The European lobster, Homarus gammarus, was sampled from September 2016 to August 2017, using pots and gillnets in the Eastern Adriatic Sea. Official landings were also analyzed (2008–2020). The majority of landings were from the Northern Adriatic and showed an increase of 18.5% over the study period. Results revealed an extremely low catch rate that fluctuated significantly by season. Dominance by specimens in the size classes of 90–110 mm carapace length (CL) was observed. Experimental design revealed spatial heterogeneity, with larger individuals caught further from the coast (>3 nm) and undersized specimens caught near the coast (<3 nm). With increasing CL and total length (TL), an increase in weight was higher in males than females. TL and abdomen width (AW) increased linearly with CL and were more pronounced in females. At 80 mm CL, females started to develop secondary sex characteristics with wider AW than males. The results suggest that the modern legal framework is appropriate for lobster fisheries and a longer fishing season is not advisable, despite a positive catch trend in the northern part of the sea. Additional efforts are desirable to reduce fishing pressure in the coastal part. The morphometric relationships could reveal population characteristics required as inputs in stock assessment analysis for effective management.

Integrated otolith chemistry and muscle tissue stable isotope analyses were performed to allocate juvenile Diplodus puntazzo and Diplodus vulgaris to nurseries in the Adriatic Sea. Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) was used to quantify the concentrations of chemical elements in the otoliths. Fish muscle samples were analysed for δ¹³C and δ¹⁵N. In general, Ba/Ca and Sr/Ca ratios and isotopes varied between sites and species. Values of δ¹³C and δ¹⁵N were significantly different between species and sites. Multivariate analysis detected a significant difference in the element signature between species while there was no evidence for a significant interaction for sites. A clear pattern across the four groups of interest, D. puntazzo_Estuary > D. vulgaris_Estuary > D. puntazzo_Coastal > D. vulgaris_Coastal, following decreases in δ¹³C, and increases in δ¹⁵N were found. It seems that these species are feeding on the same local food web within more productive estuarine site while at costal site, feeding segregation among investigated species is evident. Both species were re-allocated correctly to the estuarine waters based on the otolith chemistry and stable isotopes information and higher value of δ¹⁵N. Combining otolith chemistry with tissue isotope ratios of juvenile fish provided complementary information on nursery habitat use at different spatial scales and elucidated ecological and environmental linkages.

This study aims to determine if otolith chemistry can differentiate between coastal lagoons and shallow coves and if it can effectively re-assign Sparus aurata specimens to the nearest nurseries. Young-of-the-year (Y-O-Y) and young adults were collected at fifteen sites within three nurseries along the eastern Adriatic. LA-ICP-MS was used to quantify the concentrations of 12 chemical elements in the otolith region corresponding to the juvenile nursery stage. The multivariate element concentration differed significantly among nurseries. Based on CAP analyses, using a suite of five trace elements (Sr, Mg, Zn, Ba and Pb), 41% S. aurata specimens were correctly re-allocated to the nurseries and a higher rate of success (46%) was achieved for shallow cove than for coastal lagoons. A separate CAP analysis explained 94% of element variance, with 100% discrimination for Sr:Ca, Mg:Ca and Pb:Ca, enabling re-allocation to shallow cove nurseries. The lowest success of Ba as a discriminant reduced re-allocation to shallow coves. The results suggested that number of shallow coves with continuous, submarine, freshwater springs along the coast, making them similar to coastal lagoons, could significantly contribute to the S. aurata recruitment, expanding attention from the protection of individual nursery towards a wider part of the coast.

Shallow coastal areas are used as nursery habitats by many fish species as they are highly productive environments. Their role as nurseries for early life stages of many species, as well as foraging and spawning grounds, has been clearly documented in number of previous studies across globe. Studies of fish otolith geochemistry have contributed to the understanding of the early life history and nursery identification of different fish species. Otoliths are paired calcified structures located in the inner ear of teleost fishes. They have been widely used in marine ecology and fishery research to describe population age structure, assess connectivity between fish stocks and study individual migration patterns. The aim of this study is to investigate differences in otolith composition among juvenile of gilthead sea bream, Sparus aurata captured in different habitats. Juvenile fish of S. aurata were collected by beach seine net in three estuarine locations (Ploče, Pantan and Prosika), in the eastern Adriatic, during March and May 2018. Upon collection, fish were kept frozen and transported to the lab for further preparations. Three similar sized specimens were selected for subsequent analysis. The otoliths have been extracted, cleaned and prepared for transverse sections through the otolith core with a low-speed saw. Further sample preparation was done at the Johannes Gutenberg University (JGU; Mainz, Germany) where the concentrations of Li, Na, Mg, Ca, Mn, Zn, Sr, Mo, Pb i U were determined by means of LA-ICP-MS in line scan mode along maximum growth rates. Concentration of Ba:Ca and Sr:Ca in otolith core varied within otoliths from same location as well as between otoliths from different locations. Obtained concertation were compared to salinity. Higher concentrations of Pb, Mn and Zn were found in the estuary of river Neretva which can be related to an anthropogenic effect from surrounding agricultural area that contribute to the increase of these elements. The otolith core Mg:Ca ratio was highest for the estuary of river Pantan. These preliminary investigations serve as a basis for future research to investigate connectivity between juvenile and adult’s individuals within Nursefish project.