In this study, we quantified the relevance of natural controls (e.g., geology, catchment physiography) on suspended sediment yield (SSY) in headwater streams managed for timber harvest. We collected and analyzed six years of data from 10 sites (five headwater sub-catchments and five watershed outlets) in the Trask River Watershed (western Oregon, United States).
This report evaluates the general effects of forestry practices on biodiversity along streams in the Pacific Northwest and northern California.
Aquatic ecologists working in small streams are challenged with the task of identifying stream habitats, the spatial distribution and temporal persistence (i.e., rate of change) of habitat, and the timing and manner in which habitats are used by stream fishes. Because temporal variation of stream habitats and the mobility of stream fishes complicate species abundance-habitat association models (Van Horne 1983), the identification of high quality aquatic habitats is often problematic. In an attempt to assess habitat quality of a stream network in western Oregon, we evaluated the persistence of abundance patterns and habitat associations of coastal cutthroat trout Oncorhynchus clarkii clarkii by monitoring stream sections of high and low relative abundance for 13 months. Simultaneous habitat evaluations provided insight into factors affecting distribution patterns in main stem and tributary streams.
The shape and configuration of branched networks influence ecological patterns and processes. Recent investigations of network influences in riverine ecology stress the need to quantify spatial structure not only in a two-dimensional plane, but also in networks. An initial step in understanding data from stream networks is discerning non-random patterns along the network. On the other hand, data collected in the network may be spatially autocorrelated and thus not suitable for traditional statistical analyses. Here we provide a method that uses commercially available software to construct an empirical variogram to describe spatial pattern in the relative abundance of coastal cutthroat trout in headwater stream networks. We describe the mathematical and practical considerations involved in calculating a variogram using a non-Euclidean distance metric to incorporate the network pathway structure in the analysis of spatial variability, and use a non-parametric technique to ascertain if the pattern in the empirical variogram is non-random.
The Salmon Research and Restoration Plan for the Arctic-Yukon-Kuskokwim Sustainable Salmon Initiative (AYK-SSI) recognizes the need for approaches to characterize determinants of salmon population performance at broader scales. Here we discuss data and modeling tools that have been applied in western Oregon to understand how landscape features and processes may influence salmonids in freshwater.
Little information is available on the effects of implanting 23-mm passive integrated transponder (PIT) tags in salmonids less than 90 mm fork length (FL). Using juvenile steelhead Oncorhynchus mykiss (range, 73–97 mm FL), we compared instantaneous growth rates and survival among three experimental groups: control, surgery with no tag, and surgery with tag.
To examine seasonal and spatial factors affecting prey consumption by Oncorhynchus trout, we examined trout diet from mainstem and tributary sites at Hinkle Creek, Oregon.
To investigate effects of headwater logging on downstream coastal cutthroat trout (Oncorhynchus clarkii clarkii) populations, we monitored stream habitat and biotic indicators including biomass, abundance, growth, movement, and survival over 8 years using a paired-watershed approach.
The Alsea Watershed Study Revisited in the Oregon Coast Range provided a unique opportunity to investigate and compare the stream temperature responses to contemporary forest harvesting practices (i.e., maintenance of riparian vegetation) with the impacts from historical (1960s) harvesting practices (i.e., no riparian vegetation).
The importance of multiple processes and instream factors to aquatic biota has been explored extensively, but questions remain about how local spatiotemporal variability of aquatic biota is tied to environmental regimes and the geophysical template of streams. We used an individual-based trout model to explore the relative role of the geophysical template versus environmental regimes on biomass of trout (Oncorhynchus clarkii clarkii). We parameterized the model with observed data from each of the four headwater streams (their local geophysical template and environmental regime) and then ran 12 simulations where we replaced environmental regimes (stream temperature, flow, turbidity) of a given stream with values from each neighboring stream while keeping the geophysical template fixed. We also performed single-parameter sensitivity analyses on the model results from each of the four streams. Although our modeled findings show that trout biomass is most responsive to changes in the geophysical template of streams, they also reveal that biomass is restricted by available habitat during seasonal low flow, which is a product of both the stream’s geophysical template and flow regime. Our modeled results suggest that differences in the geophysical template among streams render trout more or less sensitive to environmental change, emphasizing the importance of local fish–habitat relationships in streams.