I spent much of the spring and summer of 2020 during the pandemic at home with my son, who was not yet 2 years old at the time. During that time, I learned, among other things, that there is a time in perhaps every small boy’s life when he realizes that nothing is more exciting than throwing rocks in the water. And so that is what we did. Almost everyday, as I remember, I used to take him to some body of water in order to throw rocks. We lived in Springfield, Oregon, at the time, and we used to visit the Willamette River quite regularly. Clearwater Park was a favorite spot, as well as various locations at Alton Baker Park in Eugene. It was fun to try to find new spots to throw rocks, although it may be that the finding of new spots was mostly for me, for my son probably would have been content to throw rocks in the same place everyday.
The best spot that we found, at least in my opinion, was at Dorris Ranch, a large park in Springfield. Dorris Ranch is located right along the Middle Fork of the Willamette River, and it has lots of trails, but it doesn’t really have any good river access, at least not unless you walk for a while to the east. As you can see in the map below, the main trail in yellow doesn’t really touch the water at all except in one place at the bottom left, and in that place the bank is steep and the current fairly swift.
But one day my kid and I found a new trail, an unofficial social trail, that led south towards the river. As we walked, the old growth Douglas fir changed to old growth cottonwood and then we reached the river, at the spot on the map above where the north bank of the river touches the edge of the image. It was fun because this spot was hidden, because there is a fantastic gravel bar there where shallow water gentle threads downstream, and because this was where I first found the freshwater mussels.
Living Rocks
At the river’s edge, there was a shallow side channel, about 18″ deep layered with large cobbles, and across the channel, there was a almost-submerged gravel bar of small pebbles, where water from the main channel trickles through. I helped my kid across the side channel, onto the pebbles, and I knew we had found the perfect place for rock throwing. We threw some rocks, had a snack and then started throwing some more rocks, as was our routine. It was about then that I noticed the large elongated shell among the pebbles. I picked it up to examine it. It was about five inches long. The outer layer of the shell was a dark black with the edge on both sides peeling away into white and gold layers. The inside was a white-ish color with a hint of purple iridescence. It looked something like this:
At the time I didn’t even know that freshwater mussels existed. As someone born and raised in Oregon, I had long familiarity with the mussels found in multitudes during low tide on the coast. So upon finding this mussel-looking shell among the rocks at this secret riverside location with my rock-throwing toddler — quite far from the ocean — at first I was confused. What was a mussel shell doing here?
But soon enough it became clear that these creatures in fact lived here, in this little lazy corner of the Willamette, because after a brief survey, I noticed mussels that were still alive at the bottom of the river. As the flow of the main channel comes around the gentle corner in the river, water trickles across the gravel bar (visible as a white speck in the center of the photo below) and flows into the narrow side channel. The mussels were congregated in this side channel, clustered around the places where these trickles of water from the main channel entered. The mussel species I had found, I learned later, are called Western Pearlshell Mussels.
I was amazed, fascinated by these creatures. They seemed like living rocks. And indeed they do blend in with the rocks that surround them, their shells similar in color and texture to stones and pebbles. It just seemed so interesting to me, that there were these living stones in the rivers and creeks, just existing, in secret, blending into the cobbled river bottoms. And yet their life cycle is complex, I learned later, and they are entirely dependent on native fish for their reproduction.
Aggressive Parasites
Scientists have studied the similar species of freshwater mussels across North America and Europe for 100s of years. The mussel reproductive process, including for the Western Pearlshell, works something like this. The female mussel lays eggs, which are deposited in her gills. The male releases sperm which drifts through the water and hopefully arrives at the egg-laden gills of a female. With admirable honesty, one writer notes that “we have no clue” how the male and female manage to coordinate this, given that they are only slightly more mobile than stones. Dutch scientist Antonie van Leeuwenhoek first discovered eggs in the gills of mussels, around 1695, and he accurately identified them as larval forms of mussels, but the true extent of their life cycle was still unknown.
After being released from their gill nursery, the young mussels do not immediately drop to the bottom and start living the mussel life. Instead they float through the water and eventually attach themselves to fish, either to their gills or fins. As one writer memorably puts it in North American Freshwater Mussels: Natural History, Ecology, and Conservation:
“The seemingly well mannered and unobtrusive demeanor of freshwater mussels belies the fact that they are aggressive parasites.” Haag, W. R. (2012).
