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The potential impacts of marine aquaculture are reviewed, focussing both on small-scale local effects near the farm environment and a broad spatial scale of many kilometres that impacts a number of different ecosystem components. Local changes in productivity, biodiversity and behavioural changes of wild fauna affected by nearby farm habitats were examined. Global aquaculture trends of growth perspectives as related to seafood supply, impacts on wild stock and biodiversity depletion, genetic changes in wild fish populations due to the escapement of cultured fish, capture-based aquaculture and its potential impacts on marine habitats were discussed. Adopting integrated principles in planning aquaculture development and respecting the assimilative capacity of a potential farming zone may reduce negative consequences of the aquaculture industry on the marine ecosystem.

Farm escapees and their offspring impose a significant impact on the environment and may therefore alter the future evolutionary trajectories of wild populations. To date, there is no management plan in place in Mediterranean countries to prevent fish escapes. Here, we investigate microsatellite length variations in three candidate genes, including prolactin (PRL), growth hormone (GH), and the receptor activity modifying protein 3 gene (RAMP3), to study the genetic structure of the main fish species farmed in the Mediterranean, gilthead seabream (Sparus aurata). We also evaluate the performance of microsatellites in discriminating fish origin (wild or farmed). Results from 298 individuals, including farmed, wild adult and juvenile fish were compared with results from 19 neutral markers used in a previous study. All loci were polymorphic, selectively neutral, and had the statistical power to detect significant population differentiation. Global FST was similar to that estimated using 19 loci (0.019 and 0.023, respectively), while pairwise comparisons identified farmed populations as the main drivers of genetic divergence, with a much higher magnitude of overall genetic differentiation within farmed populations (0.076) than that estimated using the 19 neutral microsatellite loci (0.041). Bayesian structural analysis showed that the PRL, GH, and RAMP3 markers were able to distinguish farmed from wild populations, but were not able to distinguish different wild groups as 19 neutral microsatellite markers did. Farmed populations of different origins were assigned to a separate cluster with a high individual assignment score (>88%). It appears that the candidate markers are more influenced by artificial selection compared to neutral markers. Further validation of their efficiency in discriminating wild, farmed, and mixed fish origins using a more robust sample size is needed to ensure their potential use in an escaped fish monitoring programme.

Non-native Pacific oyster Magallana gigas (Thunberg, 1793) was introduced to the Mediter-ranean Sea for aquaculture purposes in the 1960s. Although this species was not introduced for aquaculture to the Croatian part of the Adriatic Sea, in the 1970s, it was reported in the Lim Bay, in the North-eastern Adriatic. Until recently, there has been no research on the species in the Croatian part of the Adriatic. The aim of this research was to summarize existing and novel data on the distribution of M. gigas in coastal areas of the Eastern Adriatic and to provide a baseline for the future monitoring and assessment programmes of the species. Distribution of M. gigas was determined by three different methods: (i) a visual census of the presence of M. gigas specimens in the medio-littoral zone; (ii) DNA identification of M. gigas larvae in the water column; and (iii) the presence of M. gigas in the subtidal zone at depth between 25 and 40 m. Magallana gigas has a well-established population in the medio-littoral zone of natural and anthropogenic habitats along the coast of the North-eastern Adriatic Sea (west coast of Istria peninsula), but it is not present in the deeper layers . In the Central-eastern and South-eastern Adriatic Sea, the species was either absent or sporadically recorded with no evidence of fully established populations. Considering the great invasion success of M. gigas worldwide and effects that this species could have on the invaded ecosystem (e.g. competition for food and space with native species), detailed future monitoring is needed for the Eastern Adriatic Sea.

The age of sexual maturity of the Atlantic bluefin tuna (Thunnus thynnus; ABFT) is a reference point for stock assessment and management. The International Commission for the Conservation o...

Morphological and ecophysiological traits of wild, farmed and wild farm-associated gilthead seabream Sparus aurata were used to assess the degree of phenotypic adaptation of the species to their respective environments. Geometric morphometrics revealed clear body shape differentiation amongst the 3 types of populations, whereby sig nificant differences were noted in head profile and the anterior- body region of the fish. Morphological resemblance was recorded among 2 gilthead seabream populations associated with tuna farms, indicating that they share the same phenotypic responsiveness pattern. Adaptation in reproductive investment strategy was observed in individuals from farm-associated origin, displaying the highest gonadosomatic index but lowest condition in comparison to their farmed and wild counterparts. Multinomial logistic regression revealed that sex change from male to female with increasing length was more pronounced in farm-associated fish than in farmed and and wild fish. These findings demonstrate a significant influence of the environmental factors inherent to tuna farms on the phenotypic characteristics of gilthead seabream, providing a basis for further research on the ecological effects of tuna farms on local marine populations.

