SURVEY OF UPPER RATTLESNAKE CREEK, A TROUT-SPAWNING TRIBUTARY OF THE CLARK FORK RIVER (MT), FOR TUBIFEX TUBIFEX

Rattlesnake Creek is a tributary of the Clark Fork River that flows through parts of western Montana and through Missoula. Currently, an effort is underway to increase spawning habitat for bull and westslope cutthroat trout in the Clark Fork drainage. One proposal in this effort includes the modification or removal of the Mountain Water Company dam on lower Rattlesnake Creek that currently blocks fish passage. The removal or modification of this dam would open miles of prime spawning habitat. However, the Clark Fork River is known to be contaminated with Myxobolus cerebralis, the causative agent of salmonid whirling disease. The presence of this parasite in the Clark Fork River has lead to concerns that removal/modification of the dam would allow the parasite to spread into the upper reaches of Rattlesnake Creek, endangering the wild trout populations already established there. Therefore, the objective of this study was to survey the upper portions of Rattlesnake Creek for the presence of the aquatic oligochaete, Tubifex tubifex. T. tubifex is an obligatory host for M. cerebralis and the parasite cannot be transmitted to trout in its absence. An earlier, cursory study by another investigator did not detect T. tubifex in the Rattlesnake, so we conducted a more comprehensive survey of the creek for this oligochaete. Further, these worms were screened for the presence of M. cerebralis triactinomyxons (TAMs; stage of parasite that infects trout)