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Keywords:

  • Atlantic salmon;
  • ecology;
  • streamflow;
  • climate change

Abstract

For the past 22 years, we have monitored hydro-meteorological conditions and fish population dynamics in Catamaran Brook, a 52 km2 catchment in the Miramichi River system of New Brunswick, Canada. Given the long-term nature of the multidisciplinary dataset, we are able to provide an overview of the complex interaction between streamflow and fish population dynamics drawing on previously published material as well as new data analyses. For autumn-spawning fishes like the Atlantic salmon, access to headwater reaches was directly related to streamflow during late October (when they ascend spawning tributaries), as well as the propensity of beaver dams in the stream (also a function of streamflow). Winter streamflow was positively correlated with egg survival, except when rain-on-snow conditions induced severe ice break-up events that likely caused the highest mortalities on record for salmon and other fishes. Juvenile recruitment was significantly influenced by density-dependent processes of growth and competition but further mediated by density-independent factors like winter flow. In spring, fry emergence was largely temperature-driven, although peaks in fry drift were sometimes synchronized with secondary discharge peaks and temperature. Tributaries like Catamaran Brook provide thermal refugia for coolwater fishes like salmon and trout during the summer when wide, shallow main-stem Atlantic rivers experience low discharge and high water temperatures that induce physiological and behavioural stress (i.e. > 23 °C). These phenomena are discussed in detail, especially in terms of how they may be compromised by future changes in hydrologic conditions resulting from predicted climate change scenarios. Copyright © 2012 John Wiley & Sons, Ltd.