Commercial net-pen mariculture of Seriola dumerili recently started in Mediterranean countries. While the introduction of new species allows for product diversification and strengthens the European seafood market, net-pen farming and escape events can lead to a number of socio-economic and ecological interactions in the coastal zone. To assist in the genetic management of broodstocks and mitigate the effects of escape events, the potential of morphological and genetic traits of wild, farmed and escaped S. dumerili from the Balearic and the Adriatic Sea were examined as a proxy of wild and farmed origin. Body shape, head profile and mouth position allowed correct classification between fish groups (82%). The global FST of 0.053 across all loci showed significant subdivision between wild and farmed fish, and allowed correct assignment of escapees. Integration of both genetic and morphometric data using the R package assignPOP improved the assignment results of the escaped group with unknown origin. Potential ecological and socioeconomic implications of escape events are discussed, along with guidelines promoting sustainable development of coastal net-pen aquaculture in a future to come.

Highlights: • Feeding overlap was highly expressed between native and non-native oyster. • Differences were recorded in zooplankton but not in phytoplankton consumption. • O. edulis larvae in C. gigas stomach content was confirmed by DNA analysis. • O. edulis had broader isotopic niche than C. gigas. Abstract: In order to detect the possible regulatory effect of non-native C. gigas on the native O. edulis, under aquaculture conditions, feeding interactions between them were investigated in a highly productive environment of Lim Bay (Adriatic Sea). The present study uses a multi-methodological approach, including stomach content, DNA barcoding and stable isotope analysis to elucidate the feeding ecology of two oyster species. The research confirmed a high overlap throughout the year in the feeding traits among native and non-native oyster species. Competition for food was not the only relationship that exists between the investigated species as the presence of O. edulis larvae in C. gigas stomach content was confirmed by DNA analysis. Findings are not in favour of introducing C. gigas to commercial aquaculture in any new areas in the Adriatic Sea and support the need to improve the existing O. edulis aquaculture and conserve its wild stocks.

The Pacific oyster Magallana gigas, globally one of the most translocated marine species, has never been commercially farmed in any part of the Croatian eastern Adriatic Sea, where the native flat oyster Ostrea edulis is the only cultured oyster species. The Pacific oyster has, however, established populations on the west coast of the Istria peninsula, in the northeast Adriatic Sea. Current distribution, abundance and size structure of the flat and Pacific oysters were studied there along spatial and depth gradients in natural and artificial habitats to assess their potential for coexistence. This is the first quantitative assessment of native and non-native oyster populations on a Mediterranean-wide scale providing a baseline for determining future changes in their distribution. Both species were omnipresent, with the Pacific oyster displaying a more pronounced variability in abundance and size in relation to survey regions and depths. The population density of flat oysters was low, generally less than 1 individual/m2, with no difference among regions. The density of the Pacific oyster was significantly higher, being on average 5 individuals/m2. Dense, reef-forming aggregations of Pacific oysters were contained in Lim Bay, a nationally-important shellfish aquaculture area, where its mean density was 107 individuals/m2. Along the open coastline its densities were considerably lower and followed a latitudinal gradient. The observed abundance and size distribution patterns of the Pacific oyster suggest that Lim Bay was the introduction point, with feral settlement likely originating from short-lived experimental aquaculture trials and subsequently dispersing by prevailing local currents. The flat oysters were larger in size and settled at different depths compared to the Pacific oysters. The vertical range of Pacific oysters was mostly contained in the tidal zone, while flat oysters were present in the subtidal exclusively. Such spatial partitioning likely resulted from introduced oysters occupying a vacant ecological niche and not due to interspecific competitive exclusion. Habitat type had a strong effect on proliferation of Pacific oysters. Artificial hard substrata harboured more abundant and larger Pacific oysters than the natural rocky shore habitat. The possibility of multiple local introduction pathways in ports and marinas is also discussed. Currently, there seems to be no spatial competition between the two oyster species, but as it is hard to predict future possible impacts of non-native species, we strongly suggest regular monitoring of the Pacific oyster, prioritising sensitive and protected areas as well as areas at the edge of its distribution.

A small escape incident of gilthead seabream (Sparus aurata) tagged with acoustic transmitters (N = 25) from a commercial farm located in a coastal bay of the eastern Adriatic Sea was simulated to enable evaluation of recapture strategies and escapee management. Over a three-month monitoring period, tagged individuals showed spatial distribution closely related to fish farms, where 72% and 68% of tagged fish were present at the farm during the second and third weeks of post-release. Upon initial release, escaped seabream had a small total home range (0.142 km2) that encompassed the farm site. Short term residence differed among tagged fish. Few fish (28%) remained in the proximity of the fish farm for longer than one month ; most were likely angled or moved outside the acoustic array. Fish that moved elsewhere, have the potential to cause the greatest ecological and genetic impact as they likely will be the quickest to adapt to natural conditions. Considering the capture impact of the limited recreational fishery on this small scale escape event, fish recapture by this type of fishery within two weeks of escape could be feasible and is highly recommended.

This study tests the suitability of the gilthead seabream scales as a proxy for origin selection in wild and anthropogenically pressured environments. Scale morphology and microchemistry were used to discriminate the habitat selection of two wild, farmed and wild farm-associated populations where landmark and outline-based scale morphometrics, trace-element chemistry and scale microstructure characteristics were analysed. The morphometric techniques successfully differentiated between the farmed and wild origin scale phenotypes. Reduced discrimination sensitivity between the wild and wild farm-associated origin was, however, reported. The discrimination based on microchemistry (B, Ba, Mn, K, Sr and Zn) classified the scales with high accuracy according to their origin (wild vs. farmed vs. wild farm-associated) and sampling locations, thus proving itself as a powerful tool in provenance study of gilthead seabream. Disparity in scale microstructure characteristics accounted for radii, circuli and inter-circulus spacing, hence unveiling the differences in growth and environmental conditions between the wild and farmed fish. In brief, scale shape was found to be a potent exploration tool for farmed fish identification, whereas scale microchemistry yielded a good resolution in identifying gilthead seabream membership among different habitats. Considering the importance of this species in aquaculture and fisheries throughout the Mediterranean, more research is needed to assess the usefulness of scales as nonlethal biogeochemical tags.

