The occurrence of sea-spawning whitefish and vendace larvae was surveyed in the Intersik project in the Gulf of Bothnia at 653 sampling sites in years 2009-2011 and in the VELMU project in the south and southwest coasts of Finland at altogether 64 sampling sites in years 2009-2013. A beach seine was used as the main survey method to locate the fish larvae. As by-catch also information of the occurrence of e.g. cyprinids, gobies, and sticklebacks was gathered. ## Method description The occurrence of sea-spawning whitefish and vendace larvae was surveyed in the Intersik project in the Gulf of Bothnia at 653 sampling sites in years 2009-2011 and in the VELMU project in the south and southwest coasts of Finland at altogether 64 sampling sites in years 2009-2013. Selected study areas were stratified according to their exposure and bottom quality, but avoiding the river mouths and anadromous whitefish stocking sites. Sampling was started in spring after the ice break and it was continued until May. A beach seine was used as the main survey method to locate the fish larvae. As by-catch also information of the occurrence of e.g. cyprinids, gobies, and sticklebacks was gathered.

2022