Detection of Regional Trends in Salmonid Habitat in Coastal Streams, Oregon

Abstract

Abstract Freshwater habitat quality is broadly recognized as fundamental to the viability of salmonid populations. Temporal trends in freshwater habitat have rarely been quantified, however, perhaps owing to a lack of methodical and rigorous time series data sets. We present an approach for evaluating change in freshwater habitat using data from a long-term program to monitor salmonid populations and their habitats in coastal drainages of Oregon. Our goals were to (1) evaluate the presence and magnitude of an underlying linear trend in freshwater habitat condition across coastal watersheds in Oregon and (2) determine the effectiveness of the current sampling design for meeting the monitoring objectives. Four features were selected to characterize freshwater habitat: percent of pool area, large wood volume, quantity of fine sediment, and stream size. We developed a statistical model to describe the trend in these features that incorporated an error structure to account for site, year, and site-by-year vari...