the Isle of Mull’s shores. They are active predators and scavengers, feeding on small invertebrates and organic material, and they play a crucial role in recycling nutrients within intertidal ecosystems. Rag worms are strong burrowers and can quickly retreat into their tubes when threatened. Observing them at low tide reveals their wriggling movements and their characteristic eversible jaws, which they use to catch prey. They are an essential part of the shore’s hidden biodiversity.
Where to Look: Sandy tidal flats, under rocks, and in shallow sand burrows at low tide.
Fun Fact: Rag worms can extend a muscular proboscis with tiny jaws to grab prey and retract it quickly into their burrow.
Sand Hopper (Talitrus saltator)
Sand hoppers are small, agile crustaceans that hop and dart along sandy beaches and dune areas. They feed on decaying seaweed and organic matter, recycling nutrients and supporting the food web. Active mostly at night or under moist conditions, they avoid predators and harsh sunlight by burrowing into damp sand. Sand hoppers are an important link between the shore and dune ecosystems, serving as prey for birds and larger invertebrates. Observing them at low tide shows their remarkable jumping behaviour and rapid movement as they navigate the sandy environment. They are a vital and often overlooked component of the beach ecosystem.
Where to Look: Sandy shores and around decaying seaweed.
Fun Fact: They can jump many times their own body length to escape predators.
Moon Jellyfish
Moon jellyfish are delicate, translucent creatures that can often be seen floating near the surface or washed up on the Isle of Mull’s beaches. Recognisable by their pale, moon-like bodies and four pink or purple rings in the centre, they move gracefully through the water with gentle pulsations. Moon jellyfish feed on plankton and tiny sea creatures, using their tentacles to capture food. Although they can sting, their sting is extremely mild and harmless to most people. They are a beautiful reminder of the gentle rhythms of the sea that surround Mull.
Where to Look: Floating close to shore, in calm bays, or washed up on sandy beaches after high tide.
Fun Fact: The four circles visible inside a moon jellyfish are its stomachs, which glow slightly when the jellyfish feeds.
Lion’s Mane Jellyfish
The lion’s mane jellyfish is one of the largest and most striking jellyfish found around the Isle of Mull. With long, flowing tentacles that can stretch several metres, and a reddish-orange bell that resembles a lion’s mane, it is both beautiful and awe-inspiring. These jellyfish drift close to the shore during warmer months, feeding on plankton, small fish, and other jellyfish. Their sting is much stronger than the moon jellyfish’s, so it’s best admired from a safe distance. Despite their size, lion’s mane jellyfish are delicate creatures, playing an important role in the marine food web along Mull’s coast.
Where to Look: In shallow coastal waters or washed ashore after storms, especially in summer.
Fun Fact: The lion’s mane jellyfish is the largest known jellyfish species in the world, with tentacles that can exceed 30 metres in length.
For more wildlife adventures on Mull, check out Encountering Mull’s Big 5: A Wildlife Spectacle.
