Uncovering SGI intertidal life
- Richard Philpot
- Feb 1
- 16 min read
Updated: May 16
“The Pacific Northwest coast is one of the world’s richest, most diverse habitats for intertidal marine life.” Wow, not many places can say that. I can’t get enough of exploring the Southern Gulf Islands’ intertidal zones. The bizarre variety of species to be uncovered and learned about is worth the time commitment. And when planning your ocean shoreline adventure, timing is everything.
Table of Contents
Photographs, videos, audio, and text Copyright © 2026 Richard Philpot/SGIOUTSIDE.ca.
A group of youngsters exploring the Middle Intertidal Zone at Arbutus Point, Portland Island (0924).
“The Pacific Northwest coast is one of the world’s richest,
most diverse habitats for intertidal marine life.” (D. Sept 1999 & 2024)
Tides Change
Sea levels rise and fall due to the gravitational pull of the moon, the sun, and the Earth’s rotation. In our part of the world, this alternating movement of water occurs twice daily and is called a tide change. The tide cycle is predictable, meaning you can easily plan your intertidal zone outing.
Knowing tide heights at your destination will put you there at the appropriate time to search for intertidal inhabitants.
Log on to the Government of Canada’s Tide Stations website, type in Southern Gulf Islands in the map’s search bar, and choose the green box closest to the beach you’d like to explore. Click on View Station Data, confirm the date, choose Feet under Select Units, then scroll down to Hourly Predictions. The table of hourly tides covers 24 hours over 7 days. I prefer tide heights in Feet because they clearly show the lowest tide times and the water level falling and rising. If you’re unsure whether you’ve read the tide table correctly, ask a local kayak tour operator or a boater coming ashore or on the docks at a marina.
Intertidal Zones of the SGI
Intertidal zones, or intertidal habitats, can be divided into two broad categories: soft and hard. Soft habitats are environments such as sandy beaches and mudflats. Marine life in these areas is buried part of every day and may only be detected by a small dimple or hole at the surface. Hard habitats, like rocky shorelines, are the most common in the Southern Gulf Islands. Most marine life inhabiting these environments lives in cracks and crevices or is attached to rocks. A wide variety of aquatic organisms live in more than one habitat (042325).
Soft Habitats
Sand Beaches and Mudflats. Beaches and mudflats are home to fewer marine creatures than rocky shorelines.
What you may find on beaches and mudflats: Mud beaches are often populated with worms, crabs, and clams. Lewis’s Moonsnail and soft-shell clams are found in the sand and mud.
Hard Habitats
Rocky Shoreline. The rocky intertidal habitat is divided into the splash zone and the high, middle, and low intertidal zones.
Splash Zone. The species residing here are out of the water more than in it.
What you will find here: Barnacles and limpets clinging to shoreline rocks.
High Intertidal Zone. The toughest of the intertidal neighbourhoods. This zone is submerged infrequently, resulting in extreme stress on the marine organisms residing here, including wide temperature fluctuations, wave stress, desiccation (drying out), and a higher risk of bird predation. This habitat is characterized by high algal productivity. Here, kelps and seaweeds thrive, acting as food sources for grazers. As the tidal height decreases, tide pools of standing water remain within the recesses of the rocky shoreline. These pools play an important role in intertidal habitats, acting as water-filled refuges from the harsh, drying effect of the sun.
What you will find here: California mussels, barnacles, and chitons along exposed shorelines and anemones and limpets tucked in crevices on the underside of rocks. Seaweeds cover the sides and tops of rocks, able to withstand long periods above the waterline.
Middle Intertidal Zone. The middle intertidal zone is exposed during most low tides and submerged during most high tides. This zone’s organisms must endure the physical stresses of desiccation and temperature fluctuations. Again, tide pools persist in the nooks and hollows of the rocks.
What you will find here: Mobile predators, such as crabs and starfish, or algal grazers, such as snails, are prevalent in the middle intertidal zone.
