The Atlantic blue crab, Callinectes sapidus, is a highly invasive species that poses a significant threat to Mediterranean ecosystems. In the last two decades, it has become established in several ...marine and estuarine areas of the eastern Adriatic Sea, resulting in a decline in commercial catches and damage to fishing gear. This article reviews the current status of blue crab invasion in Montenegro and Croatia and analyses its abundance and population structure. Overall 619 crabs were sampled (male:female ratio, 1:1.91). Both carapace width and weight differed significantly between males and females, with males having a wider carapace and more weight. There was a significant difference in carapace width and weight among sites. For the total population, the mean male and female carapace width was 130.3 ± 30.8 and 108.8 ± 41.4 mm, respectively. In addition, the mean male and female weight was 187.2 ± 85.6 and 132.5 ± 39.1 g, respectively. Coefficient b between the weight and carapace width of blue crabs was significant at all locations, although it varied between males and females. This work will also document the impacts of the blue crab invasion on local ecosystems and provide comprehensive overview of populations structures and shed light on this important aspect of blue crab ecology.
The paper describes the energy consumption and GHG production comparison of three transport modes – road, rail and waterborne. The calculations are done according to the legislation in force – ...standard EN 16 258:2012 Methodology for calculation and declaration of energy consumption and GHG emissions of transport services (freight and passengers). The results have high informative value because they take into account energy consumption and emissions from primary and secondary consideration. The calculation is done by real fuel consumption values (road and waterborne) and by simulation of energy consumption (railway). The energy and emission coefficients from the standard EN were used for estimating the results according to the well-to-wheels and tank-to-wheels principles.
This paper presents thermodynamic (energy and exergy) analysis and comparison of two different marine propulsion steam turbines based on their operating parameters from exploitation. The first ...turbine did not possess steam reheating and had only two cylinders (high-pressure and low-pressure cylinders), while the second turbine possesses steam reheating and has one additional cylinder (intermediate-pressure cylinder). In the literature at the moment, there cannot be found a direct and exact comparison of these two marine steam turbines and their cylinders based on real exploitation conditions. Along with energy and exergy analyses, the research it is investigated the sensitivity of exergy parameters to the ambient temperature change for both turbines and each cylinder. It is also presented the influence of the steam reheating process on the energy and exergy efficiency of the entire power plant. For both observed turbines and their cylinders it is valid that relative losses and efficiencies (both energy and exergy) are reverse proportional. The operation of an intermediate pressure cylinder from a steam turbine with reheating is the closest to optimal. Due to the different origins of losses considered in energy and exergy analyses, each analysis detects different turbine cylinders as the most problematic ones. The steam reheating process decreases losses and increases efficiencies (both energy of each turbine cylinder and the whole turbine. The whole turbine with reheating has an energy efficiency equal to 81.46% and an exergy efficiency equal to 86.48%, while the whole turbine without reheating has energy and exergy efficiencies equal to 76.47% and 80.94%, respectively. Exergy parameters of a steam turbine without reheating as well as its cylinders are much more influenced by the ambient temperature change in comparison to the steam turbine with reheating and its cylinders. The steam reheating process will increase the efficiency of the whole power plant in real exploitation conditions between 10% and 12%.
Adriatic Sea as a part of the Mediterranean is settled by many introduced species which extend their range northward. Among them is the rayed pearl oyster Pinctada radiata, a mollusk of Indo-Pacific ...origin that colonises habitats throughout the Mediterranean. P. radiata established a population in a fish farm on the island of Mljet in the Adriatic Sea, which was observed in 2017. To determine the status of the population, 48 specimens of P. radiata were randomly sampled from the ropes of a fish farm in 2019. Morphometric parameters were determined using a digital calliper. The recorded parameters showed that shell height ranged from 50.55 mm to 72.98 mm, shell length from 46.66 mm to 71.15 mm, and shell width from 19.98 mm to 58.54 mm. During additional visual survey in 2020 the presence of the spat within population at Mljet fish farm was not observed. It appears that only adult specimens are present, and it is unclear if the population is reproducing. In addition, P. radiata spat was observed in the shallow waters of Lokrum Island in 2021 and 2022, indicating the possibility of survival of larvae naturally dispersing from pre-existing populations. An adult specimen of P. radiata was also observed in Mali Ston Bay on two occasions, in 2009 and 2021. P. radiata, a highly adaptable species that tolerates a wide range of environmental factors, has successfully colonised new habitats.
