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We examined how the growth rate and food consumption of juvenile Coho Salmon Oncorhynchus kisutchvaried in relation to natural turbidity regimes in a coastal stream of northern California. Instream sensors were used to continuously monitor the location, turbidity, and temperature exposure of juvenile Coho Salmon fitted with passive integrated transponder tags. We observed that overwinter growth rate and food consumption varied in relation to the duration and magnitude of turbidity and temperature exposure. Growth rate and food consumption were positively associated with low‐to‐moderate turbidity exposures that ranged from >3 NTUto >20 NTUand negatively associated with elevated turbidity exposures that ranged from > 55 NTUto >150 NTU. This shift to negative associations for fish that experienced long exposures at turbidity levels > 55 NTU suggests a threshold for assessing potential risk of impairment. However, our analyses show that the influence of turbidity on consumption and growth rate is complicated by a fish's temperature exposure history, which varies among fish depending on individual movement patterns and duration of residency within different stream reaches. Consequently, Coho Salmon growth reflects the net effect of turbidity, temperature, and other environmental factors that are associated with specific life history patterns. These findings advance our understanding of how natural turbidity regimes may influence Coho Salmon growth and offer insight for assessing biological impairment in streams. Moreover, our findings indicate how knowledge of environmental context is crucial for understanding the applicability of laboratory‐derived turbidity thresholds for fish populations in streams. Such findings corroborate other field‐based studies and add to evidence that laboratory‐derived turbidity thresholds alone may be inadequate predictors of biological impairment to stream fish populations.

We evaluated trends in fish habitat condition and their relationship to natural and management-associated disturbances in forests of coastal Southeast Alaska. Monitoring data spanning 9–19 years (1994–2012) from 14 stream reaches were examined using linear mixed-effects models to evaluate patterns and trends in fish habitat condition. Modeling detected multiple patterns of habitat change that included postharvest pulses in large wood (LW) recruitment and reductions in substrate particle size, both followed by long-term trends (average LW density increased by 0.8–0.9 pieces/year; median substrate particle size decreased by 0.6–1.3 mm/year) that were observed up to two decades after harvest. Trends in spawning gravel followed patterns of change in substrate except at higher-gradient, cobble-dominated reaches, where the reduction in substrate particle size improved spawning habitat. Trends in pool habitat were not detectable over the short term for most attributes but exhibited gradual changes after harvest that became strongly evident over the long term (average residual pool depth increased by 0.5 cm/year, wood-formed pools increased by 0.9% per year). The changes in habitat conditions and correlations with riparian forest attributes (buffer strip length and wind exposure) suggested that the habitat responses were related to increased tree windthrow after timber harvest. Furthermore, the degree to which LW recruits functioned in forming pools appeared to influence long-term trends in stream habitat. We observed that only 26% of new LW recruits, on average, were functioning to form habitat and that wood function increased over time, peaking (72% of recruits were functioning) about three decades after recruitment. Our monitoring over two decades enabled us to discern slowly evolving trends, showed how trends in pool habitat that are not initially evident may be associated with buffer disturbances (windthrow and landslides), and demonstrated the long-term consequences of management actions. Received August 2, 2016; accepted May 5, 2017 Published online July 12, 2017

AbstractWe evaluated trends in fish habitat condition and their relationship to natural and management-associated disturbances in forests of coastal Southeast Alaska. Monitoring data spanning 9–19 years (1994–2012) from 14 stream reaches were examined using linear mixed-effects models to evaluate patterns and trends in fish habitat condition. Modeling detected multiple patterns of habitat change that included postharvest pulses in large wood (LW) recruitment and reductions in substrate particle size, both followed by long-term trends (average LW density increased by 0.8–0.9 pieces/year; median substrate particle size decreased by 0.6–1.3 mm/year) that were observed up to two decades after harvest. Trends in spawning gravel followed patterns of change in substrate except at higher-gradient, cobble-dominated reaches, where the reduction in substrate particle size improved spawning habitat. Trends in pool habitat were not detectable over the short term for most attributes but exhibited gradual changes after harvest that became strongly evident over the long term (average residual pool depth increased by 0.5 cm/year, wood-formed pools increased by 0.9% per year). The changes in habitat conditions and correlations with riparian forest attributes (buffer strip length and wind exposure) suggested that the habitat responses were related to increased tree windthrow after timber harvest. Furthermore, the degree to which LW recruits functioned in forming pools appeared to influence long-term trends in stream habitat. We observed that only 26% of new LW recruits, on average, were functioning to form habitat and that wood function increased over time, peaking (72% of recruits were functioning) about three decades after recruitment. Our monitoring over two decades enabled us to discern slowly evolving trends, showed how trends in pool habitat that are not initially evident may be associated with buffer disturbances (windthrow and landslides), and demonstrated the long-term consequences of management actions.Received August 2, 2016; accepted May 5, 2017 Published online July 12, 2017

