Resultat från övervakningen av Kustfisk: Gräsö östra skärgård (Egentliga Östersjön) 2012–2024

This report presents the results from the coastal fish monitoring at Gräsö, which has been carried out in August every three years since 2012. The test fishing is carried out with Nordic coastal multimesh gillnets, and the species composition of the catch, as well as the size and number of the fish, are studied. Environmental variables are also recorded during the study. The purpose of the monitoring is to assess whether there have been changes in the fish community since the establishment of the nature reserve in 2012. The Gräsö fishing area is located in the Gräsö Eastern Archipelago Nature Reserve, which is Uppsala County's largest nature reserve. The area is defined as worthy of protection because it constitutes an ecological boundary between the Bothnian Sea and the Baltic Proper, and the coastal water type is the inner coastal waters of the Southern Bothnian Sea. The area is generally shallow and among the aquatic vegetation there are good spawning and nursery areas for many fish species, although the area is relatively exposed to the sea. The nature reserve's regulations prevent both largescale exploitation and slowly increasing small-scale settlements. Perch and roach are the most common species, accounting for almost 70% of the catch. Relatively large perch indicate a good status of the species. The relatively high catches of cyprinids may indicate eutrophic conditions. No trends in catch per effort, diversity and mean trophic level have yet been detected, indicating that there have been no clear changes in the fish community over the period 2012–2024. In 2024, however, the total catch was higher than in previous years, which could indicate good recruitment of several fish species and future changes in the fish community.