Low Intertidal Zone. The low intertidal zone is only occasionally exposed. It features the four intertidal habitats’ most varied and plentiful marine life. Organisms in this zone do not need to adapt to the harsh physical stresses of changing temperatures and desiccation. Still, they must deal with the natural pressures of predation and competition. The most common predators are sea stars and rock crabs.
What you will find here: Look for the 24-ray Sunflower star, Purple Sea urchins (that look more like a pompom than a sea creature), and brittle stars hidden in rock crevices. Soft-bodied organisms, such as anemones, sponges, and tunicates, make their home here, as do Bryozoan colonies (found on kelp blades) and nudibranchs (Bryozoan predators).
Micro Habitats
Floating docks and pilings. Observing seashore life here isn’t restricted to low tides.
Human-made structures attract anemones, various crab species, and, at times, large aggregations of Moon jellies.
The intertidal zone is the ocean shoreline that is exposed at low tide and submerged at high tide.
Pacific Moon jellies at the Port Browning Government Dock, North Pender Island (101006).
Four rules to remember when observing nature’s intertidal life
Step carefully. Although a mussel can withstand the weight of a human, and a barnacle will recolonize within a year after being crushed, be mindful when walking through intertidal zones. Try to stick to stepping on sand and rock (but remember that the seaweed covering the rocks is very slippery).
Restore its habitat. If you turn over a rock shelter to expose the intertidal residents, don’t just drop the rock back in place, but guardedly return it to its original position.
Handle with care. Instead of handling marine life, I use a magnifying glass to observe these fascinating living creatures. Wear rubber gloves to prevent transferring your scent if you must touch them. Regularly wet your gloves with seawater to protect the species’ slimy coat. Return what you’ve handled to the exact spot you found it, and keep their time out of the water to a minimum to lessen their chance of injury. Using a clear plastic pail or bag to scoop water containing various species is an ideal way to observe them up close.
No souvenirs. Photographs are the only souvenirs you should take home.
A more detailed look at some of the SGI’s intertidal species
Sea Stars*
Once called starfish, sea stars are the intertidal species everyone hopes to see. They’re not fish; they don’t have scales, can’t swim, and aren’t edible. They are closely related to brittle stars, sea urchins, sea cucumbers, and sand dollars. Sea stars move about using tube feet on the underside of their arms (i.e., rays). All have the remarkable ability to regrow lost arms; a single ray can regenerate into a whole new sea star. That’s an impressive injury recovery.
Commonly seen sea stars in the SGI:
Ochre star (or Purple star) is the most common sea star found in our waters; various colour hues—purple, orange, brown, and yellow; usually five thick arms covered in small, rough spines; up to 50 cm (20 in) in diameter; favourite prey are California mussels and Goose barnacles. Habitat—Middle and Low intertidal zones to 90 metres (295 ft).
Leather star. The second most-seen sea star in the area; mottled reddish-brown to orangish-grey pattern with soft, leathery surface; up to 30 cm (12 in); typically has five broad, flexible arms; known for its sulphur or garlic-like smell (which may deter predators); swallows anemones, sea urchins, and other soft-bodied invertebrates whole. Habitat—Low intertidal zone to 90 metres (295 ft).
Pacific Blood star. Vivid red or orange colouration with five slender, tapering arms; smooth texture covered in tiny, soft spines (papulae) used for respiration; 10-20 cm in diameter (4-8 in); filters microscopic plankton and organic particles from the water. Habitat—Low intertidal zone to 400 metres (1,320 ft).
Bat Star. Named for its bat-wing appearance; highly variable colour—purple, red, yellow; typically with five short, broad, webbed arms; bumpy texture; diameter to 25 cm (10 in); feeds on plants and animals, dead or alive. Habitat—Low intertidal zone to 302 metres (1,000 ft).
Morning Sun star. This carnivorous predator feeds on other sea stars! Typically grey to yellow to reddish-brown, resembling the warm hues of a sunrise; grows to 40 cm (16 in) across and usually has 11-13 arms; rough-looking texture. Habitat—Low intertidal zone to 420 metres (1,380 ft).