Hundreds of millions of dollars have been spent on stream restoration projects to benefit salmonids and other aquatic species across the Pacific Northwest, though only a small percentage of these projects are monitored to evaluate effectiveness and far fewer are tracked for more than 1 or 2 years. The Washington State Salmon Recovery Board and the Oregon Watershed Enhancement Board have spent more than US$500 million on salmonid habitat restoration projects since 1999. We used a multiple before-after–control-impact design to programmatically evaluate the reach-scale physical and biological effectiveness of a subset of restoration actions. A total of 65 projects in six project categories (fish passage, instream habitat, riparian planting, livestock exclusion, floodplain enhancement, and habitat protection) were monitored over an 8-year period. We conducted habitat, fish, and macroinvertebrate surveys to calculate the following indicators: longitudinal pool cross section and depth, riparian shade and cover, large woody debris volumes, fish density, macroinvertebrate indices, and upland vegetation condition class. Results indicate that four categories (instream habitat, livestock exclusions, floodplain enhancements, and riparian plantings) have shown significant improvements in physical habitat after 5 years. Abundance of juvenile Coho Salmon Oncorhynchus kisutchincreased significantly at fish passage projects and floodplain enhancement projects, but significant results were not detected for other fish species. Moreover, the biological response indicators of juvenile salmonid abundance and macroinvertebrate indices showed declines at instream habitat and habitat protection projects, respectively. Our results indicate that a subset of projects can be effectively evaluated programmatically, but power and sample size estimates indicate that two or more years of preproject data are necessary to adequately determine the effectiveness of many project types, particularly for fish. Programmatic evaluations of project effectiveness should include adequate preproject sampling and multiseason monitoring for fish species to address issues of variability that are likely to be encountered in large-scale monitoring programs. Received September 16, 2015; accepted February 7, 2016 Published online June 6, 2016

AbstractHundreds of millions of dollars have been spent on stream restoration projects to benefit salmonids and other aquatic species across the Pacific Northwest, though only a small percentage of these projects are monitored to evaluate effectiveness and far fewer are tracked for more than 1 or 2 years. The Washington State Salmon Recovery Board and the Oregon Watershed Enhancement Board have spent more than US$500 million on salmonid habitat restoration projects since 1999. We used a multiple before-after–control-impact design to programmatically evaluate the reach-scale physical and biological effectiveness of a subset of restoration actions. A total of 65 projects in six project categories (fish passage, instream habitat, riparian planting, livestock exclusion, floodplain enhancement, and habitat protection) were monitored over an 8-year period. We conducted habitat, fish, and macroinvertebrate surveys to calculate the following indicators: longitudinal pool cross section and depth, riparian shade and cover, large woody debris volumes, fish density, macroinvertebrate indices, and upland vegetation condition class. Results indicate that four categories (instream habitat, livestock exclusions, floodplain enhancements, and riparian plantings) have shown significant improvements in physical habitat after 5 years. Abundance of juvenile Coho Salmon Oncorhynchus kisutchincreased significantly at fish passage projects and floodplain enhancement projects, but significant results were not detected for other fish species. Moreover, the biological response indicators of juvenile salmonid abundance and macroinvertebrate indices showed declines at instream habitat and habitat protection projects, respectively. Our results indicate that a subset of projects can be effectively evaluated programmatically, but power and sample size estimates indicate that two or more years of preproject data are necessary to adequately determine the effectiveness of many project types, particularly for fish. Programmatic evaluations of project effectiveness should include adequate preproject sampling and multiseason monitoring for fish species to address issues of variability that are likely to be encountered in large-scale monitoring programs.Received September 16, 2015; accepted February 7, 2016 Published online June 6, 2016