The capture-based aquaculture of the Atlantic bluefin tuna (Thunnus thynnus) starts with the catch of wild individuals, a slow-operating transport to the rearing facilities, introduction to rearing cages, and adaptation to the captive environment; all bearing significant risks for the onset of stressful conditions that consequently can result in unexpected mortalities.In order to explore whether the survival success through the farming cycle might be monitored at the genetic level and linked to several immunity and stress response associated genes, we have developed a new set of 13 EST-SSRs for T. thynnus and subsequently analysed 334 samples of juvenile wild-caught tuna and captive-reared adults during two consecutive farming cycles in the Adriatic Sea.The results evidenced a low FST value (0.005) with similar allele frequencies and no major allele loss between investigated groups. Two tested approaches for the identification of loci under selection did not indicate departure from neutrality for any of the 13 EST-SSRs, suggesting that the latter could not be considered adaptive in the studied context.Our results are in agreement with other studies that attempted to detect adaptive signals in T. thynnus, stressing the problem associated with the sampling design of a species with complex migratory behavior, reproduction and particular zootechnical practices employed at the farms. Nonetheless, characteristics of 13 new polymorphic loci reported here contribute to the broadening of the existing EST-SSRs resource, being a useful asset in future genetic studies of T. thynnus.

It is essential from both the consumer perspective and the environmental sustainability aspect, to delve more deeply into the specific traits and conditions of fish reared in a pisciculture setting. Among the many factors that affect the latter, one of the most important is the cycling of chemical compounds in intensive rearing systems. For this reason, we analysed the stomach contents and trace metal levels (cadmium, copper, chromium, lead, and zinc) in the muscles of several fish species that aggregate around mid-Adriatic cages of reared Atlantic bluefin tuna (Thunnus thynnus), attracted by the organic leftovers found in farmed waters. The metals were also analysed in samples of reared bluefin tuna, fish species used as tuna feed (baitfish), and their non-farm-associated counterparts. Finally, to better follow the dietary relationships and metal-acquisition pathways, we also analysed the stable isotopes. The results revealed that wild fish consume a great deal of trophic resources deriving from the cages, mainly in the form of baitfish remains. The isotopes suggest the reared tuna consume high levels of herring baitfish (Clupea harengus), there is an increased trophic level for the wild omnivorous bogue (Boops boops), and this decreases for the carnivorous garfish (Belone belone). No significant differences in metal concentrations were detected between farm-associated and non-farm-associated wild fish, with the exception of the zinc levels in bogue, which were in lower concentrations in specimens aggregating around the farm. Most importantly, the concentrations of trace metals in the tuna, baitfish (sardine, Sardina pilchardus, and herring), and wild fish (garfish and bogue) did not exceed the recommended limits established by European legislation. However, the cadmium values in the garfish, bogue, and sardine were close to, but not over the legal limit value. The reasons behind these results and their potential consequences should be further investigated, although there is only a moderate degree of concern with regard to the metal content of fish stocks captured in the area under study. This study was financially supported by the Generalitat Valenciana regional government, Spain, through the programme VALi+d (reference APOSTD/2012/044).

In gilthead seabream the number of domesticated individuals increased annually, and escape events occur regularly in the Adriatic Sea. Still there is a lack of population genetic characteristics and evidence of the extent and geographic scale of interbreeding resulting from fish-farm escapees. We screened 1586 individuals using a panel of 21 neutral microsatellite loci in several consecutive years and here report on the medium-scale detection of hybrid and farmed seabream in the natural environment. Wild adults showed a lack of genetic structure within basin and sampling years and reduced connectivity with wild offspring collection, suggesting their temporal residency within the Adriatic. On the contrary, by linking the results of multiannual genetic analyses with the results of coupled hydrodynamic and individual based models (IBM-Ichthyop), we observed a strong connection of wild seabream associated with tuna-aquaculture sites and offspring from the nursery grounds, indicating that the surroundings of tuna sea-cage farms can function as a spawning grounds. The study results present the genetic baseline of wild and farmed strains from the eastern Adriatic Sea, as a first step toward development of a mitigation strategy for fish escapees aimed at controlling further erosion of genetic integrity.

