PULASKI COUNTY, Va. (WFXR) — The summertime can already be difficult on striped bass in Pulaski County’s Claytor Lake, but considering more than 100 dead striped bass have been reported around the lake in the last week, wildlife officials believe this year’s conditions are exceptionally tough on the fish.

According to the Virginia Department of Wildlife Resources (DWR), the striped bass in Claytor Lake need to choose between water at preferred temperatures and water with enough oxygen to keep them alive.

The DWR says that striped bass require water temperatures less than 75 to 77 degrees Fahrenheit, as well as dissolved oxygen levels greater than 2 to 3 milligrams per liter (mg/l).

Officials say the Department of Environmental Quality’s (DEQ) recent water quality sampling near Claytor Dam indicated the dissolved oxygen concentration in the water below about 23 feet dropped to less than 2 mg/l.

Even though most fish would be stressed at such low dissolved oxygen levels, largemouth and smallmouth bass, sunfish, catfish, and other species are able to avoid that stress by staying at shallower depths, according to the DWR. However, striped bass also require cooler water temperatures, which are normally found at deeper depths.

The water temperatures observed during the recent DEQ sampling reportedly surpassed the preferred range for striped bass all the way down to about 50 feet, with dissolved oxygen levels less than 1mg/l in areas with favorable water temperatures.

The conditions that lead to this “habitat squeeze” result from a normal phenomenon that occurs in nearly all lakes known as thermal stratification. As the upper layer of water in a lake warms during late spring or summer, the deeper and colder waters become isolated from the upper layer. The upper layer of water is generally well oxygenated through wind and wave action. Since colder water is denser than warmer water, the layers don’t mix and the water lower in the lake does not receive additional oxygen inputs from the upper layer. This limits the amount of oxygen in deeper waters, and what oxygen is in those waters is eventually consumed by fish through normal biological activity.

Statement released on July 26, 2022 by the Virginia Department of Wildlife Resources

As the available oxygen in the lower waters is consumed while the upper waters heat up over the course of the summer, the striped bass get trapped between the upper, warmer layer of water with plenty of oxygen and the deeper, cooler water that does not have enough oxygen to support them, which is typically when the DWR says it sees a “striped bass kill.”

On Thursday, July 21, DWR Aquatics staff noticed 43 dead striped bass — ranging in length from 18 inches to more than 30 inches — between Claytor Dam and the Claytor Dam State Park. In addition, anglers on the lake reported at least 60 more dead striped bass to the DWR on Saturday, July 23 and Sunday, July 24, officials say.

According to the department, “striped bass kills” are not uncommon on Claytor Lake, adding that they’re usually more severe during periods with high air temperatures and low inflow from the New River, which the region recently experienced.

In addition, wildlife officials tell WFXR News that hybrid striped bass are stocked in Claytor Lake, where they do better since they have a higher temperature tolerance and can usually move higher in the water column where oxygen is more available.

The DWR says it will continue to monitor the situation on Claytor Lake, but there is not much it can do to fix the immediate habitat conditions.

If the conditions that lead to striped bass deaths on Claytor Lake do become more frequent, though, the department plans to evaluate this species’ management strategies.

For more information, you are asked to email fisheries@dwr.virginia.gov.