Primary research paper


, Volume 603, Issue 1, pp 183-196

First online:

Summer temperature variation and implications for juvenile Atlantic salmon

  • Martha E. MatherAffiliated withU.S. Geological Survey, Massachusetts Cooperative Fish and Wildlife Research Unit, Department of Natural Resources Conservation, University of Massachusetts Email author 
  • , Donna L. ParrishAffiliated withU.S. Geological Survey, Vermont Cooperative Fish and Wildlife Research Unit, The Rubenstein School of Environment and Natural Resources, 312 Aiken Center, University of Vermont
  • , Cara A. CampbellAffiliated withU.S. Geological Survey, Leetown Science Center, Northern Appalachian Research Branch
  • , James R. McMenemyAffiliated withVermont Department of Fish and Wildlife
  • , Joseph M. SmithAffiliated withMassachusetts Cooperative Fish and Wildlife Research Unit, Department of Natural Resources Conservation, University of Massachusetts

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Temperature is important to fish in determining their geographic distribution. For cool- and cold-water fish, thermal regimes are especially critical at the southern end of a species’ range. Although temperature is an easy variable to measure, biological interpretation is difficult. Thus, how to determine what temperatures are meaningful to fish in the field is a challenge. Herein, we used the Connecticut River as a model system and Atlantic salmon (Salmo salar) as a model species with which to assess the effects of summer temperatures on the density of age 0 parr. Specifically, we asked: (1) What are the spatial and temporal temperature patterns in the Connecticut River during summer? (2) What metrics might detect effects of high temperatures? and (3) How is temperature variability related to density of Atlantic salmon during their first summer? Although the most southern site was the warmest, some northern sites were also warm, and some southern sites were moderately cool. This suggests localized, within basin variation in temperature. Daily and hourly means showed extreme values not apparent in the seasonal means. We observed significant relationships between age 0 parr density and days at potentially stressful, warm temperatures (≥23°C). Based on these results, we propose that useful field reference points need to incorporate the synergistic effect of other stressors that fish encounter in the field as well as the complexity associated with cycling temperatures and thermal refuges. Understanding the effects of temperature may aid conservation efforts for Atlantic salmon in the Connecticut River and other North Atlantic systems.


Global climate change Salmo salar Thermal regime