Hampshire fishery lakes to be poisoned to kill Topmouth Gudgeon 5 November 2013 Last updated at 05:55 Several lakes at a fishery in Hampshire are to be poisoned to wipe out a highly invasive species of Japanese fish that can kill salmon and trout. Topmouth Gudgeon are believed to have entered British waterways in the 1980s but only recently become widespread. The Environment Agency removes native species from the water and then adds poisons - the treatment it is to carry out at the FLE Fishery near Romsey. But some fisheries have said the treatment affects livelihoods. The Environment Agency says the tiny fish is a "significant threat" to the ecology and wildlife in UK waters.. The FLE fishery will remain open for business during the treatment, with one lake being treated at a time in a two-stage operation, ending in April. The agency will try to remove as many fish as possible from the lake before putting in the piscicide Rotenone. Topmouth Gudgeon Small freshwater fish from Asia Brought to Europe accidentally in the 1980s through the importation of other fish Highly damaging species which often goes unnoticed due to its small size but can rapidly populate ponds, lakes and streams Has ability to dominate a habitat and food supply, often leading to a decline in numbers of native fish Critics say the poison stays in the waterways for months and sometimes years. Some businesses also say the method impacts on future business and fish stocks. However, the Environment Agency said Rotenone was a "naturally occurring organic substance" that did not affect mammals or birds. It said the chemicals would break down within a "few weeks" and they would monitor levels of chemicals to ensure the treatment has been effective. According to the Environment Agency, Topmouth Gudgeon can carry infections and parasites which can wipe out entire populations of native fish. Topmouth eat the eggs and larvae of native fish and out-compete native fish for food and habitat.