Temperature, Emergence Phenology and Consumption Drive Seasonal Shifts in Fish Growth and Production Across Riverscapes
We assessed spatial patterns and processes determining seasonal changes in juvenile Chinook Salmon (Oncorhynchus tshawytscha) size, growth and production over 30–40 km in two NE Oregon subbasins. Spatial heterogeneity in incubation temperatures corresponded to later estimated emergence timing with distance upstream in both subbasins. During spring, estimated growth rates decreased with distance upstream, and coupled with emergence patterns, resulted in pronounced longitudinal gradients in body size by July. During summer, spatial patterns of growth reversed, with greater diet ration sizes and growth efficiencies upstream than downstream. At downstream sites, up to 80% of an individual’s growth by late September occurred in spring (emergence – early July), but spring growth contributions were as low as 10% in upstream sites. Coupling longitudinal patterns of fish density and growth revealed that spring contributions to total basin production were 65% and 40% in the two subbasins. This study demonstrates that longitudinal gradients of fish growth and production can reverse across seasons, and reveals important contributions of warmer, downstream habitats to overall production that occurred during cooler times of the year.
Kaylor, M.J., C. Justice, J.B. Armstrong, B.A. Staton, L.A. Burns, E. Sedell, and S.M. White. 2021. Temperature, emergence phenology, and consumption drive seasonal shifts in fish growth and production across riverscapes. Journal of Animal Ecology 90(7):1727-1741. Online at https://doi.org/10.1111/1365-2656.13491.