SPATIAL AND TEMPORAL VARIATION IN SMALL FISH OCCURRENCE IN SHALLOW HABITATS OF THE VISTULA LAGOON (SOUTHERN BALTIC SEA)

Abstract

The aim of the study was to determine the composition and structure of small fish assemblages inhabiting coastal areas of the brackish Baltic Lagoon. Spatial and temporal variations in ichthyofauna were analysed as part of the work. Additionally, the data obtained falsified the hypothesis that the share of marine species in fish assemblages grows along with salinity. A total of 19 species belonging to eight families were recorded in shallow habitats of the Vistula Lagoon. These belonged to four ecological guilds among which freshwater species were represented most numerously. Marine species dominated quantitatively. Marine opportunist species constituted the largest part of catches although they made up just 10.5% of the 19 species recorded in the course of the four-year study. A significant variation was recorded in the fish assemblage structure in regions of the lagoon with differing water salinity. Significance of marine species in the quantitative structure of small fish assemblages increased along with the salinity gradient.