ASARCO has proposed a mine in the Rock Creek drainage, which supports a resident bull trout population. A Previous Biological Evaluation identified excess fines in spawning gravels as a major problem in the drainage. Watershed Consulting surveyed the drainage from the mouth to the headwaters, concentrating on potential spawning habitats. Substrate and fines, as well as channel stability were quantitatively evaluated. Fish population and macroinvertebrates were sampled based on geomorphic stratification criteria. The preliminary conclusions of the survey indicate that the excess of fines, as identified in the Biological Evaluation, is not a problem. Rather a lack of spawning-size substrate limits bull trout spawning habitat. This is probably due to hydraulic modifications caused by removal of large woody debris in the past. Also, five staff gauges were installed to further describe runoff and low flow distribution in the Rock Creek drainage.
Personnel involved: Igor Suchomel - project management, hydrology, geomorphology Steve Buckley - geology, geomorphology Mike Koopal - fisheries habitat and population sampling
Contact: Bill Thompson, Hydrometrics, (406) 443-4150