Skip to Main Content
Evaluating probability sampling strategies for estimating redd counts: an example with Chinook salmon (Oncorhynchus tshawytscha)Author(s): Jean-Yves Courbois; Stephen L. Katz; Daniel J. Isaak; E. Ashley Steel; Russell F. Thurow; A. Michelle Wargo Rub; Tony Olsen; Chris E. Jordan
Source: Canadian Journal of Fisheries and Aquatic Sciences. 65: 1814-1830.
Publication Series: Scientific Journal (JRNL)
Station: Rocky Mountain Research Station
PDF: Download Publication (486.91 KB)
DescriptionPrecise, unbiased estimates of population size are an essential tool for fisheries management. For a wide variety of salmonid fishes, redd counts from a sample of reaches are commonly used to monitor annual trends in abundance. Using a 9-year time series of georeferenced censuses of Chinook salmon (Oncorhynchus tshawytscha) redds from central Idaho, USA, we evaluated a wide range of common sampling strategies for estimating the total abundance of redds. We evaluated two sampling-unit sizes (200 and 1000 m reaches), three sample proportions (0.05, 0.10, and 0.29), and six sampling strategies (index sampling, simple random sampling, systematic sampling, stratified sampling, adaptive cluster sampling, and a spatially balanced design). We evaluated the strategies based on their accuracy (confidence interval coverage), precision (relative standard error), and cost (based on travel time). Accuracy increased with increasing number of redds, increasing sample size, and smaller sampling units. The total number of redds in the watershed and budgetary constraints influenced which strategies were most precise and effective. For years with very few redds (<0.15 redds km-1), a stratified sampling strategy and inexpensive strategies were most efficient, whereas for years with more redds (0.15-2.9 redds km-1), either of two more expensive systematic strategies were most precise.
- You may send email to email@example.com to request a hard copy of this publication.
- (Please specify exactly which publication you are requesting and your mailing address.)
- We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
- This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
CitationCourbois, Jean-Yves; Katz, Stephen L.; Isaak, Daniel J.; Steel, E. Ashley; Thurow, Russell F.; Rub, A. Michelle Wargo; Olsen, Tony; Jordan, Chris E. 2008. Evaluating probability sampling strategies for estimating redd counts: an example with Chinook salmon (Oncorhynchus tshawytscha). Canadian Journal of Fisheries and Aquatic Sciences. 65: 1814-1830.
KeywordsChinook salmon, Oncorhynchus tshawytscha, sampling, redds
- Scour of chinook salmon redds on suction dredge tailings
- Network-scale spatial and temporal variation in Chinook salmon (Oncorhynchus tshawytscha) redd distributions: patterns inferred from spatially continuous replicate surveys
- Temporal variation in synchrony among chinook salmon (Oncorhynchus tshawytscha) redd counts from a wilderness area in central Idaho
XML: View XML