Infralittoral fish assemblages in the Zrmanja estuary, Adriatic Sea

The infralittoral fish assemblage was investigated inside the temperate Zrmanja river estuary, Croatia, 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 estuaries the characteristics of river inflow have the potential to alter spatio-temporal patterns in infralittoral fish assemblages.Original Abstract: Infralitoralne zajednice riba su proucavane na podrucju usca rijeke Zrmanje, u Jadranskom moru. Jedinke su ulovljene malom obalnom mrezom potegacom na tri postaje, u cetiri uzorkovanja tijekom jedne godine istrazivanja. Ukupno 10 035 jedinki svrstanih u 47 vrsta i 17 porodica, je bilo zastupljeno u uzorku, od cega su Atherina boyeri (60,3%), Symphodus ocellatus (14,4%) i Pomatoschistus marmoratus (7,5%) bile najzastupljenije vrste, sacinjavajuci 82,2% od ukupnog uzorka. Prave morske i estuarijske vrste riba su bile zastupljene s 89,6, odnosno s 10,4%, dok slatkovodne ribe nisu uopce ulovljene. Utvrdjene su prostorne i vremenske razlike u zajednicama riba zbog razlicite vremenske i prostorne raspodjele nedoraslih riba. Nedorasle jedinke onih vrsta koje se mrijeste u otvorenom moru (L. mormyrus, P. erythrinus) su nadjene s povecanom udaljenoscu od samog usca rijeke. Kako su navedene jedinke rasle, tako smo ih nalazili razlicito rasprostranjene na sirem podrucju usca. Nedorasle jedinke rezidentnih vrsta (Pomatoschistus sp.) su ulovljene blizu samog usca. Stalni su estuarijski rezidenti sacinjavali 11 vrsta, 33 vrste su bil