Zonation and spatial distribution of littoral fish communities from the southwestern Finnish coast (Archipelago and Bothnian Sea, Northern Baltic Sea)

The aim of our study was to test whether the distribution of littoral fish assemblages would reflect both their immediate environment with reference to local underwater vegetation, including larger scale geographic archipelagial zonation. A total of 62 locations were sampled using beach seine and underwater video along the southwestern Finnish coastline in summer 2001. At all locations, water temperature, water transparency and benthic vegetation patterns (depth ranges of plant species or taxa) were recorded. Using correspondence analysis, our results showed a clear division of the Archipelago Sea into three separate zones based on littoral fish species assemblages. Overall, fish assemblages formed three distinct site groups, being dominated by pike and cyprinids, by percids and gobies, or by gasterosteids, and showed clear inner, middle and outer archipelago zones respectively, within the study area. Our results suggest that while vegetation in the study sites was diverse, it failed to express the zonation reflected by the littoral fish assemblages, which showed a definite zonation pattern which broadly reflected previous reports using both physical and biological parameters. We interpret our results to show that littoral vegetation is better in expressing small-scale differences between study sites, while littoral fish communities are more robust in detecting changes over a larger geographical scale.