A remnant population of native Bull Trout Salvelinus confluentus was threatened with extirpation by competition and hybridization with introduced Brook Trout S. fontinalis in Sun Creek, a second‐order headwater stream in Crater Lake National Park, Oregon. Between 1992 and 2005, artificial barriers were installed to exclude nonnative fish, and multiple applications of electrofishing and the piscicide antimycin‐A were used to remove Brook Trout from 14.6 km of stream. Several novel methods were employed, including diver‐directed and trap‐net electrofishing and the use of a portable raceway to hold Bull Trout during piscicide treatments. Electrofishing likely eradicated Brook Trout from a small headwater section of the stream but required more effort (54 person‐days/km) than antimycin treatments (17 person‐days/km) in the same reach to ensure eradication. For eradication of Brook Trout from larger downstream reaches, antimycin treatments applied in consecutive years were more successful than multiple treatments applied within a single year. Brook Trout have not been detected by annual surveys in the project area since 2005. The total effort expended to eradicate Brook Trout from 14.6 km of stream was approximately 138 person‐days/km. Between 1989 and 2010, Bull Trout abundance increased approximately tenfold, and distribution increased from approximately 1.9 km to 11.2 km. These results exemplify the response of an imperiled Bull Trout population after removal of Brook Trout. The large investment of time and resources required to restore small populations like this one may be warranted only for critical population segments with special status or local management importance.Received November 10, 2011; accepted October 31, 2012
A novel application of full-duplex passive integrated transponder (PIT) tag technology was used to investigate movements of individual subyearling Chinook salmon ( Oncorhynchus tshawytscha ; fork length ≥ 60 mm) into and out of tidally flooded salt marsh habitat in the Salmon River estuary, Oregon, USA. PIT interrogation was effective, with mean tag detection ≥ 92%. Salmon movement peaked late during both flood and ebb tide periods, indicating that salmon did not drift passively. Most movements were in the direction of tidal currents, but 20% of individuals entered the channel against the ebbing tide. Individuals occupied the intertidal channel for a median 4.9 h and as long as 8.9 h per tidal cycle, and few were detected moving when water depth was <0.4 m. Some individuals used the channel on multiple successive tidal cycles, and others entered intermittently over periods of up to 109 days. Using an individual-based approach, we characterized diversity of juvenile Chinook salmon behavior within a marsh channel, providing insight into the value of such habitats for conservation and restoration of salmon populations.
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