MEPS 454:75-82 (2012)  -  DOI: https://doi.org/10.3354/meps09643

ABSTRACT: Interspecific variations in thermal growth performance of ectotherms have received considerable recent interest fueled by the focus on ecological climate change effects. Among-population variations in growth are commonly observed in field studies. However, the role of phenotypic plasticity in shaping this variation is largely unexplored in teleost fishes. Here, we tested for the effect of incubation temperature on thermal scaling of growth and maximum growth performance of the anadromous salmonid Atlantic salmon Salmo salar L. Salmon eggs were incubated and reared until the onset of exogenous feeding at either heated or natural temperatures or transferred from natural to heated temperatures at the time of hatching, creating 3 different embryonic temperature treatments (heated, natural or mixed). We subsequently tested for juvenile growth performance of these groups at 8 temperatures ranging from 6 to 24°C. Maximum growth was significantly higher in the heated than the natural and mixed incubation temperature groups, but we did not observe differences in the thermal scaling of growth performance. Neither the upper nor lower thermal limit for growth nor the optimal growth temperature differed between the 3 incubation temperature treatments. However, thermal conditions experienced by incubating embryos affected later growth performance. Although similar results have been observed previously among reptiles, this is to our knowledge the first empirical support for this hypothesis among teleost fishes. Phenotypic plasticity in growth performance can likely explain many of the contrasting findings from previous research on countergradient growth effects in teleost fishes.

KEY WORDS:  Countergradient variation · Growth reaction norms · Salmo salar L. · Thermal adaptation · Thermal performance