Abstract
Environment–phenotype interactions are the most pronounced during early life stages and can strongly influence metabolism and ultimately ecological fitness. In the present study, we examined the effect of temperature [ambient river temperature (ART) vs ART+2°C], dissolved oxygen (DO; 100% vs 80%) and substrate (presence vs absence) on standard metabolic rate, forced maximum metabolic rate and metabolic scope with Fulton’s condition factor (K), energy density (ED) and critical thermal maximum (CTmax) in age-0 Lake Sturgeon, Acipenser fulvescens, before and after a simulated overwintering event. We found that all the environmental variables strongly influenced survival, K, ED and CTmax. Fish reared in elevated temperature showed higher mortality and reduced K pre-winter at 127 days post-hatch (dph). Interestingly, we did not find any significant difference in terms of metabolic rate between treatments at both sampling points of pre- and post-winter. Long-term exposure to 80% DO reduced ED in Lake Sturgeon post-winter at 272 dph. Our data suggest that substrate should be removed at the onset of exogenous feeding to enhance the survival rate of age-0 Lake Sturgeon in the first year of life. Effects of early rearing environment during larval development on survival over winter are discussed with respect to successful recruitment of stock enhanced Lake Sturgeon, a species that is at risk throughout its natural range.
Highlights
Phenotypic development is known to strongly influence growth trajectory and ecological fitness of individuals (Lindström, 1999)
ambient river temperature (ART) was created based on the average daily temperature profile rounded up to the nearest 0.5◦C recorded at Slave Falls on the Winnipeg River from 2013 to 2016 (Fig. 1), and 100% or 80% dissolved oxygen (DO) hereafter refers to treatments where tank water was maintained at 100% or 80% DO relative to air saturation in holding water regulated by injecting air or nitrogen gas
At 127 dph, comparison of the individual treatments revealed that Lake Sturgeon raised in ART 100% DO showed a significantly higher K than those raised in ART+2◦C 100% DO without substrate and ART+2◦C 80% DO without substrate (Fig. 2; P < 0.05)
Summary
Phenotypic development is known to strongly influence growth trajectory and ecological fitness of individuals (Lindström, 1999). The importance of the environment during early development has been well studied across taxa, and a number of models have been proposed to understand the long-term consequences (Monaghan, 2008). The environmental matching hypothesis has many implications for conservation biology in instances where captivereared individuals are released into the wild to enhance the status of endangered or at-risk populations. Environmental enrichment in artificial settings has been used to mimic key factors from the natural environment to naturalize phenotypes and promote acquisition of vital skills as well as growth performance (McAdam, 2011; Lönnstedt et al, 2012; Chivers and Ferrari, 2013). Understanding how key abiotic factors shape phenotypic development and how these phenotypes will influence survival rates in the first year of life, during the challenging first overwintering event, would directly benefit conservation programs (Johnsson et al, 2014)
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