Fishing for Södermanland-fish infested with mussel larvae 03/07/2015

Written by lea on . Posted in Karlstad University, River Svärtaån, Södermanland County, Studies


At the end of June we conducted a 4-day fishing event in the two streams Kilaån and Svärtaån in Södermanland. Fish that are infested with mussel larvae were our targets. Martin Škerlep, Helena Herngren and I electro-fished over stream stretches with present mussel populations where we also set out fish traps overnight. The idea was to transport the fish captured to the UC4LIFE-lab facility in Skåne, where we can collect juvenile mussels that fall off their fish hosts after successful transformation from a mussel larvae to a juvenile. In this way, the host fish species used by Unio crassus can be identified properly. However, as different mussel species exist in the two streams Kilaån and Svärtaån, DNA analysis of the juvenile mussels collected need to be conducted to guarantee the host fish suitability for the right mussel species.

After successful fishing, a long fish transport by car, the transfer of the fish to aquaria tanks fit with nets were juvenile mussels can be collected, we discovered the first juveniles after only one day! Over the past week more juveniles have been dropping off the fish. To mention a few host fish candidates: Common bleak (Alburnus alburnus), Bullhead (Cottus gobio), Perch (Perca fluviatilis), and Ruffe (Gymnocephalus cernuus). The results of a DNA analysis of the juveniles will soon tell us which fish species Unio crassus uses as host in Södermanland. We are all curious!

Greetings from Skåne!


Actions in River Svärtaån

Written by Ivan on . Posted in River Svärtaån

Grävskopa släpper lekgrus vid vattenytan i ån.

During last week, the restoration actions in River Svärtaån were completed and the mussels that we collected before the actions were initiated were released back to the river.

Vegetation and masses of roots have been removed and replaced by larger structures such as boulders and larger stones including gravel. Thanks to the restoration,  the river provides a much higher potential for biodiversity now than before the restoration. Hopefully the mussels and the fish will thrive!

It has been incredible intense, fun and exciting working with the Swedish Angling association, the consultants, Skogstorparn. ICA Kvantum provided us with the baskets that we used to collect mussels with.

//Tuss och Helena

River Svärtaån

Written by Ivan on . Posted in Project sites, River Svärtaån


The River Svärtaån flows 13 km, from Lake Runnviken in the north, to the Bay of Sjösa at the Baltic Sea. The catchment area covers 372 km2 and extends as it flows through the municipality of Gnesta in the north to Nyköping in the south. The River Svärtaån Natura 2000 area includes six km from the Bay of Sjösa at the Baltic Sea up to the small village of Svärta in the north. The river meanders mostly through open farmland.  However, parts of the course have been channelized and dredged. In the lower parts, the River Svärtaån runs through forested areas. However, the land adjacent to the river consists mainly of farmland. At high water levels, flooded parts of the river create important foraging and nesting sites for birds. The river also contains an interesting fauna of fish and mussel species. Among the mussels, Unio crassus and Pseudanodonta complanata have been found.

The site has a high conservation value. Is one of few areas in Södermanland County where the thick shelled river mussel (Unio crassus) has been found. The topography and the water level create important foraging and nesting sites for birds. The area shelters interesting fauna of fish and mussel species such as the perch (Perca fluviatil), the bleak ( Alburnus alburnus), The roach (Rutilus rutilus), the pike ( Esox Lucius), The ruff (Acerina cernua), the tench (Tinca tinca), the Bream (Abramis vimba), the Dace (Leuciscus leusciscus), The nine spine stickleback ( Pungitius pungitius), and the Stone loch (Barbatula barbatula).

The fish fauna in the River Svärtaån shows a large variety in species. The Perca fluviatilis (perch), Alburnus alburnus (bleak), Rutilius rutilius (roach), Esox lucius (pike), Acerina cernua (ruff), Tinca tinca (tench), Abramis vimba (bream), Leuciscus leuciscus (dace), Pungitius pungitius (nine spine stickleback) and Barbatula barbatula (stone loach) have all been found in the river.

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