An overview of four potential spawning areas in the archipelago of the Åland islands.

This project was done on the behalf of The Government of Åland, lasting from the beginning of April to end of July 2019. The purpose was to examine four previously selected bays in the archipelago of the Åland Islands as suitable spawning areas for predatory fish, such as pike (Esox lucius) and perch (Perca fluviatilis), and whether there were any crucial differences in the characteristics between bays determining their suitability. This project was prompted to provide more insight into the decline of predatory fish stocks in the Baltic Sea. The decline may have severe consequences in the whole ecosystem of the Baltic Sea. Two of the bays were situated in Vårdö (Sunnanpå and Listerbyviken), and of the remaining two, one was situated in northern Lumparn (Fladan) and one in southern Lumparn (Vadgrundsfladan). The sampling of predatory fish stocks was performed using fyke nets mid-April to the end of May 2019, the catch was measured and released. Post spawning, perch egg strains were mapped by snorkelling, along a transect from end of May to mid-June. Fish larvae were sampled by scoop and plate method. The fishing of sticklebacks (Gasterosteus aculeatus) was performed with gillnets in June. Additionally, the vegetation in the bays was mapped. The catches from the fyke nets were small and the sampling of larvae and eggs did not lead to any significant results. The fishing of sticklebacks showed there were differences in the number of sticklebacks among the bays. The largest number of sticklebacks was caught in Sunnanpå and the smallest in Fladan. The differences could be explained by the different characteristics of the bays, e.g. turbidity, exposure and macrophyte community composition such as reed coverage. Differences in epiphyte coverage between the bays could also be detected, the highest coverage in Fladan and the lowest coverage in Vadgrundsfladan, which could be explained by the characteristics of the bays, e.g. exposure, temperature and anthropogenic eutrophication