Gill lice have made an appearance in Pennsylvania.

The parasite – which attaches to the gills of brook trout – was discovered recently in Wolfe Run in Centre County. A subsequent investigation found evidence of them in nine other waters, too.

All had been stocked by the same cooperative nursery, said Brian Wisner, director of the Pennsylvania Fish and Boat Commission’s bureau of hatcheries.

The commission euthanized all of the brookies the nursery had left and replaced them with rainbow trout, which seem resistant to the bugs.

What will become of those streams in the future is harder to say, though, apparently.
Jason Detar, chief of the commission’s division of fisheries management, said there’s been limited research done on gill lice. What is known, he said, is that they’re resistant to chemical treatments and hard to control.

“We’re concerned about this,” he added.

The parasites attach to the gills of individual fish, impacting their ability to process oxygen and causing stress. Some Wisconsin research suggests they show up most often in dry summers in warm water, and can impact survival of young of the year fish, thereby hurting populations, he added.

No one can say what the long-term implications of their presence might mean, though, he added.

Commissioner Bill Sabatose of Elk County said fish with the lice pose no threat to people, however.

“They are safe for human consumption. That’s a fact,” Sabatose said.