Geology topics

Research about Clackamas River

Source-linked reports with geographic coverage including Clackamas River.

3 recordsLinked to original sources

USGS2019

A natural‐origin steelhead population's response to exclusion of hatchery fish

It is asserted that reduction or elimination of hatchery stocking will increase natural‐origin salmon Oncorhynchus spp. and steelhead O. mykiss production. We conducted an analysis of steelhead population census data (1958–2017) to determine whether elimination of summer steelhead stocking in the upper Clackamas River in 1998 increased the productivity of natural‐origin winter steelhead. A Bayesian state–space stock–recruitment model was fitted to the adult steelhead data set, and productivity was estimated as a function of hatchery‐origin spawner abundance as well as other environmental factors. When used as a predictive variable in our model, the abundance of hatchery summer steelhead spawners (1972–2001) did not have a negative effect on winter steelhead recruitment. However, spill at North Fork Dam (the gateway to the upper Clackamas River basin) and the Pacific Decadal Oscillation (an index of ocean conditions) were both negatively associated with winter steelhead recruitment. Moreover, winter steelhead abundance in the upper Clackamas River basin failed to rebound to abundances observed in years prior to the hatchery program, and fluctuations in winter steelhead abundance were correlated with those of other regional winter steelhead stocks. Our assessment underscores the need for studies that (1) directly quantify the effects of hatchery fish on the production of natural‐origin salmon and steelhead, (2) empirically test published theories about mechanisms of hatchery fish impacts on natural‐origin populations, and (3) document population responses to major changes in hatchery programs.

Oregon↗

USGS2011

Assessing the feasibility of native fish reintroductions: A framework applied to threatened bull trout

Translocations to recover native fishes have resulted in mixed success. One reason for the failure of these actions is inadequate assessments of their feasibility prior to implementation. Here, we provide a framework developed to assess the feasibility of one type of translocation—reintroduction. The framework was founded on two simple components of feasibility: the potential for recipient habitats to support a reintroduction and the potential of available donor populations to support a reintroduction. Within each component, we developed a series of key questions. The final assessment was based on a scoring system that incorporated consideration of uncertainty in available information. The result was a simple yet transparent system for assessing reintroduction feasibility that can be rapidly applied in practice. We applied this assessment framework to the potential reintroduction of threatened bull trout Salvelinus confluentus into the Clackamas River, Oregon. In this case, the assessment suggested that the degree of feasibility for reintroduction was high based on the potential of recipient habitats and available donor populations. The assessment did not provide a comprehensive treatment of all possible factors that would drive an actual decision to implement a reintroduction, but it did provide a fundamental level of feasibility assessment that is often lacking in practice.

Oregon↗

USGS2011

Seepage investigations of the Clackamas River, Oregon

Analysis of streamflow measurements and continuous records of streamflow provided insight into interaction of the groundwater system with the Clackamas River in northwestern Oregon. This report assesses gains and losses of the Clackamas River based on streamflow measurements made during previous hydrologic studies, decades of continuous streamflow data, and a detailed suite of streamflow measurements made in September 2006. Gains and losses were considered significant if, after accounting for tributary inflows and withdrawals, the difference in streamflow from a measurement site to the next site downstream exceeded the streamflow measurement uncertainty. Streamflow measurements made in 1987, 1992, and 1998 indicated minor gains and losses. Comparison of continuous records of late summer streamflow of the Clackamas River at Estacada to sites at Clackamas and Oregon City indicated gains in some years, and no losses. Analysis of streamflow measurements of the Clackamas River from Estacada to Oregon City during low-flow conditions in September 2006 enabled an estimation of gains and losses on a reach-by-reach scale; these gains and losses were attributable to the geomorphic setting. During late summer, most groundwater discharge occurs upstream of Estacada, and groundwater contributions to streamflow downstream of Estacada are minor.

Oregon↗