Salmonid Field Protocols Handbook: Techniques for Assessing Status and Trends in Salmon and Trout

Redd Counts

Sean P. Gallagher, Peter K. J. Hahn, and David H. Johnson

doi: https://doi.org/10.47886/9781888569926.ch12

The purpose of this protocol is to describe field methods for the consistent collection of salmonid redd abundance and subsequent estimation of adult salmonid breeding population size. We recommend surveys be conducted on predetermined, 3–5-km long stream reaches, using a spatially balanced rotating panel design. We suggest an annual draw of 10% of all reaches in the sampling universe as the target goal for monitoring; furthermore, to account for access problems and other barriers to sampling, we recommend that the initial sample draw should over-select reaches (sampling rate of 25%) to provide flexibility in the field. One field survey should occur prior to fish entering the spawning areas, with surveys thereafter conducted 7–14 d apart until new fish and redds are no longer observed. Surveyors will need to recognize that stream flows and/or weather conditions will have some bearing on the temporal aspects of surveys. All redds will be identified to species, measured, and georeferenced. Redd longevity and observer efficiency in redd detection will be estimated for each watershed by tracking the condition of individual redds measured during previous surveys. To document sex ratios, the sex of all live fish will be visually identified on behaviors at redds or other visual cues (dead fish will be identified, sexed, inspected for tags, and measured, per the carcass count protocol, page 59). In situations where multiple salmonid species overlap on a given spawning area, redd sizes will help differentiate the species involved.