OREGON STATE UNIVERSITY

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Factors Influencing Coastal Cutthroat Trout (Oncorhynchus clarkii clarkii) Seasonal Survival Rates: a Spatially Continuous Approach within Stream Network
Berger, A.M., R.E. Gresswell
Apr-10-2009

Mark–recapture methods were used to examine watershed-scale survival of coastal cutthroat trout (Oncorhynchus clarkii clarkii) from two headwater stream networks. A total of 1725 individuals (‡100 mm, fork length) were individually marked and monitored seasonally over a 3-year period. Differences in survival were compared among spatial (stream segment, subwatershed, and watershed) and temporal (season and year) analytical scales, and the effects of abiotic (discharge, temperature, and cover) and biotic (length, growth, condition, density, movement, and relative fish abundance) factors were evaluated. Seasonal survival was consistently lowest and least variable (years combined) during autumn (16 September – 15 December), and evidence suggested that survival was negatively associated with periods of low stream discharge. In addition, relatively low (–) and high (+) water temperatures, fish length (–), and boulder cover (+) were weakly associated with survival. Seasonal abiotic conditions affected the adult cutthroat trout population in these watersheds, and low-discharge periods (e.g., autumn) were annual survival bottlenecks. Results emphasize the importance of watershed-scale processes to the understanding of population-level survival.

DISCIPLINE: Fisheries    STUDY: Hinkle Creek    TYPE: Journal Articles    TAGS: Mark–recapture, abiotic factors, biotic factors, water temperatures, boulder cover
Patterns of Coastal Cutthroat Trout Survival in Two Headwater Stream Networks
Berger, A. M.
Jun-21-2007

Mark-recapture methods were used to examine watershed-scale survival rates of coastal cutthroat trout (Oncorhynchus clarkii clarkii) from two headwater stream networks located in the foothills of the Cascade Mountain Range, Oregon. Differences in survival were explored among spatial (stream segment, stream network [main stem or tributaries], and watershed) and temporal (season and year) analytical scales and assessed among specific abiotic (discharge, temperature, and cover) and biotic (length, growth, condition, density, and movement) factors. A total of 1,725 adult coastal cutthroat trout (>100 mm, FL) were implanted with half-duplex PIT (passive integrated transponder) tags and monitored seasonally over a 3-year period using a combination of electrofishing, portable remote tracking antennas, and stationary antennas. The effects of watershed, stream network, season, year, and fish length were the most important factors among the candidate survival models. The greatest source of variation in survival was associated with year-dependent differences among seasons. There was evidence suggesting that survival was negatively associated with periods of low stream discharge and with individual fish length. In addition, low (-) and high (+) extreme stream temperatures and boulder cover (+) were weakly associated with survival.

DISCIPLINE: Fisheries    STUDY: Hinkle Creek    TYPE: Theses    TAGS: coastal cutthroat trout, survival, passive integrated transponder, electrofishing, portable remote tracking antennas, Seasonal survival, stream discharge, fish length, boulder cover
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