Temperature Variability and Acidity Affect Incubation Time of Brook Trout Embryos

In fish, early life history stages are particularly vulnerable to environmental variability. The effects of climate change have been predicted to be far reaching, and environmental gradients such as temperature (mean and variability) and acidity will likely be affected in freshwater environments. Such changes, particularly average temperature, can have serious consequences on the phenology of hatch and emergence in fish, and this can have repercussions for survival and recruitment. In this study, we examined the simultaneous impacts of temperature variability and acidity on brook trout incubation. Embryos were individually raised to hatch in four treatments consisting of two temperatures (stable(S):5^oC and variable(V): ranging from 2 to 8^oC, mean 5^oC) at two pH levels (benign(B):6.5 and acidic(A):5.25). A preliminary Kaplan-Meier survival analysis indicates that there was a significant difference in incubation time among the four treatments (χ²₍₃₎=72.1 , p<0.0001). The variable-benign (VB) treatment had the widest 95% confidence interval (70-90) compared to the other three treatments (VA:80-90, SB:80-91, and SA:85-93). Our results show that at the same number of degree days, temperature variation and acidity affect brook trout incubation time. This can have consequences for timing of other important events, such as emergence and synchronization with peak prey abundance.