Posts Tagged ‘River Ramundsbäck Vretaån’

River Ramundsbäck Vretaån

Written by Ivan on . Posted in Project sites, River Ramundsbäck Vretaån

Vretaån

The Ramundsbäck-Vretaån project site (Natura 2000 area) consists of the River Vretaån and parts of the other tributaries; Kråkvaskaån Creek, and the Bålsjöån Creek. The River Vretaån, which originates from the bog Fjällmossen, Lake Lövsjön and Lake Bålsjön in the Kolmården forest area is the longest and most developed river ravine in the region, and it has a unique and distinct appearance as the structure is caused by the river cutting deep down into thick layers of fine-grained sand and till material.

The landscape along the river changes from lush canyons with pine forest, to grazed pastures and in lower sections deciduous and mixed swamp forests. There is a relatively large amount of coarse woody debris in the river, providing suitable habitats for fish and aquatic invertebrates. The hydro-morphology varies along the river, with fully developed meandering parts, erosion along the river banks and fast running water stretches. The variation in hydro-morphology provides good conditions for high biodiversity.

The river system of Kilaån is the most valuable reproduction and nursery area for stream spawning fish in the County of Södermanland. The Salmo trutta, Lampetra fluviatilis (the river lamprey), Cobitis taenia, Cottus gobio, Lota lota (burbot) and Lampetra planeri (brook lamprey) have all been found in the river.

The river is not regulated and relatively unaffected by drainage, which is rare in this part of Sweden leading to high conservation values. Water quality is good, showing little or no significant effects of acidification, eutrophication or other pollution impacts. The River Vretaån contains a great variety of invertebrate fauna, including oxygen demanding species, indicating clean water. For example both the mayfly Baetis niger and the caddisfly Rhyacophila fasciata are found in the river. High abundance of Gammarus spp. indicates the presence of wells. There are also red-listed species of freshwater snails, beetles and caddisflies in the river. Moreover, the area has a relatively rich stonefly fauna, eg Leuctra hippopus, Nemours cinerea and Amphinemura borealis. Findings of dragonflies, primarily of the genus Leuctra, indicate generally good water quality. Also the quite rare caddisfly Lype phaeopa has been found.

The main purpose of the Natura 2000 area is to to maintain and restore habitats to obtain favourable conservation status at bio-geographic level for the Cobitis taenia, Lutra lutra and the Cottus gobio, as well as for habitat type “Fennoscandian natural rivers”. Within the entire Kilaån River system there is a great diversity in both flora and fauna. It is one of the most species rich rivers in the region concerning unionid freshwater mussels. Six of seven native species are found including several endangered, such as Unio crassus and Pseudanodonta complanata. Thus, an overall high biodiversity in the river system and the project site makes the area unique and a thriving population of Unio crassus in the area would be valuable.

An inventory of mussels in the river system of Kilaån suggests that there are around 20 living individuals of Unio crassus in the River Vretaån (Nekoro and Sundström 2005). However, those individuals were found just outside the Natura 2000 area. Despite relatively high densities of adult Unio crassus individuals at several locations within the river system of Kilaån no juveniles have been found, suggesting problems with recruitment (Ljungberg and Svensson 2010). However, the Ramundsbäck-Vretaåns Natura 2000 site constitutes a suitable habitat for Unio crassus. Water quality, bottom structure and the presence of rare and red-listed species is the basis for what is classified as an area with high nature conservation values.

The UC4LIFE-related conservation actions focuses on removal of migration barriers and habitat improvements.

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