Sea lice possibly survive on fish that remain in the estuaries or they transfer to an as yet unknown alternate host to spend the winter. Smolt get infected with sea lice larvae, or even possibly adults, when they enter the estuaries in the spring. How sea lice distribute between fish in the wild also is not known. Adult stages of "Lepeophtheirus" spp. can transfer under laboratory conditions, but the frequency is low. "Caligus" spp. transfer quite readily and between different species of fish, and are regularly found in the plankton.