Evaluating the use of redd counts in monitoring Snake River Cutthroat in spring-fed creeks

Redd counts are a commonly used management tool for monitoring spawning salmonid population status and trends. The relative ease, low cost, and non-invasive nature of redd count surveys allow greater spatial and temporal coverage in monitoring efforts than other traditional approaches for population monitoring (e.g., mark-recapture). Redd counts  have been used to monitor Snake River Cutthroat Trout (SRC) in the Upper Snake River drainage since the 1970’s, particularly in spring-fed creeks which are considered important spawning areas within the basin.

Substantial superimposition of redds has been observed in these creeks, and is thought to bias redd count data. Superimposition of redds is common among trout and salmon species and does not appear to be explained by limited habitat availability or high spawning densities. Identifying the extent of redd superimposition is pertinent to increasing the effectiveness of monitoring populations within spring creeks.

A secondary concern is the potential effects of superimposition on recruitment as recruitment is a strong driver in salmonid population trends. Studies are divided over whether superimposition destroys the previously laid fry. A key question with respect to redd superimposition in Snake River spring creeks is how superimposition may limit juvenile recruitment.

Our goal is to evaluate the relationships between redd count data and spawning populations, spawning success, and fry emergence in spring creeks in the Upper Snake River drainage. Primary objectives include:

  1. Characterize the extent of and factors driving redd superimposition and the effects of superimposition on spawning success.
  2. Determine the relationship between redd counts and number of SRC attempting to spawn and how this relationship varies with number of spawners.
  3. Determine the relationship between redd counts and fry production.

This information will allow for more effective investigation of population status and trends, for which long-term data collection is absolutely crucial but increasingly rare as funding is often limited. Biological applications of the portfolio theory concept reveal the stabilizing effect of asynchronous population dynamics on meta-population status. Using redd counts to evaluate among-population synchrony will provide insight into the role of spring-fed creeks in the overall productivity of the SRC stock in the upper Snake River watershed. Analyses such as these may also prove useful in determining the efficacy of costly population enhancement efforts such as egg augmentation and habitat improvement, for which quantitative assessments rare.

Contact

Jeff Baldock, Masters student

Wyoming Cooperative Fish and Wildlife Research Unit

Department of Zoology & Physiology, University of Wyoming

Dept. 3166, 1000 E University Ave

Laramie, WY 82071

[email protected]

 

Annika Walters, Assistant Unit Leader

U.S. Geological Survey,

Wyoming Cooperative Fish and Wildlife Research Unit

Department of Zoology & Physiology, University of Wyoming

Dept. 3166, 1000 E University Ave

Laramie, WY 82071

[email protected]

 

Project Lead

Funding & Partners

Wyoming Game and Fish Department