Barnacles

Below are examples of barnacles you will run across on Oregon’s exposed rocky shores or washed up on the beaches. The photos on this page are from northern Oregon unless noted in the caption. My organization follows Lamb and Hanby (2005). Common names are my choice. I refer to WoRMS for scientific names, and I learn a ton by browsing the natural history riches in Kozloff (1993). Experts cover barnacles in the books, field guides, and online resources at the bottom of the page.

Balanus glandula, acorn barnacle
Acorns are the most noticeable high intertidal barnacle. They’ll inflict a scratch if you aren’t careful.

Zonation on a vertical rock wall. A band of barnacles up top. The mussel bed below.
A band of Balanus glandula up top
California mussels heavily encrusted with acorn barnacles. A few Nucella ostrina in the scene too.
Acorn barnacles are an encrusting force in the mussel beds
Fairly close-in to about forty mature, somewhat eroded, acorn barnacles.
Illustrating the characteristic line between the terga and scuta
Something created an opening in a crown of barnacles allowing you to see how tall and slender they grow when crowded. It's a view from the side
In a crowd, acorns will grow tall and slender
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Balanus nubilus, giant barnacle
Look for giants in the low intertidal or lower.

The shell exterior can be heavily occupied
Giants are large, the biggest barnacle you’ll find on the Pacific Northwest’s rocky shores
Lots of species find shelter in empty giant barnacle shells, here a granular claw crab (or two)
Pisaster finds shelter in a broken shell
Empty shells wash up in the drift, usually in kelp holdfasts | Central Oregon
Youthful architecture graces the shell of a pup
Dead level with a giant
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Semibalanus cariosus, thatched barnacle
If you’re looking for thatched barnacles, mussel beds are an excellent place to start.

Thatched barnacles on a surf-exposed rock outcrop
Thatched barnacles don’t mind a surf-swept setting
Intimate view in a niche in a mussel bed niche
Mature thatched with most of the thatch eroded away
Intimate view of a couple thatched, showing off the thatched look of the uneroded shell
Semibalanus cariosus, always at home in the mussel bed
A large, older thatched whose shell hosts a crowning younger generation
The beak-like operculum and it’s sinuous line is distinctive
Deep in the mussel bed
A mature stand
Several thatched barnacles on dislodged mussels, among other sea wrack
Thatched barnacles are fairly common in sea wrack
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Pollicipes polymerus, gooseneck barnacle (also goose, leaf)
On the exposed coast, goosenecks can be prominent in mussel beds. They can be found below the mussel beds and pioneer higher into the high intertidal where surge and splash conditions allow it.

A rock face with a broad band of Pollicipes polymerus. Swash in the foreground; in the distance, the surf zone, and beyond. Cloudy skies.
A band of Pollicipes polymerus (whitish)
Exposed low intertidal rocks. In the lower left, a gooseneck rosette on bare rock. The intertidal zones are exposed in the background, off to the right.
Pollicipes rosette
A beachscape featuring a high vertical rock in the foreground; in the midground, a sand-filled tidepool and a sandy beach. In the distance, cliffs are topped by sparse maritime forest. Bands of Pollicipes on the high rock in the foreground. Partly cloudy sky.
Looks like bands of successive age classes
Beachscape featuring a closeup of goosenecks and mussels on an intertidal rock. In the mid-ground, swash and beach sand. In the distance, high intertidal rocks and forested slopes. Mostly cloudy sky.
Pollicipes can be prominent in the mussel beds
A dozen California mussels peeking out from a mass of goosenecks.
Who’ll win the battle for space?
Closeup on a Pollicipes rosette. Giant green anemone, California mussels, and more goosenecks are in the background.
Goosenecks don’t mind being photographed at all

Sometimes you’ll see exposed Pollicipes showing off quite a bit of red. I have a sense that red goosenecks are more prevalent in sheltered or low-zone settings, but I can’t say for sure. I wrote about the reddest goosenecks I’ve come across in Pollicipes, Magical in the Morning.

Closeup on a mix of Pollicipes and Mytilus. The goosenecks have crimson areas on the capitulum's soft tissue.
A sheltered mussel bed
Closeup on a cluster of Pollicipes peeking out through a bunch of Laminaria sinclairii stipes. The goosenecks have crimson areas on the capitulum's soft tissue.
Below the mussel bed, nestled among Laminaria sinclairii
Closeup on a mix of Pollicipes and Mytilus. The goosenecks have crimson areas on the capitulum's soft tissue.
The source of red is hemoglobin

Some gulls make a point of exploring exposed clusters of Pollicipes polymerus, and they will sometimes eat them. Large Larus gulls pluck them off the rocks without much trouble. Thus, it’s not unusual to find regurgitated plates, capitulums, and even more or less whole barnacles, including their stalks.

A swarm of gull tracks in the sand at the base of a Pollicipes-covered rock. A detached barnacle capitulum with some stalk attached lays on the sand.
Tracks tell the story
Regurgitated plates and a capitulum with some stalk attached lay on gull-track-dimpled sand.
Evidence
Closeup of regurgitated Pollicipes plates from a loose pellet laying out on wet sand. 15 cm rule for scale.
A regurgitated pellet of Pollicipes polymerus plates

Redtail surfperch are a Pollicipes predator I hadn’t thought of until I found one had eaten these.

Cluster of goosenecks and a few parts in a finger bowl. No scale, but the biggest ones are on the small side.
Found among a redtail surfperch’s stomach contents

You can occasionally find Pollicipes polymerus among sea wrack, but you’ve got to move quick to beat the gulls to it.

A few goosenecks on a detached thatched barnacle resting on the sand in the swash zone. Other hitchhikers include smaller thatched barnacles and a few little browns Chthamalus dalli (I think).
Barnacles on top of barnacles
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References

Gotshall, D. W. 2005. Guide to Marine Invertebrates, Alaska to Baja California 2nd Edition (Revised). Shoreline Press.

Harbo, R. M. 2011. Whelks to Whales: Coastal Marine Life of the Pacific Northwest. 2nd ed. Harbour Publishing Co.

Kozloff, E. N. 1993. Seashore Life of the Northern Pacific Coast. 3rd ed. University of Washington Press.

Lamb, A. and B. P. Hanby. 2005. Marine Life of the Pacific Northwest. Harbour Publishing.

Sept. J. D. 2019. The New Beachcomber’s Guide to the Pacific Northwest. Harbour Publishing.


Online Resources

Biodiversity of the Central Coast’s Crustaceans page is full of great information on Pacific Northwest barnacles. Accessed 01/12/2023.

Friends of Netarts Bay WEBS Crustaceans page. Accessed 01/12/2023.

Pacific Northwest Shell Club’s Crustacean page. Accessed 11/07/2022.

It’s worth scrolling down to barnacles in Common Sea Life of Southeastern Alaska: A field guide by Aaron Baldwin & Paul Norwood. Accessed 01/12/2023.

Cowles, D. (2005). Balanus glandula Darwin, 1854. Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 11/07/2022.

Cowles, D. (2006). Semibalanus cariosus (Pallas, 1788). Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 11/07/2022.

Cowles, D. (2006). Balanus nubilus Darwin, 1854. Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 11/07/2022.

McFadden, M., Helmstetler, H., and D. Cowles (2007). Pollicipes polymerus (Sowerby, 1833). Balanus nubilus Darwin, 1854. Invertebrates of the Salish Sea. Rosario Beach Marine Laboratory. Accessed 11/07/2022.


I updated this page on November 14, 2022