Friday, July 26, 2013

Never Really Know

“I never really know exactly what we will see. I almost always see something unexpected.” I wrote in an email about what to expect to see to a prospective snorkeling trip participant. I am always amazed at how much the life in a river changes with season and time of day, so while I usually have an idea of what I might see, I never really know for sure. Principio falls is a gathering spot for herring and darter in spring. But today the falls contained many more surprises. I didn’t see any herring when I first put my face in the water, but then I didn’t expect to. They are thick in spring and return to the sea after they spawn. But I also didn’t see any darters, which I thought would be here. They always are. Schools of common shiner and black nosed dace danced in the strong current and plucked food morsels from the water with pin point accuracy. White suckers hovered near the bottom and hog suckers shot off into the distance when they noticed my presence. Stone rollers grazed their way upstream. Darters were relegated to the nooks and crannies of smooth bedrock walls in what I think is an example of habitat partitioning. In colder months when the minnows like common shiner are less common, darters dominate the whole stream. In warmer months when other competitors increase their numbers, the darters switch to bedrock where they are better adapted to survive. At least that’s my theory. Juvenile darters hop from cranny to cranny just like the adults. One of the things I love about this spot is watching darter courtship displays in the spring. Now I get to watch the result off that effort and it is reassuring to know they will continue. A juvenile catfish swims under a shallow gap beneath a rock and I worry that it is a flathead. Flathead catfish are invasive predatory catfish, that will likely rid this river of its darters pretty quickly if they are here. I didn’t get a good enough look at this fish to get a positive ID. I surface dive to the bottom and peer into the gap to find a bullhead staring back. Fortunately, the cat wasn’t a flathead. A school of juvenile bullhead catfish swirl in a large eddy silhouetted against the yellow water hue. I didn’t expect all these catfish to be here. Huge river chub swirl on the bottom. A juvenile eel pokes its head out from beneath a small cobble. A school of bluegill and pumpkin seeds huddle in the lee of a large bedrock slab and nibble on me. These fish are typical of lakes and slow moving rivers, not rushing waterfalls. For as many times as I have been here, the Principio today was a completely different river because of its different and unexpected biology. I never really do know.

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