Gillöga och Lilla Nassa - Länsstyrelserna

Summary
Stora Nassa – Svenska Högarna is one of four BSPAs (Baltic Sea Protected
Area) in the Stockholm county. The BSPAs is one result of agreements
between the Baltic Sea countries concerning the environmental work in the
Baltic Sea. The agreements include biological diversity and the BSPA-areas
are meant to protect representative networks of marine habitats. Earlier
studies in the BSPA include marine biological surveys in the two nature
reserves of Stora Nassa and Svenska Högarna.
In June 2008 Sveriges Vattenekologer AB assigned by the County
Administrative Board of Stockholm performed a marine biological survey
of the aquatic communities and carried out a habitat value evaluation of the
shallow bottoms around Gillöga – Lilla Nassa. The aim of the investigation
was to describe the vegetation and fish communities in the area and evaluate
the habitat values.
Benthic communities between 0 and 10 m depth were investigated with line
transects, quantitative samples and a test fishing study. The 12 line transects
were assessed by scuba divers and describes the species composition, cover
and depth extension of the benthic flora. Three quantitative frame samples
were taken on three of the line transects in order to estimate the abundance
of fauna within the plant community. In order to describe the fish
community in the area, a test fishing study was performed.
The habitat value analysis was based on the following aspects:
• Species richness & variation – The number of species observed in the
area was normal with regard to macroalgal communities, including its
fauna, and the fish community. The area included all types of substrate,
often with different levels of wave-exposure, which contributed to a
varied species composition in the macroalgal communities. The vascular
plant communities were, as expected, both sparse and species poor.
• Rareness / Rarity –Three of the observed species, eelpout (Zoarces
viviparus), turbot (Psetta maximus) and cod (Gadus morhua) are listed
on the endangered species list. Eelpout and turbot are listed as near
threatened, whereas cod is considered to be endangered.
• Intactness – The area was generally unexploited. The few noticable
traces of human activity on the shore and sea floor included some
buildings and piers.
• Representativity – The area represents sheltered areas in an outer
archipelago, thus less influenced by for example run-off from the
mainland than inner archipelago areas. The area included both more
wave-exposed bottoms typical for the outer archipelago as well as more
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