Distribution, diet and relationships of the invasive ctenophore Mnemiopsis leidyi with anchovies and zooplankton, in the northeastern Adriatic Sea

Blooms of invasive ctenophore Mnemiopsis leidyi can have massive consequences on fish stocks and marine food webs. The distribution, abundance diet this were investigated in the northeastern (NE) Adriatic between 2016 2019. M. was determined daily along coast Rovinj (Croatia), its spatial distribution monitored by visual census from research vessels pelagic trawl during acoustic surveys September each year. Mesozooplankton samples collected western Istria vertical tows bottom to surface. Spatial anchovy (Engraulis encrasicolus) assemblages geo-referenced hydro-acoustic sampling using a scientific echosounder. Large swarms covering several km2 regularly reported July November extending up 25 NM Istrian peninsula reaching maximum offshore densities 270 individuals per m2. areas where present evidently decreased. content leidyi’s digestive tract plankton consisted both mainly cladocerans, copepods, pteropods, echinodermata bivalvia larvae. Results indicate that may accumulate increase stagnant trophically rich northern gyres, spreading surrounding larger with currents. We assume presence correlates decrease population due competition for (zooplankton). Our findings support importance implementing an international monitoring program throughout Sea demonstrate ability current MEDIAS detect changes ecosystem surveyed areas.