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Scientific Report

Framework for Estimating Salmon Survival as a Function of Habitat Condition

Abstract

The problem of evaluating the effects of land use actions on salmon survival is difficult because of the complexity of salmon biology and freshwater ecology. Most land use actions in the tributaries do not affect salmon survival directly. Land use actions affect habitat variables, which in turn affect salmon survival. Thus, the problem can be partitioned into: 1) effects of habitat variables on salmon survival, and 2) effects of land use actions on habitat variables. This report deals with the effects of habitat variables on salmon survival. The goal of this project is to develop a framework for estimating salmon survival as a function of habitat condition. This framework can serve as a starting point for developing quantitative models that predict salmon survival as a function of one or more habitat variables. The model focuses on data specifically applicable to Snake River spring/summer chinook. The scope is restricted to the freshwater habitat used by prespawning and spawning adults, incubating embryos, pre-emergent alevins, and post-emergent juveniles. The time period in the life cycle incorporated by the model spans the time from when pre-spawning adults enter the Snake River tributaries to the time the juveniles (smolts) exit the same Snake River tributaries. During this period, salmonids live through several stages during which several biological and environmental factors act to define subsequent smolt yield. The overall input is the number of prespawning adults entering a specific Snake River tributary to spawn and the overall output is the number of juveniles leaving the same Snake River tributary as a function of key habitat variables. Specific objectives addressed in this model framework are to: 1. Organize available information on habitat-fish relations applicable to Snake River salmon through a review of published and unpublished literature and consultations with resource scientists and managers. 2. Evaluate, either qualitatively or quantitatively, the potential use of these relations as single factor predictors for survival of listed salmon species. 3. Evaluate, either qualitatively or quantitatively, the potential for predicting survival of listed salmon species as a function of the interaction of multiple habitat variables. 4. Develop a mathematical model that employs habitat/survival relationships and knowledge of current habitat condition of a stream system within the Snake River Basin to examine the effects of population size and productivity on the rate of recovery/decline of a wild/natural stock faced with current versus improved habitat conditions. Abundance of fish in the series of linked life stages modeled is a function of the survival rate by life stage and the carrying capacity of the habitat for the life stages.

Authors

Citation

Cuenco M.L. and D.A. McCullough. 1996. Framework for Estimating Salmon Survival as a Function of Habitat Condition. Columbia River Inter-Tribal Fish Commission Report reference #96-04, Portland, Oregon.

Date

Aug 19th, 1997

Report No.

96-04

Media Type

CRITFC Technical Report

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