How quickly do brook trout lose long-term thermal acclimation?

Area of Science:

• Ecology
• Environmental Science
• Aquatic Biology

Background:

• Coldwater fish populations are declining due to rising water temperatures from human activities.
• Brook trout exhibit thermal plasticity, adapting to warmer conditions.
• Understanding the rate of thermal acclimation is crucial for predicting fish survival.

Purpose of the Study:

• To determine the rate at which brook trout lose thermal acclimation as water temperatures decrease.
• To assess how prior thermal experience influences future thermal performance in brook trout.

Main Methods:

• Brook trout were acclimated to three thermal regimes (+0°C, +2°C, +4°C above ambient) for two years.
• Fish were then moved to a common, colder temperature (ambient).
• Critical thermal maximum was measured over time to quantify the loss of acclimation.

Main Results:

• Thermal tolerance decreased rapidly within the first week after temperature change.
• Complete loss of acclimation occurred within 42 days, regardless of the initial acclimation temperature.
• The rate of acclimation loss was gradual after the initial rapid decrease.

Conclusions:

• The gradual loss of thermal acclimation in brook trout may aid persistence in warming streams.
• These findings are vital for climate change impact models on aquatic ectotherms.
• Brook trout's thermal plasticity influences their resilience to environmental changes.