The 20 °C Protocol: A Life-Saving Shield for Atlantic Salmon

A heat protocol based on a target temperature of 20°C is an emergency measure designed to reduce physiological stress and mortality in salmon when the water becomes too warm.

Here's why this measure is beneficial for the species' survival:

1. Prevention of Heat Stress

Atlantic salmon are cold-water fish. Their metabolism accelerates as water temperatures rise:

At 20°C and above: Salmon enter a state of stress. They draw on their energy reserves (necessary for reproduction) simply to regulate their body temperature.

The benefit: By ceasing fishing at this temperature, we avoid adding physical stress (the fight at the end of the line) to an already weakened organism.

2. Reduced Mortality After Release

Even if an angler carefully releases their salmon (catch and release), the chances of survival drop drastically in warm water:

Lack of Oxygen: Warm water contains less dissolved oxygen. A salmon that has just exerted itself intensely to free itself struggles to recover and can die of asphyxiation or exhaustion a few hours later.

The Benefit: The protocol ensures that salmon that have successfully reached the cold pools are not disturbed, thus maximizing the number of spawners available for the spawning season.

3. Protection of "Thermal Refuges"

When the river temperature exceeds 20°C, salmon congregate, if possible, in cooler areas (stream mouths, underground springs).

Vulnerability: In these pockets of cold water, the fish are highly concentrated and become easy targets for fishing or poaching.

The benefit: The protocol protects these critical aggregation areas, allowing salmon to pass undisturbed through the heatwave.

In summary:

Strictly enforcing the 20°C threshold acts as a temporary shield. It's an adaptive management approach: the river is closed when the risk of mortality is too high, and reopened as soon as the water cools (often below 18°C ​​for 48 hours).