Commercial eel fishers say a levy introduced by Ngai Tahu for fishing at Lake Ellesmere near Christchurch could cost users up to $45,000 each.
Ngai Tahu owns the lake bed and says the permit system, under which it collects 8% of eel fishers' earnings, is designed to help protect the lake.
The South Island Eel Industry Association says fishers are prepared to pay a levy, but only about half the amount being charged.
Association president Victor Thompson says eel fishers already pay up to 15% of their gross takings to the Crown in the form of fishing quota earnings.
He says there are about 50 commercial eel fishers in New Zealand.