The rapidly expanding Atlantic bluefin tuna fattening industry is characterized by high stock densities and a high input food biomass in the form of whole bait seafood. The environmental impact of this activity must be effectively monitored within a proper sustainable development framework, to address concerns about the potential adverse effects. However, evaluation of monitoring tools for tuna farming has received less attention than other activities. Based on the principles of key taxa (Pocklington & Wells, 1992), we tested the potential use of changes in benthic macroinvertebrate assemblages, polychaetes and amphipods for this purpose. Applying a non-parametric multivariate approach for monitoring the impact of this aquaculture activity on the benthic habitat, we checked for correlations with the physicochemical environmental variables of the sediment. A hierarchical spatial design was followed, using multiple controls. Amphipods and polychaetes showed dissimilarities between impacted and control locations, with significant differences for total assemblage structure at a taxonomic level of families. Total nitrogen (TN) and total sulfur (TS) concentrations were the variables best associated with these changes for amphipods, and d 13C and total phosphorus (TP) were the best for polychaetes. However, total free sulfides (TFS) and TP were the chemical variables that best indicated the effects on sediment. Using this approach, surrogating the whole benthic assemblage to a single taxocene, our data suggest that monitoring tuna farming impact by comparing the changes in amphipod and polychaete assemblages at family level could be an optimal procedure with an excellent cost/benefit ratio. The study was funded by the Postdoctoral program of the Generalitat Valenciana for DFJ (APOSTD/2012/044).

Due to very good collaboration with one commercial purse seiner, using “Srdelara” and operating in fishing zone G, preliminary data concerning the interaction between small pelagic purse seine fishery and its predators were obtained. According to the notes taken by experience observer on-board in period from year 2013 to 2016, seems that tunas, dolphins and swordfish were the faithful companions of purse seiner fisherman with abundance of 68.6%, 22.0% and 9.4%, respectively. Although they were present all year round, their monthly pattern of appearance indicated that less tunas were recorded in May-June, more dolphins were noted from July to October while swordfish were mostly abundant in winter (January-March). Within the investigated period, slightly increasing trend of tuna and dolphins’ appearance was recorded, although statistically not significant. Analysing possible correlation between purse seine catches and predator’s abundances, revealed that appearance of tuna had negative impact on the catches (dispersion of schools), while realised catches in presence of dolphins were quite good so it seems that they tend to round up small pelagic fish schools., Zahvaljujući vrlo dobroj suradnji s ribarskim sektorom, točnije jednom komercijalnom plivaricom koja koristi plivaricu “Srdelaru” u ribolovnoj zoni G, su prikupljeni preliminarni podaci vezani uz interakciju ovog tipa ribolova i njegovih predatora. U razdoblju od 2013. do 2016. godine, prema podacima prikupljenim od strane iskusnog promatrača na palubi ove komercijalne plivarice, je utvrđeno da su tune, dupini i igluni najvjerniji pratioci ovog tipa ribolova te da je njihova abundancija redom bila 68,6%, 22,0% i 9,4%. Premda je uočeno da su navedeni grabežljivci prisutni tijekom cijele godine ipak je njihova pojavnost kolebala od mjeseca do mjeseca – najmanje tuna je zabilježeno u razdoblju od svibnja do lipnja, nešto više dupina je uočeno od srpnja do listopada, dok su igluni bili najbrojniji od siječnja do ožujka. Tijekom istraživanog razdoblja je utvrđeno blago povećanje broja tuna i dupina premda to povećanje nije bilo statistički značajno. Korelirajući ulove ostvarene istraživanom komercijalnom plivaricom i broja uočenih grabežljivaca, čini se da će u slučaju pojave tune ostvareni ulov biti manji s obzirom da ona rasprši ciljanu plovu sitne plave ribe, dok će relatvno dobar ulov ista plivarica ostvariti u prisutnosti dupina koji će uočenu plovu još više zbiti.

A combination of molecular and morphological characteristics was used to investi- gate populations of wild and farmed gilthead sea bream Sparus aurata from the largest Croatian shellfish production area, Mali Ston Bay. Identification of farmed escapees was performed in the wild in order to evaluate and compare the detection sensitivity of molecular and morphological tools. Using a traditional set of measurements and a truss network system, morphometric trait analysis of gilthead sea bream showed clear body shape differences between individuals from the wild and farmed populations. Microsatellite markers only revealed weak neutral genetic differen- tiation between farmed and wild samples from Mali Ston Bay (Wright's FST = 0.019, p > 0.05; Jost's DEST = 0.022), despite the fact that the farmed gilthead sea bream were of Atlantic origin. Using assignment tests, morphological (16%) and molecular (25%) analysis identified farmed escapees in the samples of wild gilthead sea bream in the vicinity of aquaculture sites. Morphological data showed good potential for distinguishing recent escapees in wild populations, since these charac- teristics are affected by the environment. This study demonstrates the presence of escapees in the local wild population in this region, and suggests the potential for genetic interaction.

The spawning behavior of captive Bluefin Tuna (Thunnus thynnus) was observed in cages at an Adriatic facility in summer 2011. Approximately 20,000 eggs were collected from cages and transferred to a land-based nursery, with an estimated fertilization success rate of 80%. Eggs were spherical with a diameter of 1,035.06 ± 20.16 μm and were pelagic with a single oil globule (227.63 ± 8.07 μm). Newly hatched larvae (3.08 ± 0.14 mm total length) followed scombrid larval development: melanophores were scattered over the body, head, notochord, and yolk, except finfold; eye pigmentation was observed 1.5 days posthatch, pectoral fins started to appear, and two-thirds of the yolk sac were absorbed; the mouth developed at 2.5 days posthatch, and larvae began feeding upon enriched rotifers. After mortalities occurred in the nursery (5 days posthatch), DNA was extracted from a sample of larvae. An 890 base pair fragment of the mitochondrial partial control region was amplified and sequenced to genetically con...

