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The first year of life is perilous for a salmonid, typified by a critical period of post-emergence mortality. 

To evaluate the connection between environmental variability and Coho salmon survival in the first year of life, researchers measured macroinvertebrate prey availability and appropriate temperatures for young-of-year Coho salmon in two Alaska streams – one groundwater-fed with low thermal variability and one surface-water fed with much greater temperature variability. In the surface-water stream, fry emerged when temperatures warmed to levels that maximized growth. In the groundwater-fed stream, fry emergence coincided with peaks in macroinvertebrate prey availability. There were no significant differences in observed Coho salmon growth, body lengths, or consumption between streams. Importantly, emergence timing was the same in both streams, but linked to different factors potentially influencing summer growth. This research provides insights into the first summer of life for Coho salmon and the complexities of growth dynamics that emerge when considering local environmental variability. 

Campbell, E.Y., Dunham, J.B., Reeves, G.H., 2020, Linkages between temperature, macroinvertebrates, and young-of-year Coho salmon growth in surface-water and groundwater streams: Freshwater Science, v. 39, no. 3, p. 447-460, 

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