Abstract
The effects of early thermal environment on growth, age at maturity, and sexual size dimorphism in Arctic charr (Salvelinus alpinus) are investigated. This study is a 654-day long rearing trial split into two sequential experimental phases termed EP1 and EP2 and lasting 315 and 339 days, respectively. EP1 started at the end of the yolk sac stage when the experimental fish were divided into three groups and reared at different target temperatures (7, 10 and 12 °C). During EP2, all groups were reared at the same temperature (7–8 °C) until harvest (~1300 g). Growth rates increased with temperature from 7 to 12 °C, and at the end of EP1 the 12C group had 49.0% and 19.2% higher mean weight than groups 7C and 10C, respectively. Elevated early rearing temperatures were, however, found to cause precocious sexual maturation and reduce the long-term growth performance. At the end of EP2, the 7C group had 3.6% and 14.1% higher mean weight than 10C and 12C, respectively. Elevated early rearing temperatures had a much stronger effect on the maturity incidence of females, and while male-biased sexual size dimorphism (SSD) was found in all groups, the magnitude of SSD was positively associated with temperature.
Highlights
Temperature is the most important environmental factor influencing the development and growth rate in fish
Fish have frequently been found to have a high level of plasticity during early life stages [7], and the responses to early conditions appear to be modified by epigenetic mechanisms, such as deoxyribonucleic acid (DNA) methylation [8]
The present study demonstrates that Arctic charr has a high degree of thermal plasticity, as rearing temperatures over a period of 315 days from the end of the yolk-sac stage until ~50 g can profoundly influence long-term growth performances and the incidence of precocious maturity at harvest
Summary
Temperature is the most important environmental factor influencing the development and growth rate in fish. In addition to affecting growth rate, temperature can modify a range of phenotypic traits, such as the development of the axial skeleton, muscle growth dynamics, age at puberty, and head shape [3,4,5,6]. The ability of organisms to express different phenotypes in response to environmental conditions is known as phenotypic plasticity. Fish have frequently been found to have a high level of plasticity during early life stages [7], and the responses to early conditions appear to be modified by epigenetic mechanisms, such as deoxyribonucleic acid (DNA) methylation [8]. A growing number of studies provide evidence that epigenetic mechanisms are associated with commercially important traits in aquaculture [9]
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