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The Environment Agency (EA) will be removing a non-native invasive fish from the ponds and moat in Clissold Park later this month.

The top mouth gudgeon, part of the carp family, is one of the most threatening species of fish in Europe, and is banned from sale in England and Wales.

Their presence not only poses a risk to the local biodiversity in Clissold Park but could also have disastrous effects on wildlife and habitats on a national level.

Originally imported from Asia into the UK as an ornamental species, the 8-10cm long silver and purple fish eat the eggs of other fish, breed rapidly and out-compete our native fish for food and habitat.

The topmouth gudgeon will be humanely removed using an organic ‘piscicide’ called rotenone, which is selective to fish. Mammals and birds will not be affected but invertebrates may be - however they will recover quickly.

Extensive studies indicate that rotenone does not pose a hazard to human health, either through direct or indirect oral, dermal (skin) or respiratory intake.However, in its concentrated form it can act as an irritant and, as a precaution, EA staff will carry out the operation wearing protective equipment following a strict risk assessment.

As a precaution, visitors should make sure they and their pets avoid contact with the ponds and moat until notified that it is safe to do so.The park will remain open while the EA carries out its work. However, a limited area around the moat and ponds will be restricted - but for no more than one day. 

Once the rotenone has degraded and broken down there will be no toxic chemicals remaining.