The meaning of By craig milewski
fish bones
hen I was a graduate student in South Dakota, studying the population dynamics of smallmouth bass in lakes, I used to frequent the quiet shoreline of a large wetland known as Mud Lake. Though the name doesn’t sound enticing, to an overworked graduate student, the towering cottonwoods on its edge were a shady haven on hot summer days. At the time, the writings of Aldo Leopold were a small but important part of my studies. I was impressed by the way he linked minute observations of an organism to grander issues of land use and ecological health. So when I made my weekly pilgrimage to Mud Lake, more and more, I found myself practicing those same kinds of observations. The mud flat fringing the wetland was a convenient travel corridor, not only for me and my dog, Buck, but also for others. All kinds of animal tracks were visible in the muck: raccoons, muskrats, skunks, mink, turtles, deer, great blue herons, ducks, geese, frogs, crows, grackles, and other humans, too. The human tracks, like mine, suggested somebody out for a stroll: the pace appeared contemplative, and the pauses and turns hinted at curiosity. Reading animal tracks and signs, including humans, were part of the practice. While on one of those weekly walks, I reached down and picked up a bone – a fish bone. I was surprised: I’d never seen fish swimming in this water before. How did they get here? Then I wondered whether my surprise was warranted. I found more bones, mostly vertebrae and skulls. The bone I held in my hand was an operculum, or gill cover. Some of the skulls were partially intact. All were carp and all were on the small side, which suggested the dead fish were about the same age – probably about two years old. How interesting. And why only carp? Were they the only ones to colonize this wetland or just the last to survive? I looked about the perimeter of the lake’s small basin for answers. A culvert beneath
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LEFT: Craig Milewski amidst a stand of trees in the Smitty Creek Watershed near campus. ABOVE: An example of a dead carp.
the gravel road, though high and dry and distant from the wetland, was part of the puzzle. I knew that a few years prior the landscape was completely saturated – heavy precipitation filled wetlands, aquifers rose, and roads flooded and washed out. And I knew fish are quick to colonize, swimming over the surface of the land in films of standing water into the flow of rivers and streams. Large wetlands just like this one emptied torrents of water down creek channels into permanent lakes and rivers. But now the land was like a sponge drying on the kitchen counter, and what was once a wetland was turning into a mudflat. There was another clue. The sharp odor of the water’s rich productivity and the mudflats’ decomposing matter hung in the warm air. That nutrient-rich water caused a severe bloom of blue-green algae typical of lakes in intensively farmed land – but in winter, I strongly suspected that the shallow water combined with decomposing organic matter would rapidly deplete the oxygen, and fish would suffocate and die. I looked at the creamy white operculum resting in the palm of my hand, and rendered my judgment on the cause of death: winterkill. I know this explanation is likely cor-
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rect, but it is very much incomplete. A complete answer would include the effects of water cycles on the wetland hydrology of this great prairie in the middle of North America, and how these wet and dry cycles are driven by the oscillations of El Niño in the far, far Pacific Ocean. Twenty-two years later, I am still inspired by Aldo Leopold, and pay homage to his claim that “the objective is to teach the student to see the land, to understand what he sees, and enjoy what he understands.” This claim includes the opportunity to honor the natural world through acts of quiet contemplation – an essential part of the experiential learning that we champion at Paul Smith’s, and an essential step toward lifelong learning. And as I am inspired by Leopold, I encourage students to be careful observers of the world around them and, wherever they go, be able to hold in the palm of their hands a small piece of the ecology of place, and to contemplate its full story.
» Craig Milewski is an associate
professor in the School of Forestry and Natural Resources. He specializes in fisheries, stream ecology and watershed management.
PORTRAIT BY KENNETH AARON
Sequel | Summer 2011
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