The density dilemma: limitations on juvenile production in threatened salmon populations

Ecology of Freshwater Fish
By: , and 



Density-dependent processes have repeatedly been shown to have a central role in salmonid population dynamics, but are often assumed to be negligible for populations at low abundances relative to historical records. Density dependence has been observed in overall spring/summer Snake River Chinook salmon Oncorhynchus tshawytscha production, but it is not clear how patterns observed at the aggregate level relate to individual populations within the basin. We used a Bayesian hierarchical modelling approach to explore the degree of density dependence in juvenile production for nine Idaho populations. Our results indicate that density dependence is ubiquitous, although its strength varies between populations. We also investigated the processes driving the population-level pattern and found density-dependent growth and mortality present for both common life-history strategies, but no evidence of density-dependent movement. Overwinter mortality, spatial clustering of redds and limited resource availability were identified as potentially important limiting factors contributing to density dependence. The ubiquity of density dependence for these threatened populations is alarming as stability at present low abundance levels suggests recovery may be difficult without major changes. We conclude that density dependence at the population level is common and must be considered in demographic analysis and management.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title The density dilemma: limitations on juvenile production in threatened salmon populations
Series title Ecology of Freshwater Fish
DOI 10.1111/eff.12046
Year Published 2013
Language English
Publisher Wiley
Contributing office(s) Coop Res Unit Seattle
Description Early View
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Ecology of Freshwater Fish
Country United States
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