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Gill Lice in Brook Trout in Cullasaja River Tributaries

HIGHLANDS, N.C. — Fisheries biologists with the N.C. Wildlife Resources Commission are asking for anglers’ assistance after gill lice were found on brook trout in several headwater streams of the Cullasaja River in Macon County.

Staff with the Little Tennessee Land Trust found the gill lice in September while sampling fish with the Commission near Highlands. The discovery marked the first time that gill lice have been documented in North Carolina waters. Biologists are concerned what affect these tiny, white crustaceans — also known as copepods — could have on native brook trout populations.

As their name implies, gill lice attach to a fish’s gills, which can traumatize gills and inhibit the fish’s ability to breathe. While most fish are able to tolerate a moderate infestation of gill lice, if they’re suffering from other stressors, such as drought and high water temperatures, fish kills and population impacts are more likely to occur.

“We really do not know how widely distributed gill lice are or the ultimate impacts they may have on our native brook trout populations,” said Jacob Rash, the Commission’s coldwater research coordinator. “We are particularly concerned about those populations in areas where water quality is marginal or non-native species have been introduced and are competing for resources.”

Rash is requesting anglers who catch a brook trout with gill lice to contact him at 828-659-3324, ext. 225, or by email at jacob.rash@ncwildlife.org. Although anglers may be concerned about consuming trout with gill lice, Rash says they are safe to eat, if cooked properly.

After discovering the gill lice in September, biologists sent samples of the copepods to the U.S. Fish and Wildlife Service’s Warm Springs Health Center to identify the specific gill lice species. Experts identified the lice as Salmincola edwardsii, which affects brook trout and not brown or rainbow trout. Biologists have also provided specimens to geneticists with U.S. Geological Survey for further testing. Results will let them know if the strain observed on North Carolina’s brook trout is the same that has been seen in waters in northern states.

In addition to working with anglers, Commission staff will continue to partner with the Little Tennessee Land Trust to sample other brook trout populations in the area. Staff also will continue routine monitoring of brook trout populations across the mountains of North Carolina.

While they don’t know how gill lice got into these tributaries of the Cullasaja River, biologists are concerned about them spreading to other bodies of water in western North Carolina.

“Gill lice can be spread when anglers move fish from one stream to another,” Rash said. “Furthermore, illegal introductions of brown and rainbow trout could have significant impacts to brook trout populations that are stressed because of gill lice.”

Because illegal stockings can result in unwanted introductions that can have irreversible consequences, the Commission requires a stocking permit to stock any fish into North Carolina’s public waters.

“The brook trout is our state’s only native trout species and is a very valuable resource,” Rash said. “Please do not stock or move brook trout — or any fish for that matter — without consulting the Commission first.”

Biologists think the primary means of transmitting gill lice is from fish to fish, but anglers can do their part by properly cleaning and caring for their fishing equipment to prevent the spread of other aquatic invasive species by:

Removing any visible mud, plants, fish or animals before transporting equipment;
Eliminating water from equipment before transporting; and,
Cleaning and drying anything that comes into contact with water.