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Fish and water body surveys analyse the condition of water bodies in Kotka

The conducted surveys in the area of the planned cathode active material plant and in the Salminlahti area give us a starting point on the basis of which development plans are made.


25. April 2024

The surveys collected data on the initial state of the Nummenjoki and Suuroja river systems and the Salminlahti bay area to obtain the broadest possible understanding of their current condition. This is necessary for planning potential improvement measures.

The surveys conducted in the Suuroja and Nummenjoki areas included water quality and benthic studies, and other surveys concerning fish and harmful elements in the sediment. The water samples were analysed for solids, electrical conductivity, pH, turbidity, total nitrogen and other factors that typically affect water quality. A preliminary survey of fish stock in the lower part of the Nummenjoki river was conducted using exploratory electrofishing, in which the fish were stunned, measured, weighed and freed.

The results indicate that, due to its stream flow seasonality, Suuroja does not offer ideal conditions for salmonid breeding.

“Suuroja, which is connected to the Korkeakoski branch of the River Kymi, is located in an important place for migratory fish. Its catchment area is small and drained, which means that the channel almost dries up during low-water periods,” says Esa Korkeamäki, Executive Director of the Water and Environment Association of the River Kymi.

Valuable data about water bodies and species

Analyses of the Nummenjoki river system provided valuable data about the concentrations of total nitrogen, ammoniacal nitrogen and total phosphorus at two measurement points: Nummenjoki 1 is located downstream near Salminlahti, while Nummenjoki 2 is located upstream in Saksala. The results indicate that nutrient concentrations vary according to both the seasons and weather conditions, which reflects both natural processes and the potential impact of human activity. Although Nummenjoki is a nutrient-poor inland river, it is prone to seasonal fluctuations; and particularly in ammoniacal nitrogen, whose rise may indicate emissions from organic matter or its decomposition.

The results show that Nummenjoki‘s fish stock consists of perch and pike, which are commonly found in all kinds of water bodies. In the spring, the river becomes a spawning ground for many species of fish and enables migratory movement between freshwater and saltwater areas. The river flows into the northern part of Salminlahti bay, which is very shallow and overgrown with reeds. This affects the river’s fish species. No sightings of actual freshwater fish were made in the Tommolankoski rapids in the lower part of the Nummenjoki river.

Nummenjoki flows into Salminlahti bay, which is a Natura 2000 area. The importance of the Salminlahti bay area for fishing and fish as a whole was surveyed, and the fish species that live and spawn there were identified. The surveys were conducted using non-harmful methods, such as exploratory net-fishing, catching juvenile fish, and conducting a digital survey of joint property management associations. Based on the exploratory netting, roughly two-thirds of Salminlahti’s fish are perch and roach. It is also a place where many fish species go to spawn and an important recreational area for humans.

“It’s very important for us to ensure that the project does not have a negative impact on the surrounding bodies of water. For example, as Suuroja is as a spawning area for several species, we are investigating whether it would be possible to improve the condition of the river so that it would provide better living conditions for salmonids. Restoration efforts could also improve the recreational opportunities afforded by bodies of water in the vicinity of the project, which would be particularly beneficial to those living within the project’s immediate sphere of influence,” says Timo Strengell, Project Director of the CAM project in Kotka.

For more information

Timo Strengell, SVP, Battery Value Chain, Finnish Minerals Group,
firstname.surname(at), +358 40 738 4860

Read also

A CAM plant is planned in Kotka


The mission of Finnish Minerals Group is to responsibly maximise the value of Finnish minerals. We manage the State’s mining industry shareholdings and strive to develop the Finnish value chain of lithium-ion batteries. Through our work, we contribute to Europe moving towards electric transport and a more sustainable future.


25. April 2024