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The extant graptolite Rhabdopleura recondita has been so far recorded only as inhabiting a bryozoan skeleton. Its larval settlement and metamorphosis are possible in the absence of a bryozoan zoarium, whereas further colony development may require that the larva is hidden inside the bryozoan host. This dependence may constrain the development of R. recondita tube and tubaria compared to the other Rhabdopleura species that develop without a host. We report here on larval settlement and metamorphosis in the absence/presence of a bryozoan host skeleton. We also make the first attempt to test the phenotypical response of R. recondita tubes and tubaria under variable hydrodynamic regimes in laboratory conditions. After 40 days, no significant variation was detected in the number or length of the newly formed tubes. These findings suggest that R. recondita eventually resides in a narrow velocity range and that tube and tubarium development is largely invariable.

To date, 13 species of Trichoptera from 11 genera and 8 families have been reported for the Adriatic islands of Cres, Krk, Pag and Hvar. Relatively recent research has been conducted on the islands of Cres, Krk and Pag, where 329 adults of Trichoptera belonging to 10 species from 8 genera and 6 families were collected. Most dominant was Ecnomus tenellus with 235 specimens collected (islands of Krk and Cres), followed by Leptocerus tineiformis (Krk) with 51 specimens collected. Only one specimen of the each species Stenophylax mitis (Cres) and Mystacides azurea (Krk) was recorded. Most of the species were recorded on the island of Krk (7), and the lowest on the island of Pag (2). Faunistically most interesting was the first finding of species Stenophylax mitis McL. for the fauna of Croatia., Na području jadranskih otoka (Cres, Krk, Pag, Hvar) utvrđeno je do sada 13 vrsta Trichoptera iz 11 rodova i 8 porodica. Novija istraživanja provedena su na otocima Cresu, Krku i Pagu u kojima je prikupljeno 329 adultnih oblika Trichoptera s 10 vrsta iz 8 rodova i 6 porodica. Najdominantnije vrste bile su Ecnomus tenellus s 235 prikupljenih primjeraka (Krk i Cres) i Leptocerus tineiformis (Krk) s 51 prikupljenim primjerkom, a samo s jednim primjerkom zabilježene su vrste Stenophylax mitis (Cres) i Mystacides azurea (Krk). Najveći broj vrsta utvrđen je na otoku Krku (7), a najmanji na otoku Pagu (2). Faunistički najzanimljiviji je nalaz vrste Stenophylax mitis McL. koja je ovim istraživanjima utvrđena po prvi puta u fauni Hrvatske.

Although there is a high number of publications listing fish species in the Adriatic, only a few have focused on chondrichthyans, while their conservation status has been investigated even less. Thus, this paper aims to provide an updated and annotated checklist of the chondrichthyans occurring in the Adriatic waters with their presence and conservation status. Each species is evaluated against the criteria defined in IUCN (International Union for Conservation of Nature) Red List Categories and Criteria and according to the guidelines for national and regional level assessments. In total, 60 chondrichthyan species from 27 families and 42 genera are listed. The list contains 33 species of sharks, 26 species of rays and one chimera. Assessment of the conservation status reveals that three species are now considered Regionally Extinct (namely Squatina oculata, Pristis pectinata and Rhinobatos rhinobatos). A total of 21 species are assessed as Critically Endangered, 8 are Endangered and 10 are Vulnerable. Of the remaining species, six are Near Threatened and the same number of species are Least Concern and Data Deficient. Considering that the principal driver of chondrichthyan decline and regional extinction is overfishing, it is recommended that the Adriatic countries adopt the same management measures and strengthen their coordination.

Analysis of statolith growth increments was used to determine age and describe growth pattern of broadtail shortfin squid Illex coindetii in the central eastern Adriatic Sea, an important demersal resource in the Adriatic basin. Size-at-age data were obtained from a large sample (N = 476, including 249 males and 227 females) of individuals with dorsal mantle length (ML) from 55 to 216 mm and body weight (BW) from 5.7 to 356.9 g. Estimated age ranged from 52 to 186 days, with an average of 108 days, suggesting the species has a life span of six months. No statistically significant difference in statolith length was found between the sexes. The back-calculation analysis showed that Adriatic I. coindetii hatches continuously throughout the year, with two alternative spawning periods, in summer and winter. Therefore, a generation born in summer reproduces in winter, and generation born in winter reproduces in summer. Hatchlings of the autumn–winter period were significantly larger and heavier with slower growth than their offspring hatched in summer and spring that exhibited faster growth and matured at younger age. Estimated age at first maturity were 137.4 and 109.2 days, for females and males, respectively. Growth was best described by Schnute and logistic model that display asymptotic tendencies by the end of the life span. There were no major differences in growth pattern between different cohorts of each sex, with faster growth recorded at younger age.

Završni rad analizira kruzing odredišta Jadranskog mora. Države uključene u analizu su: Hrvatska, Italija, Slovenija, Crna Gora i Albanija. Analiza je napravljena na temelju podataka o dolasku kruzing brodova i broju putnika. Nakon analize luka po državama Jadranskog mora, napravljena je usporedba luke Dubrovnik i luke Venecija. Razlog odabira luke Dubrovnik i luke Venecija je zbog srodnosti jer je riječ o najrazvijenijim i najprometnijim kruzing pomorskim lukama na Jadranu. Zbog velikog broja brodova u obje luke uvedena su ograničenja broja brodova i putnika jer dolazi do negativnih faktora koji utječu na okoliš i domicilno stanovništvo. Osim toga, Dubrovnik i Venecija su gradovi bogate povijesti, kulture i pod zaštitom su UNESCO-a. Nakon analize, prikazan je utjecaj kruzing turizma na ekologiju koja je bitan faktor koji utječe na turizam i na njegov razvitak u budućnosti. Kruzing turizam ima velik potencijal za razvoj u Republici Hrvatskoj, ali su potrebna ulaganja u infrastrukturu i potpora nadležnih ministarstava., The final paper analyzes the cruising destinations of the Adriatic Sea. The countries included in the analysis are: Croatia, Italy, Slovenia, Montenegro and Albania. The analysis was made on the basis of data on the arrival of cruise ships and the number of passengers. After analyzing the ports by the countries of the Adriatic Sea, a comparison was made between the port of Dubrovnik and the port of Venice. The reason for choosing the port of Dubrovnik and the port of Venice is due to the similarity because they are the most developed and busiest cruise seaports on the Adriatic. Due to the large number of ships in both ports, restrictions on the number of ships and passengers have been introduced due to negative factors affecting the environment and the domicile population. In addition, Dubrovnik and Venice are cities rich in history, culture and are under UNESCO protection. After the analysis, the impact of cruising tourism on ecology, which is an important factor influencing tourism and its development in the future, is presented. Cruising tourism has great potential for development in the Republic of Croatia, but investments in infrastructure and support from relevant ministries are needed.

