Juvenile Trout Study |
Fish Tales: An Update on the Juvenile Trout Project Martin Koenig Although the sun was unusually bright for a March morning, the air still had the familiar chill of winter in the valley. It was as though spring had already begun to arrive, chasing the ephemeral blanket of snow from the valley floor. Before I began the long and tedious drive back to Utah State where the rigors graduate student life awaited me, I thought I would take a casual glance at Fox Creek before heading over the hill. As I reached the small tributary gliding slowly under the 600 South bridge, it became all too obvious that the pair of sandhill cranes in the distant field were not the only travelers to arrive a bit early this year. Almost a year has gone by since my arrival on the Juvenile Trout Project. Over the past eleven months, the Juvenile Trout Project has made significant steps towards finding those elusive answers to questions about the valley’s trout. Beginning in August, 2004, several reaches of Teton Creek, Fox Creek and the mainstem Teton River were sampled for juvenile trout. Later in October last year, a crew on loan from the US Forest Service Rocky Mountain Research Station in Logan, Utah completed a second round of trout sampling, this time with more locations added to the previous sites. The goal was to get an initial idea of how juvenile trout might be spread throughout the valley floor, and what species are dominating. The results of these initial surveys show some interesting trends. Eastern brook trout (EBT) were found in all reaches of all streams, indicating that they have widespread presence throughout the valley. Eastern brook trout made up a significant portion of the catch in all streams, but dominated the catch from the upper Teton River almost exclusively. Yellowstone cutthroat trout (YCT) were also present in all streams, but only in very low numbers. Rainbow trout (RBT) and their hybrids (HYB) were found to have a strong presence only in Fox Creek. Recently hatched trout, or young-of-the-year (YOY) that were born that summer were present in only a few locations. “Unnamed Creek”, a small spring creek tributary to Teton Creek, contained the highest percentages of YOY fish. Yellowstone cutthroat trout have precipitously declined in recent time throughout the Teton valley in recent time. Understanding the distribution of juvenile Yellowstone cutthroat trout and the patterns that govern this distribution will be key to developing recovery strategies for these native trout. The 2003 survey data reveal that only Fox, Teton and Unnamed Creek held YOY fish. In the upcoming season, the Juvenile Trout Project will expand its reach to include other tributaries to strengthen our understanding of where juvenile cutthroat are, and why. Whirling disease has long thought to be factor affecting trout populations in the Teton River and its tributaries. With help from the Idaho Department of Fish and Game Eagle Fish Health Laboratory, ten sites were tested for the severity of whirling disease infection. Like many had suspected, whirling disease is present in much of the valley. Results from this first round of tests indicate that whirling disease severity is highly variable throughout the valley. In addition, spore counts from the experiment suggest that whirling disease may not be responsible for the large declines in trout populations throughout the valley, but perhaps only in some locations, such as lower Teton Creek (Steel Bridge). When compared to other streams in Idaho heavily affected by the parasite, the Teton River shows low to moderate numbers of spores per fish. Before any firm conclusions can be made regarding the role of whirling disease, more data needs to be collected. Next month, a second round of tests will focus more heavily on spawning tributary streams where juvenile trout are most vulnerable to the disease.
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