How repeatable is CT_max within individual brook trout over short- and long-time intervals?

Area of Science:

• Aquatic Ecology
• Fish Physiology
• Climate Change Biology

Background:

• Rising stream temperatures threaten cold-water fish populations.
• Understanding thermal tolerance is crucial for predicting species adaptation.
• Critical thermal maximum (CTmax) is a common but often unvalidated measure of thermal tolerance.

Purpose of the Study:

• To assess the repeatability of CTmax as a metric for thermal tolerance in brook trout.
• To determine if CTmax is a consistent measure within individual fish over time.

Main Methods:

• Individually marked adult brook trout (Salvelinus fontinalis) were held in a laboratory setting.
• CTmax was measured three times for each fish over a period of approximately one year.
• Repeatability of CTmax measurements within individuals was statistically analyzed.

Main Results:

• CTmax was found to be a repeatable trait in brook trout (Repeatability ± S.E.: 0.48 ± 0.14).
• Individual male brook trout exhibited consistent CTmax values over time.
• Female brook trout showed a slight increase in CTmax over the study period.

Conclusions:

• CTmax is a robust and repeatable metric for estimating thermal tolerance in brook trout.
• This finding supports the use of CTmax in studies investigating fish adaptation to warming waters.
• Repeatability of CTmax is essential for reliable predictions of climate change impacts on fish populations.