Physiological responses to a short-term, environmentally realistic, acute heat stress in Atlantic salmon,Salmo salar

Melanie J Gallant,Suzanne Currie,Sacha Leblanc,Tyson J Maccormack,Karen Kidd

doi:10.1139/facets-2016-0053

Melanie J Gallant, Suzanne Currie + Show 3 more

Open Access

https://doi.org/10.1139/facets-2016-0053

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Abstract

Atlantic salmon populations are declining, and warming river temperatures in the summer months are thought to be a significant contributing factor. We describe the time course of cellular and metabolic responses to an ecologically relevant short-term thermal cycle in juvenile Atlantic salmon. We then examined whether this heat event would affect tolerance to a subsequent heat shock in terms of critical thermal maximum (CTmax). Fish induced heat shock protein 70 in red blood cells, heart, liver, and red and white muscle; whole blood glucose and lactate transiently increased during the heat cycle. In contrast, we observed no significant effect of a prior heat shock on CTmax. The CTmaxwas positively correlated with Fulton’s condition factor suggesting that fish with greater energy reserves are more thermally tolerant. Atlantic salmon activate cellular protection pathways in response to a single thermal cycle and appear to cope with this short-term, ∼1 d heat shock, but this challenge may compromise the ability to cope with subsequent heat events.

Highlights

Temperature remains one of the most significant abiotic factors affecting the biology of fishes (Fry 1958; Hochachka and Somero 2002; Currie and Schulte 2014) primarily because their body temperatures change concomitantly and rapidly with ambient temperatures (Stevens and Sutterlin 1976)
We examined whether this heat event would affect tolerance to a subsequent heat shock in terms of critical thermal maximum (CTmax)
We assessed whether this heat challenge would affect tolerance to a subsequent heat shock in terms of CTmax

Summary

Introduction

Temperature remains one of the most significant abiotic factors affecting the biology of fishes (Fry 1958; Hochachka and Somero 2002; Currie and Schulte 2014) primarily because their body temperatures change concomitantly and rapidly with ambient temperatures (Stevens and Sutterlin 1976). High water temperatures in the summer months have been implicated in the decline of the Atlantic salmon (COSEWIC 2010) in Canada, one of the country’s most important commercial and recreational fishes. Atlantic salmon runs, is reaching exceptionally high water temperatures during the summer months (e.g., 27–30 °C; Caissie et al 2014), exceeding the 23 °C proposed upper tolerance limit of Atlantic salmon as often as 62 d/year (Lund et al 2002; Caissie et al 2012). It is important that we understand tolerance limits and the physiological changes underpinning temperatures representative of thermal events that Atlantic salmon would normally experience in the wild

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