11 pages, 6 figures, 1 table, supplementary material http://www--int-res--com.csic.debiblio.com/articles/suppl/m634p147_supp.pdf, Marine recreational fishers accumulate a vast amount of local ecological knowledge (LEK) during their fishing activity that can be of paramount importance for monitoring how climate change affects fish assemblages. We assessed LEK of recreational fishers to investigate the increase in the abundance of 5 northward-expanding indigenous thermophilic fish species in 2 Mediterranean subregions. We accessed LEK through an online survey completed by 794 recreational fishers (386 from the Adriatic/Ionian subregion and 408 from the Tyrrhenian/Ligurian subregion). The species perceived to have increased most in abundance were Pomatomus saltatrix (71% of replies) followed by Sphyraena viridensis (58%). The remaining species (Sparisoma cretense, Balistes capriscus and Coryphaena hippurus) ranged between 17 and 25%. Recreational fishers have a stable system of beliefs about meridionalization, which is perceived homogeneously between recreational anglers and recreational spearfishers. Our results indicate that latitude is negatively correlated with meridionalization in the Adriatic/Ionian, but not in the Tyrrhenian/Ligurian Seas, suggesting that meridionalization of the Adriatic/Ionian Seas could be a process that has temporally lagged with respect to the Tyrrhenian/Ligurian Seas. Our study demonstrates that LEK of recreational fishers can be easily accessed on a large geographical scale and can be useful to monitor changes in the distributions of data-limited species such as those studied here, This study was supported by the Interreg Med Programme (Grant number Pr MPA-Adapt 1MED15_3.2_M2_337) 85% co-funded by the European Regional Development Fund and by the Croatian Science Foundation (HRZZ), under project IP-2016-06-525, With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

Oyster shells are substratum for different epibiontic and endobiontic organisms, including pests and parasites. Rocellaria dubia is endolithic and facultative tube-dwelling bivalve, boring in different calcareous substrates, including the shells of bivalves. In 2020, R. dubia was found as endolithic in the shells of the Pacific oyster Magalana gigas, from an oyster farm off the Sacca di Goro lagoon (Emilia-Romagna region, Northern Adriatic Sea, Italy). The purpose of this study was to describe this newly recorded association. Altogether, 136 specimens of R. dubia were found in 15 oysters, photographed under a stereoscope, and their length was measured. Heavily infested oysters hosted tens of R. dubia borers, which were perforating the whole thickness of the oyster valves. The flesh of these oysters was heavily damaged, suggesting parasitic association. R. dubia specimens were categorized into three age classes (0–1, 1–2, and 2–3 years old). M. gigas/R. dubia might be a widespread association, overlooked due to the very scarce research on macrofauna associated with M. gigas. Considering the negative effects of R. dubia endobiosis on oyster fitness, and possible impacts on oyster aquaculture, further research should be conducted in order to elucidate the distribution and ecological characteristics of this parasitic association.

Based on field investigations and using the Braun-Blanquet approach, the paper describes the chasmophytic association Portenschlagiello ramosissimae-Campanuletum portenschlagianae, from Croatian Mediterranean cliffs.

We herein review the Adriatic opisthobranch fauna, provide an updated checklist of 223 species and assess their distribution at regional and country levels. New Adriatic records are provided for 67 opisthobranch taxa, adding three new records for the Italian coastline, five new records for Albania, eight for Croatia and 15 for Montenegro. The presence of Hermaea bifida (Montagu, 1815), Hermaea variopicta (Costa A., 1869) and Facelina annulicornis (Chamisso & Eysenhardt, 1821) is reported for the first time from anywhere in the Adriatic Sea. Including the new findings, our inventory includes 28 species from Albania, 163 from Croatia, 178 from the Italian coastline of the Adriatic, 41 from Montenegro and 74 from Slovenia. No records were available from Bosnia and Hercegovina. Ninety species (40.4%) are widespread, and were recorded from all three main divisions (Northern, Western and Eastern Adriatic), whilst 79 species (35.4%) were reported from only one of them. At sub-division levels, the Albanian inventory is the most dissimilar to the other country/regional lists, presumably because of the lack of targeted field surveys. The highest similarity is observed amongst the Western Adriatic, Croatia and the Italian Ionian coastline. Seven alien, one possible alien and three cryptogenic opisthobranchs were reliably recorded from the Adriatic Sea. The first Mediterranean records of five species were in the Adriatic Sea, of which four species have not been found elsewhere in the Mediterranean. Shipping and aquaculture are the probable pathways for most of the alien species. A steady rate of one to two alien introductions per decade since the 1970s was evident. The Northern Adriatic coasts are the most affected by alien invasions, probably due to repeated local introductions along with shellfish transfers (oysters, mussels, Manila clams), and heavy maritime transport.

Sport and recreational marine fishery can significantly contribute to the national budget through its economic and social effects. The main aim of this research is to define the economic and social significance of sport and recreational fishing in Croatia through the assessment of the lower limit of its economic value. This is done by analyzing the segments of sport and recreational fishing together with the economic and other activities which are closely related to it. When expressed by the number of stakeholders involved in sport and recreational fisheries and the share in the gross domestic product, it can be concluded that the economic effects of these activities are only slightly lower than in commercial fisheries. This research provides the groundwork for pointing out the basic guidelines of the social significance of sport and recreational marine fishery in Croatia. Hence, it can be noted that sport and recreational fishing in local coastal communities support the overall development of rural areas and the local communities in particular.

Marine litter places significant burden on beaches, marine surface, marine bottom and biota of the Adriatic Sea. It results mainly from inappropriate waste management on land. The paper analyses quantities and composition of marine litter and its sources, the threat of plastics, the approach to circular economy and waste management in Croatia and presents proposals for circular flow of materials with minimum leakage into the ecosystems and novel approach to marine litter issue. The solution of marine litter problem is in waste management involving source separation, numerous local sorting facilities, home composting, municipal composting and biogas production, with minimum resources left for disposal as well as implementing the policies to reduce and modify packaging, the materials used therefor and to avoid one-use and disposable plastic materials, that implying a change of habits, intervention in supply chain and increasing domestic supply.

Adriatic, the northernmost part of the Mediterranean Sea, due its oligotrophy, topography, and hydrology dynamics, and complex circulation patterns, was suggested as an important study site for rapid climatology impacts. Its southern part is mainly oligotrophic and dominated by picophytoplankton, with cyanobacteria as main representatives. Diversity and distribution patterns of different Prochlorococcus ecotypes were investigated by molecular tools and flow cytometry during the winter convection event in the southern Adriatic (BIOTA winter cruise; February/March 2015). Phylogenetic diversity based on clone libraries of the 16S–23S ribosomal DNA ITS region, as well as flow cytometry (histograms of red fluorescence), indicated presence of 2 different Prochlorococcus in the Adriatic. HLI, as a typical clade for Mediterranean Sea, was likewise found to be dominant Prochlorococcus in the Adriatic, followed by less abundant LLI clade. In addition, Prochlorococcus were found to co-occur with diverse Synechococcus population (53% and 47% of obtained ITS sequences, respectively). Different Prochlorococcus ecotypes had similar patterns of vertical distribution, predominantly occupying upper 100 m depth layer, but their distribution was clearly affected by the heterogeneity of hydrological conditions, nitrogen concentration and temperature along vertical and horizontal sampling points. Different studies pointed out that, as a consequence of climate changes, serious alteration of biological and ecological patterns are already taking place Therefore, understanding of the distribution and abundance of picophytoplankton in Adriatic, being still limited, is much needed baseline for predicting possible biogeochemical impact of future environmental changes.

