Low summer discharge in the Lostine River can be exacerbated by irrigation withdrawals. In some years the concurrent needs for irrigation water and instream flow for fish exceed available water, and sections of river have been completely dewatered. Since the 1950s, numerous assessments have identified low stream discharge as having negative effects on fish populations. Specifically, low discharge and diversion structures can prevent upstream migration of adult Chinook salmon. This poses a serious threat to the reproductive success of these salmon. Basic information on the migratory behavior and ability of adult Chinook salmon is needed to evaluate this low-flow issue.
Goals & Objectives
The Nez Perce Tribe Department of Fisheries Resources Management and the Freshwater Trust proposed a study to provide irrigators, fisheries managers, funding entities, and other decision-makers with relevant information to address low summer flow issues in the Lostine River. Clarifying fish passage concerns and needs was a priority. Based on that goal, we developed three study objectives:
- Monitor the migration of spring Chinook salmon as they move through the Lostine River, including behavior at irrigation diversion structures and in low discharge reaches of the river.
- Estimate instream discharge necessary to allow spring Chinook upstream passage through the Lostine River to vital spawning habitat.
- Monitor and identify the final fate (spawning locations) of spring Chinook salmon in the Lostine River relative to their arrival timing in the river, stream discharge, and water temperature.
Use of Radio Telemetry
To accomplish these study objectives, we use radio-telemetry techniques to monitor the migratory behavior of adult spring Chinook upstream from the Lostine River weir. Radio telemetry has a long history of successfully tracking the movements of migrating fish. Radio telemetry is well suited for shallow, turbulent, low-conductivity streams like the Lostine. Radio receiving antennas do not require contact with the water. Hence, they can be used to search large areas and track highly mobile species like salmon. Radio tags can provide easy identification of many animals at the same location and time. Fish movement can then be correlated with environmental or habitat variables.
Project Status & Benefits
This is an on-going project that began in 2008. The Nez Perce Tribe is actively partnering with the Freshwater Water Trust in implementing this project. Information is also disseminated to the Oregon Department of Fisheries and Wildlife, Grande Ronde Model Watershed, and other co-managers.
The empirical movement data generated in this study provide a foundation for identifying problem areas and prioritizing and evaluating restoration. For example, we verified improved passage time for adult Chinook following the rehabilitation of the City of Lostine Diversion. We are also using telemetry data to evaluate the efficacy of minimum discharge agreements. The project also provides near real-time information to inform timely management decisions, such as whether to transport adult fish around low-discharge sections of river or allow natural migration.