Metabolic rates of embryos and alevin from a cold-adapted salmonid differ with temperature, population and family of origin: implications for coping with climate change

Early developmental stages of cold-adapted ectotherms such as brook trout (Salvelinus fontinalis) are at higher risk of mortality with increasing water temperatures. To determine the amount of variation present in early life, which may allow for potential adaptation to increasing temperature, we examined the routine metabolic rates (RMR) of wild-origin brook trout embryos and alevins reared at normal (5°C) and elevated (9°C) temperatures. The experiment was structured to examine variation in RMR within and among several levels of biological organization (family, population and ancestral type (native vs. mixed ancestry)). As expected, family and temperature variables were most important for predicting RMR and body mass, although population-level differences also existed when family was excluded for more detailed analysis. Additionally, body mass strongly influenced RMR at all life stages except for eyed embryos. When family identity was removed from the analysis, population became the most significant variable. Variation in RMR and mass within and among populations may indicate existing adaptive potential within and among brook trout populations to respond to predicted warming under climate change scenarios.

A RE-EXAMINATION OF THE TAXONOMIC POSITION OF THE AURORA TROUT

Results of a field study are used in considering the taxonomic position of the aurora trout. Coloration and morphology of aurora and brook trout are compared. There are at best only minor differences—in some aspects of coloration, in epidermal thickness, and in behavior—between these fish. These differences are genetically controlled. Aurora trout fill the brook trout niche in lakes which they inhabit. Characteristics of the home range lakes are given. Aurora and brook trout are fully interfertile, but reproductively isolated sympatric populations existed in one lake. It is suggested that the aurora trout is a race of the brook trout worthy of nomenclatural recognition as a subspecies, and that it should be classified as Salvelinus fontinalis timagamiensis Henn and Rickenbach.