Interesting tides and reads

This post is by Randal Mindell, leader of the CVN Shoreline Group, from an email to members of the group on April 15.


Hope this finds you all well. We just passed through a great set of spring tides over the weekend.  I know some of you got out there to enjoy them. This email will recount some of the interesting things out at this time of year as well as some recent literature that might be of interest. Remember you can always stop by (and contribute to) the group’s iNaturalist page to check on more than 1000 local observations and almost 270 shoreline species.

Intertidal Spring

Group members Roxanne and Mary-Lynn were keeping an eye on all sorts of echinoderms in the Willow Point area. In addition to watching as giant leather stars loitered and purple sea stars consumed limpets, they caught sight of the giant pink sea star, Pisaster brevispinus. These can grow up to 65 cm in diameter. I’m pretty sure the one at Willow Point on Friday was close to that boundary. Apparently it bulks up on sand dollars, geoducks and giant acorn barnacles. In the picture below, note the boots and purple sea stars for scale:

Giant pink sea star (Pisaster brevispinus)

Mystery Eggs and Shorebirds

If you look around sand bars at this time of year, you might catch these 1-2 cm gelatinous sacs of spirally arranged eggs. For years these had baffled me. I assumed they belonged to a type of polychaete worm because I had seen something similar around Boundary Bay that was found in association with the Pacific Lugworm. However, a scientist from California who specialized in marine gastropods pointed out that these in fact belong to the Albatross aglaja, Melanochlamys diomedia. The organism that lays them is a little black peanut-shaped marine slug. He is particularly interested in any observations people might have about birds that might feed on these egg sacs. If you are at Kye Bay, Seal Bay, Williams Beach or elsewhere and you see these and any birds feeding on them, you should record your observation.

Recent Publications

Like some other group members, I love the field guide called Between Pacific Tides. The original edition was written by Ed Ricketts and coauthors. Ricketts was the inspiration for the “Doc” character in Steinbeck’s Cannery Row. Earlier editions of Between Pacific Tides have a forward by Steinbeck which draws on shared experiences of the two from past marine biology expeditions (see Log from the Sea of Cortez). Anyways, Ricketts travelled to Comox and other locales in the 1930s. These natural history expeditions were recently reviewed in the Archive of Natural History journal. You can find an accessible preprint here.

Plainfin Midshipman

If you head out to cobbly, bouldery shores at this time of year, you might hear the mysterious sounds of the plainfin midshipman. This is an intertidal fish which can survive quite a long time without air. Like the penguin, this species finds males often responsible for the care of developing eggs. This recent paper (abstract only) shows how males in the species deal with the respiratory stresses of the intertidal.

History and Significance of Mariculture on the West Coast

We hear often about the Garry Oak ecosystems as an example of the historical landscape management for indigenous food systems. Along the shorelines of British Columbia is a record for food production systems stretching back just short of 12,000 years. This paper uses an example from Quadra Island to show changes in productivity and size of the giant butter clam over this large expanse of time. The authors point out that this method of mariculture was sustained over millenia at high levels of productivity and posit it as an example of the technology required for sustainable food systems going forward.

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