How do you determine the number of salmon, trout, or steelhead a stream can support?
Cramer Fish Sciences uses an analytical tool developed by
Steve Cramer called the
Unit Characteristic Method, or UCM.
Using habitat measurements from standard
stream surveys, the UCM utilizes quantitative methods to determine
cause-and-effect relationships between habitat and fish production.
It's all virtual so you can change various habitat parameters and see
how fish populations are affected.
Stream habitat has delineable units — pools, riffles, or runs —
which are the building blocks that determine fish densities. Different fish require
different habitat, and the UCM can be used to analyze the habitat needs of steelhead
trout, rainbow trout, spring and fall Chinook salmon, bull trout, and even cutthroat trout.
By varying additional attributes of the stream, such as depth, cover, temperature,
turbidity, and even nutrient loading, the UCM can effectively provide answers and
guidance to those concerned with stream fish production.
The UCM is especially valuable when comparing the
benefit or impact to fish when stream features are altered or protected. Habitat
factors that impact fish production can be identified. Some specific examples of
how the UCM has helped PGE and Bonneville Power:
- The Deschutes River Basin was analyzed to determine the number of steelhead that could be supported if passage above the dams was restored.
- The Hood River Basin was analyzed to determine the number of wild steelhead and Chinook that hatchery supplementation should support.
- The Yakima River Basin was analyzed to determine if irrigation drainage channels can support salmonids.
The UCM has also been considered for urban land-use planning to design land use regulations
that would protect key fish habitat.
The UCM projects for PGE and Bonneville Power have utilized the following services:
- Assembly of stream habitat data from standard surveys and water quality monitoring
- Quantified relationships between salmonids and habitat features
The key outcomes of these projects has included:
- Estimation of fish carrying capacity by stream reach
- Distinction of stream suitability for different salmonids
- Quantitative estimates of benefits or impacts from stream alteration
Cramer Fish Sciences continues to modify and improve the UCM. Currently, we are
working with the Washington Department of Ecology to develop UCM as a tool for
estimating changes in salmonid carrying capacity due to flow alterations.