Effective practices for thermal tolerance polygon experiments using mottled catfish Corydoras paleatus

Area of Science:

• Environmental Physiology
• Aquatic Ecology
• Climate Change Biology

Background:

• Temperature significantly influences fish metabolic resource allocation and physiological processes.
• Assessing thermal limits is vital for predicting fish responses to climate change.

Purpose of the Study:

• To construct a complete thermal tolerance polygon for the Mottled catfish (Corydoras paleatus).
• To evaluate the minimum number of acclimation temperatures required for accurate polygon construction.

Main Methods:

• Utilized Critical Thermal Methodology (CTM) and Chronic Lethal Methodology (CLM) experiments.
• Chronically acclimated fish to six temperatures (7°C to 32°C) for approximately two weeks.
• Determined Chronic Lethal Maxima (CLMax), Chronic Lethal Minima (CLMin), Critical Thermal Maxima (CTMax), and Critical Thermal Minima (CTMin).

Main Results:

• Mottled catfish exhibited CLMax of 34.9°C and CLMin of 3.8°C.
• The highest CTMax recorded was 38.4°C (acclimated to 32.2°C), and the lowest CTMin was 3.36°C (acclimated to 7.2°C).
• A thermal tolerance polygon of 785.7°C² was established, with slopes indicating upper and lower tolerance gains of 0.55°C and 0.32°C per degree of acclimation, respectively.
• Three acclimation temperatures proved sufficient for accurately determining the complete thermal tolerance polygon.

Conclusions:

• The study provides a comprehensive thermal tolerance polygon for Mottled catfish.
• A simplified method using three evenly spread acclimation temperatures, CLMax/CLMin estimates, and CTMax/CTMin measurements is sufficient for constructing thermal tolerance polygons.
• This methodology serves as a template for future research on fish thermal tolerance and climate change impacts.