Abstract

Decreases in body sizes of animals related to recent climate warming can affect population persistence and stability. However, direct observations of average sizes over time and their interrelationships with underlying density-dependent and density-independent processes remain poorly understood owing to the lack of appropriate long-term datasets. We measured body size of two species common to headwater streams in coastal and Cascades ecoregions of the Pacific Northwest of North America over multiple decades, comparing old-growth and managed forests. We found consistent decreases in median length of Coastal Cutthroat Trout Oncorhynchus clarkii clarkii, but a coexisting species, the Coastal Giant Salamander Dicamptodon tenebrosus, appears to be more resilient to size changes over time. Based on observed trends, adult trout have decreased in length by 6–13% over the last 30 years. Length decreased more in larger compared to smaller animals, suggesting that these effects reflect changes in growth trajectories. Results from a model-selection approach that included hydroclimatic and biological information as covariates in one of our study ecoregions demonstrated that stream temperature alone did not explain observed length reductions. Rather, a combination of density-dependent (animal abundances) and local density-independent factors (temperature, habitat, and streamflow) explained observed patterns of size. Continued decreases in size could lead to trophic cascades, biodiversity loss, or in extreme cases, species extirpation. However, the intricate links between density-independent and density-dependent factors in controlling population-level processes in streams need further attention.

Details

Title
Shrinking sizes of trout and salamanders are unexplained by climate warming alone
Author
Arismendi, Ivan 1 ; Gregory, Stanley V. 1 ; Bateman, Douglas S. 2 ; Penaluna, Brooke E. 3 

 Oregon State University, Department of Fisheries, Wildlife, and Conservation Sciences, Corvallis, USA (GRID:grid.4391.f) (ISNI:0000 0001 2112 1969) 
 Oregon State University, Department of Forest Engineering, Resources and Management, College of Forestry, Corvallis, USA (GRID:grid.4391.f) (ISNI:0000 0001 2112 1969) 
 USDA Forest Service, Pacific Northwest Research Station, Corvallis, USA (GRID:grid.497403.d) (ISNI:0000 0000 9388 540X) 
Pages
13614
Publication year
2024
Publication date
2024
Publisher
Nature Publishing Group
e-ISSN
20452322
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
3067582834
Copyright
© The Author(s) 2024. This work is published under http://creativecommons.org/licenses/by/4.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.