The definition of conservation units is crucial for the sustainable management of endangered species, though particularly challenging when recent and past anthropogenic and natural gene flow might have played a role. The conservation of the European grayling, Thymallus thymallus, is particularly complex in its southern distribution area, where the Adriatic evolutionary lineage is endangered by a long history of anthropogenic disturbance, intensive stocking and potentially widespread genetic introgression. We provide mtDNA sequence and microsatellite data of 683 grayling from 30 sites of Adriatic as well as Danubian and Atlantic origin. We apply Bayesian clustering and Approximate Bayesian Computation (ABC) to detect microgeographic population structure and to infer the demographic history of the Adriatic populations, to define appropriate conservation units. Varying frequencies of indigenous genetic signatures of the Adriatic grayling were revealed, spanning from marginal genetic introgression to the collapse of native gene pools. Genetic introgression involved multiple exotic source populations of Danubian and Atlantic origin, thus evidencing the negative impact of few decades of stocking. Within the Adige River system, a contact zone of western Adriatic and eastern Danubian populations was detected, with ABC analyses suggesting a historical anthropogenic origin of eastern Adige populations, most likely founded by medieval translocations. Substantial river-specific population substructure within the Adriatic grayling Evolutionary Significant Unit points to the definition of different conservation units. We finally propose a catalog of management measures, including the legal prohibition of stocking exotic grayling and the use of molecular markers in supportive- and captive-breeding programs.

00000 ăWOS:000384167300004; International audience; Morphological and molecular tools were combined to resolve the misidentification between Glycymeris glycymeris and Glycymeris pilosa from Atlantic and Mediterranean populations. The ambiguous literature on the taxonomic status of these species requires this confirmation as a baseline to studies on their ecology and sclerochronology. We used classical and landmark-based morphometric approaches and performed bivariate and multivariate analyses to test for shell character interactions at the individual and population level. Both approaches generated complementary information. The former showed the shell width to length ratio and the valve asymmetry to be the main discriminant characters between Atlantic and Mediterranean populations. Additionally, the external microsculpture of additional and finer secondary ribs in G. glycymeris discriminates it from G. pilosa. Likewise, landmark-based geometric morphometrics revealed a stronger opisthogyrate beak and prosodetic ligament in G. pilosa than G. glycymeris. Our Bayesian and maximum likelihood phylogenetic analyses based on COI and ITS2 genes identified that G. glycymeris and G. pilosa form two separate monophyletic clades with mean interspecific divergence of 11% and 0.9% for COI and ITS2, respectively. The congruent patterns of morphometric analysis together with mitochondrial and nuclear phylogenetic reconstructions indicated the separation of the two coexisting species. The intraspecific divergence occurred during the Eocene and accelerated during the late Pliocene and Pleistocene. Glycymeris pilosa showed a high level of genetic diversity, appearing as a more robust species whose tolerance of environmental conditions allowed its expansion throughout the Mediterranean.

It is widely accepted that bivalve shell growth responds to environmental factors, however, few studies analyze the influence of biological drivers on growth, including reproduction. We evaluated the reproductive cycle of Callista chione as a potential driver of shell formation rate. C. chione is a commercially important species and due to its longevity (> 20 years) is an interesting target for sclerochronological studies. Sampling was conducted in two different environmental settings along the eastern Adriatic coast: Pag – a semi-enclosed bay, and Cetina – a coastal site near a river mouth. The monthly collection was carried out for a 18-month period from May 2014 until October 2015. Temperature was measured hourly, whereas Chl a and δ13CPOM were determined monthly. Satellite data for Chl a was also included in the study. The Gonadosomatic Index (GSI) was used as a unit of measure for variation in gonadal mass. The oxygen isotope composition of several shells (δ18Oshell), once converted into seawater temperature, was used to determine the duration of the main growth season. Minimum monthly temperatures differed by ca. 4°C between Pag and Cetina (8.9°C and 12.7°C, respectively), whereas maximum temperatures were similar. Chl a and δ13CPOM values showed distinct temporal trends. A clear seasonal cycle in GSI was observed, however, it was not synchronous between sites. In Pag, GSI started to increase in early spring and reached maximum values during the summer, with a main spawning peak in July. In Cetina, increasing GSI values were observed during winter reaching maximum values in early spring, whereas spawning took place on several occasions during late spring and summer. Based on δ18Oshell values, the fastest shell growth occurred between the winter and summer (> 70%). The difference in temperature ranges may explain the spawning lag observed between sites. The highest temperatures in Pag in 2015 coincided with the main spawning peaks, while in Cetina temperature was inversely related to the GSI throughout the year. A correlative allocation of energy to growth and reproduction was observed at both sites, with a decline in growth after spawning. The highest peaks in Chl a concentration occurred mostly between November and April, a period with an increase in production of gonads. During this period, an inverse relationship of Chl a and δ13CPOM values was observed. More positive δ13CPOM values, indicative of fresh material, were related to periods following the main spawning peaks when the GSI was low ; conversely, more negative values were observed during the most ripe stages and maximum spawning peaks. This suggests that the allocation of energy to growth was higher during earlier reproductive stages when nutrients were more abundant, followed by a shift of energy investment toward gonad production and a decrease in nutrients.

Quantitative variability of the copepod assemblages in the northern Adriatic Sea were investigated at two stations, during 43 cruises, from January 1993 to October 1997. Samples were taken at 0.5, 10, and 20 meters, as well as near the bottom, using five-litre Niskin bottles. For inter-annual variation in the density of copepod assemblages data were presented as total number of nauplii and copepodites with adult copepods of following groups: Calanoida, Cyclopoida-oithonids, Cyclopoida-oncaeids and Harpacticoida. Moreover, hydrographic conditions, both fractions of phytoplankton, nonloricate ciliates and tintinnids were taken in considerations. Nauplii are the most numerous fraction at both stations with an average over 74% in the total number of all copepod groups. Their number were significantly higher at western eutrophic station, while at the eastern oligotrophic station, an absolute maximum of 693 ind.l-1 was noted. The maximum values of calanoids and oithonids occur generally during summer and always more numerous at the western station 33 to 50% and 50 to 63% respectively. The most abundant taxa identified were calanoid Paracalanus parvus and cyclopoid Oithona nana. Oncaeid species Oncaea waldemari and Monothula subtilis dominated during late autumn and winter. An atypical increase abundances of oncaeids during the summer of 1997, could be related to an invasion and mass occurrence of the calycophoran siphonophore Muggiaea atlantica. It can be concluded that these dominant copepods are responsible for the stabilization of very complex processes. Atypical appearances of major copepod groups and disturbances in the copepod population structure itself can significantly influence changes in the ecosystem of this very sensitive region.

21 páginas, 6 figuras, 4 tablas., Habitat classifications provide guidelines for mapping and comparing marine resources across geographic regions. Calcareous bio-concretions and their associated biota have not been exhaustively categorized. Furthermore, for management and conservation purposes, species and habitat mapping is critical. Recently, several developments have occurred in the field of predictive habitat modeling, and multiple methods are available. In this study, we defined the habitats constituting northern Adriatic biogenic reefs and created a predictive habitat distribution model. We used an updated dataset of the epibenthic assemblages to define the habitats, which we verified using the fuzzy k-means (FKM) clustering method. Redundancy analysis was employed to model the relationships between the environmental descriptors and the FKM membership grades. Predictive modelling was carried out to map habitats across the basin. Habitat A (opportunistic macroalgae, encrusting Porifera, bioeroders) characterizes reefs closest to the coastline, which are affected by coastal currents and river inputs. Habitat B is distinguished by massive Porifera, erect Tunicata, and noncalcareous encrusting algae (Peyssonnelia spp.). Habitat C (non-articulated coralline, Polycitor adriaticus) is predicted in deeper areas. The onshore-offshore gradient explains the variability of the assemblages because of the influence of coastal freshwater, which is the main driver of nutrient dynamics. This model supports the interpretation of Habitat A and C as the extremes of a gradient that characterizes the epibenthic assemblages, while Habitat B demonstrates intermediate characteristics. Areas of transition are a natural feature of the marine environment and may include a mixture of habitats and species. The habitats proposed are easy to identify in the field, are related to different environmental features, and may be suitable for application in studies focused on other geographic areas. The habitat model outputs provide insight into the environmental drivers that control the distribution of the habitat and can be used to guide future research efforts and cost-effective management and conservation plans., This study has been funded by the Italian Ministry of Education, Universities and Research within the scientific research program of national interest "Coastal bioconstructions: structures, functions, and management" (2010-11 PRIN prot. 2010Z8HJ5M_003) and by the INTERREG Ita-Slo 2007-2013 Program (Project TRECORALA - TREzze e CORalligeno dell'ALto Adriatico: valorizzazione e gestione sostenibile nel Golfo di Trieste.http://www. trecorala.eu/it-IT/7-avvio-del-progetto-trecorala).

