Making my way over and between barnacled, blunt-edged rocks and boulders along the north shore of Bowman Bay, quiet clickings increase in proportion to my pace. Shore crabs in a dozen different colors drop from the rocks on which they rest as I pass by, then scurry to safety. It’s one of several super-low-tide days in late July that expose many sea creature species, some common, like sea stars and anemones, some less so, like sea squirts and encrusting sponges. In my quest to prove that a two-inch long blob clamped tightly to a rock is a sea squirt, I return three times to the same damp, cramped foot wide space between boulders for photographs.
Digital photos in camera, I plead my case to Dr. David Cowles at Rosario Laboratories, a researcher and professor who hosts the Invertebrates of the Salish Sea site and has answered my marine biology creature questions in the past. His reply to the message and photos I email him, “We have a very odd species of sea cucumber here, Psolus chitonoides, that is just that color and size. It holds on to rocks with 3 rows of tube feet on a flat ‘sole’ on the bottom, while the dome-shaped top is covered with burnt-orange or rust-colored plates. It has two openings like a sea squirt-one for its mouth and one for its anus. It doesn’t usually live as shallow as the intertidal zone, but can be found at a minus tide. When it is feeding under water it has a beautiful circle of reddish, branching tentacles around its mouth.” As much as I hoped he was wrong, photos and other evidence force me to concede defeat.
My beachcombing adventures at Bowman Bay weren’t without danger. The first time I ventured out wearing stiff-soled shoes, which led to several bloody barnacle scrapes on my arms that left scars. During my second trip, I lost track of time and the incoming tide. Heading east towards the sandy beach and parking lot at the park, I didn’t realize until I rounded the last big bend before the shore how high the tide had climbed. I was forced to walk through a short section of nearly knee-deep water atop the already slimy, seaweed-covered rocks.
While scrambling across rocks and boulders, I spent a lot of time photographing, and little trying to figure out what I was seeing. So I didn’t realize until I went through the digital downloads that I’d stumbled upon what should have been obvious: a pink sea squirt (Cnemidocarpa finmarkiensis) commonly known as a Broadbase tunicate with conspicuous x-marks-the-spot siphons, possibly several of the colonizing kind, and maybe even an invasive type (Didenmum vexillum) in addition to encrusting sponges in different colors like red, yellow and gray.
The most plentiful species of the day award belonged to the scientific classification Brachyura, the true crab. I consulted Gregory C. Jensen’s book Pacific Coast Crabs and Shrimps to distinguish between species. Based on the variety of colors, I thought I’d seen about ten different types of shore crabs, but according to the author, there are only three (p 13), “Shore crabs typically have squarish carapace and fairly large eyes, and are considerably faster and more agile out of water than most other crabs. All three of the common Pacific coast species live fairly high in the intertidal zone and can be found in a surprisingly wide range of habitats and substrates.” Their diet consists of “smaller animals” as well as “diatoms,” and “algae” that they scrape off the surface of rocks. And, in fact, these were all members of two species, Purple shore crabs and Green shore crabs, the primary difference being the hair (setae) on the Green’s legs versus the nude legs of the Purple’s.
In addition to shore crabs, I observed and photographed three other species
With the four crab species I’d seen previously at Cornet Bay, my observed Deception Pass State Park crab species rose to nine.
Beachcombing at Bowman Bay is possible only during extreme low tides (-1.5 feet or less) that occur during daytime hours on limited days from May through August, which limits your opportunity to about 30 days each year. And traipsing half a mile from the parking lot to the point between Bowman Bay and Sharpe Cove across wet, super slippery, barnacled rocks isn’t for the faint of heart. My advice: wear a pair of old minimalist or swim shoes that have about an eighth-inch thick sole. To reduce the chance of scrapes, wear long sleeves. Bring a friend. And if you have kids under ten, skip the activity altogether. You will find plenty of shore crabs along the westernmost part of the beach without having to brave your way across the rocks. Lastly, do what crab expert Dr. Jensen recommends (p 2), “When looking under rocks, always turn them back to their original position while taking care not to crush the animals underneath. A good rule of thumb is not to flip over rocks that are too heavy for you to replace gently under control. With proper care, our beaches can continue to offer the thrill of discovery for generations to come.” Hear, hear!