Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 7948
Title: Habitat complementation, ecological neighbourhoods, and local factors predict the distribution and abundance of spawning by steelhead (Oncorhynchus mykiss) across a complex riverscape
Author: Jeff A. Falke, Jason B. Dunham, Chris E. Jordan, Kristina M. McNyset, Gordon H. Reeves
Publication Year: 2013
Journal: PLoS ONE
Keywords: anadromous fishes, count regression, life cycle, spatial ecological processes, species occurrence, stream networks,
Abstract:

1. We assessed the relative influence of landscape spatial processes and local habitat characteristics on patterns in the distribution and abundance of spawning steelhead (Oncorhynchus mykiss), a threatened salmonid fish, across ~15,000 stream km in the John Day River basin, Oregon, USA.


2. We used hurdle regression and a multi-model information theoretic approach to identify the relative importance of covariates representing key aspects of the steelhead life cycle (e.g., site access, spawning habitat quality, juvenile survival) at two spatial scales: local sites and ecological neighbourhoods.


3. Based on Akaike’s Information Criterion, models that included covariates describing ecological neighbourhoods provided the best description of the distribution and abundance of steelhead spawning given the data.


4. Among these covariates, our representation of offspring survival (growing-season-degree-days, °C) had the strongest effect size (7x) relative to other predictors.


5. Predictive performances of model-averaged composite and neighbourhood-only models were better than a site-only model based on both occurrence (percentage of sites correctly classified = 0.80 ± 0.03 SD, 0.78 ± 0.02 vs. 0.62 ± 0.05, respectively) and counts (root mean square error = 3.37, 3.93 vs. 5.57, respectively).


6. The importance of both temperature and stream flow for steelhead spawning suggest this species may be highly sensitive to impacts of land and water uses, and to projected climate impacts in the region and that landscape context, complementation, and connectivity will drive how this species responds to future environments.

Theme: Habitats to Support Sustainable Fisheries and Recovered Populations
Foci: Characterize relationships between habitat and ecosystem processes, climate variation, and the viability of organisms.