The gudgeon can spread a parasite deadly to native fish species
A fast-breeding fish found in Devon waters which was threatening native species, has been wiped out from the county, the Environment Agency says.
The topmouth gudgeon was discovered in two lakes in east Devon in 2004, and then turned up in the Colaton Raleigh Stream, which feeds the River Otter.
The 3cm to 4cm (1.2in to 1.6in) long fish can out-compete native species and also carry a damaging parasite.
The agency said it used a piscicide (poison) after removing native species.
Topmouth gudgeon, a small Asiatic member of the carp family, appeared in mainland Europe in the 1960s.
The species matures at one-year-old and can breed up to four times a year.
The parasite it carries can interfere with the breeding cycle of salmon and trout.
The fish were first found in Devon at Bicton College and Bicton Park Botanical Gardens, near East Budleigh, in 2004.
The agency decided in March 2007 to begin eradication after previous plans to control them, including using filters, failed, and their numbers reached an estimated 100,000 fish.
Fisheries officers removed native species, including carp, from the two lakes and the River Otter to temporary holding ponds.
They then used the poison Rotenone, which is a piscicide that only targets fish and quickly breaks down in the environment.
It does not harm other aquatic life such as insects, mammals or birds.
Dave Brogden of the Environment Agency said: "The signs are very encouraging. We couldn't find any when we carried out our first survey in October 2007.
"Instead, they've been replaced by a very healthy population of carp in the lakes. We have plans with Bicton College to introduce other species into the lake soon.
"In the meantime, we are doing a follow-up survey that hopefully will show the eradication has been successful."