Abstract
Temperature and individual egg size have been long studied in the development of fishes because of their direct effects on individual fitness. Here we studied the combined effects of three important factors for fish development, i.e. egg size, social environment and water temperature. Arctic charr (Salvelinus alpinus), a coldwater fish known to be phenotypically plastic, was used to investigate how these factors may affect growth and foraging behaviour of juvenile fish in a benign environment. We accounted for the social environment during early development by comparing fish raised in groups and in isolation. We examined the effect of egg size and a 2 °C difference on foraging behaviour, activity and growth a few weeks after first feeding. Growth trajectories of fish originating from large and small eggs were similar within each temperature: larger fish coming large eggs were at all time larger than smaller fish. There was no indication that small fish raised at a higher temperature grew faster than larger fish raised at a lower temperature. A 2 °C difference in temperature affected the behaviour of fish differently according to body size and/or social context. The foraging probability difference between fish raised in groups and fish briefly isolated was higher at 4.5 °C than at 6.5 °C for both size fish. Finally, there was no repeatability in foraging behaviour and mobility for isolated individuals. These results highlight the importance of small changes in temperature when evaluating growth and behaviour of fishes, and reveal the importance of considering the interaction of temperature with other factors, e.g. individual size and social environment, especially at early stages of development in fishes. We discuss these findings in the context of rapid changes in temperature and how temperature and its interaction with other factors may affect the phenotypes, ecology and evolution of coldwater fishes.
Highlights
In fishes, the correlation between egg size and female body size [1,2], as well as the relationship between egg size, offspring size and survival at hatching, [3,4] has been well studied
A gradient was observed as large fish from large eggs at 6.5 ̊C were larger than those at 4.5 ̊C, themselves being larger than small fish coming from small eggs raised at 6.5 ̊C, those being larger than small fish coming from small eggs raised at 4.5 ̊C
The aim of this study was to assess the interactive effect of egg size, social condition and temperature on early body size and behaviour of Arctic charr S. alpinus, a cold-water species, at early life stages of development
Summary
The correlation between egg size and female body size [1,2], as well as the relationship between egg size, offspring size and survival at hatching, [3,4] has been well studied. Offspring from larger eggs typically have higher fitness, e.g. higher survival, and greater resistance to starvation [6,7] These effects are believed to be limited to a short period following hatching, i.e. they tend to decline rapidly throughout development, especially when fish start feeding [8]. In Chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (Oncorhynchus mykiss), offspring from smaller eggs often grew faster than offspring from larger eggs and were capable of catching up in size with the latter or even becoming larger [10,11,12,13] This reduction in maternal effects during ontogeny can be partly explained by the overall environment experienced by the fish during development, and by additive genetic variance [14]. The persistence of correlations between egg size and phenotypic traits of the offspring may be different across species and environments and may have potential implications for both juvenile and adult phenotypes
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