The ecological effects of tuna fish farms are largely undocumented. This study confirmed their high capacity to attract surrounding wild fish. The aggregation effect persisted year round, without detectable seasonal differences. Farm impact was restricted to close proximity of the sea cages, and was more prominent over the bottom than in the water column strata. Tuna fish farms proved to be high energy trophic resources, as indicated by the enhanced fitness status of two focal species, bogue and seabream. Under abundant food supply, seabream appear to allocate the majority of energy reserves to gonad development. Farm associated bogue had greater parasite loads, with no detrimental effect on fitness status. Overall, tuna fish farms can be regarded as population sources for aggregated wild fish, and under the no fishing conditions within the leasehold areas, can serve as functional marine protected areas.

In order to study the effect of water propolis extract (WEP) on Dicentrarchus labrax under low temperature stress, sea bass juveniles were randomly divided into three groups: a control group fed with basal diet and two treatment groups fed with basal diet supplemented with 1.25 and 2.5 g kg-1 of water propolis extract. At the end of a ten week feeding trial sea bass were exposed to low temperature stress at 12°C for 24 hours. The growth performance, RNA/DNA ratio and changes in serum biochemical parameters were investigated. Dietary intake of propolis stimulated the specific growth rate (SGR), feed conversion efficiency (FCE), RNA/DNA ratio and ALP enzyme activity, while decreasing plasma triglycerides and AST activity. Supplement of 2.5 g kg-1 WEP in diet significantly increased the mean SGR and FCE up to 9% and 13.4% respectively in comparison to the control group. Low temperature stress elevated serum triglycerides, glucose and cortisol levels in all groups, however glucose and cortisol reached significantly lower end values in group receiving highest amount of propolis in diet. The present study suggests that ingestion of basal diet supplemented with 2.5 g kg-1 of propolis extract could prevent adverse effects of low temperature stress and promote the growth of sea bass.

A dramatic decline has been recorded in Croatian shellfish production in recent years. Among the many factors that may have contributed to the decline of mussel production, i.e. EU import barriers and consequently small domestic market, great variability in larval dispersion and settlement, it is suspected that fish predation plays an important role in shellfish sustainability. Following this hypothesis, the abundance and diversity of fish assemblages around the Marina mussel farm, situated along the eastern coast of the Adriatic Sea, was monitored for a two-year period, and the mussel recruitment losses, potentially driven from fish predation, after the ‘early thinning-out’ process was quantitatively evaluated by measuring the percentage of consumed or destroyed ropes of longlines. Overall, a total of sixteen fish taxa were recorded at the mussel farm, as opposed to fifteen taxa registered at all control locations. The asymmetrical design of the multivariate analyses revealed a statistically significant impact of the farm on fish assemblages, with expressed seasonal species variation. At mussel farm, the most abundant species observed were gilthead seabream Sparus aurata, sand smelt Atherina hepsetus and mullet Mugilidae species in summer and autumn; sand smelt A. hepsetus and bogue Boops boops in winter; and the sand smelt A. hepsetus, mullet Mugilidae species and seddled bream Oblada melanura in spring. At control locations, characterised with significantly lower fish assemblage abundances, the most abundant species were sand smelt A. hepsetus and mullet Mugilidae species in summer, sand smelt A. hepsetus and seddled bream O. melanura in autumn, sand smelt A. hepsetus and picarel Spicara flexuosa in winter, sand smelt A. hepsetus and bogue B. boops in spring. Gilthead sea bream was extremely abundant at mussel farm, with 5936 individuals censused in 155 of 192 fish counts (80%), and a maximum abundance of 285 individuals per 5000 m3. Stomach content analysis confirmed the presence of mussel Mytilus galloprovincialis as the dominant prey. During August (2009), monitoring of 423 ropes revealed that 276 m of mussel ropes or approximately 828 kg of mussels with an average shell length of 34.3 ± 2.54 mm were destroyed within the first week of mussel deposition into the sea. The recorded recruitment losses of 54% in only one month of monitoring indicate a strong negative impact on farm management stability.

Gilthead sea bream (Sparus aurata) is considered the most important finfish aquaculture product in the Mediterranean Sea, but inadequate number of domestic hatcheries has reflected in fact that 70% of fingerlings are imported, mainly from Italy and France. In order to assess potential genetic differentiation between wild and cultured sea breams, we screened eight microsatellite loci. Analyses evidenced heterogeneous genotypic distributions for each population, with extensive polymorphism and overall expected heterozygosity levels >71%. Such a high admixture and weak population structuring has previously been reported in the rest of the Mediterranean Sea. Results imply that farmed escapees are involved in genetic pollution of adjacent wild populations showing lower differentiation among themselves. Inference of such a situation strongly encourages strengthening of routine aquaculture practice in the Adriatic through development of genetic-based management for broodstock, fingerlings and farmed fish, as well as better zootechnological protocol related to maintenance of nets and cages.

