Declining patterns of Pacific Northwest steelhead trout (Oncorhynchus mykiss) adult abundance and smolt survival in the ocean

• Published in: Canadian journal of fisheries and aquatic sciences Vol. 74; no. 8; pp. 1275 - 1290
• Main Authors: Kendall, Neala W, Marston, Gary W, Klungle, Matthew M
• Format: Journal Article
• Language: English
• Published: Ottawa NRC Research Press 01.08.2017; Canadian Science Publishing NRC Research Press
• Subjects: Abundance; Animal populations; Aquatic sciences; Autoregressive models; Coasts; Conservation; Correlation analysis; Distribution; Forecasts and trends; Marine; Oncorhynchus mykiss; Physiological aspects; Populations; Rainbow trout; Rivers; Salmon; State space models; Survival; Time series; Trout; Canada; British Columbia Canada; United States > US; Washington (state); Pacific Northwest; INE, North Pacific
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/cjfas-2016-0486

Examination of population abundance and survival trends over space and time can guide management and conservation actions with information about the spatial and temporal scale of factors affecting them. Here, we analyzed steelhead trout (anadromous Oncorhynchus mykiss) adult abundance time series from 35 coastal British Columbia and Washington populations along with smolt-to-adult return (smolt survival) time series from 48 populations from Washington, Oregon, and the Keogh River in British Columbia. Over 80% of the populations have declined in abundance since 1980. A multivariate autoregressive state-space model revealed smolt survival four groupings: Washington and Oregon coast, lower Columbia River, Strait of Juan de Fuca, and Puget Sound – Keogh River populations. Declines in smolt survival rates were seen for three of the four groupings. Puget Sound and Keogh River populations have experienced low rates since the early 1990s. Correlations between population pairs’ time series and distance apart illustrated that smolt survival rates were more positively correlated for proximate populations, suggesting that important processes, including those related to ocean survival, occur early in the marine life of steelhead.