Mottled Star. Often mistaken for a bland-coloured Ochre star, it has longer, slenderer arms with a rough, spiny texture; colour shades vary from orange, brown, and blue-gray to green, purple, or red, with a mottled or speckled pattern; it can grow to 40 cm (16 in) in diameter but is generally smaller; feeds on mussels, barnacles, snails, clams, and other small invertebrates. Habitat—Low intertidal zone to 75 metres (250 ft).
Sunflower star. The SGI’s largest and fastest sea star! Gets its name from its striking bright-yellow to orange coloration, similar to a sunflower’s petals; sometimes a brown, pink, red, or purple hue; typically one metre (39 in) in diameter, with up to 24 arms radiating from a central disc; preys on larger clams and crustaceans, using its strong, flexible arms to pry open the shells, then extends its stomach out to digest the prey externally. Habitat—Low intertidal zone to 437 metres (1,500 ft).
Giant Pink star. Kids on a school field trip called it “Super Star,” measuring 99 cm (39 in) from arm tip to arm tip, larger than any sea star previously recorded in British Columbia. The young naturalists carefully lifted it from the water in Burrard Inlet, took measurements, and returned it to its original location. Typically, a Giant Pink star spans 65 cm (25 inches); its colour is usually vibrant pink to almost white, with a spiny surface and five broad arms; its diet primarily consists of clams, mussels, barnacles, and other invertebrates. Habitat—Low intertidal zone to 182 metres (600 ft).
*Sea Star Wasting Disease (SSWD).
The cause(s) of SSWD are as yet not conclusive. An outbreak of the devastating disease struck the Canadian and U.S. West Coast in the 2010s, resulting in skin lesions, tissue decay, body disintegration, and a mass die-off of an intertidal species crucial to maintaining ecosystem biodiversity. Other die-offs occurred in the 1970s, 80s, and 90s. Learn more about SSWD:
Melting away: The fight against Sea Star Wasting Disease (Canadian Geographic)
Sea Star Wasting Disease (Sea Stars of the Pacific Northwest/Neil McDaniel)
Sea Star Wasting Disease (UC Santa Cruz, Multi-Agency Rocky Intertidal Network/ MARINe)
Ochre stars piled under a rocky ledge covered in rockweed (070205).
Giant Acorn barnacle
“Don’t get around much” would be an appropriate theme song for this barnacle. Adults glue themselves, for life, to a solid surface. Unless a Giant Acorn barnacle attaches itself to a boat hull or a whale, their “getting around” days are over. Its natural adhesive is strong enough to withstand even the most powerful surf and wave action.
Dirty white shell with purple, yellow, or red tissue near its beak-like opening.
Feeds itself by waving 5 cm (2 in) long feathery legs to pull in plankton from passing water.
Males and females can change sex at any time. Measuring up to 8 cm (3 in) in diameter and 12 cm (5 in) tall, the Giant Acorn barnacle is blessed with, proportionately, the longest penis in the animal kingdom, uncoiling outside its shell to up to twenty times its body length.
Habitat—Rocks and docks; mid-intertidal zone to 91 metres (300 ft); leaves a scar when “freed” from a rock.
Crabs
These invertebrates (animals with no backbone) come in a variety of shapes and sizes.
Their internal organs (head, thorax, and gills) are protected by a hard cover, or exoskeleton, called a carapace; all have a carapace, one pair of chelipeds (claws or pincers), and four pairs of walking legs.
The chelipeds, a crab’s most distinguishing feature, are used for holding and carrying food, digging, cracking open shells and warning off predators.
They have a keen sense of distance and direction, aided by two feelers (antennae) and eyesight capable of detecting movement at 20-30 metres (65-100 feet); their eyes can be lowered beneath the carapace for protection.
Steer clear of Red Rock crab; their heavy claws can easily break a finger.
Why do crabs only walk sideways? Because that’s the only way their legs will take them.
Habitat—Tide pools beneath or between rocks, mudflats, under algae, in eelgrass beds, on kelp, and in rocky and sandy areas, from the high intertidal zone to 436 metres (1,430 ft).
