Latitudinal variation in growth and otolith‐inferred field metabolic rates of Canadian young‐of‐the‐year Arctic charr

Abstract

Countergradient variation (CGV) is defined as genetic variation that counteracts the negative influences of the physical environment, minimising phenotypic variability along an environmental gradient. CGV is thought to have relevance in predicting the response of organisms to climate variability and change. To test the hypothesis that growth rate increased with latitude, consistent with CGV, young-of-the-year (YOY) Arctic charr, Salvelinus alpinus, were examined along a~27°latitudinal gradient in central and eastern Canada. Growth rates were estimated from fork lengths standardised by the thermal opportunity for growth based on experienced water temperatures derived using otolith oxygen stable isotopes. Results demonstrated patterns consistent with CGV, where northern populations demonstrated faster growth rates. A secondary aim was to test for similar geographical patterns in otolith-inferred metabolic rates, which reflect the energetic costs of standard metabolic rate (SMR) and other processes such as feeding, locomotion, thermoregulation, reproduction and growth. Results demonstrated a significant, positive relationship between otolith-inferred metabolic rate and latitude, which may reflect an increase in one, or a combination, of the above-noted physiological processes. The similar latitudinal pattern in growth and otolith-inferred metabolic rates suggests greater intake of food per unit of time by northern fish. The phenotypic variation in physiological traits observed here demonstrates the significant adaptability of Arctic charr to different thermal regimes with different growing season lengths. Determining the relative contributions of phenotypic plasticity and genetic variation to the observed latitudinal variation will be critical to predicting the responses of Arctic charr to climate change more accurately.

Evidence of counter‐gradient growth in western pond turtles (Actinemys marmorata) across thermal gradients

“…Similar patterns of growth compensation have been observed in numerous other ectotherms, including fish (Chavarie et al, 2010;Rypel, 2013;Sinnatamby et al, 2015), amphibians (Berven, Gill & Smith-Gill, 1979) and invertebrates (Trussell, 2000;Heilmayer et al, 2005). When the growth compensation is shown to be the result of genetic adaptation, the phenomenon is called counter-gradient variation (Conover & Present, 1990;Conover & Schultz, 1995;Conover, Duffy & Hice, 2009).…”

Thermal habitat segregation among morphotypes of whitefish (Coregonus lavaretus: Salmonidae) and invasive vendace (C. albula): a mechanism for co‐existence?

“…Higher values of M indicate higher metabolic rates, as an increase in metabolic rate results in an increased concentration of metabolically derived carbon in the bloodstream and endolymphatic fluid (Solomon et al, 2006). Values of M at both our sites are high relative to laboratory studies (17-32%) (Høie et al, 2003;Solomon et al, 2006;Tohse & Mugiya, 2008;Elsdon et al, 2010), but overlapped with field-based ranges reported by Sinnatamby et al (2014) Vendace M values were significantly higher in the CE site relative to the ID site, and within the CE site, they were significantly higher than LSR and SSR values. The higher M values for vendace occupying lower temperatures suggest that these M values are driven by activity (e.g.…”

“…In addition to providing insight into dietary resource use, d 13 C oto can be used to make inferences about metabolic rate from the calculation of M, that is the contribution of metabolically derived carbon to d 13 C oto (e.g. Lin et al, 2012;Kahilainen et al, 2014;Sinnatamby et al, 2014). Higher values of M indicate higher metabolic rates, as an increase in metabolic rate results in an increased concentration of metabolically derived carbon in the bloodstream and endolymphatic fluid (Solomon et al, 2006).…”

“…Therefore, d 18 O values can be used to estimate the water temperature at which fish have lived (Devereux, 1967). Furthermore, as the d 13 C value of otoliths is derived from ambient dissolved inorganic carbon (DIC) and respired metabolic carbon (Weidman & Millner, 2000), otoliths can provide information on habitat (Pruell, Taplin & Karr, 2010;Dufour et al, 2008;Murdoch & Power 2013), diet (Elsdon et al, 2010;Nelson et al, 2011) and metabolic rate (Lin et al, 2012;Sinnatamby et al, 2014).…”

Field metabolic rates of teleost fishes are recorded in otolith carbonate

“…Earlier studies have used measurements of δ 13 C oto as a proxy for metabolic rate without being able to convert the values into oxygen consumption. Hence, these studies were limited to qualitative estimates of differences in FMR among life stages or groups of fish 41 or correlative studies between δ 13 C oto or M oto and growth rate 42 . Our study calibrates the M oto to measured oxygen consumption and provides strong evidence for the accuracy of this FMR proxy.…”