And in fact I found quite a enlarged diagrams and photos that make these tiny infant mussels look like vicious deep sea creatures.
And these:
By 1797 Norwegian zoologist Jens Rathke described the small creatures attached to the fins and gills of fish. But he thought they were different species completely. Although incorrect, Rathke is where the name glochidium comes from, which is still used to this day to describe these immature mussels. Glochis in Ancient Greek meant “point” or “barb,” which these parasites use to attach themselves to the fish. And according to the naming conventions of the 18th and 19th century, the Latin-style ending -ium was added to glochid- to create a new and very scientific sounding word, with “glochidia” as the plural.
The glochidia can attach to any fish, and even non-fish things like sticks and rocks. Some species of mussels can survive on almost any species of fish; others can survive on only a few certain species. Western Pearlshell mussels are thought to use only salmon and trout species as their hosts. Glochidia are released in a mucus-y mass called a conglutinate. There is some speculation that these conglutinates look like something a fish would want to eat, which helps aid in their dispersal. Within six hours of attaching to the fish gill or fin, the fish’s body forms a cyst around the glochidium. While attached to the fish, the glochidia undergo metamorphosis and within a few days or months, depending on the species, they release themselves from the fish and settle on the river bottom as juvenile mussels. Some evidence suggests that as few as 1 glochidium in 1,000,000 glochidia survive the process to become a juvenile mussel. Despite the risks, the payoff is worth it: movement. It is thought that mussels have this extra step in their life cycle because otherwise they would never be able to spread upstream, as the glochidia themselves have no means of propulsion. This secret connection between the glochidia fish parasites and mussels was finally figured out in 1882 by German scientist Franz Leydig.
Here is an image of a “conglutinate” of glochidia in the wild:
Some conglutinates being released:
And here are some rather unsettling images of glochidia cysts on fish:
Revisiting the Mussels
Last summer, 2025, I returned to this secret spot along the Middle Fork of the Willamette near Doris Ranch. I walked along the social trail with my son, who was now old enough to walk on his own, rather than being carried. We walked through the dry summer grass, between the towering Douglas Fir and cotton woods. At the river’s edge, we removed our shoes and waded through the side channel, to the secret gravel bar where the mussels live. Now there is a little bit of an odd dynamic that I am sure many parent experience and it goes something like this. As babies turn into toddlers and young children, the parent sees through their child’s eyes their discoveries, the wonder of nature, of worms and sand and water and leaves. It is a chance for the parent to relive or at least revisit their own childhood. It is a fascinating time albeit challenging too at times. But then the young child continues to grow and the wonder is gone, or at least the wonder gets focused on other things. And it leaves the parents hanging a bit. “But just yesterday it seems you watched a potato bug crawl on a log for 20 minutes!” Anyway, there was a little bit of that going on when we found this gravel bar again. My kid still likes creeks and rivers but throwing rocks was no longer the most fascinating activity in the world.
As long as we were there, though, I was interested in observing the mussels again. What I did notice immediately is that there seemed to be more shells lying around. This suggested more deaths. And Western Pearlshell Mussels while not officially an endangered species, are considered “near threatened” by the International Union for Conservation of Nat, given that populations are declining, likely due to a combination of decreasing water quality and increasing water temperatures. I looked throughout the side channel –where I had found so many before — at first I didn’t see any living mussels at all. Even more empty shells were visible in the water too. Only after several minutes of close observation did I begin to see some mussels that were still alive, their shells closed, hidden among the rocks.
In the five or so years since I had last been to this spot, my art practice had deepened, and I felt I needed to make some kind of art about mussels and I now had developed skills and vision enough to do so. I wanted to capture something of this secret resident of the river, and capture too some of that childlike wonder I felt when I first discovered them with my son. It began with some simple sketches:
And then it became slightly more complicated. And in fact the rough layout of the final painting is apparent in this initial sketch.
I tried a series of studies. In the first study I did, the spacing of the mussels seemed off. Also the “peeling” portions of the shell, where some of the underlying structure was visible, seemed too dominant.
After a few more studies, I went to “full sheet” which is 30 inches by 22 inches. I tried to soften the transitions on the surfaces of the shells. But I pushed the dark values too hard and my “secondary” interest shells – the clam and crayfish shells – were too small and out of proportion.
Finally, it seemed like I had all of the elements in proportion, the values correct. And it told the story I was interested in, shells scattered across the stones, only hinting of the lives that their invertebrate owners once lived beneath the water.
