Freshwater lakes in North America and Europe are turning browner due to climate change and reduced acid rain. This change is reducing populations of trout, bass, perch and whitefish while boosting numbers of northern pike and walleye.
The darkening of water, known as freshwater browning, stems from higher temperatures and increased runoff that carry more carbon compounds from soil into lakes and streams. Reduced acidic emissions have also altered soil chemistry, further increasing the flow of dissolved plant matter that stains the water.
A study published in 2025 analyzed data from 871 lakes across the two continents and 303 Canadian lakes. It found slower growth rates and smaller populations for lake trout, lake whitefish, yellow perch, largemouth bass and smallmouth bass in darker waters. Northern pike and walleye populations increased, aided by specialized vision and sensory systems suited to low visibility.
Anglers may need to adapt by using vibrating or scented lures instead of visual ones. The shifts could alter lake ecosystems and fishing patterns for millions of people.