18. Noteworthy fauna: (indicating, e.g., which species are unique, rare, endangered, abundant or biogeographically important; include count data, etc.)
The site contains several localities rich in birds, including several rare and threatened species. Around 100 species nest in the site. Among species included in the Swedish Red List and/or in annex I of the Wild Birds Directive, the following could be mentioned as breeding species: bittern Botaurus stellaris (declining; one well-known stronghold is found in Sörfjärden Bay), whooper swan Cygnus cygnus, garganey Anas querquedula, shoveler Anas clypeata, pochard Aythya ferina, white-tailed eagle Haliaetus albicilla, marsh harrier Circus aeruginosus, osprey Pandion haliaetus, spotted crake Porzana porzana, crane Grus grus, common tern Sterna hirundo, black tern Chlidonias niger, yellow wagtail Motacilla flava flava, great reed warbler Acrocephalus arundinaceus, bearded tit Panurus biarmicus, penduline tit Remiz pendulinus (not regularly), and red-backed shrike Lanius collurio. Among regularly occurring passage migrants of large interest, at least the following should be mentioned: bean goose Anser fabalis, pintail Anas acuta, smew Mergus albellus, hen harrier Circus cyaneus, merlin Falco columbarius, little ringed plover Charadrius dubius, golden plover Pluvialis apricaria, ruff Philomachus pugnax, curlew Numenius arquata, wood sandpiper Tringa glareola and bluethroat Luscinia svecica.
The insect fauna is interesting, and contains several species living in wood, as well as several butterfly species. Many are relicts from warmer periods, and some of them are believed to have their northernmost outpost in the world here. The rare beetle Mesosa curculionoides occurs in the Tidö area as well as the hermit beetle Osmoderma eremita. Lindön has a very interesting invertebrate fauna connected to the large trees, especially the limes, with a lot of red-listed species. The high level of nutrients, in the water within the site, favours the fish fauna including asp Aspius aspius and spined loach Cobitis taenia.
Around 30 species of mammals have been observed in the area. Other animals worth mentioning are; smooth snake Coronella austriaca and the molluscs Vertigo angustior and Succinea oblonga.
19. Social and cultural values: (e.g. fisheries production, forestry, religious importance, archaeological site etc.)
Human settlements in the area are known since the 11th century. There are ancient graves on many islands. In the 17th century, the king had a shipyard in the archipelago; this favoured the cultivation of oak, necessary for shipbuilding. Cultural and historical values are thus close connected to natural values.
The whole site is of national interest for commercial fishing and target species are e.g. eel Anguilla anguilla, pikeperch Stizostedion lucioperca, vandace Coregonus albula and the introduced crayfish Pacifastacus leniusculus.
20. Land tenure/ownership of: (a) site (b) surrounding area
(a) Protected areas are owned privately and by the state. Unprotected areas are mainly privately owned. (b) Mainly privately owned.
21. Current land use: (a) site (b) surroundings/catchment
(a) Grazing, cattle farms on two islands and in the surrounding mainland, limited but locally intensive forestry, fishing and hunting.
(b) Agriculture, forestry, grazing, fishing and hunting.
22. Factors (past, present or potential) adversely affecting the site's ecological character, including changes in land use and development projects: (a) at the site (b) around the site
(a) Since many fauna elements depend on continuous grazing and/or mowing of shore meadows, discontinuation of this practice would have detrimental effect. Other potential threats include large-scale removal of the emergent water vegetation in the north-western part of the site, and turning shore meadows into farmland, locally already practised. Eutrophication may also pose a problem particularly in the southern bay.
(b) The site is part of Lake Mälaren, which is an important fairway for commercial shipping. An accident, including oil spill or release of toxic substances, will no doubt have significant adverse impact on many shore habitats.
23. Conservation measures taken: (national category and legal status of protected areas - including any boundary changes which have been made: management practices; whether an officially approved management plan exists and whether it has been implemented)
There are four nature reserves within the site;
Asköviken Nature Reserve - 452 ha. Protected since 1985. Owned privately. Management plan under revision.
Tidö Nature Reserve - 423 ha. Protected since 1991. Owned privately. Management plan under revision.
Ridö-Sundbyholmsarkipelagen Nature Reserve - 5700 ha. Protected since 1984. Owned mainly by the state. Management plan under revision.
Söderfjärden Nature Reserve - 210 ha. Protected since 1968. A management plan is planned during the autumn of 2001.