The discovery of a troublesome fish parasite known as gill lice has been confirmed in sportsmen’s club trout nurseries in Lebanon and Dauphin counties and the backlash has already affected a popular children's fishing derby in Lancaster County this Saturday.

At a special meeting Monday, the Cocalico Sportsmen’s Association decided to not allow children to take home trout they catch at its annual fishing rodeo.

The club had discovered gill lice on trout it had purchased from Crystal Spring Trout Hatchery, a private hatchery in Newmanstown, Lebanon County, that raises and sells trout for stocking.

At least eight sportsmen’s clubs in Lancaster County that raise trout have been alerted to look for infected fish.

The Pennsylvania Fish and Boat Commission says none of the trout it raises and stocks in 24 Lancaster County streams is infected with gill lice. The county’s trout season opened last Saturday.

Trout with gill lice are not harmful to eat.

Gill lice are tiny crustaceans that attach to the gills of trout and other fish and feed on blood. They look like tiny rice and are only found inside the gills.

They can make breathing hard, slow down the fish’s development and affect reproduction. In Wisconsin, officials reported a 77 percent decline in new brook trout over a one-year period.

The first confirmed case of gill lice in trout in Pennsylvania occurred last fall when both wild and stocked brook trout were found during a routine survey of a Centre County stream. An investigation turned up infected trout in nine other nearby streams.

The source of the infected trout was traced to a cooperative nursery. All trout there were killed.

This winter, anglers reported catching large rainbow trout with gill lice in Deep Creek Dam, a lake in Montgomery County stocked by both the Fish and Boat Commission and Montgomery County.

Mike Kaufmann, the Fish and Boat Commission’s area fisheries manager, said shocking of fish in a stream that feeds the lake found “20 rainbows with lots of them (gill lice).”

The agency’s fish pathologist then examined trout at its Huntsdale trout hatchery and found no gill lice.

The investigation then turned to the trout stocked by Montgomery County. Those trout were purchased from the private Crystal Spring Trout Hatchery in Lebanon County, Pam Murray, parks supervisor of Green Lane Park, told LNP.

The Fish and Boat Commission investigated two sportsmen’s clubs with nurseries downstream of Crystal Spring and found infected trout in both.

Some 4,500 trout were killed by the agency at the Mill Creek Rod & Gun Club in Lebanon County and another 4,000 trout were killed at a nursery jointly operated by the Milton Hershey School and the Quittapahilla Rod & Gun Club in Dauphin County.

The Crystal Spring hatchery has not been checked as of yet as the Fish and Boat Commission and state Department of Agriculture haggle over which is responsible.

Crystal Spring owner Merle Good did not return requests for comment over several days.

  So far, two strains of gill lice have surfaced in Pennsylvania. One affects native brook trout and has probably been occurring naturally. The other affects rainbow trout, not a native fish to Pennsylvania.

“We don’t know if both diseases have been in wild trout because we haven’t looked for it,” said Andy Shiels, the Fish and Boat Commission’s Bureau of Fisheries director.

“We really don’t know how widespread it is and if it has a big impact on the wild trout populations yet.”