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The Problem Warm Springs National Fish Hatchery located on the Deschutes River, Oregon, is a unique program in the Columbia River basin. The operation of the hatchery is considered pivotal for enhancing salmon stocks to meet tribal trust responsibilities and is also managed to preserve the genetic integrity and characteristics of hatchery and wild fish. Managers are concerned about fall releases of juvenile spring chinook salmon because hatchery fish that over-winter may interact with wild fish. The U.S. Fish and Wildlife Service's review of National Fish Hatcheries practices identified a need to assess the fate of hatchery-reared fish and their potential effect on the aquatic community. Additionally, the National Marine Fisheries Service recommended monitoring and evaluation of ecological interactions between hatchery and wild fish. Quantifying the freshwater fate of juvenile chinook salmon released in the fall from Warm Springs National Fish Hatchery has been problematic. Development of new techniques and adaptation of those techniques has allowed U.S. Geological Survey to respond to this research need. The US Fish and Wildlife Service has funded the U.S. Geological Survey to conduct a study in 2002 and 2003 to investigate the potential effect of hatchery-reared fish released from the hatchery on the aquatic community in the Deschutes River. This project is funded under reimbursable agreement with the U.S. Fish and Wildlife Service.
Objectives The objectives of this study are to determine the distribution of fall-released hatchery spring chinook salmon, evaluate migration behavior, assess microhabitat, and address potential interactions within the wild fish community in the Deschutes River. Methodology The primary tool used to meet this research need is radio telemetry. A sub-sample of the hatchery population is captured after they are volitionally released from the hatchery and enter the Deschutes River. These fish are then surgically implanted with miniature radio transmitters. Stationary monitoring sites like the one shown in Figure 1 and used to monitor the movements of the tagged fish as they migrated through the river. In addition to these sites, mobile tracking techniques using boats and vehicals (Figure 2) are used to investigate areas within the river that fish reside in for long periods of time. This information is used to determine if fish are moving directly out of the river or staying in the river to over-winter and subsequently moving out of the system the following spring. If they stay in the system, the mobile tracking date is used to determine where they are holding and what impact they might be having in the wild fish population.
Highlights and Key Findings In 2000, the pilot study determined the distribution of fall-released fish in the Deschutes River and investigated methods to assess habitat use. Fifty-four fish were implanted with radio transmitters and tracked for 45-75 days. Over the study period, we found that 65% of the radio-tagged fish remained in the Deschutes River, indicating that there were a substantial number of fish remaining over the winter. With the majority of fish remaining in the Deschutes, there could be a potential impact on wild juvenile spring chinook salmon, bull trout, steelhead, rainbow trout, and other resident fish. Habitat assessments conducted during the pilot study at sites where radio-tagged fish were found indicated that these fish select discrete microhabitat. If there is interspecies overlap in microhabitat use and potential antagonistic behavior caused by hatchery-released fish, managers may need to review current practices. However, if there is not much interspecies interactions or overlap in microhabitat utilization, the hatchery-released fish may be able to coexist in the Deschutes River. Where Are We Headed In 2003 The proposed study for 2003 is intended to expand the work conducted in 2000 and further develop the habitat assessment and ecological interactions. The study will focus on determining the distribution of fall-released hatchery spring chinook salmon, assessing microhabitat, and addressing potential interactions upon the fish community in the Deschutes River. Project Contact Noah Adams Email: noah_adams@usgs.gov Publications |
