Staff from the Department of Conservation and Fish & Game say they were devastated to learn that a noxious fish has been illegally released into a West Coast lake.
Officials have found Rudd in Lake Ianthe, which lies just south of Hokitika, and is popular with tourists and trout and salmon fishers. They are now worried the pest fish may have been released into other West Coast lakes.
"What we're doing is setting several different-sized nets and traps around the water body to see if we can get a bit of a handle on how many Rudd are here," DOC ranger Helen McCaughan told ONE News.
Rudd fish are native to Europe and can ruin an existing fishery by out-competing native fish, trout and salmon for food.
DOC was alerted to the problem last week when a local fisherman caught a large orange fish in Lake Ianthe. The fish was later confirmed as a Rudd, a pest which is part of the goldfish family.
Rudd eat native plants and invertebrates and it is illegal to be in possession of the fish on the West Coast.
However, some anglers enjoy catching Rudd and it is thought that they could be responsible for the release.
"Most legitimate sports fish anglers will be devastated about this - it's the worst possible news you can have for a sports fishery," said Dean Kelly from Fish & Game.
DOC and Fish & Game have so far found Rudd of different sizes throughout the lake, indicating they were released as much as four or five years ago.
"It could devastate the fishery," said Kelly. "They have a tendency to overpopulate, eat the place out, then outcompete with the sports fish for their food source."
DOC and Fish & Game will now extend their survey in the hope that they do not find more Rudd in West Coast lakes.