Steven E. Jacobs

Seasonal Movement and Distribution of Fluvial Adult Bull Trout in Selected Watersheds in the Mid-Columbia River and Snake River Basins

From 1997 to 2004, we used radio telemetry to investigate movement and distribution patterns of 206 adult fluvial bull trout (mean, 449 mm FL) from watersheds representing a wide range of habitat conditions in northeastern Oregon and southwestern Washington, a region for which there was little previous information about this species. Migrations between spawning and wintering locations were longest for fish from the Imnaha River (median, 89 km) and three Grande Ronde River tributaries, the Wenaha (56 km) and Lostine (41 km) rivers and Lookingglass Creek (47 km). Shorter migrations were observed in the John Day (8 km), Walla Walla (20 km) and Umatilla river (22 km) systems, where relatively extensive human alterations of the riverscape have been reported. From November through May, fish displayed station-keeping behavior within a narrow range (basin medians, 0.5–6.2 km). Prespawning migrations began after snowmelt-driven peak discharge and coincided with declining flows. Most postspawning migrations began by late September. Migration rates of individuals ranged from 0.1 to 10.7 km/day. Adults migrated to spawning grounds in consecutive years and displayed strong fidelity to previous spawning areas and winter locations. In the Grande Ronde River basin, most fish displayed an unusual fluvial pattern: After exiting the spawning tributary and entering a main stem river, individuals moved upstream to wintering habitat, often a substantial distance (maximum, 49 km). Our work provides additional evidence of a strong migratory capacity in fluvial bull trout, but the short migrations we observed suggest adult fluvial migration may be restricted in basins with substantial anthropogenic habitat alteration. More research into bull trout ecology in large river habitats is needed to improve our understanding of how adults establish migration patterns, what factors influence adult spatial distribution in winter, and how managers can protect and enhance fluvial populations.

Utility of a Probabilistic Sampling Design to Determine Bull Trout Population Status Using Redd Counts in Basins of the Columbia River Plateau

Abstract Redd counts are commonly used to monitor the current population status, trends in abundance, and distribution of bull trout Salvelinus confluentus. In many cases redd counts are conducted at subjectively selected sites, and there has been limited evaluation of statistical sampling designs. We evaluated the utility of the generalized random tessellation stratified (GRTS) sampling design to determine bull trout population status through redd counts. We tested a sampling effort that would be economically practical to implement on a continuous basis in multiple drainages within the southeastern Washington and Oregon portions of the Columbia River plateau. We evaluated the logistics of a pilot application of the GRTS design, compared GRTS-based estimates of redd abundance with those from census surveys, determined the precision of the GRTS estimates and the associated power for abundance comparisons, and compared the performance of the GRTS design with that of other probability sampling designs throug...

Comparison of Stream Reach Lengths Measured in the Field and from Maps

Abstract We evaluated two methods of stream reach length measurement: hip chain measurements and map measurements made with MapTech Terrain Navigator software. Fifty stream segments ranging from 0.3 to 4.2 km were selected for measurement in Oregon coastal watersheds. Each stream segment was measured twice with each method by each of two surveyors, for a total of eight measurements per site. Map measurements were more precise than hip chain measurements. The difference between the two methods of measurement was slight but significant. The 95% confidence interval of the difference between the two measurements ranged from 0.035 to 0.225 km. Map-based lengths explained 85% of the variation in stream lengths measured with a hip chain. The coefficients of the regression equations indicated a 1:1 correspondence between the two methods of measurement. Our results suggest that map-based estimates provide a less-intrusive alternative to stream reach measurements made with a hip chain.

Effects of Redd Superimposition by Introduced Kokanee on the Spawning Success of Native Bull Trout

Intra- and interspecific competition for spawning space is a commonly observed interaction in salmonids that can result in progeny loss. This study examined the impacts of redd superimposition by kokanee Oncorhynchus nerka on the reproductive success of bull trout Salvelinus confluentus in the Deschutes River basin, Oregon. The activities of high-density spawning groups of kokanee were hypothesized to place the eggs and alevins of bull trout at risk of displacement and damage wherever the spawning habitats of these two species overlap. Bull trout egg pocket depths and kokanee scouring depths were measured. Fry emergence from redds, a proxy for bull trout reproductive success in the presence of kokanee, was compared between superimposed and undisturbed redds by using fry emergence traps. Our results indicate that groups of spawning kokanee did not scour the stream bed deeply enough to reach bull trout eggs. Data on bull trout fry emergence revealed that kokanee redd superimposition did not affect bull trout egg-to-fry survival rates.

Population Structure and Genetic Divergence of Coastal Rainbow and Redband Trout in the Upper Klamath Basin

Abstract Freshwater-resident coastal rainbow trout Oncorhynchus mykiss irideus and the anadromous form of the subspecies, coastal steelhead (summer and winter runs), are present throughout the lower Klamath River–Trinity River system. Although coastal steelhead and other anadromous salmonids historically migrated into the Upper Klamath Basin (which encompasses the upper Klamath River and Upper Klamath Lake) and associated tributaries, the construction of Copco Dam in 1918 and Iron Gate Dam in 1962 stopped all upstream migration of fish past these barriers. In the Upper Klamath Lake basin, native Upper Klamath Lake redband trout O. mykiss newberrii are found along with coastal rainbow trout that were trapped above the dams or stocked from hatchery sources. However, relatively little is known about the genetic relationships among the O. mykiss populations within the Upper Klamath Basin. A population genetic analysis based on data from 17 variable microsatellite loci was conducted for samples collected in th...

Status and Distribution of Native Fishes in the Goose Lake Basin, Oregon

Abstract We describe the current distribution of native and non-native fishes in the Goose Lake basin, Oregon, with comparisons to prior unpublished surveys. We employed a generalized random tessellation stratified design to achieve a spatially-balanced sampling distribution across the drainage, including samples representative of both public and private lands. We collected all 9 native Goose Lake fishes, including 4 endemic fishes and the endangered Modoc Sucker. Two native fish species, the Modoc Sucker and the Pit Sculpin, were rarely encountered. The Modoc Sucker was limited to the upper Thomas Creek drainage; however, we documented a range expansion from that known at the time of listing in 1985. We collected the Pit Sculpin from only 2 sampling locations, indicating that the Oregon distribution of Pit Sculpins has contracted in the past 50 y. We also documented the apparent expansion of 2 non-native fishes, Fathead Minnow and Brown Bullhead, in the drainage. Within the Goose Lake fish assemblage, we describe 3 species groups that are correlated with land use and physical habitat parameters. The results of this study provide a baseline to assess trends in fish community structure over time and under different climatic conditions, measure the effects of restoration projects, and guide future restoration efforts.