Patterns of Coastal Cutthroat Trout Survival in Two Headwater Stream Networks
Berger, A. M.

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
Sampling Headwater Stream Networks for Spatial Autocorrelation Detection and Autocovariance Parameter Estimation
Som, N., L.M. Ganio, R.E. Gresswell, D. Hockman-Wert

Spatial autocorrelation is common in data collected for ecological studies, and the use of statistical models for spatial autocorrelation has evolved. Initially, these models were used to improve linear model parameter estimation uncertainty, but more recently ecologists have considered spatial autocorrelation as a valuable tool for describing ecological patterns. The structure and water-driven continuity of stream-networks makes these landscapes unique, and has prompted development of new models for describing spatial autocorrelation within these networks. We evaluate the spatial autocorrelation detection and parameter estimation of four sampling protocols applied to complete censuses of coastal cutthroat trout (Oncorhynchus clarkii clarkii) habitat unit fish counts. We consider two cluster- and two non cluster-based sampling protocols. Spatially distributed clusters were the most apt to contain spatial autocorrelation. Spatial autocorrelation detection was also associated with headwater basin attributes. Differences among sampling protocols in regards to autocorrelation parameter estimation were less distinct.

DISCIPLINE: Fisheries    STUDY: Hinkle Creek    TYPE: Journal Articles    TAGS: Spatial autocorrelation, parameter estimation, cluster-based sampling protocols


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