West-east variability of abundance and population structure of calanoid copepods was studied in 2002-2006 period at two stations in the northern Adriatic (NA), influenced to a different degree by the freshwater discharge of the Po River and regional circulation pattern shaped by the Istrian Coastal Countercurrent (ICCC) and Eastern Adriatic Current (EAC). Species-specific calanoid distribution and abundances were related to concurrently obtained salinity, temperature, Po River discharge and phytoplankton data. Significant differences between stations were determined for salinity, phytoplankton biomass and abundance, total calanoid density, total number of species and Shannon-Wiener biodiversity. The paper is especially concentrated to extremes in Po discharge recorded during the investigated period, which are discussed with respect to the observed variability in plankton components at each investigated station. At the western station, the proximity of the freshwater sources and consequent nutrients load was strongly coupled to the phytoplankton cycle and more tightly reflected in the calanoid abundances, whereas at the eastern station this link was appreciably weaker. Analysis of the community structure revealed the lack of true discriminating species between stations, while fairly stable pattern of occurrence and relative abundances was recorded for six key calanoid species (Pseudocalanus elongatus, Paracalanus parvus, Acartia clausi, Ctenocalanus vanus, Temora longicornis and Centropages typicus) at both sites. The role of EAC was significant in transport of open middle Adriatic species into the NA, which were more frequently recorded at the eastern station and extended their areal westwards more often in winter due to strengthening of the EAC.

We synthesise reported stable isotope values for domesticates and wild herbivores from sites spanning the Neolithic in coastal Croatia, Slovenia, and Italy (6000–3500 calBC). Carbon and nitrogen stable isotope values are analyzed as proxies of diet and environment, with differences between species possibly indicating anthropogenic influence. Results are used to characterise diets and address questions of the origin and development of husbandry strategies, especially transhumance, in early farming communities. Changes in pig carbon and nitrogen isotope values through time suggest alterations in practices, whereas values remain relatively constant for cattle and ovicaprids during most of the Neolithic, despite assumptions of seasonal mobility.

Longevity of bivalves has been an intriguing issue, especially for those species of interest for human consumption. Reliable age and growth estimates often require the combination of several methods. In this study, we analyzed changes in shell structure including ridges on the external shell surface and growth lines observed in acetate peel replicas of shell sections of the European date mussel Lithophaga lithophaga, as well as the oxygen and carbon isotope values (δ18O and δ13C) of the shell. High variations in growth rates between individuals were noted. Ontogenetic ages of analyzed shells varied from 10 to 54 years (30.6–93.6 mm). According to results of generalized von Bertalanffy growth function, L∞ was 107.6 mm, and k was 0.03 year−1. δ18O results strongly suggest that growth ridges visible on the external shell surface of L. lithophaga are formed annually. The δ18O values ranged from −0.2 to 2.7 ‰ ( $$\bar{x} = 1.15 \pm 0.72$$ ‰), which equates to a temperature range of 13 °C. The reconstructed seawater temperatures (Tδ18Oshell) ranged between 12 and 25 °C, a range in good agreement with measured temperature. Stable carbon isotope values decreased through ontogeny and ranged between −2.05 and 2.32 ‰ ( $$\bar{x} = 0.01 \pm 0.89$$ ‰). Results of this study provide the first stable isotope data for L. lithophaga shells and show the potential of this species as a geochemical sclerochronological archive.

Sabellaria alcocki Gravier, 1906, described for the Indian Ocean, should not be present in the Mediterranean area. Though S. spinulosa alcocki, a Mediterranean variety, can be well-distinguished from S. alcocki, it has recently been referred to as S. alcocki. Thus, S. alcocki appears in the Italian coast checklist. The recent finding of S. spinulosa reefs along the southern Adriatic coast, the first report of these biogenic constructions in the Mediterranean area, allowed us to compare its morphological variability with that of S. alcocki. A morphometric analysis of the opercular paleae showed a great deal of intrapopulation, size-independent variation, which cannot justify the existence of varieties within S. spinulosa. Moreover, the analysis of post-settlement development showed that opercular features change during individual growth. Recently settled individuals resemble S. alcocki, while the more advanced life stages become closer to S. spinulosa. Accordingly, we hypothesize that part of the erroneous Mediterranean records of S. alcocki could correspond to specimens of S. spinulosa at different stages of development. Sabellaria alcocki Gravier, 1906, descrita en el Océano Índico, no debería estar presente en el Mediterráneo. A pesar de que S. spinulosa alcocki, una variedad mediterránea, es fácilmente diferenciable de S. alcocki, esta especie ha sido recientemente citada como S. alcocki. Como consecuencia, esta última aparece en la lista faunística de las costas italianas. El reciente hallazgo de arrecifes de S. spinulosa en el sur del Adriático, la primera cita de estas formaciones biogénicas en el Mediterráneo, ha permitido comparar su variabilidad morfológica con la de S. alcocki. El análisis morfométrico de las características de las paleas operculares mostró una gran variabilidad intrapoblacional, independiente de la talla, lo cual no justifica la existencia de variedades en S. spinulosa. Por otro lado, el análisis del desarrollo post-asentamiento mostró que las carac- terísticas operculares cambian con el crecimiento individual. Los individuos recién asentados son más similares a S. alcocki, mientras que se asemejan más a S. spinulosa en etapas posteriores. Así pues se sugiere que una parte de los registros erróneos de S. alcocki en el Mediterráneo podrían corresponder a especímenes de S. spinulosa en diferentes etapas de desarrollo

The Noah's Ark shell Arca noae is a widely distributed and locally abundant bivalve in the coastal waters of the eastern Adriatic Sea where it is commercially exploited. Information regarding its basic biology is lacking, and little is known about its population structure, recruitment, reproduction, growth and longevity. We estimated the age of three populations of A. noae collected from the Croatian Adriatic using external surface growth rings, pallial line scars on the inner shell surface, and growth lines in acetate peel replicas of sections of the umbo and outer prismatic shell layer. All the age determination methods used were successful in estimating the age of A. noae, however counts of the prismatic growth lines provided a less ambiguous estimate of the age of the shells. Arca noae is a slow-growing species reaching a size of 70 mm and an age of up to 16 years. Croatian populations might be vulnerable to over-exploitation.

