Environmental factors influencing freshwater survival and smolt production in Pacific Northwest coho salmon (Oncorhynchus kisutch)

• Published in: Canadian journal of fisheries and aquatic sciences 2004-03, Vol.61 (3), p.360-373
• Main Authors: Lawson, P W, Logerwell, E A, Mantua, N J, Francis, R C, Agostini, V N
• Format: Article
• Language: English
• Subjects: Agnatha. Pisces; Air temperature; Animal and plant ecology; Animal behavior; Animal, plant and microbial ecology; Animals; Autoecology; Biological and medical sciences; Climate change; Climate effects; Climate variability; Environmental conditions; Environmental factors; Fish; Fish hatcheries; Fisheries; Fisheries management; Fresh water; Freshwater; Freshwater ecology; Freshwater environments; Fundamental and applied biological sciences. Psychology; Intermittent streams; Marine; Marine environment; Oncorhynchus kisutch; Rivers; Salmon; Sea surface temperature; Sex ratio; Spawning; Stream discharge; Stream flow; Survival; Survival analysis; Temperature; Vertebrata; Wildlife
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/f04-003

Climate variability is well known to affect the marine survival of coho salmon (Oncorhynchus kisutch) in Oregon and Washington. Marine factors have been used to explain up to 83% of the variability in Oregon coastal natural coho salmon recruitment, yet about half the variability in coho salmon recruitment comes from the freshwater life phase of the life cycle. This seeming paradox could be resolved if freshwater variability were linked to climate and climate factors influencing marine survival were correlated with those affecting freshwater survival. Effects of climate on broad-scale fluctuations in freshwater survival or production are not well known. We examined the influence of seasonal stream flows and air temperature on freshwater survival and production of two stock units: Oregon coastal natural coho salmon and Queets River coho salmon from the Washington Coast. Annual air temperatures and second winter flows correlated strongly with smolt production from both stock units. Additional correlates for the Oregon Coast stocks were the date of first fall freshets and flow during smolt outmigration. Air temperature is correlated with sea surface temperature and timing of the spring transition so that good freshwater conditions are typically associated with good marine conditions.