Not only trout but also larger pikes have been affected.

"The prolonged heat wave has raised the temperature of the water to a level where the amount of oxygen in the shallow upper reaches and in part of the middle reaches of the cold-water Minija has reached the limit values for fish, triggered a massive fish die-off," Erlandas Paplauskis, environmental specialist at Pajurio Regioninis Parkas (Seaside Regional Park), told the website.

"A long section of the bottom is covered by dead fish," he said after diving to inspect the river bed.