The larval areas of pikeperch, perch, Baltic herring and smelt were surveyed in the VELMU project in years 2007-2014 in the Finnish coasts at altogether 673 sampling sites. Paired Gulf samplers were used as the main survey method. As by-catch also information of the occurrence of larval gobies was gathered. Survey data has been used for distribution modelling of the larval fish habitats and it is suitable for coastal spatial planning. ## Method description The larval areas of pikeperch, perch, Baltic herring and smelt were surveyed in the VELMU project in the Finnish coastal area in years 2007-2014. The larval fish survey comprised a total of 1788 sampling occasions at 655 distinct sampling sites in 5 sea areas Sampling sites covered the whole Finnish coast. Survey was usually conducted during one summer in one sea area, but during the sampling period every sampling site was visited 2 - 4 times at two weeks intervals. Paired Gulf samplers were used as the main survey method. The sampling was systematically conducted during the day (8 am to 8 pm) over transects of 400 m (in 2007–2008) or 500 m (in 2009–2014) at a speed of 2.2 kn and only in good weather conditions (wind speed < 8 m/s, wave height < 30 cm). The paired samplers had fixed depths of 0.5 m and 1.0 m, and the catch and effort were pooled to form one sample observation The samples were stored and species identification and measurement took place later in a laboratory. As by-catch also information of the occurrence of larval gobies was gathered.

2022