Understanding Late Summer Fish Mortality Events in Lake James
In September, visitors to the Linville side of Lake James and below the dam may notice a troubling sight: dead walleye and other fish floating to the surface. While wildlife officials investigate each incident, this recurring issue is actually the result of an ecological chain reaction that started decades ago.
An Important Factor: In the early 2000s, invasive fish species called blueback herring and alewife were introduced to Lake James—either intentionally or by accident. They quickly multiplied and became a primary food source for the lake's resident walleye. Unfortunately, this new food source eventually became a major threat to the walleye's survival.
Why Do the Fish Die? The problem peaks as the seasons change. In September, temperature shifts cause the lake's water layers to mix, which changes where oxygen is available deep underwater:
- The blueback herring and alewife cram into thin, unstable bands of oxygenated water.
- The hungry walleye follow these “bait” fish into these narrow spaces.
- Because the oxygen bands are small and shift easily, walleye often get trapped in "dead zones" with almost no oxygen. As dissolved oxygen levels decline, the walleye can experience severe stress or mortality and may later be observed floating at the surface.
A Bigger Ecosystem Crisis: These late-summer die-offs are just one visible sign of the damage. Blueback herring, alewife, and other invasive species have severely limited the walleye's ability to naturally reproduce in Lake James. Today, fish stocking plays a dominant role in maintaining the Lake James walleye fishery.
How You Can Help: Local wildlife officials are monitoring this ongoing issue. It serves as a reminder of how easily invasive species can permanently damage a lake's natural balance. To help protect our waters and stop the spread of invasive species, please do your part: Anglers and boaters can help prevent the spread of aquatic invasive species by draining water from boats and livewells, removing aquatic plants and debris, and thoroughly cleaning equipment before visiting another waterbody.
Finally: It is important to report observations of possible water quality problems. The NC Department of Environmental Quality has a website where you can report fish kills and algal blooms. Other suspected water pollution problems can be reported to your regional DEQ office.
