Hermosa Creek Workgroup Meeting 5 Summary August 5 2008 Draft

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limestone provides minerals necessary for skeletal growth. Hermosa Creek is accessible by road, which facilitates transporting fish and constructing barriers in the stream, and it lies mostly on public land. Brook and rainbow trout were stocked in Hermosa Creek over the years. In the past, any cutthroat was considered a native cutthroat, so those that were stocked were typically hybrids or non - native species. The result is that native cutthroat have been replaced by other species. Samples taken in 2004 and 2007, the last two sample years, found that 80 percent of the fish in the creek were brook trout, which are technically a char rather than a trout. Brook trout spawn in the fall and thus are able to out -breed the native cutthroats; in addition, they are more aggressive in competing for food. Natural barriers in the creek and its tributaries will keep non - native species from invading the headwaters after the project. Some cutthroat trout may swim downstream after the reintroduction and hybridize with rainbow trout, but the non - natives will not be able to move upstream. Key to the effort is establishing a man -made fish - migration barrier across a steep, narrow stream section. Such a barrier was constructed by the Forest Service in November 2007 just below Hotel Draw, but it was subsequently destroyed during high waters. It will be rebuilt, but the exact date is not known. It will have to be studied carefully to establish what went wrong the first time so the new barrier will be more durable. Jim said re- establishing the native Colorado River cutthroat trout in Hermosa Creek will require chemically treating the headwaters with rotenone, a botanical fish pesticide (piscicide), to kill the fish currently in the headwaters, although some fish may be salvaged and moved to below the fish - migration barrier before the treatment. After the treatment with rotenone, the waters will be detoxified. Then, by electrofishing, DOW biologists will verify that all fish have been killed. Finally, the headwaters will be restocked with the native trout. Jim said the use of rotenone is controversial because it is a toxin and no one likes the idea of poisoning fish. However, it appears to be the best method available to establish a site where the cutthroat trout can be reintroduced. Electrofishing has been tried but with little success. Rotenone will be applied at a rate of 2 parts per million for about two hours. It will take about two days to kill all the fish. The treated water travels downstream to the migration barrier. Potassium permanganate is applied at the barrier to detoxify the waters. The creek is monitored downstream through the use of fish in live cages. Fish will be placed upstream of the barrier and their health will be monitored for 24 hours to make sure the stream has been successfully detoxified. If all goes well, Colorado River cutthroat trout from a genetically pure brood stock originally collected from the Piedra River Basin will be reintroduced upstream from the barrier about six weeks after the treatment. The weaknesses in the plan, Jim said, are the barrier itself, which must be in good shape, and the complexity of the drainage. With a drainage so complex, the treatment might have to be applied twice. He explained that rotenone is an organically derived pesticide made from a tree root. It works only on gill- breathing animals, blocking the biochemical pathway to oxygen use at the celullar level. It degrades within about 48 hours. Rotenone is considered very safe for humans; it does not cause cancer, birth defects, reproductive dysfunction or genetic mutations. It does not harm birds or other wildlife that may eat the killed fish. It will kill invertebrates in the water, but they usually recolonize from areas downstream within six 14