Middle Fork Salmon River, Idaho, Chinook salmon redd count database, 1995-2021

The Middle Fork Salmon River (MFSR) in Idaho is managed as a designated wild anadromous fish sanctuary with the objective of preserving the genetic integrity of wild, native salmonids. Despite abundant, high-quality natal (spawning and rearing) habitat, absence of hatchery fish, and low harvest rates, MFSR Chinook salmon and steelhead remain at risk of extirpation, primarily from factors outside the MFSR basin within the migration corridors of the Columbia and Snake rivers, estuaries, and the ocean. Habitat conditions throughout most of the MFSR are in excellent condition, and key limiting factors affecting these populations are from outside natal spawning and rearing areas. Concern for the persistence of Snake River Chinook salmon culminated in a final rule that listed Snake River spring-summer Chinook salmon as “Threatened” under the Endangered Species Act (ESA) of 1973.

This data publication contains tabular (comma-separated values file) and vector spatial data (shapefile and geopackage) of a spatiotemporal analysis of Chinook salmon distribution in the Middle Fork Salmon River drainage. The data were compiled from spatially continuous redd surveys (nest counts) encompassing all potential Chinook salmon spawning areas within the MFSR. Spatially continuous surveys were conducted via low-level helicopter flights and/or ground observers annually from 1995-2021 after Chinook salmon had completed spawning and while redds remained visible. The surveys were timed to coincide with the period of maximum spawning activity on a particular stream, and each transect was therefore assigned a target count-time window based on historic observations. Data include the longitude and latitude of the MFSR redds locations, name of the stream, year, and survey method (ground or helicopter).
Since 1995, the USDA Forest Service, Rocky Mountain Research Station (RMRS) biologists have conducted spatially continuous redd surveys (nest counts) encompassing all potential Chinook salmon spawning areas within the MFSR. RMRS goals were to improve monitoring of ESA-listed MFSR Chinook salmon populations and to improve understanding of the spatial and temporal characteristics of salmon population dynamics. The spatially continuous surveys were also developed to complement index-area redd surveys, provide more accurate escapement estimates, and increase analytical power.