There is a resident common bottlenose dolphin population inhabiting the Kvarnerić area of the northern Adriatic Sea, Croatia. The observed decline in population size between 1995 and 2003 led to the declaration of a part of the Kvarnerić as the Cres-Lošinj Special Marine Reserve (CLSMR) in 2006. Protection lasted 3 years, before lapsing. A boat based photo-identification study was conducted between 2004 and 2011 with the aim to estimate the number of bottlenose dolphins inhabiting the CLSMR area, investigate the factors influencing their habitat use and explore the possibility that this area is representative of the population for the whole Kvarnerić. Standard mark–recapture methods and the Mth estimator of Chao for closed populations were applied. The lowest value was estimated in 2008 (N = 112 ; 95% CI = 94–150) and the highest in 2006 (N = 310 ; 95% CI = 265–392). The statistically significant inter- annual variability is likely to reflect natural and anthropogenic driven shifts in habitat use rather than real changes in population size. The average monthly sighting rate was lower in the tourist season (Jun–Aug) than in the pre- and post tourist-season, suggesting that developed nautical tourism may influence shifts in habitat use. Other potential causes are distribution of prey and fishing effort. Inclusion of data from the rest of the Kvarnerić for the years of 2005 and 2011 did not reveal a significant increase in estimated abundance (2005: z = −0.413, P = 0.3398 ; 2011: z = −1.749, P = 0.0401). This indicates that the CLSMR area is representative of the whole Kvarnerić. The number of bottlenose dolphins using the CLSMR area seems to have increased compared with the previous study (1995–2003). This could be due to a shift in habitat use or an increase in population size. However, yearly variations indicate processes causing displacements within the dolphin population home range. Conservation measures aiming at reducing the displacements are proposed.

Phylogeny of Northern Adriatic Salmo trutta is still not resolved, leading to taxonomic controversies and hindering reasonable conservation and fisheries management. We report on the genetic screening of 467 brown trout from 25 sites within Adige, Brenta and Po River drainage basins (Italy). Our main aim was to identify native (Adriatic) brown trout within the central part of the Northern Adriatic area. D-loop lineage screening evidenced a predominance of the Atlantic clade with a frequency of 0.87, followed by the Marmoratus clade with 0.11, and, finally, the Adriatic clade with a frequency of 0.02. The Adriatic clade was found exclusively in specimens from Pianetti River and was represented by haplotype Adcs1. However, microsatellite-based analysis of population structure within Pianetti River specimens failed to identify Adriatic brown trout, but pointed to a nuclear genomic replacement of the former by Atlantic strains. In conjunction with earlier phylogenetic studies, our results contrast with a present-day widespread distribution scenario of Adriatic brown trout within the Northern Adriatic region. From a conservation viewpoint, the punctiform occurrence of Adriatic haplotypes, their ambiguous provenance, and, finally, the presumable genomic replacement at the nuclear genetic level, might hinder reasonable conservation actions and call for revised fisheries management guidelines.

Biological invasions and introgressive hybridization are major drivers for the decline of native freshwater fish. However, the magnitude of the problem across a native species range, the mechanisms shaping introgression as well as invader's dispersal and the relative role of biological invasions in the light of multiple environmental stressors are rarely described. Here, we report extensive (N = 665) mtDNA sequence and (N = 692) microsatellite genotypic data of 32 Northern Adriatic sites aimed to unravel the invasion of the European Barbus barbus in Italy and the hybridization and decline of the endemic B. plebejus. We highlight an exceptionally fast breakthrough of B. barbus within the Po River basin, leading to widespread introgressive hybridization with the endemic B. plebejus within few generations. In contrast, adjacent drainage systems are still unaffected from B. barbus invasion. We show that barriers to migration are inefficient to halt the invasion process and that propagule pressure, and not environmental quality, is the major driver responsible for B. barbus success. Both introgressive hybridization and invader's dispersal are facilitated by ongoing fisheries management practices. Therefore, immediate changes in fisheries management (i.e. stocking and translocation measures) and a detailed conservation plan, focussed on remnant purebred B. plebejus populations, are urgently needed.

Squids are especially frequent as paratenic hosts of helminth parasites, particularly to those that have elasmobranchs and mammals as final hosts. Among those parasite species, anisakid nematode larvae and cestode plerocercoids are most effectively transferred through the trophic chain by oegopsid squids. A total of 439 short-finned squids, Illex coindetii (245 males, 190 females and 4 unsexed) were sampled in the central part of the eastern Adriatic Sea in order to assess their helminth component community and parasite dynamics with respect to host sex, maturity, seasonality, and feeding behavior. Two larval helminths were isolated, i.e., larvae of Anisakis pegreffii, characterized by molecular tools at the species level, and plerocercoids of Phyllobothrium sp., with prevalences of 30.5% and 2.3%, respectively. Highly significant seasonal variation in diet consumption, congruent with seasonal variation in anisakid intensity, was observed, underlining the tight role of squid prey in the trophic transmission of parasite. Likewise, the highest helminth prevalence and intensity of infection was recorded in autumn, when the fish prey, mostly Maurolicus muelleri, comprised the greatest proportion of diet. This helped to assign the Adriatic broadtail shortfin squid not as a first, but as a second, paratenic host for the anisakid, unlike as suggested previously. The presence of larval A. pegreffii confirms its previously reported zoogeographical distribution in the Mediterranean and Adriatic Seas. The presence of 2 helminths in I. coindetii describes the feeding patterns of the squid, as well as clearly defined and coevolved predator-prey relationships.

[1] A network of high-frequency (HF) radars was installed in the northern Adriatic in the second half of 2007, aimed to measure surface currents in the framework of the North Adriatic Surface Current Mapping (NASCUM) project. This study includes a detailed analysis of current measurements from February to August 2008, a period in which three radars were simultaneously operational. Current patterns and temporal evolutions of different physical processes were extracted by using self-organizing map (SOM) analysis. The analysis focused on subtidal frequency band and extracted 12 different circulation patterns on a 4 × 3 rectangular SOM grid. The SOM was also applied on a joint data set that included contemporaneous surface wind data obtained from the operational hydrostatic mesoscale meteorological model ALADIN/HR. The strongest currents were recorded during energetic bora episodes, being recognized by several current patterns and having the characteristic downwind flow with magnitudes exceeding 35 cm/s at some grid points. Another characteristic wind, the sirocco, was represented by three current patterns, while the remaining current structures were attributed to weak winds and the residual thermohaline circulation. A strong resemblance has been found between SOM patterns extracted from HF radar data only and from combined HF radar and wind data sets, revealing the predominant wind influence to the surface circulation structures and their temporal changes in the northern Adriatic. These results show the SOM analysis being a valuable tool for extracting characteristic surface current patterns and forcing functions.

[1] Diurnal coastal upwelling was previously observed when sea breezes were exceptionally strong, or when the process occurred close to critical latitudes (30°N, 30°S) where local inertial oscillations may be resonantly excited. Our data collected in the Adriatic show that the pronounced diurnal upwelling is also possible under milder wind-forcing and outside critical latitudes. It is found that the thermocline recorded in the summer of 2006 at the south coast of the island of Lastovo was subject to diurnal variability with a maximum range of about 30 m, and that the corresponding currents measured off the west coast of the island pointed to internal waves propagating around the island in a clockwise direction. We suggest that the summertime stratification occasionally promotes coastal waves that revolve daily around the island, creating the conditions needed for resonant excitation by sea breezes. Numerical modeling reveals that the 24-h waves are trapped around the island due to the influence of both the Coriolis force and bottom slope, and that the 12-h waves radiate away from the island. The biogeochemical data show that the diurnal upwelling may stimulate primary production in the area but may also adversely affect benthic organisms.