Déjà vu
In 1999, North Pender Island scuba diver and exceptionally skilled underwater photographer Derek Holzapfel (naturediver.ca) was diving a crevasse 25 metres (80 ft) below the ocean surface off Brooks Point, South Pender Island, when he encountered a Puget Sound King crab. Nothing unusual.
Six years later, Derek was diving in the same spot and recognized what he thought was the same crab. Possible? A closer look revealed he was wrong. This crab’s arms were as big as Derek’s forearms, and its pinchers were as big as his hands!
It’s a special treat to visit Derek’s website. His stock photographs are breathtaking.
Lewis’s Moonsnail’s rubber-plunger-like egg case, partially covered by sea lettuce (070205).
Lewis’s Moonsnail
This ferocious carnivore bulldozes through sand and mud, preying upon resident clams and other bivalves. It first smothers a clam with its enormous pink, fleshy foot and then dines on the clam’s insides by drilling a hole in its shell near the hinge and sucking out the meaty flesh inside.
Off-white/yellowish shell of rounded whorls; size up to 14 cm (5.5 in).
Drills through its prey’s shell with its radula, a drill-like tongue.
It is known for its unique rubber-like egg case resembling the moon (or the broken end of a toilet plunger); the case or collar is a mix of eggs and sand held together by a mucous secretion, all formed around the moonsnail’s fleshy foot.
When the female has laid her eggs in the spring or summer, she tows the collar to higher ground, moves from beneath it and leaves the eggs—up to 500,000—to hatch six weeks later.
Habitat—Sand, mud, and gravel in low intertidal to 91 metres (300 ft).
A Lewis’s Moonsnail first smothers a clam with its enormous pink, fleshy foot and then dines on the clam’s insides by drilling a hole in its shell near the hinge and sucking out the meaty flesh inside.
Bell-shaped Jellies
Two bell-shaped jellies seen in the SGI are Lion’s Mane and Pacific Moon. Paddlers will identify Lion’s Mane by their large size, reddish-orange-brown colouring, and trailing tentacles, seen rhythmically pulsing near the ocean surface. Landlubbers see the species stranded or dead on many beaches at low tide. Smaller and translucent Pacific Moon jellies aren’t as obvious but are around.
Lion’s Mane.
Largest jelly in the world. Average diameter—50 cm (20 in) with tentacles to 3 metres (10 feet); largest recorded—3 metres (10 feet) and 36 metre-long tentacles (119 feet).
Reddish-orange, yellowish, or pink bell with long, flowing tentacles.
Poisonous—human reaction to the toxins varies from burning pain, rash, allergic reactions, and even death.
Habitat—Found near the ocean surface and stranded or dead on beaches.
Pacific Moon.
Size: Diameter—10-40 cm (4-16 in); height—7.5 cm (3 in).
Translucent, saucer-shaped bell with four horseshoe-shaped gonads/reproductive organs (I’ve seen white, purple, and orange gonads); short trailing tentacles can cause a rash when touched.
Pulses its bell to move, but mostly drifts with the ocean current.
Habitat—Found near the ocean surface. Occasionally gathers in harbours during spring plankton bloom; spawning may occur.
Lion’s Mane jelly alongside my kayak near Blunden Islet, South Pender Island (062320).
My favourite SGI Intertidal Life Viewing
What is the best time of year? Summer—when the tides are near, at, or below zero. *GINPR—Gulf Islands National Park Reserve
Inner Islands
Arbutus Point, Portland Island (GINPR) • Boat access only
The many tidal pools are revealed when the tide drops below 6.5 feet (2 metres); lower is better. The late Dr. Bill Austin, Stanford-trained marine biologist, former Executive Director of The Marine Ecology Centre in Sidney, and co-founder of the Bamfield Marine Station (now the Bamfield Marine Sciences Centre), studied marine life along the North American Pacific Coast for nearly 60 years. When I asked him in 2005 what the best spot was to observe intertidal life in the Southern Gulf Islands, he answered Arbutus Point. He’d catalogued more than 250 species on Portland Island’s east side. Walking along the rocks at Arbutus Point, I’ve seen Aggregating anemones, Shield limpets, Lewis’s Moonsnail, Sitka periwinkles, mussels, Acorn and Giant barnacles, Bread Crumb and Purple sponges, Orange Sea cucumbers, Leather, Sunflower and purple Ochre stars, sea squirts, worms and a variety of seaweeds. Pacific harbour seals and River otters can be seen on the south side of the point.
