Fisheries biologists from the Virginia Department of Wildlife Resources recently identified gill lice on rainbow trout in a southwestern Virginia stream.
DWR is now asking anglers to help us determine the extent of gill lice by being on the lookout while fishing their favorite trout stream.
Trout infected with gill lice have been observed on Blue Springs Creek, a tributary of Cripple Creek, located in Smyth and Wythe counties. Blue Springs Creek supports a population of wild rainbow trout, but gill lice have been observed on wild trout as well as hatchery trout.
Gill lice are tiny parasitic copepods, a type of zooplankton, that attach themselves to the gills, mouth and fins of trout. A minor gill lice infection can usually be tolerated, but a severe infection can negatively impact a fish’s respiratory capacity. The degree of impact on a trout population may depend on the level of infection and the presence of any other stressors such as high water temperature.
The gill lice recently discovered in southwestern Virginia are likely Salmincola californiansis, a species that specifically uses rainbow trout and related species as a host. Another species of gill lice, Salmincola edwardsii, only infects brook trout. DWR biologists collected gill lice samples and submitted them to the U.S. Fish and Wildlife Service’s Lamar Health Center for identification.
As they have been found on rainbow trout, however, they are likely Salmincola californiansis and pose little threat to native brook trout populations.
DWR staff are currently working to determine if gill lice infections are isolated to Blue Springs Creek, are present in other parts of the Cripple Creek watershed, or have been introduced to other state waters. Once the extent of gill lice has been assessed, DWR will develop a plan to limit the spread to uninfected waters and reduce impacts in waters where gill lice are found.
Trout infected with gill lice are safe to eat as long as they are thoroughly cooked. Anglers can help the DWR by reporting trout infected with gill lice. Additionally, anglers are encouraged to clean and dry their fishing gear after use, especially if they intend to travel to different waters.
For more information, visit dwr.virginia.gov/gill-lice and to report gill lice, email Fisheries@dwr.virginia.gov.