Recover a lahontan cutthroat trout metapopulation within the mcdermitt creek basin by eliminating non-native salmonids using a piscicide

Objectives: phase 1(pre-PROJECT) - identify upper distributions of LCT and non-native salmonids (rainbow trout and brook trout) in mcdermitt creek, tributaries of mcdermitt creek, sage creek, tributaries of sage creek, line creek and corral basin creek using EDNA. Phase 1(pre-PROJECT) - identify if pure LCT populations still exist in cottonwood creek and indian creek, tributaries to indian creek using EDNA and that non-native salmonids have not recolonized the cottonwood creek watershed. The mcdermitt basin spans the oregon-nevada border in southeast oregon and north central nevada and contains threatened lahontan cutthroat trout (LCT). The mcdermitt basin is part of the northwest geographic management unit (NW GMU) and is located within the quinn river recovery unit (quinn RU). Historically, a genetically pure LCT metapopulation inhabited many of the streams within mcdermitt basin and are now isolated to a few hundred meters in the upper reaches of sage, line and corral creeks due to hybridization and competition with non-native salmonids. The recovery of lahontan cutthroat trout within the quinn RU can?T occur without the removal of non-native salmonids. The distribution of native LCT and non-native rainbow trout and brook trout were identified as knowledge gaps that need to be addressed to ensure PROJECT success. Collecting and analyzing environmental DNA (EDNA) is phase 1 of this PROJECT. Genetic EDNA was collected from july to september 2025 for section 6 grant funding to process the samples. Samples will be stored until section 6 funding is available for processing in FY 26. Phase 1 - the upper distributions of pure LCT and non-native salmonids will initially be determined using EDNA sampling. Sampling will collect two samples per site with 5 L of filtered water per sample. The genetic lab will pool EDNA from both samples and provide results of detections of rainbow trout, brook trout and LCT to odfw and other partners. Once the results are received electrofishing will be conducted at sites reporting pure LCT to collect tissue for genetic analysis as a second verification that only pure LCT occur and confirming this area should not be included in the piscicide PROJECT. IT is estimated that up to 50 EDNA samples will need to be processed. Odfw or other partners will cover the cost of processing clipped genetic samples. A piscicide treatment could be implemented in july 2026 provided all state and federal processes are complete and staff capacity is available from odfw and partners.