Infralittoral fish assemblages in the Zrmanja estuary, Adriatic Sea

Abstract

           The infralittoral fish assemblage was investigated inside the temperate Zrmanja river estuary, Adriatic Sea. The specimens were caught using a beach seine at three stations and four times over the year. A total of 10 035 individuals, belonging to 47 species and to 17 families were represented in the catch, out of these Atherina boyeri (60.3%), Symphodus ocellatus (14.4%) and Pomatoschistus marmoratus (7.5%) were most abundant, comprising 82.2% of the total catch. Marine and estuarine species represented 89.6 and 10.4%, respectively, while freshwater species were not observed in samples. Differences in fish assemblages were observed with respect to sampling dates and stations mostly due to different temporal and spatial distributions of juvenile fish settlers. Juveniles of open sea spawners (L. mormyrus, P. erythrinus) were found with increased distance from the river mouth. As they progressively grow, they disperse throughout the estuary. Juveniles of resident species (Pomatoschistus sp.) stayed closer to the river mouth. Permanent estuary residents comprised 11 species, 33 species were opportunists and the remaining 3 were transients. The data thus show that even in small temperate estuariesthe characteristics of river inflow have the potential to alter spatio-temporal patterns in infralittoral fish assemblages.