Heatwave threatens trout and salmon in shallow Danish waters

A recent heatwave may have pushed water temperatures high enough to stress or kill trout and salmon in Denmark’s shallow streams and lakes, a biologist with the Danish Anglers Association has warned.

Kaare Manniche Ebert, a biologist at the association, said warm water in low-lying, shallow bodies of water leaves the fish with no cooler refuge. Trout and salmon begin to suffer stress when water reaches 22–23°C and die at 26–27°C, he explained. Wild species such as carp and pike tolerate temperatures well above 30°C.

While the current heatwave was brief and the immediate threat has passed, Ebert warned that prolonged high temperatures could make Danish waterways increasingly inhospitable for trout and salmon, potentially altering fish populations in the long term.

At Hedensted Put and Take, a pay-to-fish lake, owner Martin Secher Henriksen reported that 5–10 trout died after being transferred from cold holding water into the warm lake. He noted that extended heat could have caused wider losses but said the short duration limited the damage. Weekend visitor numbers also dropped due to the heat, he added.