Use of Stream Habitat Surveys to Predict Rearing Capacity of Juvenile Steelhead Steven P. Cramer & Nicklaus K. Ackerman S.P. Cramer & Associates, Inc. 600 NW Fariss Rd. Gresham, OR

Today’s Topics 1.The Unit Characteristic Method: Helping Bridge the Gap in our Understanding of Habitat and Fish 2. UCM Driving Functions and Justifications 3. Investigating the accuracy of UCM capacity estimates

Today’s Topics 1.The Unit Characteristic Method: Helping Bridge the Gap in our Understanding of Habitat and Fish 2. UCM Driving Functions and Justifications 3. Investigating the accuracy of UCM capacity estimates

The UCM: Helping Bridge the Gap in our Understanding of Habitat and Fish Understanding stream capacity is important to fisheries management and conservation. Stream capacity is related to availability of habitat resources. The UCM uses relationships between steelhead rearing densities and habitat features, at the life stage that is most limiting to production, to determine a stream’s capacity.

Capacity Bottleneck Habitat for summer rearing of parr is typically limiting Graph from Ward and Slaney 1993

Today’s Topics 1.The Unit Characteristic Method: Helping Bridge the Gap in our Understanding of Habitat and Fish 2. UCM Driving Functions and Justifications 3. Investigating the accuracy of UCM capacity estimates

Functions of the UCM

Standard Parr Densities Represent the capacity of unit types to hold parr. Based on observations from fully seeded coastal Oregon streams.

Cover Wood: In pools and glides Boulders: A velocity refuge and feeding station in riffles

Depth Steelhead prefer greater depths in pools and riffles because depth is a form of cover. Within riffles, usage drops as depths exceed 1 meter because velocities in deep riffles begin to exceed parr preferences.

Food Riffles produce the drift invertebrates upon which juvenile salmonids feed. A stream must be composed of at least 50% riffle to produce enough food for steelhead. Turbidity reduces light penetration which in turn reduces primary production. Primary production is correlated to invertebrate production which is correlated to fish production.

Fine Sediments in the Substrate Fine sediments in the substrate reduce cover by filling in spaces in cobble, and also can reduce drift invertebrate production. Fish Density % Fines Graph taken from Bjornn and Reiser (1991) Excessive Fines

Alkalinity Streams in different regions inherently produce different numbers of fish in part due to their geochemical makeup. Alkalinity has been shown in the literature to be directly correlated to fish production.

Overwinter Survival Juvenile steelhead overwinter in the interstices of substrate. Ample cobble relatively free of fines is crucial to overwinter survival.

Functions of the UCM

Today’s Topics 1. The Unit Characteristic Method: Helping Bridge the Gap in our Understanding of Habitat and Fish 2. UCM Driving Functions and Justifications 3. Investigating the accuracy of UCM capacity estimates

Model Validation Compare model estimates of capacity to observed production in fully seeded basins. Oregon Test Basins Watershed Area: 26-1,420km 2 Anadromous Stream Length: 660km Years of Juvenile Monitoring: 5-11 Average Smolt Production: 2,100-26,000 Oregon

Catherine Creeknot fully seeded

1:1 (Obs = Exp) Regression

Conclusions 1. Model functions reflect relationships known to exist between steelhead production and habitat. 2. The model incorporates data from standard habitat surveys. Subjectivity is minimized, data are widely available, and model simulations can be done quickly. 3. Testing of UCM predicted capacities indicates model results are typically within +/- 35% of observed capacity. 4. Among the test basins, the model tended to underestimate capacity in smaller basins, and overestimate in larger basins. We will add a channel width variable to account for this.

Additional Uses of UCM 1. The UCM may be used to estimate changes in capacity that result from habitat alterations. 2. The UCM can be used to examine how changes in low flow affect stream capacity. This use is soon to be tested and published. 3. The UCM may be used for other species. A spring Chinook model has been developed and applied, but has not yet been validated.