The authorities on Monday started to remove an invasive fish species called the pumpkinseed (Lepomis gibbosus) from the Laihalampi pond, located in the Hakjärvi nature reserve in Nuuksio, Espoo, said the City of Espoo in a press release.
The City of Espoo and the Uusimaa Centre for Economic Development, Transport and the Environment (ELY Centre) removing the fishes to prevent the spread of the pumpkinseed and its negative effects on other species.
The fishes are being removed using a biodegradable rotenone-based solution.
The pond has been treated with a chemical solution, and the use of the pond is prohibited from Monday (11 August) to 14 September 2025.
Fishing and swimming in the pond are not allowed, nor should pets be allowed to swim in or drink from the pond.
Visitors are also advised to avoid the Laihalampi loop on the Sorlampi nature trail during this period.
Removing the pumpkinseed from Laihalampi is especially important because the pond is connected to a larger body of water.
If the invasive species spreads to Lake Pitkäjärvi in Nuuksio and beyond, it will pose a major threat to the biodiversity of the local waters.
“Several alternatives were considered for removing the pumpkinseed, but due to the pond’s location and surrounding terrain, these were found to be extremely difficult, if not impossible, to implement. Using rotenone is the most cost-effective and lowest-risk option in terms of preventing the spread of the species,” said invasive species specialist of the Uusimaa ELY Centre Paula Salomäki.
Rotenone is toxic to fish and other aquatic organisms, but less harmful to mammals and birds. Rotenone breaks down in a few weeks and, when diluted in water, does not pose a risk to human health.
If anyone came into contact with Laihalampi pond water during this time and develop symptoms, the person was urged to contact the Poison Information Center or seek medical attention immediately.
The pumpkinseed is a North American fish species known for its bright colours and popularity as an aquarium and pond fish. Within the EU, it is classified as an invasive species, and it is prohibited to import it into the EU or release it into the environment.
The pumpkinseed weakens the living conditions of native species by reducing their living space and increasing competition for food.
- Invasive fish
- Espoo
- Pond
Source: www.dailyfinland.fi
