A growing body of research suggests that “freshwater browning” is changing fish populations in lakes across northeastern North America and northern Europe.

The darkening of lakes is caused by increasing amounts of dissolved organic carbon entering the water through climate-driven runoff and changing soil chemistry. As water becomes darker, visibility decreases, making it more difficult for many fish species to feed and avoid predators.

Researchers found that browner lakes are associated with lower populations of lake trout, lake whitefish, yellow perch, largemouth bass and smallmouth bass, while brook trout showed no measurable change.

In contrast, northern pike and walleye appear to benefit from darker water. Scientists believe their specialized senses allow them to hunt more effectively in low-visibility conditions.

The findings also suggest anglers may need to adapt by using lures that create vibration or scent rather than relying primarily on visual attraction in stained water.