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Topmouth gudgeon are small freshwater fish native to Asia and are highly territorial. Recognised as harmful to the environment, the Environment Agency have an active programme of eradication.
| Scientific name | Pseudorasbora parva |
| Family | Gobionidae |
| Diet | Eggs of other fish species and a wide variety of zooplankton |
| Predators | Pike, zander and perch |
| Size | 4-8cm |
| Weight | 10gm |
| Lifespan | 2-4 years |
A small, introduced species from Asia, the topmouth gudgeon eats invertebrates, small fish and fish eggs. It was brought to the UK as an ornamental pond fish, but has spread quickly to a number of ponds, lakes and rivers.
They are extremely invasive, causing great harm to local ecosystems. Topmouth gudgeon breed prolifically, out-competing native fish and readily eat the eggs and larvae of native species.
Topmouth gudgeon are round with elongated bodies. They’re silver in colour with shimmering purple sides. They have a characteristic up-turned lower jaw, and mature males have a prominent hump behind the head.
Topmouth gudgeon are highly territorial, with males guarding the eggs – and sometimes, there are more than 60 fish per square metre.
Spawning takes place at one year old in water temperatures of 15-19°C between May and August. Topmouth gudgeon can spawn up to four times per year in a wide range of spawning substrates.
Topmouth gudgeon are considered a nuisance species and generally aren’t targeted by anglers. If you catch one of these non-native fish and can humanely kill it with the permission of the fishery owner, you should do so. You must not take it home live.
Enter a town or postcode into our fishery search tool to find good local fishing spots
Last Edited: 24 April 2025
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