Fisheries managers are hopeful that a significant die-off of larger smallmouth bass in spring of 2014 will not have a long-term impact on the South Fork of the Shenandoah River.
“Impacts from this year’s mortality/disease events on the Shenandoah were fairly heavy,” the Virginia Department of Game and Inland Fisheries (DGIF) revealed. “However, DGIF sampled the fish community in the fall of 2014 and found an abundance of 9- to 11-inch fish and a lot of very young smallmouth bass.
“Barring any future disease outbreaks, the 9- to 11-inch fish should grow into the 11- to 15-inch range over the next two years.”
But fisheries managers remain at a loss to explain what caused the death of an estimated 20 percent or more of adult smallmouth bass and redbreast sunfish and what contributed to lesions and other abnormalities on additional fish.
“Determining the cause of these mortality/disease events has proven to be extremely difficult,” VDGIF added. “Scientists have and continue to conduct in-depth studies on fish health, pathogens, water quality, and contaminant exposure, and recently have begun looking at possible toxins related to bacteria.”
Biologist Brad Fink said, “Things were looking pretty good from 2011 on, until we started getting reports from anglers that there weren’t as many fish.”
Spring mortality and disease events have occurred several times on the Shenandoah during the past decade, and also showed up on the Upper James River from 2007 to 2010. But they have been less common since 2010.
In 2014, VDGIF also noted affected fish on the North Fork of the Shenandoah, but the percentage was lower than on the South Fork. Additionally, the agency said, “Things were fairly quiet on the Cowpasture, Jackson, and Upper James River.”
The incidents have not been uniform in location or severity, with smallmouth bass, redbreast sunfish, and rock bass the species most vulnerable. Affected fish typically exhibit open sores or “lesions” on the sides of their bodies, while dead and dying fish often show no visible external abnormalities.
Here’s a look back at a die-off that began in 2003: Questions remain 10 years after Shenandoah River fish kill