"I dipped my green net and held it on the bottom of the Swan River. It was mid-October, and I was taking part in a field course exploring watersheds in Montana. I could feel the force of the water as I pulled the net out to inspect what I caught. Flopping nervously in the bottom of my net were two small brown fish. I dropped them into a glass jar to show my instructor. She told me the two specimens were common in western Montana's rivers, and were both slippery sculpins. I returned them to the river without much thought.
It wasn't until a few months later that these small fish grabbed my attention again. While I was flipping through the newspaper I saw that a new species of sculpin had been discovered in the Clark Fork River basin. The article said that sculpin often develop special traits unique to the places where they live. I wanted to take a second look at these fish that I had disregarded the first time around. As it turns out, sculpin are pretty interesting fish. They are genetically diverse, have developed some incredible adaptive traits, and their mannerisms make them perfect organisms to study the health of our waterways.
Containing over 756 species ranging from marine to freshwater, the sculpin family is huge. Montana has six known species, but only two are common, and they're separated by the Continental Divide. West of the divide is the Columbia slippery sculpin; east of the divide is the Rocky Mountain sculpin. It takes an expert to distinguish between the two species, which look almost identical: mottled brown skin, spiky fins and weird bulgy eyes.
Freshwater sculpin play a large role in their river ecosystems. They are an important food source for many fish, birds and mammals. They also control the population of other fish by feeding on their eggs. Yet another way sculpin influence their river ecosystems is by hosting parasites which can carry disease and impact the health of individual fish and other animals.
Rivers and streams rise and fall throughout the year. When these changes occur, organisms can be trapped in isolated pools. Since the water is not flowing in these pools, they cannot absorb oxygen and become hypoxic, meaning that the oxygen content is extremely low. Hypoxic environments can also occur in areas with high agricultural runoff. Hypoxia can be a major problem for fish because they, like us, need oxygen to survive. Researchers at the University of British Columbia found that the brains of sculpin in hypoxic environments had higher levels of lactate dehydrogenase, an enzyme that allows cells to produce energy without oxygen. They linked the high levels of this enzyme to sculpins' survival in hypoxic environments.
We love our Montana rivers. It is important for us to keep our river ecosystems cold, clear and connected. To evaluate the health of these ecosystems, scientists often use salmonids, which generally migrate over the course of their lives, moving from streams to rivers or from rivers to lakes. Sculpins, on the other hand, stay in a much smaller area. Their nest sites are very sensitive to changes in flow and sediment levels. These two traits make sculpin a better indicator species than salmonids. Unlike salmonids that may carry contaminants from other sources, sculpin could be used to easily pinpoint areas of disturbance in a habitat.
When I yanked those poor slippery sculpins from their riverbed homes I had no idea about their adaptability or their potential as an indicator species. Maybe because they are so common and weird-looking and are of little value to commercial fishermen, they are overlooked. But these little fish can play an important role in improving restoration and conservation work in our rivers."
(Broadcast: "Fieldnotes," 4/26/15. Listen weekly on the radio, Sundays at 12:55 p.m., or via podcast.)