Pender Islands
Canal Road Midden/Canal Road Bridge, South Pender Island
Access to the shell midden via a short trail next to a roadside cairn on the North Pender Island side of the single-lane canal bridge. The plaque on the cairn tells the story of Xelisen (Helisen), meaning “lying between,” which describes the isthmus that once connected North and South Pender Island. First Nation peoples lived here 2,000 to 6,000 years ago. From their encampment, they harvested food resources from nearby waters and beaches. In the early 1980s, Simon Fraser University archeologists excavated thousands of artifacts from the shell midden. Harpoon heads, bone fishhook barbs, a shell rattle, an antler spoon, spear points, and a chisel were among the prehistoric items found, most dating to 2,500 to 4,000 years ago. At the lowest tides, walk from either side of the road on the west side of the bridge down to the criss-crossed bridge supports. You’ll see mussels and Ochre stars clinging to the wood posts, buried clams in the mud squirting water, Red Rock crabs out for a walk in the shallow shoreline water, and occasionally a Sunflower star. Paddlers hugging the South Pender shore near the bridge will see stars, cucumbers, anemones, chitons, sea urchins, and piddocks.
Gowlland Point/Brooks Point Regional Park/Higgs Beach, South Pender Island
From the peninsula, you may glimpse Southern Resident or Bigg’s orcas transiting Boundary Pass. The conglomerate rock hollows at Brooks Point and along Higgs Beach are excellent places to observe tide pool fishes, crabs, limpets, sea urchins, cucumbers, anemones, chitons, snails, and different species of stars and seaweeds.
Salt Spring Island
Ruckle Park (BC Parks), between Beaver and Bear Points and the campground’s shoreline tidepools.
The rocky cove on the north side of Beaver Point is an excellent spot to see a variety of intertidal species: Six-Rayed and Pacific Blood stars, Flattop crab and Painted anemone, as well as a mixture of seaweeds. The campground’s shoreline tidepools offer an array of invertebrate life, and you’ll likely see Pacific harbour seals, maybe River otters, and possibly a small pod of Bigg’s orcas.
Fernwood Point Beach and Dock
A terrific beach at low summer tides. You can walk along sandy mud flats out to a sandbar (left of the dock) and discover a wide variety of sea life, including the bizarre-looking Lewis’s Moonsnail (see description above). Pacific sand dollars reside under the dock and along the beach, so tread carefully. Live sand dollars are a dark, velvety purple; if turned upside down, they cannot right themselves and eventually die. The off-white shell with a five-leafed pattern of tiny holes is a dead shell. To the right of the dock, the shoreline becomes rocky, creating tidal pools containing hermit crabs and Painted anemones.
Mayne Island
Bennett Bay Beach
Whether you’re a walker, cyclist or kayaker, you’ll end up here—exploring the driftwood-littered beach or setting a course in your kayak for the Belle Chain Islets. This long, sandy beach is the finest on the island. At the lowest tides, the intertidal exploration among the rocks on the south side of Campbell Point is terrific.
Georgina Point Heritage Park and Lighthouse (GINPR)
Low summer tides guarantee you’ll see a plethora of intertidal life. In the tide pools and at the bottom of the bluffs, explorers see Bladder, Soft-shell and Japanese Littleneck clams, Green anemones, Tara’s and Heath’s dorid, Checkered periwinkle, Nuttal’s cockle, Bluespine hermits, Tidepool sculpins, and the list goes on. And Pacific harbour seal sightings are probable, porpoise and Southern Resident and Bigg’s orca sightings are possible.
