Temperate fish community variation over seasons in relation to large-scale geographic seascape variables

In shallow-water marine environments, ecosystem functioning is a complex interworking of fine-scale characteristics and region-wide factors, and the importance of these variables can vary on multiple temporal and spatial scales. This underwater video study targeted seasonal changes in the fish community of seagrass habitats along the Swedish west coast and the influence of offshore seascape variables (latitudinal position, wave exposure, open ocean, and deep water). Results showed that fish assemblage structure exhibited seasonal changes between summer and autumn and strong spatiotemporal variations in the importance of offshore factors affecting shallow-water fish communities. In summer, abundance from the Gobiidae family responded to wave exposure, whereas the Gadidae family and juvenile migrant habitat preference guild responded to latitudinal position and proximity to deep water. In autumn, deep water was related to abundance of Gadidae and juvenile migrants, whereas latitudinal position influenced Gasterosteidae. These findings underscore the importance of understanding the influence of offshore factors on facets of coastal fish assemblages to address large-scale geographic connectivity along nearshore– offshore gradients

Factors affecting the local distribution of the Long-tailed Duck Clangula hyemalis in Baltic offshore waters

The Long-tailed Duck Clangula hyemalis is the main offshore wintering seaduckspecies in the Baltic region, although numbers have declined steeply since the early 1990s. The reasons for the decline are not well understood and information about habitat choice is scarce. Blue Mussels Mytilus edulis are the main food source for Longtailed Ducks in the southern Baltic Sea and here we have used both modelled and measured raw data on Mytilus abundances, patchiness and various bathymetric parameters to study Long-tailed Duck habitat preferences. Long-tailed Ducks were most abundant at depths of 10–30 m and in areas of high Mytilus densities. Patchiness of the resource was also very influential, especially when overall Mytilus densities were low. Bird abundance was intermediate to high in areas of low patchiness and lowwhere Mytilus patchiness was high. This suggests that the birds seek areas thatoptimise their feeding efficiency