Age‐specific aggregation of wild juvenile Atlantic salmon Salmo salarat cool water sources during high temperature events

• Published in: Journal of Fish Biology
• Main Authors: Breau, C., Cunjak, R. A., Bremset, G.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2007
• Subjects: Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1111/j.1095-8649.2007.01591.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1095-8649.2007.01591.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1095-8649.2007.01591.x

This study quantified the use of cool water sources by wild 0+, 1+ and 2+ year Atlantic salmon Salmo salar during high water temperatures ( i.e. >23° C) in summer 1995 and 2004. During these events, 0+ year Atlantic salmon did not aggregate or increase in abundance in cool water sites. Interestingly, 1+ and 2+ year Atlantic salmon numbers increased in cool water sites. In addition, these older juveniles formed numerous, discrete aggregations along the plume created by a tributary with aggregation locations being similar between years. Aged 2+ year fish aggregations were at the coolest sources whereas 1+ year aggregations were in locations cooler than the main river. Fish in aggregations on average used deeper sections (average depth: 380 mm) compared with the coolest available habitat in the thermal plume (average depth: 230 mm). Hence, during high temperature events, older juvenile Atlantic salmon moved to cooler water sites and then aggregated in deeper microhabitats.