Summary The aim of this study was to provide a detailed description of the biometry of the juvenile Atlantic bluefin tuna (FL = 50–127 cm) of Mediterranean Sea origin. Regarding meristic features, there were 31.5 (SD = 2.1) gillrakers found on the first gill arch, 13.41 (SD = 0.494) spines in the first dorsal fin, 33.56 (SD = 2.124) soft rays in the pectoral fin, 9.86 (SD = 0.464) dorsal finlets and 8.90 (SD = 0.412) ventral finlets on the tail. Results of morphology analyses indicate that, on average, the head length contributes 28.84% (SD = 0.745); first predorsal length contributes 31.86% (SD = 0.915); preanal length contributes 61.45% (SD = 1.632); maximum body height contributes 26.90% (SD = 1.001); second dorsal fin height contributes 11.11% (SD = 1.457); pectoral fin length contributes 20.09% (SD = 1.550); and caudal fin width contributes 28.60% (SD = 1.842) of the fork length. Eye diameter comprises 13.14% (SD = 1.471), snout length 33.11% (SD = 1.332) and postorbital length 53.75% (SD = 1.354) of the head length. The significant change in body proportions, as fish grow in length, has been noted and leads to the conclusion that the juvenile bluefin body does not grow isometrically in size. Continuous decrease in the mean condition factors as body length increased, and a length–weight relationship describing negative allometric growth [ln WW (g) = −3.2965 + 2.8546 ln FL (cm)], indicate elongation of the juvenile bluefin body shape during early life, corresponding mostly to the period preceding sexual maturity.

The aim of this study was to investigate effects of reduced feeding to the growth, blood and body chemical composition of bluefin tuna (BFT) juveniles caged in the Central Eastern Adriatic. Stocked fish was randomly placed to two separate cages. Experimental cages were submitted to different feeding regime. One was fed daily to apparent satiation ; the second one was given 22% less amount of food compare to the first one. The fish were sampled just after capture in May 2008. and at the end of experiment in November 2008. Analyzes of selected blood chemical parameters (protein, glucose, triglyceride, cholesterol and HDL-cholesterol) and muscle chemical contents (dry matter, protein, lipid and ash) were done. Individual biomass of fish fed to satiation has increased 230% compare to 190% increase of less fed fish. The mean levels of selected blood chemical parameters were found as follows: wild fish (total protein – 52.4 g l-1 ; glucose – 254.2 mg dl-1 ; triglyceride – 186.7 mg dl-1 ; cholesterol – 156.8 mg dl-1 ; HDL – cholesterol 105.0 mg dl-1), fish fed to satiation (total protein – 59.7 g l-1 ; glucose – 265.3 mg dl-1 ; triglyceride – 277.6 mg dl-1 ; cholesterol – 193.2 mg dl-1 ; HDL – cholesterol 126.5 mg dl-1), less fed fish (total protein – 69.9 g l-1 ; glucose – 271.1 mg dl-1 ; triglyceride – 258.5 mg dl-1 ; cholesterol – 174.9 mg dl-1 ; HDL – cholesterol 122.8 mg dl-1).According to the present results, the blood chemical values of the reared BFT were significantly higher then those of wild, except glucose. Higher blood protein level in less fed fish indicates to a metabolic difference among the fish exposed to different feeding regimes. The body fat content of wild BFT was lower compared to the fed fish, while no appreciable differences in fat content was found among farmed fish.

The vastness of the ocean and our limited ability to observe and monitor the organisms therein make molecular markers particularly useful tools in the investigation of the ecology and evolutionary biology of fish. Nowadays, due to increased demand of fish foods, genetic researches are focused on new candidate species for aquaculture, such as Seriola species. Here, the analyses of eight polymorphic nuclear microsatellites loci and three mitochondrial (mt) DNA genes (16S-rRNA, Cyt-b, and D-Loop) in the greater amberjack, Seriola dumerili, detected breakpoint between Atlantic and Mediterranean populations, presumably arisen by the oceanographic features of the Almeria-Oran Front opposed to the gene flow of the species. Still, an absence of heterogeneity between the sampling locations within the Mediterranean Sea was noted, although an observed dichotomous structure of the phylogenetic mtDNA tree revealed two clades, with no spatial division within the basin. The origin of these two clades likely predates the late Pleistocene or Holocene colonization of the species from the Atlantic Ocean into the Mediterranean Sea. In addition, some preliminary genetic information are provided for Seriola rivoliana, the species that has been recently recognized as an Atlantic migrant in the Mediterranean.

