A follow-up of the fish population in lakes Vargsundet, Markusbölefjärden, Långsjön, Östra Kyrksundet and Västra Kyrksundet, as well as the crayfish population in lake Vargsundet

The fish population in the five lakes, Vargsundet, Markusbölefjärden, Långsjön, Östra Kyrksundet and Västra Kyrksundet, was studied in the summer of 2009. In lake Vargsundet a study of the crayfish population was also conducted. The aim of the study was to follow up the development of the fish populations, and concerning Vargsundet also the crayfish population, in the lakes. To get comparable results, the used methods corresponded with those used in earlier studies. The fish population in lake Vargsundet was investigated in June, July and August. The juvenile fish in the lake was studied twice by net seining. The crayfish population was studied in July, August and September. In the rest of the lakes the fish populations were investigated in July and August. No drastic changes were noticed in the fish populations, the perch (Perca fluviatilis) populations showed an increase in all of the lakes, while the roach (Rutilus rutilus) populations to some extent had decreased. Lakes Markusbölefjärden, Långsjön and Östra Kyrksundet had large standing stocks of fish. In Vargsundet and Västra Kyrksundet the fish populations were of moderate sizes. In lake Vargsundet the net seining showed recruitment of perch and cyprinids. Both the crayfish population and the individual crayfish of the lake were small. All lakes were somewhat eutrophicated, and the nutrient concentrations were especially high in the bottom layers of the former brackish lakes. Continued monitoring of the fish populations in the five lakes is recommended. To get a more precise picture of the crayfish stock in lake Vargsundet, more thorough investigations of the crayfish population are suggested