I was a little better prepared for mudflat exploration at the end of the second day of the workshop at the Filberg Lodge in Comox, British Columbia. After my experience on Saturday, I wore my rubber boots and was ready to spend an hour or so out in the fine muck, gravel and clam shells. After being cooped up inside for the better part of the day it was great to poke around and see what I could find on the flats.
Most of the shells on the flats in this part of the Comox Bay belong to the Japanese Littleneck Clam (Venerupis phillippinarum) although I did find several more Bent-nosed Clams as well. The Japanese Littleneck, like the name suggests, is not native to British Columbia. When Japanese Oyster (Crassostrea gigas) spat was introduced in British Columbia as early as 1914, the seed of the Japanese Littleneck came with it. Since all bivalves reproduce through broadcast fertilization (sperm and egg mix in the water), their larvae are free floating and spread wherever the currents take them. Efauna BC lists a whole host of the other marine organisms that came with the Japanese Oyster.
I started picking through shells trying to find some that weren’t covered with barnacles or stained with mud and algae. It was fairly challenging but eventually I did find a couple of shells that were good representatives of the Japanese Littleneck Clam.
The diagnostic field mark of this species that can be used to easily separate it from the Native Little Neck (Protothaca staminea) is the distinctive purple colouration at the posterior margin. Over time this marking becomes faded and I had to look at several before I found a shell that was clearly marked with purple inside.
Other field marks that can be used to distinguish these two similar looking clams are the elongated shape and the mountain range like patterns on the outer surface of the shell of the Japanese Littleneck. Native Littlenecks tend to be rounder and mature specimens lack the patterns on their surfaces.
I was glad that I had worn my gumboots since the mudflats were very wet and very muddy. The flats had more secrets to share, but those will have to wait for another day.
Beach explorers might want to consider Rick Harbo’s Shells and Shellfish of the Pacific Northwest, as a valuable resource.