The feeding habits of the stargazer Uranoscopus scaber Linnaeus, 1758 were analysed using 360 stomachs of specimens collected in southern Adriatic Sea between October 2011 and September 2012. The ...total body length of the specimens ranged from 9.7 to 32.1 cm (18.89 ± 3.34 cm) and weight from 11.7 to 618.7 g (112.79 ± 63.17 g). In the sampled population there were 213 females (59.17%) and 147 males (40.83%). Stargazer is carnivorous fish and its diet in Adriatic Sea was composed of teleost fish, cephalopods and crustaceans. According to numerical abundance fish predominated followed by crustaceans, while according to the gravimetric composition fish predominated followed by cephalopods. Teleost fish were dominant prey in all seasons, and the principal prey were hake Merluccius merluccius and argentine Argentina sphyraena. Argentine was primary food in summer (IRI = 61.63), while hake occur in other seasons. In relation to the total body length teleost fish dominated in diet of stargazer whose total body length was < 25 cm. In size group I and II (TL < 20 cm) A. sphyraena was the main food, while M. merluccius was dominant prey in the size group III (TL = 20 – 25 cm). Vacuity index in the sampled population was relatively low (%V = 11.11%). During seasons the percentage of empty stomachs varied significantly with the highest value in winter (%V = 15.55%) and the lowest in spring (%V = 7.78%). In relation to the total body length the highest vacuity index was recorded for size group II (%V = 5.83) and the lowest for group VI (%V = 0).
Groupers are important predator marine fish species, and also economically important to commercial and recreational fisheries, but threatened by overfishing worldwide. The dusky grouper (Epinephelus ...marginatus) is the most common species that historically occurred in the southern and central Eastern Adriatic, while other species were mostly restricted to the southern part of the region or were not recorded in the Adriatic Sea. However, the warming of the sea caused by recent climate change has caused some grouper species in the Eastern Adriatic to expand northward. This spread has been poorly documented, largely because rocky coastal habitats, which are less accessible to conventional research methods that often rely on specific fishing gears, have received far less attention than other more accessible habitats i.e. soft bottoms. Reports of recent grouper expansion are primarily anecdotal and mainly based on the extensive observations of recreational fishermen who mainly utilize rocky coastal habitats. In order to gain insight into this phenomenon, we conducted a survey to investigate the distribution of groupers along the Croatian coast of the eastern Adriatic using the Local Ecological Knowledge methodology. Semi-structured interviews were carried out to record fishers' knowledge and perceptions of changes in their catches, as well as personal observations. The data collected provided information on the spatial and temporal expansion of groupers in the eastern Adriatic over the last 60 years, as perceived by local recreational fishermen.
Previous work on ocean acidification highlighted contrasting response between marine species and population. This so-called species-specific response was hypothesized to be partly a consequence of ...local adaptation to the present range of natural variability in the carbonate chemistry. Under that hypothesis, species tolerance threshold should be correlated to its environmental pH niche. This paper aims to evaluate shell growth rate of Hexaplex trunculus, an important predatory gastropod in benthic communities of Mali Ston Bay. A long-term experiment (310 days) was designed to test a range of pH treatments covering present and future pH levels relevant in the context of future ocean acidification (7.95-7.22 pHT) at the sampling site. Sex had an effect on the shell growth rate irrespective of pH, and was only significant after 236 days. As growth rate in all pH treatments followed seasonal patterns correlating to changes in seawater temperature, the data were divided into 3 time periods. A positive relationship between shell growth rate (SGR, mm day-1) and pH was observed for the period 1-59 days (temperature ranging between 26.5 & 18.8 °C), whereas SGR decreased significantly with pH for the following period (60-236 days, temperature ranging between 20.6 & 8.5 °C). After 236 days (temperature ranging between 27.5 & 14.1 °C), there was no significant difference in SGR among pH. Similar temperature was experienced between the first and third period and the difference in response could be explained as a consequence of an acute negative response versus a longer exposure indicating possible potential for acclimation. Our results highlight the modulating effect of temperature and the importance of long-term experiments to better assess impacts of ocean acidification on marine organisms.
