Resultat från övervakningen av kustfisk: Vaxholm (Egentliga Östersjön) 2016–2025

This report presents the results from coastal fish monitoring in Vaxholm, which has been conducted annually in August since 2016. The study is a part of the regional environmental monitoring of coastal fish. Fish monitoring is carried out with Nordic coastal multimesh gillnets, and the species composition of the catch, diversity, trophic level, abundance of predatory fish and cyprinids, as well as the size and number of the fish are studied. Environmental variables are also noted during the sampling. Age determination of perch and pikeperch is carried out after the sampling is completed. The monitoring area is in the municipality of Vaxholm in Stockholm County, and the coastal water type is ‘Stockholms inre skärgård and Hallsfjärden’. With its diverse environment and bottom types, the area offers spawning and nursery areas for many of the Baltic Sea's commonly occurring coastal fish species, such as perch, cyprinid fish and whitefish. The area is affected by heavy shipping traffic to and from Stockholm, is relatively eutrophic, and both recreational boat traffic and the use of nearshore areas are extensive. The survey area in Vaxholm is characterized by low salinity and high turbidity. Despite significant anthropogenic influence, the fish community is both abundant and species-rich. Catches are characterized by high and increasing fish abundance, particularly of perch and cyprinids. Despite good status in terms of predatory fish abundance, the predator community is dominated by a single species, perch, which represents a vulnerability for ecosystem function and stability. The increasing catches of cyprinids indicate continued high nutrient loading with no clear signs of improvement. At the same time, certain biological indicators suggest potential impacts from environmental stressors such as eutrophication. Overall, the fish community appears productive but ecologically imbalanced, with risks associated with low functional diversity and the establishment of invasive species.