title: Climate and ecosystem linkages explain widespread declines in North American Atlantic salmon populations.
abstract: North American Atlantic salmon (Salmo salar) populations experienced substantial declines in the early 1990s, and many populations have persisted at low abundances in recent years. Abundance and productivity declined in a coherent manner across major regions of North America, and this coherence points toward a potential shift in marine survivorship, rather than local, river-specific factors. The major declines in Atlantic salmon populations occurred against a backdrop of physical and biological shifts in Northwest Atlantic ecosystems. Analyses of changes in climate, physical, and lower trophic level biological factors provide substantial evidence that climate conditions directly and indirectly influence the abundance and productivity of North American Atlantic salmon populations. A major decline in salmon abundance after 1990 was preceded by a series of changes across multiple levels of the ecosystem, and a subsequent population change in 1997, primarily related to salmon productivity, followed an unusually low NAO event. Pairwise correlations further demonstrate that climate and physical conditions are associated with changes in plankton communities and prey availability, which are ultimately linked to Atlantic salmon populations. Results suggest that poor trophic conditions, likely due to climate-driven environmental factors, and warmer ocean temperatures throughout their marine habitat area are constraining the productivity and recovery of North American Atlantic salmon populations.
authors.affiliation: School of Marine Sciences, University of Maine, Aubert Hall, Orono, ME, 04469, USA; Gulf of Maine Research Institute, 350 Commercial Street, Portland, ME, 04101, USA.
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Mills
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Pershing
authors.forename: Timothy F
authors.initials: TF
authors.lastname: Sheehan
authors.forename: David
authors.initials: D
authors.lastname: Mountain
mesh_terms: D000818:Animals; D001267:Atlantic Ocean; D002170:Canada; D002980:Climate; D017753:Ecosystem; D008962:Models, Theoretical; D036441:Osmeriformes; D010839:Phytoplankton; D011156:Population Density; D020317:Salmo salar; D014481:United States; D015048:Zooplankton
keywords: Northwest Atlantic; capelin; chronological cluster analysis; climate change; dynamic factor analysis; phytoplankton; regime shift; sea surface temperature; zooplankton