The discovery of individuals of softmouth trout Salmo obtusirostris in the marine environment has been recorded several times in the period from 2015 to the present day in the wider area of the ...Neretva River delta and southern Adriatic coast. Although this phenomenon appears to be happening more frequently along the Adriatic coast, scientific reports regarding family Salmonidae species found in the marine environment are still very rare in the eastern Adriatic, especially for the softmouth trout. The findings reported here represent the first marine records of this endemic freshwater species. An increasing frequency of these findings may indicate that a higher number of individuals are ending up in the coastal environment during heavy storm events or other unusual hydrologic occurrence. Extreme weather conditions have become more frequent in recent years, mainly as a result of climate change and have led to unexpected phenomena and impacts on nature. The long-term effects on fish and community structure of rivers flowing into the sea require further research, as these weather-induced situations can be expected to become more common. Further investigation into the physiological costs and population consequences of these unusual ecological findings is warranted.
The trim tab and interceptor have been utilized to optimize the running trim and motion control of planing boats at varying speeds in calm water. Increasing the height of the interceptor can create ...excessive drag and bow-down trim. The effectiveness of the interceptor can be increased by integrating it with a horizontal flap. This research focuses on the impact of the influence caused by interceptor flaps on the pressure distribution and fluid flows around the vessel.To simulate trim and sinkage measurement, the environment was modeled in the two-degree of freedom condition. Variation of integrated interceptor flaps has been analyzed with Finite Volume Method (FVM) based on RANS (Reynolds-Averaged Navier-Stokes) equation using overset mesh.The turbulent K-ε and VOF (Volume of Fluid) models are used to model the water and air phases. The grid convergence study is performed to establish the parallel solver's grid independence. To confirm the accuracy of the test in the bare hull condition, the numerical approach was tested experimentally. The result of drag, trim, and sinkage was calculated and it has been proved that the added flaps into interceptors are very useful in drag reduction and trim control. The percentage of interceptor height is directly proportional to the resulting lift force. Higher lift force can more effectively improve trim and reduce drag. Overall, this study shows an improvement in ship performance when using an interceptor and interceptor flap. One of the model configurations in the study has been shown to reduce drag by up to 33.3% at Froude number 1.45 when compared to ships without an interceptor.
Previous work on ocean acidification highlighted contrasting response between marine species and population. This so-called species-specific response was hypothesized to be partly a consequence of ...local adaptation to the present range of natural variability in the carbonate chemistry. Under that hypothesis, species tolerance threshold should be correlated to its environmental pH niche. This paper aims to evaluate shell growth rate of Hexaplex trunculus, an important predatory gastropod in benthic communities of Mali Ston Bay. A long-term experiment (310 days) was designed to test a range of pH treatments covering present and future pH levels relevant in the context of future ocean acidification (7.95-7.22 pHT) at the sampling site. Sex had an effect on the shell growth rate irrespective of pH, and was only significant after 236 days. As growth rate in all pH treatments followed seasonal patterns correlating to changes in seawater temperature, the data were divided into 3 time periods. A positive relationship between shell growth rate (SGR, mm day-1) and pH was observed for the period 1-59 days (temperature ranging between 26.5 & 18.8 °C), whereas SGR decreased significantly with pH for the following period (60-236 days, temperature ranging between 20.6 & 8.5 °C). After 236 days (temperature ranging between 27.5 & 14.1 °C), there was no significant difference in SGR among pH. Similar temperature was experienced between the first and third period and the difference in response could be explained as a consequence of an acute negative response versus a longer exposure indicating possible potential for acclimation. Our results highlight the modulating effect of temperature and the importance of long-term experiments to better assess impacts of ocean acidification on marine organisms.
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