Patrick Norton, Crystal Springs Partnership, July 18, 2018
Recently our family was on an outing with some friends to Reed Canyon, the uppermost source of Crystal Springs Creek, and as usual, I was on the lookout for one of my favorite denizens of the local waterways. When we came to the dam and the viewpoints over the fish ladder I spotted a mussel shell on the downstream side. What I first mistook for the eroded outer surface of the shell turned out to be the shining inside. Just a shell, probably washed down from the lake above where they have been identified before (and see blog post here) but it was partially buried in the sediment in the manner of a live one, so it is possible that it was a resident at that location previously.
The particular freshwater mussel genus here (the particulars of the species involved are currently under taxonomic review) is Anodonta, or floater mussels, though I could not be really sure of the ID from this sighting. There is a population of another type, Margaritifera falcata, the western pearlshell, in the main stem of Johnson Creek, and also in the Willamette, but they favor faster flow and rockier bottoms and none have ever been located in Crystal Springs Creek. Anyhow, we saw one probable Anodonta in the first pool below the downstream side of the dam at the fish ladder at Reed Lake. It was probably washed down from the lake after expiring (these mussels only live ten to fifteen years, as opposed to the western pearlshell's 150+ year lifespan). Sorry, no photo- didn't have the telephoto lens with a polarized filter.
Recently our family was on an outing with some friends to Reed Canyon, the uppermost source of Crystal Springs Creek, and as usual, I was on the lookout for one of my favorite denizens of the local waterways. When we came to the dam and the viewpoints over the fish ladder I spotted a mussel shell on the downstream side. What I first mistook for the eroded outer surface of the shell turned out to be the shining inside. Just a shell, probably washed down from the lake above where they have been identified before (and see blog post here) but it was partially buried in the sediment in the manner of a live one, so it is possible that it was a resident at that location previously.
The particular freshwater mussel genus here (the particulars of the species involved are currently under taxonomic review) is Anodonta, or floater mussels, though I could not be really sure of the ID from this sighting. There is a population of another type, Margaritifera falcata, the western pearlshell, in the main stem of Johnson Creek, and also in the Willamette, but they favor faster flow and rockier bottoms and none have ever been located in Crystal Springs Creek. Anyhow, we saw one probable Anodonta in the first pool below the downstream side of the dam at the fish ladder at Reed Lake. It was probably washed down from the lake after expiring (these mussels only live ten to fifteen years, as opposed to the western pearlshell's 150+ year lifespan). Sorry, no photo- didn't have the telephoto lens with a polarized filter.
View of waterfall (L) with live mussel at right, Deeper part of pool is to he right. Then we were at the little pool above the waterfall fed by the pipe from the lake. The output is hidden in the cobbles and finer sediment, but you can see the water welling up. A week or so ago my daughter Samara and I were there and she spotted a nice example of a floater mussel shell (empty) near the north edge. It was interesting, but not proof that there were live mussels in this little pool perched above a waterfall. This Sunday I didn't see that shell but found a live floater just by the waterfall itself (see photo) and then Samara found a feeding midden on a rock at the east edge of the top of the waterfall. There were raccoon tracks in the mud at the other side, by the chain embedded in the concrete. My friend grabbed the mussel and I photographed it (please don't do that- it stresses the mussels to be exposed to air, higher temperatures, and threat of death) and handling them is prohibited by Oregon law- but he did not know it was alive, and neither did I! I assumed it was an empty shell until I held it but it was alive, with the foot and siphons retracted to be sure, but complete and just waiting for death or to be put back in the water. We put it back and a minute later it buried itself in the sediment.
For beautiful colors of both the growth rings and rays, the Floaters (genus Anodonta spp.) have no parallel among the western freshwater mussels. Approximately 3.5 in (9 cm) length. Right side (the foot comes out near the lower left margin).
I couldn't figure out how the young mussels got there. There are sculpins of some sort or other in the pool, which are a reputed a host species, but that leads to the question of how the sculpins got there in the first place. I did find one reference on the internet of the Paiute sculpin using its pectoral fins to climb a waterfall in the Yellowstone River, but that seemed a long shot.
The left-hand side. More beautiful? I'm not sure, Same individual.
Then my friend pointed out that they both probably came from the lake via the pipe. Occam's razor states that, all things being equal, the simplest explanation is the most likely one. The young sculpin (carrying mussel larvae or not) and/or the immature mussels, probably got there via the pipe from Reed Lake which is resupplied with mussel larvae (glochidia) by Coho salmon, three-spined stickleback, one or more sculpin species, and possibly other fish that are host to Anodonta glochidia, via the fish ladder. Freshwater mussels are not immobilized throughout their adult lives by their own sticky threads as saltwater mussels are adhered to rocks, and although freshwater mussels can use their extensible foot to move through the substrate to find better conditions for filter-feeding, they probably travel only a few meters in their lifespans. So, to expand or even to maintain their range in a watershed they rely on more mobile animals; they hitch a ride on the gills or fins of fish.
Location where a raccoon (probable) has fed upon mussels beside the waterfall below Reed Lake. Several fractured shells are visible.
My daughter Samara then found a feeding platform used by a predator of freshwater mussels on the far side of the waterfall. There were several broken shells both above and below the uppermost rock, and with raccoon tracks visible in the mud of the near shore, it seems that the culprit was a raccoon instead of a mink, otter, or muskrat, all of which eat mussels and have been seen in the canyon and which are known to consume freshwater mussels.
Three-spined stickleback with glochidia on its gills (too small to see). Anyway, you get the idea. Painting by author. To see more about the life-cycle, ecological importance, and sheer beauty of western freshwater mussels please see these links:
Xerces Society PNW mussel book
OregonLive mussel article
2017 Freshwater Mussel Rescue and Relocation
These mussels, aside from being fascinating creatures in their own right, and, by far the largest fraction of animal biomass in many stretches of the creek, do an enormous favor to salmon, trout and steelhead by clarifying the water by their filter-feeding of fecal matter (mostly duck and fish poop) and other suspended matter from the water column, thus simultaneously clarifying the water so that salmon can find their prey, and also reducing water temperatures (clouded water absorbs more heat from sunlight than clear water). In turn, native salmonid species transport mussel glochidea throughout the watershed, including upstream where the mussels could not themselves colonize.
Anodonta mussels, a juvenile Coho salmon (a host species) a river otter (predator species) and Northern casemaker caddisfly larvae and Western brook lamprey ammocete (juvenile), co-inhabitants of the creek. Detail of painting by author. Copyright Patrick Norton 2018.
So I hope you keep an eye out for these marvelous inhabitants of the watershed whenever you visit the creek. The live individuals are usually very difficult to spot, and if you see a symmetrical shell under 1.5 inches it is a non-native Corbicua clam (especially common below Westmoreland Park) but they are there in the tens of thousands (in some stretches of the creek). And as they are filter-feeding most of the hours of the year, consider the clarity of the water to be significantly dependent upon these hidden marvels of the creek.
RSS Feed
