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.
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.
This study measured the impacts of two harvest entries on the monthly streamflow and other measures of the streams below and adjacent to harvest. Statistically significant increases in sediment yield, as suspended sediment, were detected as a consequence of timber harvest in the South Fork Hinkle Creek. These increases were detected at the small, headwater watershed scale as well as the large watershed scale. Unlike the increases in water yield, these increases were not consistent with the literature. The results of the seminal paired watershed studies showed very large increases in sediment yield, often as much as two or three times greater than sediment yields before timber harvest. The results from contemporary forest practices are much more muted and the increases are in the range of 20 to 30 percent increases in sediment yield. The increases are in order with and correlate well with the increases in water yield. That the increases in sediment yield are a result of increased stream power due to increases in water yield is a reasonable hypothesis to put forward to explain these observations. The greatest improvement in forest practices over the past several decades were directed toward reducing the impacts of timber harvest on sediment yield. These improvements include; clearcut size limits and adjacency constraints, improved yarding systems (in this case slackline, skyline cable systems), the prescription of buffer strips, and changes in site preparation practices.
One of the overarching objectives of the Hinkle Creek Paired Watershed Study was to investigate the impact of contemporary forest practices on stream temperature for non-fish-bearing streams and the cumulative impacts downstream on the fish-bearing tributaries and the main stem. This presentation is a large collection of data gathered about to conditions in Hinkle including canopy closure, minimum and maximum daily temperature, residence time, and groundwater influx. Statistically significant decreases in minimum daily temperature were detected for all of the treatment streams. Clearcuts adjacent to the fish-bearing tributaries and the main stem resulted in statistically significant increases and decreases to maximum daily stream temperatures. There was no empirical evidence that the changes in stream temperature detected at the scale of individual stream reaches were propagated downstream.
The Hinkle Creek Paired Watershed Study was initiated to carry out two overarching goals: to investigate the environmental impact of contemporary forest practices on non-fish-bearing streams and downstream in tributary and main stem fish-bearing streams. This presentation serves as a summary of some of the results for the studies in Hinkle Creek. Statistically significant increases in water yield, summer low flows, peak flows, and storm flows were detected as a consequence of timber harvest and the subsequent silvicultural activities. Statistically significant increases in sediment yield were also detected. The increases in sediment yield were not consistent with the literature; however they were highly correlated with the observed increases in water yield. Statistically significant increases and decreases were detected in maximum and minimum daily stream temperatures in the non-fish-bearing tributaries, fish-bearing tributaries, and the main stem as a consequence of the two harvest entries. Statistically significant increases in nitrogen were detected as a consequence of the timber harvest and the subsequent silvicultural activities. Nitrogen was the only nutrient that responded to the silvicultural activities. In Hinkle Creek the pacific giant salamander was the only amphibian that was abundant enough to study. In the two years after the first harvest entry, the data did not support the hypothesis that there was any change in the abundance of salamanders.
Our studies of stream invertebrate responses to contemporary timber practices compared treated to control sites prior to and following harvest at Hinkle, Alsea and upper Trask watersheds. In each watershed the BACI study design and robust replication has been crucial in accounting for natural variations in macroinvertebrate distributions while examining patterns of change in response to harvest. As these basins vary physically in association with regional and geologic differences, initially we observed distinctive invertebrate assemblage composition for each watershed. In addition the proportion of chironomid midges and total benthic densities were higher at Alsea and Trask headwaters than at Hinkle. Our ability to detect responses to harvest within basins was enhanced when we found no pre-harvest differences in macroinvertebrate densities, percent chironomids, or taxa richness between control and treatment reaches of similar size at Hinkle and Trask watersheds. However significant invertebrate community differences were observed between the two Alsea tributaries, likely due to differences in tributary sizes or other physical and chemical differences. Though benthic invertebrate densities increased at headwater sites post-harvest, there were no detectable density differences at mainstem sites. Prey consumption by trout, whose densities at mainstem sites increased following harvest, possibly explained the lack of change observed for invertebrate densities.
Here we evaluate the response of a headwater fish community to forest management using a before, after, control, impact (BACI) study design. Annual fish abundance and biomass estimates are from a census of pool and cascade habitat units over the fish-bearing portion of both the reference and treatment catchments. Movement, survival, and growth were estimated from the monitoring and recapture of salmonids marked with passive integrated transponder (PIT) tags. Sampling consisted of an annual electrofishing and marking event during the low-flow period (2001-2011), and beginning in the winter of 2003, there were three annual mobile antenna PIT-tag survey events in December, March, and June. Additionally, continuously operating swim-through antennas were located at the downstream end of each stream segment. The study calibration phase occurred 2001-05. Treatment-1 (2006-2008) consisted of stream adjacent logging without retention of standing tree buffers with harvest units occurring in channels upstream from channel sections inhabited by fish. During Treatment-2 (2009-2011), there was stream adjacent logging with standard buffers as prescribed by current forest practice regulations. Analysis occurred at two spatial scales, tributaries only and catchments. Overall, very few detectable changes in habitat or biologic parameters were observed in conjunction with either treatment.