Distribution and abundance of the sand star Astropecten irregularis (Pennant, 1777) (Echinodermata, Asteroidea) on the continental shelf in the northern and middle Adriatic Sea

The sand star Astropecten irregularis (Pennant, 1777) is a very common species in the Adriatic Sea. This study establishes the distribution, biomass and abundance of that species on the continental shelf of the open waters in the northern and middle Adriatic Sea based on experimental sampling by bottom trawl during 11 cruises of the 'Pipeta' Expedition (1985-1994). Five hundred and eighteen bottom trawl hauls were performed at 56 predetermined permanent stations along ten transects, over different sediment types at depths of 10 to 430 m. Astropecten irregularis was recorded in 82.2% of the hauls, with the highest biomass and abundance indices at depths from 10 to 50 m. The deepest record was in a haul from 313.5 to 412.5 m depth. Even though it was recorded all over the investigated area, it was most abundant in some areas of the northernmost part of the Adriatic, and very abundant in the areas along the western coast. The highest average biomass and abundance indices were recorded on sand-silt-clay sediment, on silty sand and sandy silt and on the clayey silt and silty clay.Original Abstract: Morska zvijezda Astropecten irregularis (Pennant, 1777) je uobicajena vrsta u Jadranskom moru. Glavni ciljevi ovog istrazivanja su bili ustanoviti njezinu distribuciju, biomasu i abundanciju na kontinentskoj podini otvorenih voda sjevernog i srednjeg Jadrana na osnovi eksperimentalnog uzorkovanja pridnenom kocom za vrijeme 11 putovanja ekspedicije Pipeta (1985.-1994.). Obavljeno je 518 potega pridnenom kocom na 56 unaprijed odredjenih stalnih postaja uzduz deset transekata, na razlicitim tipovima sedimenta na dubinama od 10 do 430 m. Vrsta A. irregularis je zabiljezena u 82,2% potega, s najvecim vrijednostima indeksa biomase i abundancije na dubinama od 10 do 50 m. Najdublje je zabiljezena tijekom potega od 313,5 do 412,5 m. Iako je vrsta zabiljezena na cijelom istrazivanom podrucju, najabundantnija je bila na nekim podrucjima najsjevernijeg dijela Jadrana, te vrlo abundantna na podrucjima uzduz zapadne obale. Najvece srednje vrijednosti indeksa biomase i abundancije su zabiljezene na pijesku-siltu-glini, siltoznom pijesku i pjeskovitom siltu te na glinovitom siltu i siltoznoj glini.