[1] The western Adriatic margin (eastern Mediterranean), part of the Apennine foreland, is characterized by a differentiated tectonic setting, showing high subsidence rates (up to 1 mm/yr) in the northern area and tectonic uplift (on the order of 0.3–0.5 mm/yr) in the southern part corresponding with the so-called Apulia swell. The central Adriatic marks the transition between these two areas. To calculate subsidence values, the stratigraphy of the central Adriatic has been investigated through the borehole PRAD1.2 (European project Profiles across Mediterranean Sedimentary Systems), the first continuous Quaternary marine record in the Adriatic basin (71.2 m long) reaching the top of Marine Isotope Stage 11 (MIS 11). Subsidence calculations were performed first by applying the backstripping procedure to PRAD1.2, in order to investigate the contribution of sediment load and tectonic driving forces to subsidence. Despite the large error bars, mostly caused by the uncertainties in paleowater depth reconstructions, the values obtained demonstrate that tectonics is the main driver for subsidence in this area. In order to better estimate the subsidence rates, an independent approach is introduced, based on the correlation of the present-day burial depth of past shorelines deposited during the main glacial lowstands, from MIS 2 to MIS 10. The average subsidence rate of about 0.3 mm/yr appears greater than the average sediment supply rate (0.15 mm/yr), and this fact explains the overall backstepping of the 100 kyr regressive depositional sequences on the margin. The results obtained help to improve the understanding of the regional tectonics and can be used for quantitative reconstruction of Quaternary sea level changes in the Adriatic region. In general, the paper shows that even a short (71 m) borehole across a relatively short time span (340 kyr) can be useful for subsidence calculations, provided that a high-resolution definition of its stratigraphy is available and a correlation can be drawn with the geomorphologic proxies such as paleoshoreline deposits.

[1] On the morning of 21 June 1978, exceptional sea level oscillations with a trough-to-crest height of 6 m and a period of 10–20 min were observed in Vela Luka Bay. Slightly less pronounced variability was observed in a wider middle and south Adriatic east coastal area and, with some delay, along the west coast. In this paper, one of the original hypotheses put forward to interpret the event, relating it to a mesoscale air pressure disturbance, is reconsidered by using all the available data as well as state-of-the-art meteorological and oceanographic models. A fresh look at the meteorological data confirms that the atmospheric disturbance propagated at about 22 m/s in a northeastward direction. Additionally, the data suggest that it had the shape of the boxcar function characterized by an air pressure offset of 3 mbar and duration of 10 min. The meteorological model employed (Weather Research and Forecasting (WRF)-Advanced Research WRF) proves unable to reproduce the mesoscale disturbance coinciding with the surge, but it shows that the background atmospheric conditions were favorable for the development of such disturbances. The oceanographic model Advanced Circulation Model for Shelves, Coasts and Estuaries (two-dimensional depth integrated), forced by the described air pressure disturbance, successfully reproduces sea level variability in Vela Luka Bay reaching a few meters and thus surpassing the inverted barometer response by two orders of magnitude. The enhancement appears to be due to a four-phase process. The model also suggests that the scattering due to the variable bathymetry and the reflection from the east Adriatic coast resulted in waves that returned towards the west coast and generated considerable sea level activity there.

The shaping forces of parasite community structure still is the main subject in the ecological parasitology whilst community predictability and repeatability showed that hardly a generally applicable role is ever going to be assessed. Defining and describing parasite communities can be very useful from the epizootiological point, in order to help in the assessment of the medical and economical impact of certain parasitosis, moreover when hosts are economically valuable species. Since parasite assemblages in reared European sea bass (Dicentrarchus labrax) and sea bream (Sparus aurata) in Adriatic cage systems can play an important role in the economic feasibility of the rearing process, we evaluated their character through assessing diversity indices, nestedness of parasite communities and their differences in respect to season and composition, as well as fish growth. We observed colonization of a new monogenean species (Furnestinia echeneis) and general impoverishment of parasites populations over time in the Adriatic-reared fish parasite assemblages. Parasite assemblages differed significantly between seasons for both fish species, while species richness, evenness, diversity indices and nestedness of parasitic communities in the sea bream showed to be significantly higher compared to those in the sea bass. Such characteristics define parasite communities of both Adriatic-reared fish as species poor although structured and ordered assemblages.

[1] Numerical simulations of the Adriatic Sea were performed with the Navy Coastal Ocean Model (NCOM) during the Dynamics of the Adriatic in Real Time (DART) Experiments conducted between October 2005 and September 2006. Grid resolution was 1 km. Model forcing included tides, surface fluxes from the Aire Limitee Adaptation Dynamique Developpement International (ALADIN) atmospheric model, relaxation to a daily satellite sea surface temperature analysis, extensive river and runoff discharges, and open boundary conditions south of Otranto specified from a global model. Currents predicted by the model were compared with currents from 12 Acoustic Doppler Current Profiler (ADCP) moorings located along a line between the Gargano Peninsula, Italy, and Split, Croatia. The nontidal comparisons were performed with detided currents. Correlations between the model and ADCP currents were highest in the Western Adriatic Current (WAC), which flows southeastward along the Italian coast. Lowest correlations were in the interior of the Adriatic, likely because of instability processes. Correlations between the ALADIN winds and the model and ADCP currents at the mooring locations were also highest in the WAC. For November 2005 through August 2006, the model and ADCP mean WAC transports were 0.321 and 0.304 Sv, respectively, with a temporal correlation of 0.79. Comparison of current variance showed best agreement near the Italian and Croatian coasts. In the interior, the NCOM current variance compared fairly well with that of the ADCPs for November–January but decreased significantly relative to the ADCPs for February–August. Spectral analyses indicate most of the difference in variance to be at periods exceeding 2 days.

Diel vertical migration (DVM) of medusae was investigated at a fixed station in the oligotrophic Southern Adriatic Sea at several depths during summer (July) 2003. We hypothesized that medusan DVM is considerably influenced by environmental variables such as hydrographic features, light intensities, and potential prey densities. We used short-term repetitive sampling as an approach to detail these relationships. Of the 26 species collected, the highest abundance was in the layer between the thermocline (15 m) and 100 m depth, where Rhopalonema velatum predominated, reaching the maximum count of 93 individuals per 10 m3. Seven species were observed over a wide depth range: Solmissus albescens (15–1200 m), R. velatum (0–800 m), Persa incolorata (50–1200 m), Octophialucium funerarium (200–1200 m), Arctapodema australis (200–1200 m), Amphinema rubra (100–800 m), and Rhabdoon singulare (15–600). According to the medusan weighted mean depth (WMD) calculations, the longest DVMs were noted for the deep-sea species S. albescens, O. funerarium, and A. australis. The shallowest species, Aglaura hemistoma, was primarily non-migratory. Certain medusan assemblages were associated consistently with a particular depth layer characterized by a particular light intensity. The interplay of environmental factors and trophic relationships explains some of the features of medusan migratory patterns. These findings thus contribute to understanding the variables that determine patterns of medusan vertical migratory behavior.