Acoustic surveys in the Adriatic Sea have been performed annually by the research vessels “Dallaporta” and “Bios”, equipped with SIMRAD echo-sounders (EK-500 and EK-60), and working with 38 kHz split-beam transducer (ES38B). Since the vessels have different characteristics and use different pelagic trawls for fish sampling, there is uncertainty regarding the comparability of the results obtained. In order to evaluate comparability of the results, a comparison between research vessels was performed. That included comparisons of vessels’ noise, acoustic data collection, and fish samples composition and size structure analyses. The noise generated by both vessels was sufficiently low to allow a single fish detection up to 200 m depth. Acoustic data collected by the two vessels showed similar trends, no significant differences in average SA-values, and highly significant correlation between SA-values. Therefore, unbiased acoustic data collected by vessels could be combined in future stock assessments. Concerning collection of fish samples, anchovy resulted as the most abundant species in the samples collected by both vessels even if size compositions of anchovy were significantly different., Eho-monitoring u jadranskome moru provodi se jednom godišnje korištenjem istraživačkih brodova “Dallaporta” i “bios”, opremljenih s ehosonderima SIMraD (ek-500 i ek-60), te pretvaračima podijeljenog snopa radnih frekvencija od 38 kHz (eS38b). Budući da ovi straživački brodovi imaju različite značajke, a koriste i različite pelagijske koće za uzorkovanje sitne plave ribe, postoje sumnje glede usporedivosti prikupljenih podataka. S ciljem procjene usporedivosti prikupljenih podataka, napravljena je usporedba u prikupljanju podataka ovim istraživačkim brodovima. Uspoređena je buka pojedinih brodova, prikupljanje akustičkih podataka, te usporedbe prikupljenih uzoraka riba s obzirom na sastav i strukturu uzoraka. utvrđeno je da buka koju proizvode oba broda je dovoljno niska da dozvoljava detekciju pojedinačnih riba do dubine od 200 m. Akustički podaci prikupljeni dvama istraživačim brodovima pokazuju slične trendove, bez značajnih razlika u srednjim Sa-vrijednostima i s vrlo značajnom povezanošću među njima. Potvrđeno je da se budućim procjenama ribljih naselja nepristrani akustički podaci ovih brodova mogu međusobno nadopunjavati. Glede prikupljanja uzoraka riba, došlo se do spoznaje da je inćun bio najzastupljenija vrsta u uzorcima koje su sakupila oba istraživačka broda iako je njihova veličinska struktura bila značajno različita.

The garpike Belone belone (L.) is an epipelagic fish abundant in the Mediterranean, parasitized by two coelozoic myxosporidians in the gall bladder — Myxidium sphaericum Thélohan, 1895 and Ceratomyxa beloneae Lubat, Radujković, Marques et Bouix, 1989. In order to redescribe these intriguing and taxonomically complex species, whose original descriptions are limited only to line drawings based on light microscopy, we studied the morphology and ultrastructure of their vegetative and sporogenic stages. M. sphaericum has an oval to sigmoid or mild crescent shape in the frontal view, large conical polar capsules, opening at the spore end, in opposite direction of the spore length, with 8–9 coils of polar filament. C. beloneae has elongated and slightly arched valves; symmetrical and smooth, with the posterior surface almost straight and anterior surface mildly inclinated, having 5 coils of the polar filament.

Although information about embryonic and larval development of garpike, Belone belone (Linnaeus, 1761), is present in the published literature, the bulk of research concerns garpike from the northeastern Atlantic Ocean and the Baltic Sea. The present work describes the embryonic and larval development of garpike, Belone belone, from the Adriatic Sea, and methods used for incubation of fertilized eggs in aquarium conditions. Because garpike is, as suggested by some authors, divided into subspecies, we conclude that some differences in embryonic development could also be expected. In the present study, eggs were fertilized using the dry fertilization method and were incubated in a tank equipped with aeration and constant sea water flow. Salinity and content of dissolved oxygen were constant, and the temperature varied between 19.4 and 22.3°C. Eggs were spherical, measuring 3071.9 ± 75.73 μ m in diameter. Yolk sacs were homogeneous and did not contain oil globules. The first larvae hatched 329 h and 47 min after fertilization. Absorption of the yolk sac occurred 17 h – 48 h after hatching and the total length of newly hatched larvae was 9.78 mm. The peculiarities observed in the embryonic and early larval development are evidence of an exceptional plasticity and adaptive potential, which could be considered as helpful features in extending the natural range of occurrence of this species.

In the Mediterranean area, wild fish have often been suggested as either the reservoirs of the causative agents or at least the carriers of the pathogens responsible for disease outbreaks in cultured fish. However, no epidemiological investigations on actual pathogen/ disease interactions between farmed and wild fish have been conducted even for the most important fish pathogens. Only sporadic isolations and identifications of various pathogens in wild fish have been done and real associations with the pathological conditions that exist within the farm environment and vice versa have not been established. Monogenean ectoparasite Sparicotyle chrysophrii and isopod Ceratothoa oestroides are commonly found in the Mediterranean cage-reared sea bream and sea bass and in the surrounding wild fish population. Both species were recognized as pathogens that seasonally inflict serious losses in fingerlings and juveniles of sea bream and sea bass, being potentially propagated and exchanged during wild and caged fish interaction. In order to evaluate the degree of pathogens transfer between wild and farmed fish, we investigated genetic population structures of these two important parasitic pathogens inferred by mtDNA cytochrome oxidase I locus. Parasites isolated from wild and farmed fish on the two most productive Adriatic fish farms showed genetic heterogeneity, contradicting widely accepted hypothesis of cross-contamination, at least in case of S. chrysophrii and C. oestroides. As far as we know, this is the first report that in a study of pathogen transfer molecular evidence was employed to asses the genetic population structure of shared parasites.

