Endangered Fish
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Increase abundance in restored waterscapes
Data collection in progress
Koitajoki
Finland
Problem: The draining of peatlands through ditching leads to organic matter from the peatlands running into the ditches, eventually ending up in nearby streams and rivers. This organic loading changes the colour and chemical composition of the water, and leads to peat material settling on the bottom of the riverbed. Typically, the riverbed would be kept clear by moving water, and fish species can therefore spawn on these open riverbeds. With organic matter accumulating on the riverbeds, fish cannot successfully spawn, leading to dwindling abundances. In other areas, dams prevent fish from accessing their migratory routes that are key for successful reproduction.
Action: Snowchange is working to block the ditches in key peatlands preventing erosion, and increase the woody material in river systems to prevent more organic matter from ending up in riverbeds. They add gravel material into rivers where none is available, which creates new spawning grounds, and they remove barriers to enable migratory fish an appropriate access to these areas. They improve juvenile fish habitats and reintroduce water moss as well. In select sites, they also work with traditional fishermen using seine nets, a low-impact fishing activity that clears the riverbed and promotes fish abundance.
Indicator: Presence and abundance of four key fish species will inform successful restoration of spawning grounds, and access to them through increased river connectivity.
Methods
Trout, grayling, whitefish and Atlantic salmon are being monitored by two main techniques: electrofishing and eDNA surveys.
Electrofishing is occurring at nine sites, where the abundance of each fish species is recorded. Sampling occurs once per summer season and this data is collected annually.
eDNA surveys will also be conducted in 2024, and compared to electrofishing results to test this method as a more scalable fish monitoring approach for the larger Koitajoki watershed. Currently nine sites are being sampled for eDNA, two of which overlap with electrofishing areas, and seven of which will provide new presence/absence data for the key fish species.
Snowchange also uses local traditional knowledge to construct historical baselines, to which they can compare their present-day baseline, and future surveys. This documentation of observed changes in trout, grayling, whitefish and Atlantic salmon and their spawning locations can be compiled from oral history and fish diaries.
Results
Baseline electrofishing data has been collected at nine sites. Due the the sensitive nature of this data, we will not publish baseline data of endangered fish at this time. However, Snowchange will revisit these sites after river restoration to see if abundances of these key species has changed over time.
An example of Snowchange’s work to restore gravel to riverbeds. Photo: Snowchange Cooperative.
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