Seagrass meadows have been hypothesized to protect mobile macrofauna from preda- tion by providing structural complexity that interferes with predator movement and vision. However, if ambush predators are common in seagrass, they may exclude many prey species, resulting in lower total abundance and diversity in seagrass relative to neighboring bare substrates, and segregation of predators and their prey into different habitats. We tested these abundance and diversity predictions using visual censuses of fish and invertebrates employing georeferenced videography to quantify habitat and pinpoint every observation, and using bait stations and drop nets over 38 km of scuba transects in all 4 seasons and by day and night in an enclosed estuary of the northeast Adriatic (Novi- grad Sea, Croatia). The primary fish predators at our study site were the ambush or stalk-attack predators, grass goby Zosterisessor ophiocephalus and European eel Anguilla anguilla, and we found that these species strongly preferred seagrass habitat. In contrast, most other fish, including small juveniles, avoided seagrass and preferred bare sediment to vegetated habitats. Species strongly pre- ferring seagrass were primarily sessile invertebrates not preyed on by the goby or eel. Both total macrofaunal density and total taxon richness were greatest on bare sediment and lowest in dense seagrass habitats. The 3-dimensional aspect of habitat structure was as important in delineating the communities as the presence or absence of habitat structure. These results are consistent with the hypothesis that ambush predators reduce the value of seagrass habitat for their prey relative to neighboring bare sediment or rock; that structured habitat might carry a higher mortality risk for many prey species, and that neighboring unvegetated habitat, including bare sediment, can be at least as important as seagrass in harboring biodiversity.

On 23 July 2007 a very rare specimen of the live sharksucker Echeneis naucrates was caught in the Ombla River near Dubrovnik, in the south-eastern Adriatic. First data on biometric lengths and morphology of this species are presented for the eastern Adriatic.

Marine bivalves as filter - feeders play important role in function of marine ecosystems and have a great contribution in zoobenthic biomass in many ecosystems. Although Callista chione (Linnaeus, 1758) is one of the commercial important bivalve species no previous studies were conducted on this species in the eastern Adriatic. Specimens of Callista chione were collected from a commercial catch in middle Adriatic Sea during the summer 2007. Shells (N=106) were aged based on formation of growth rings on the external shell surface and on formation of internal growth bands, gathered data were fitted to the von Bertalanffy growth function for height. Growth parameters (H∞ and k) were also estimated using Gulland – Holt plot where growth rates were plotted against the mean height and relative growth function was constructed. Age and growth rate data showed that this is a long – living species with the most intensive growth in first year (12.7 mm in height). Growth rate decreased with age and after 8 years growth rate is reduced to about 1mm per year. Based on two methods applied, modified Von Bertalanffy equations for height were constructed: Ht = 55.64 (1 – e – 0.26 (t-to)) and Ht = 53.53 (1 – e – 0.22 (t-to)). The estimated asymptotic shell lengths were 74.70 and 70.81 mm, respectively.

The smooth clam Callista chione (Linnaeus, 1758) is a shallow-burrowing filter feeding Venerid bivalve that inhabits sandy sediments. Although this is common and commercially valuable species there is still lack of information regarding its biology and ecology. The main objectives of this research were to obtain information of growth, age and condition index of Callista chione from the Kaštela bay. Samples were collected monthly from commercial catch in the period from July 2007 till May 2008 in the Kaštela bay. Shells were aged based on formation of growth rings on the external shell surface and on formation of internal growth bands. Gathered data were fitted to the von Bertalanffy growth function for height. Growth parameters (H∞ and k) were estimated using Gulland – Holt plot where growth rates were plotted against the mean height and relative growth function was constructed. Age and growth rate data showed that this is a long – living species with the most intensive growth during first year. Growth rate decreased with age and after 8 years growth rate is reduced to about 1mm per year. Based on two methods applied, modified Von Bertalanffy equations for height were constructed: Ht = 55.64 (1 – e – 0.26 (t-to)) and Ht = 53.53 (1 – e – 0.22 (t-to)). The estimated asymptotic shell lengths were 74.70 and 70.81 mm, respectively. Condition index showed seasonal oscillation with several small peaks.

[1] A winter oceanographic field experiment provided an opportunity to examine the atmospheric marine conditions over the northern Adriatic. Mean February winds are from a northeasterly direction over most of the Adriatic and a more northerly direction along the western coast. Wind speeds are fastest in jets over the NE coast during bora events and weakest in the mid-northwestern Adriatic. Diurnal air temperature cycles are smallest on the NE coast and largest in the midwestern Adriatic. The maximum sea-air difference is +10°C on the eastern coast and near zero on the midwestern Adriatic. Boras are northeasterly (from) wind events that sweep off Croatia and Slovenia, bringing slightly colder and drier air over the northern Adriatic. The main bora season is December to March. Winter 2002–2003 was normal for bora events. Synoptic-scale temporal variations are correlated over the northern Adriatic. Fastest Bora winds and highest wind stress over the northern Adriatic is concentrated in four topographically controlled jets. The strongest is the Senj Jet, while the Trieste Jet extends across the entire northern Adriatic. Between each two jets is a weak wind zone. The greatest mean net heat loss is in bora jets in the NE Adriatic, where it was −438 W m−2 and is weakest in the midwestern northern Adriatic, where it was near zero. Wind stress is concentrated over the NE half of Adriatic in four bora jets, while wind stress is weak in the NW Adriatic. There is significant variation in wind stress mean and standard deviation structure over the northern Adriatic with each bora event.

Age, growth and population structure of Modiolus barbatus from Mali Ston Bay, Croatia were determined using modal size (age) classes in length frequency distributions, annual pallial line scars on the inner shell surface, internal annual growth lines in shell sections of the middle nacreous layer and Calcein marked and transplanted mussels. The length frequency distributions indicated that M. barbatus attain a length of ~40 mm in 5-6 years indicating that a large proportion of the population in Mali Ston Bay is 6 years) was determined from the middle nacreous lines in shell section, which formed annually in winter between February and March ; the wider dark increments forming during summer (June to September). The oldest mussel, determined from the middle nacreous lines, was >12 years, with the majority of mussels aged between 3 and 6 years of age. The ages of mussels ascertained using the growth lines were not dissimilar to the ages predicted from the length frequency distributions. Age at length curves produced using modal size class data were not different from the data obtained using the pallial scar rings and internal growth lines. Taken together these data suggest that M. barbatus attains a length of 40 mm and 50 mm within 5 and 8 years respectively. Eighty one percent of individual M. barbatus injected with a Calcein seawater solution, (300 mg Calcein.L-1), into their mantle cavity successfully deposited a fluorescent line which was visible in suitably prepared shell sections under ultra violet light. Incorporation of Calcein into the mussel shells was seasonally variable with the lowest frequency of incorporation in mussels marked in February and recovered in May. Seasonal shell growth was observed with significantly higher growth rates in mussels marked in May and removed in August (ANCOVA, F3, 149=23.11, P2.5 mm.month-1 compared with a mean mussel growth rate of 1.2± ; ; ; 0.6 mm.month-1. At other times of the year mussel shell growth ranged from immeasurable to 1.48 mm.month-1.

[1] Measurements performed in winter 2002/2003 and spring 2003 off the east Adriatic coast showed that the East Adriatic Current (EAC) peaked in January/February (as expected from previous findings) and again in May (not expected). The first maximum corresponded with the considerable cross-shore variability of seawater properties, the colder, fresher water prevailing close to the coast, the warmer, saltier water dominating the open sea. The second maximum coincided with the massive intrusion of warm, saline water from the south Adriatic. Meteorological and hydrologic forcing was anomalous over the measurement interval: during winter 2002/2003 the cooling and river outflows were strong, during spring 2003 the pronounced warming coincided with exceptional dryness. In order to interpret the two EAC maxima a simple numerical model reproducing response of the Adriatic-Mediterranean system to the wintertime forcing was developed. It was found that the first maximum could be related to the coastal freshwater input and offshore evaporation in the Adriatic area, and that the second maximum was probably due to the wintertime surface cooling of the Adriatic while warmer conditions prevailed above the Mediterranean. The resulting horizontal density gradients supported two different circulation systems, one within the Adriatic, the other between the Adriatic and east Mediterranean, and they differed not only in spatial but also in temporal scales, therefore supporting the occurrence of two distinctive EAC maxima.

