An email back from the local fish manager

Len,
It is unlikely gill lice will destroy all of the brookies in **** Creek although I have seen infestations that were heavy enough (**** Creek, Monroe Co.) to interfere with the fish's respiration leaving them vulnerable if dissolved oxygen levels are reduced. The infestations seem to worsen when fish are stressed (low water levels or high water temps) but may totally disappear when conditions are good. We are aware of the problem and will continue to monitor but there is little that can be done (the only good way to remove gill lice from fish is with a formalin dip).
Dave

David Vetrano
Fisheries Supervisor
3550 Mormon Coulee Rd.
La Crosse WI, 54601
608-785-9009
David.Vetrano@dnr.state.wi.us