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In the last few decades all around the globe, and so the Adriatic region is not excluded, there have been a remarkable growing problem with marine litter, specially of plastic origin. Around 80% of marine litter originates from the mainland and is usually brought to the sea by wind (eg. from the landfills), rivers, sewage discharges, waste industrial water or is deliberately thrown into the sea. It is of great importance to identify pollution hot spots and sensitive areas in order to prioritize the location of efforts to reduce marine litter. The highest litter densities on the croatian part of the Adriatic were observed in areas that are under great influence of human activities in the populated coastal areas (aquatorium around cities Split, Trogir, Dubrovnik, Pula) and around famous nautical tourist destination (Kornati islands, Brijuni, Telašćica). Channel waters are loaded with greater variety of litter mostly derived from nearby mainland, while the more distant areas are mainly dominated by plastics originating from the neighboring countries. Plastic materials float and takes longer to sink to the seabed and its distribution primarily depends on the currents. Occasionaly large quantities of floating litter are discharged with Neretva river due to uncontrolled dumping yards. On the southern shores of peninsula Pelješac and islands Mljet, Korčula, Lastovo and Vis, due to geographical position and orientation towards the currents, winds and waves, the appearance of large amounts of litter is observed repeatedly, particularly massive one in 2010. In addition to the general surface cyclonic circulation in the Adriatic, occurs several cyclonic gears, of which the most prominent are those in south and central Adriatic. Both areas, especially Jabuka pit, are significant fishing area and important routes of maritime transport. Therefore, we can assume that the fishing and merchant ships are the main source of industrial waste. According to unpublished data, seabed of Jabuka and south Adratic Pit are rather polluted with marine litter.

Marine litter is defined as any persistent, manufactured or processed solid material discarded, disposed of or abandoned in the marine and coastal environment. High concentrations of litter are usually found near shipping routes, around fishing areas and in oceanic current convergence zones. Fishing for litter is effective way to clean up marine waters by removing solid waste, which poses a threat to marine organisms and has negative economic and social impacts on coastal communities and tourism. Data on marine litter are collected in fishery port Vira on island of Hvar within DeFishGear project. Fishermen are asked to collect marine litter that accumulates in their nets as a part of their normal fishing activities. Total of seven trawl vessels are participating in fishing for litter activities. Fishermen are fulfilled data sheets after every fishing day. Data sheets contain information about date, location, type and amount of collected litter. Fishing for litter activities in fishery port Vira are carried out since November 2014. Presented results of marine litter are collected from November 2014 to May 2015. Total of 7034, 29 kg of marine litter are collected during this time period. Among the various types of litter, plastic is the most represented.

The work examines the level of metals in various tissues of wild caught Muraena Helena from Adriatic sea in the year 2010 by the atomic absorption spectrometry (Perkin-Elmer Analyst 600 Zeeman equipped with a THGA-600 graphite furnac). The analysis shows that Hg and As had highest levels in muscle, gills and especially liver while Pb and Cd had highest levels in skin.

A short-term study of the coastal fish community was conducted from May till August 2003 in the special reservate in Mali Ston Bay (southern Adriatic, Croatia), using a 25 m long beach seine. A total of 4038 fish specimens, belonging to 14 families and 28 species were caught. Atherinidae (88, 18%) dominated the catch: Atherina boyeri (81, 87%) was the most numerous, while A. hepsetus (6, 31%), Gobius geniporus (2, 15%), Mullus barbatus (1, 95%) and M. surmuletus (1, 11%) comprised 11, 52% in total. The remaining species contributed less than 0, 3% of the catch. Most species were present as juveniles. The overall value of richness (D) was 3, 25, diversity (H) values were 0, 94 and evenness (J) was 0, 11. Our preliminary results provide a contribution to the knowledge of the fish assemblage of the Mali Ston Bay.

Two ichthyoplankton surveys (June – July 2019 ; 2020) were conducted along the eastern side of the Adriatic Sea (Croatian fishing ground). Ichthyoplankton samples were obtained by standard vertical plankton tows using a WP2 sampler (mouth opening, 0.255 m2 ; mesh size, 0.200 mm) and preserved in 96% ethanol. In the laboratory, ichthyoplankton was isolated under the binocular and its taxonomy was determined using DNA barcoding with cytochrome c oxidase subunit I (COI). Overall, 1381 fish eggs and 407 larvae were collected and they belonged to 39 fish taxa. Quantitatively, the dominant taxa was Engraulis encrasicolus (L.). Biodiversity indices (Species richness (S), Simpson’s Index of Diversity (D), Shannon-Wiener Index (H), Evenness (E), Jaccard Index (J)) pointed out that samples obtained within two summers were quite similar (J=81.8%).