A 4-year study (May 1997–December 2000) of the reproductive biology of pink dentex Dentex gibbosus (Rafinesque) from the Adriatic Sea revealed that this species is a rudimentary hermaphrodite. The smallest mature males and females captured were 38.70 cm in total length (TL) and 39.80 cm in total length (TL) respectively. The von Bertalanffy growth parameters estimated for the entire population were: L∞=107.24, K=0.12 and t0=−0.90. Fifty per cent of the population were sexually mature at 41.50 cm TL, while 100% of the specimens were sexually mature at 57.00 cm TL. Both monthly gonadosomatic index and macroscopically determined gonad stages strongly indicate that the pink dentex from the Adriatic Sea spawn partially in August, September and October. The mean value of absolute fecundity (F) was 1672 × 106 eggs. The results of great fertility of the pink dentex, partial spawning and relatively late sexual maturation suggest that the pink dentex has a high potential for commercial culture.

The principal objective of the paper is to describe the growth pattern of small northern bluefin tuna (Thunnus thynnus) in floating cages in the Adriatic Sea. For this purpose, several sampling and tagging experiments on live small tunas (mean weight: 10.47&plusmn ; 5.817 kg) in various growth-out floating cages were carried out during different rearing periods. Length and weight data of live fish were analyzed at sampling and tagging time, and recapture data eventually at harvesting time. Based on the obtained data condition parameters (K), specific growth rates (SGR) and relative growth rates (RGR) and thermal growth coefficient (TGC) were calculated. Additionally, weight– frequency distributions at sampling and harvesting time are compared. It was observed that biomass of tagged fish, as a consequence of post-tagging related stress, decrease due to starvation (SGRb0), although fish were able to recover to initial biomass (SGR=0) within 2– 3 months. Significant differences in K between wild tuna (1.95&plusmn ; 0.136) and farmed tuna (2.33&plusmn ; 0.216) were noticed. Also, no significant increase of K-value between tagged tunas (2.12&plusmn ; 0.246) and recaptured tunas (2.21&plusmn ; 0.231) in the rearing cages was noticed. However, after rearing for extended periods (N1 year), one-year old tuna considerably increased their biomass (RGR%= 342.79). Such a production of tuna biomass using capture-based aquaculture, may satisfy increasing market demands without additional impact on fish mortality.

The paper describes methodology of sampling small bluefin tuna from the growth-out floating cages, by hook and line. Also, different approaches of sampled fish handling in course of takeing nacessary measurements in lenght and weight are described, and compared with respective post-tagging mortality rates.

The embryonic and early larval development of the laboratory-reared tub gurnard, Trigla lucerna are described. The eggs ranged in diameter from 1·33 to 1·40 mm, with a mean of 1·36±0·236 mm, were pelagic and spherical with a homogeneous and unsegmented yolk. There was single oil globule in the eggs. Globule ranged in diameter from 0·25 to 0·29 mm (mean 0·28±0·012 mm). Embryonic development lasted 115 h 2 min at mean temperature 13·5 °C. Newly-hatched larvae were 3·09±0·014 mm in total length. Absorption of the yolk sac was complete after the sixth day, when larvae reached 4·85±0·015 mm in total length. The only character for identifying eggs among species could be diameter, since the values obtained are lower than those obtained for Eutrigla gurnardus and Aspitrigla cuculus, but larger than those for Trigloporus lastoviza. The length of newly hatched yolk-sac larvae of tub gurnard is significantly lower (t-test, P

WOS: 000373863800003, An ecological niche modelling (ENM) approach was used to predict the potential feeding and spawning habitats of small (5-25 kg, only feeding) and large (>25 kg) Atlantic bluefin tuna (ABFT), Thunnus thynnus, in the Mediterranean Sea, the North Atlantic and the Gulf of Mexico. The ENM was built bridging knowledge on ecological traits of ABFT (e.g. temperature tolerance, mobility, feeding and spawning strategy) with patterns of selected environmental variables (chlorophyll-a fronts and concentration, sea surface current and temperature, sea surface height anomaly) that were identified using an extensive set of precisely geo-located presence data. The results highlight a wider temperature tolerance for larger fish allowing them to feed in the northern high chlorophyll levels latitudes up to the Norwegian Sea in the eastern Atlantic and to the Gulf of Saint Lawrence in the western basin. Permanent suitable feeding habitat for small ABFT was predicted to be mostly located in temperate latitudes in the North Atlantic and in the Mediterranean Sea, as well as in subtropical waters off north-west Africa, while summer potential habitat in the Gulf of Mexico was found to be unsuitable for both small and large ABFTs. Potential spawning grounds were found to occur in the Gulf of Mexico from March April in the south-east to April May in the north, while favourable conditions evolve in the Mediterranean Sea from mid-May in the eastern to mid-July in the western basin. Other secondary potential spawning grounds not supported by observations were predicted in the Azores area and off Morocco to Senegal during July and August when extrapolating the model settings from the Gulf of Mexico into the North Atlantic. The presence of large ABFT off Florida and the Bahamas in spring was not explained by the model as is, however the environmental variables other than the sea surface height anomaly appeared to be favourable for spawning in part of this area. Defining key spatial and temporal habitats should further help in building spatially-explicit stock assessment models, thus improving the spatial management of bluefin tuna fisheries. (C) 2016 The Authors. Published by Elsevier Ltd.