Oyster Bay
This small rock-strewn beach faces the Strait of Georgia and the mainland mountain range and is protected by an offshore reef. At low water, sandy tidal pools reveal a fascinating array of intertidal marine life: Red sea urchins, Bread Crumb sponges, Bat stars, and various crabs and limpets.
Saturna Island
Winter Cove (GINPR)
Be sure to look down at the colourful marine life in Boat Pass. Below the northeast-facing walking trail, a series of tide pools awaits, but be very careful when climbing down the slippery rocks. Here, you will find Pacific oysters, various clams, at least five species of sea stars, including the Sunflower star, and several anemones. River otters, Pacific harbour seals, and sea lions (winter months) enter the bay to feed.
Russell Reef
Worth a visit whenever the tide is below 3 feet. The first step down to the rocky shoreline is big and requires a cautious descent. The tidal pools seem to go on forever, revealing a host of intertidal marine life—at least six species of crab, Mudflat snails, and sea stars. Rockweed is everywhere.
Galiano Island
Due to the paddling distance to Galiano, I don’t get back to Galiano as frequently as I would like.
Dionisio Point Park (BC Parks) • Boat access only (nearest kayak launch is from the Spanish Hills Public Dock, 1.8 NM to Coon Bay) • Camping available.
Fast-flowing tidal currents in Porlier Pass, reaching nine knots on the flood and eight on the ebb, encourage a rich intertidal life in Maple Bay and Coon Bay. Purple and Mottled sea stars, Orange-Spotted nudibranchs and Lined chitons can be found in the low intertidal pools of Parry Lagoon. At times, large quantities of Smooth Pink Scallop shells litter the beaches. The sand beach at Coon Bay joins Dionisio Point and its Arbutus-studded sandstone cliffs to the rest of the park. Look for California and Steller sea lions (November-May), Pacific harbour seals, and the occasional orca swimming east through Porlier Pass.
Montague Harbour Marine Park (BC Parks)
On the impressive shell middens on Gray Peninsula, you’ll find Pacific Littleneck and Butter clams that seek sanctuary by burrowing beneath the shells and Acorn and Giant barnacles alongside mussels and oysters. Look for Plumose anemones, Ochre and Mottled stars, Red Rock crabs and sea snails like the Sitka periwinkle in the tide pools.
Final thoughts
I have no formal scientific education. I’ve learned about the Southern Gulf Islands’ intertidal world through reading, listening, and observing. I carry printed field guides when hiking and paddling, and capture what I find intriguing with my Samsung S21 Ultra smartphone. Recently, I’ve been using a phone app called Seek by iNaturalist to broaden my knowledge and improve identification accuracy. I cross-reference my photography database with this app tool and my reference books. If you discover errors in this blog post, please let me know. Thanks.
Don’t forget to always look around . . . ahead, sideways, up and down, and behind. It’s the only way to see all that our islands have to offer. Please enjoy yourself with a wondering nature and be respectful. See you outside.
Recommended Resources
The New Beachcomber’s Guide to the Pacific Northwest: Second Revised Edition by J. Duane Sept • Paperback • $34.95 • 416 pages • Harbour Publishing, 2024. While it’s too heavy to carry in my day pack compared to the much lighter 1999 edition, the revised guide has sixteen pages of shell photographs, expanded species profiles, updated text, and an illustrated glossary.
Whelks to Whales: Coastal Marine Life of the Pacific Northwest, Newly Revised and expanded Third edition by Rick M. Harbo • Paperback • $28.95 • 352 pages • Harbour Publishing, 2022. A comprehensive guide featuring a vast array of Pacific Northwest marine life (intertidal and marine mammals).
Marine Life of the Pacific Northwest, A Photographic Encyclopedia of Invertebrates, Seaweeds and Selected Fishes by Andy Lamb & Bernard Hanby • Hardcover • $69.95 • 398 pages • Harbour Publishing, 2005. Superb colour photographs of over 1,400 species allow the reader to recognize virtually any coastal organism.
Ruckle Park campground tide pools, Salt Spring Island (090506).