In February 2003, we observed the response of the shallow, 40 m deep northern Adriatic Sea to strong surface forcing by 40 knot winds and 300 W m-2 net upward heat flux related to cold bora winds blowing onto a relatively warm sea through gaps in the Croatian mountains. Ocean turbulence throughout the water column was observed with a microstructure profiler and a bottom-mounted, upward-looking, 5-beam, acoustic Doppler current profiler (ADCP), part of the "bottom lander". Microstructure-based dissipation rates (") were of the order of 10-6 W kg -1, and corresponded approximately to similarity scaling of the surface wind stress. The surface buoyancy flux, related to oceanic heat loss, was much smaller than the observed", an indication that the turbulence was dominantly related to the surface shear stress rather than convectively forced. However, convective surface forcing was reflected in sustained unstable stratification. Macroscale RMS turbulent velocities from the bottom lander were of the order of 0.02 m s-1. The turbulence was horizontally isotropic but showed higher horizontal than vertical variance. Velocities are resolved at periods larger than about 2 min, with the surface gravity wave signal also rising above the instrumental noise. At first glance, the turbulent velocity field appears random with little coherent structure. The typical vertical scale was 10 m, much smaller than the water depth, and there was no correlation in the vertical structure of adjacent 2-min averages. However, there also was small, yet significant vertical coherence to scales approaching the water depth. In the velocity spectra, we identify an "energy-containing band", a shoulder at frequencies of 1-30 cycles per hour. In this band, distributions of the vertical velocity were skewed with an excess of relatively large downward and relatively small upward motions. The energy-containing band shows large, broadband coherence between the vertical velocity and the horizontal velocity in the direction of the low-frequency currents. The preceding indicates the existence of broadband, anisotropic overturning motions with a tendency toward narrow, faster downdrafts and broader, slower updrafts. These motions were aligned with the direction of the mean current and had widely varying angles to the direction of wind and waves. The turbulence measurements were embedded in surveys of the mesoscale ocean variability. Part of the observations were set in a sharp, 100-200 m wide front with little density contrast. As the bora wind relaxed, the front began to develop a highly stratified "foot" undergoing intense mixing. This work is part of the DOLCEVITA Experiment (Dynamics of Localized Currents and Eddy Variability in the Adriatic).

International audience; The year-to-year variability in the timing, duration, and spatial extent of the surface phytoplankton bloom over the winter-spring period is examined in the southern Adriatic Sea using Sea-viewing Wide Field-of-view Sensor (SeaWiFS)-derived chlorophyll images for three years (1998, 1999, and 2000). Each year's image time series shows that blooms were intermittent and differed in onset, duration, and intensity with relatively low values observed in 2000. The relation between atmospheric forcing and interannual variability of the bloom timing and intensity is investigated using a coupled physical-biological model. The simulations focus on the effect of cumulative buoyancy loss on convective depths and its implications on surface nutrient availability, chlorophyll concentrations, and other ecosystem components during the study period. We test the hypothesis that the south Adriatic bloom is essentially controlled by the local winter climatic conditions (i.e., maximum convective depth), as suggested by recent findings, rather than the available nutrient pool at the intermediate depths (200-800 m), which also varies from year to year. For all three years the simulations produced convective depths that were in good agreement with in situ observations. However, the fluctuations in SeaWiFS phytoplankton biomass could be reproduced only if the particular year's nutrient pool was also taken into account. Thus the most probable explanation for the low SeaWiFS phytoplankton biomass observed in 2000 is the reduced nutrient pool because of the return from the transient phase to the pretransient regime of the Mediterranean Sea. Our results indicate that the south Adriatic bloom is a complex phenomenon and cannot simply be explained by interannual changes in convective depth.

Bottlenose dolphins are the only regularly sighted cetaceans in Croatian waters. The Adriatic Dolphin Project (ADP) has monitored the resident bottlenose dolphin population of the Lošinj and Cres archipelago since 1987. Research has particularly focused on the socio-ecology of the population. Data was collected, using photo-identification of natural markings of individual dolphins, from May to October of the years 2001 and 2002. Population abundance was then estimated by using the software SOCPROG. The data was examined using analytical methods applied to minimise bias. It was found that a ‘ Mortality + Trend Model’ , was best fit to describe the population. The estimated number of dolphins with long-term markings accounted for 100 individuals (95% CI = 82.3 – 125.5, SE = 12.1). This is well below the IUCN’ s classification of ‘ critically endangered isolated populations’ with less than 250 individuals. The combined mortality, mark change and emigration rate was estimated at 0.02 % per year with a positive trend of 0.04 % per year. A lagged identification model also showed that during the field season individuals emigrated from, and re-immigrated back into the study area. These results also indicate that the study area is only part of the home range of the dolphins frequenting the area. It is essential to determine the population size and trend of animal species to establish and develop the implementation of management and conservation strategies for vulnerable populations. Further studies are necessary before an accurate status of the bottlenose dolphins in Croatian waters can be determined.

Juveniles of 33 non-resident fish collected in three sheltered shallow coves (eastern Adriatic) fell into three groups: (a) occasional (10 species); (b) present in the study site only for short periods and at small sizes, in transit to a nearby Krka Estuary (11 species); and (c) species that spend most or all of their juvenile phase in sheltered coves (12 species). This note provides suggestive evidence that shallow water habitats inside sheltered coves could play an important role as nurseries for fish groups (b) and (c) during their early life stages.

Low-frequency (0.01-0.1 cpd) variability of air pressure, wind, and sea level is examined through 6- to 8-year records of data collected at three locations along the east ; coast of the Adriatic and one on the west coast. Seasonal energy spectra show that processes at these timescales are more energetic in winter than in summer. There is substantial wind energy at timescales corresponding to planetary atmospheric waves. In order to explain the stronger-than-isostatic adjustment of sea level at low frequencies to the air pressure forcing, recorded in different parts of the Mediterranean, the present empirical analysis is based on a physically more tractable model, relating sea level slope to the air pressure gradient and wind stress integral. The multiple input regression and the cross-spectral analysis yield a spatially variable response: over the deeper sea region sea level slope is fully explained by isostatic adjustment to the air pressure gradient alone ; over the shelf a much stronger-than-isostatic response (-1.7 cm/mbar) is greatly reduced (-1.3 cm/mbar), but ; not fully accounted for, by the action of wind. Next the multiple linear regression method is carefully reexamined ; a simple statistical model is developed to show that in multiple-input linear models with mutually correlated inputs, small errors in. one of the inputs produce biased estimates of all the response parameters. The apparent discrepancy between the theoretically predicted and the estimated response is attributed to the bias.

The occurrence of early stages (eggs) of scalloped ribbon fish, Zu cristatus, is reported for the first time in the Adriatic waters. Four eggs with a diameter between 1.85 and 2.10 mm were found in ichthyoplankton collections taken at Station 205, location Duce (43degrees25.8'N, 16degrees40.2'E, eastern central Adriatic). The capture of Z. cristatus in September is in agreement with the proposedseasonal life cycle of species in the Mediterranean Sea.