Invasive species removal in progress at Laihalampi in Nuuksio – use of pond prohibited until 14 September 2025

The fish are being removed using a biodegradable rotenone-based solution. Laihalampi was treated with the solution on 11 August 2025, and therefore the use of the pond is prohibited until 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.

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 you come into contact with Laihalampi pond water during this time and develop symptoms, contact the Poison Information Center (tel. 0800 147 111) or seek medical attention immediately.

Operation helps preserve large ecological area

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. It defends its territory aggressively and reproduces and spreads efficiently. This leads to the disappearance of other species and the deterioration of biodiversity.

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,” says invasive species specialist Paula Salomäki from the Uusimaa ELY Centre.

Do not release invasive species into the wild

Because the pumpkinseed is classified as an invasive species, it is prohibited to import, breed, sell or possess it or release it into the environment. In addition to penalties prescribed by law, those responsible for spreading the species may be required to cover the costs of removal. In the case of Laihalampi, the total cost is around EUR 10,000.

“Removing invasive species from water bodies is often challenging – and therefore also expensive,” Salomäki says.

Report invasive species sightings

Successful control of invasive species depends on continued reporting through the website: vieraslajit.fi. When possible, include a photo of the sighting.

An invasive species is a plant, animal or other organism that has been moved – either intentionally or unintentionally – outside its natural range by human activity. Invasive species threaten biodiversity and related ecosystem services.

Learn more about the pumpkinseed at vieraslajit.fi.

Report a sighting through vieraslajit.fi

Further information:

• Uusimaa ELY Centre – customer service for environmental matters: ympariston.asiakaspalvelu@ely-keskus.fi
• City of Espoo – Urban Environment Customer Service, tel. +358 9 81625100

Further information for media:

Pumpkinseed – distribution and control:

• Paula Salomäki, Nature Conservation Specialist, Uusimaa ELY Centre, paula.salomaki@ely-keskus.fi, +358 29 502 1292 (available 11 August and from 21 August onwards)
• Sanna Kuningas, Senior Researcher, Natural Resources Institute Finland (Luke), sanna.kuningas@luke.fi, +358 29 532 6026
• Teemu Niinimäki, Conservation Officer, member of the invasive species advisory council of the Ministry of Agriculture and Forestry, WWF Finland, teemu.niinimaki@wwf.fi, +358 50 524 3206

Nature conservation:

• Katrin Aia, Environmental Planner, City of Espoo, katrin.aia@espoo.fi +358 46 877 3806