Ice age fish in a warming world: minimal variation in thermal acclimation capacity among lake trout (Salvelinus namaycush) populations.

N I Kelly,J L Mcdermid,G Burness,C C Wilson

doi:10.1093/conphys/cou025

Abstract

In the face of climate change, the persistence of cold-adapted species will depend on their adaptive capacity for physiological traits within and among populations. The lake trout (Salvelinus namaycush) is a cold-adapted salmonid and a relict from the last ice age that is well suited as a model species for studying the predicted effects of climate change on coldwater fishes. We investigated the thermal acclimation capacity of upper temperature resistance and metabolism of lake trout from four populations across four acclimation temperatures. Individuals were reared from egg fertilization onward in a common environment and, at 2 years of age, were acclimated to 8, 11, 15 or 19°C. Although one population had a slightly higher maximal metabolic rate (MMR), higher metabolic scope for activity and faster metabolic recovery across all temperatures, there was no interpopulation variation for critical thermal maximum (CTM) or routine metabolic rate (RMR) or for the thermal acclimation capacity of CTM, RMR, MMR or metabolic scope. Across the four acclimation temperatures, there was a 3°C maximal increase in CTM and 3-fold increase in RMR for all populations. Above 15°C, a decline in MMR and increase in RMR resulted in sharply reduced metabolic scope for all populations acclimated at 19°C. Together, these data suggest there is limited variation among lake trout populations in thermal physiology or capacity for thermal acclimatization, and that climate change may impact lake trout populations in a similar manner across a wide geographical range. Understanding the effect of elevated temperatures on the thermal physiology of this economically and ecologically important cold-adapted species will help inform management and conservation strategies for the long-term sustainability of lake trout populations.

Highlights

Global climate change is predicted to impact ecosystems significantly over the century (Magnuson et al, 1997; Schindler, 1997; Pörtner, 2002; Brander, 2010), with expected implications for species and populations (Walther et al, 2002; Parmesan, 2006; Eliason et al, 2011; Pauls et al, 2013)
Lake trout acclimated to 15°C weighed significantly less than fish acclimated to 11°C (Tukey’s honestly significant difference (HSD), P < 0.05)
Lake trout acclimated to 15°C were significantly smaller than fish acclimated to 8 or 11°C, and fish acclimated to 19°C were smaller than fish acclimated to 8°C (Tukey’s HSD, P < 0.05)

Summary

Introduction

Global climate change is predicted to impact ecosystems significantly over the century (Magnuson et al, 1997; Schindler, 1997; Pörtner, 2002; Brander, 2010), with expected implications for species and populations (Walther et al, 2002; Parmesan, 2006; Eliason et al, 2011; Pauls et al, 2013). Predicted effects include changes in the geographical distribution of species (Perry et al, 2005; Pinsky et al, 2013), alterations to phenological processes (Bradshaw and Holzapfel, 2006; Shuter et al, 2012) and species interactions (Tylianakis et al, 2008). Overall, this may potentially result in the extinction or extirpation of many terrestrial, marine and aquatic species over the century (Thomas et al, 2004; Xenopoulos et al, 2005; Somero, 2010)

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