Quantitative assessment of the area of shallow habitat for fish on the Swedish west coast

Much effort has been focused recently on juvenile and adult fish habitat use in shallow coastal areas. However, to understand fully the importance of such habitats for fish production it is necessary also to quantify the area of existing habitat types. We inventory and quantify the area of major habitat types in a 1000 km(2) area of the Swedish west coast, on a scale appropriate for coastal-zone management. An echosounder and GPS-transmitter mounted on a small boat were used to estimate the distribution of habitat along transects in seven regions of differing coastal morphology. The signal from the echosounder separated major habitat types, and recordings were verified by video documentation and visually. The information was used with GIS-software to estimate the quantitative extent of bottom habitats at depth ranges of 0-3, 3-6, and 6-10 m. Of the major habitat types, soft substrata dominated all except one region, and increased in size with depth in all regions. There were rocky substrata in all regions, but as steep rock walls in the north and more gently sloping substrata with pebbles and boulders in the south. Approximately half the rocky habitat was in the shallowest depth range. Seagrass meadows on soft substrata were mainly in the shallow protected archipelago of the central coast.