ScholarWorks at University of Montana

Could Silver Bow Creek tributaries serve as source populations to recolonize Silver Bow Creek?

A remediation goal in Silver Bow Creek is to restore trout populations which provide recreational angling opportunity and are an indication of ecosystem recovery. Remediation has been in progress since 1998. All of the mainstem fish populations were lost as the creek received more than a century of copper mine tailings. Several tributary fish populations survived, including genetically unaltered westslope cutthroat trout Oncorhynchus clarki lewisi in German Gulch. In 2009, we tagged 977 fish (259 westslope cutthroat trout, 664 brook trout Salvelinus fontinalis, 54 longnose sucker Catostomus catostomus) with Passive Integrated Transponder (PIT) tags in three tributaries to Silver Bow Creek; German Gulch, Brown’s Gulch, and Blacktail Creek. Stationary antennas at tributary confluences continuously monitored the timing and direction of fish movements between Aug-7 and Nov-15, 2009. In German Gulch 7.4% (n=256) of tagged westslope cutthroat trout and 8.0% (n=158) of tagged brook trout moved into Silver Bow Creek. 23.1% (n=169) of the brook trout tagged in Brown’s Gulch moved into Silver Bow Creek. Once they moved into the mainstem, nearly all fish remained in Silver Bow Creek throughout the study. In Blacktail Creek, only 1.1% (n=350) of the fish tagged were detected in Silver Bow Creek. Of 54 longnose sucker tagged, none moved into Silver Bow. German Gulch and Brown’s Gulch trout populations may provide an important population subsidy to Silver Bow Creek’s nascent trout population. Blacktail Creek’s relatively large population of brook trout may be functionally disconnected from Silver Bow Creek, and may not provide the same benefit to upper Silver Bow Creek.