Antibiotics are widely recognized as significant chemical pollutants that enter the environment and ultimately the food chain. They are extensively used in both aquaculture and terrestrial animal breeding. Antibiotic residues in cultured fish pose significant public health risks, including the potential for antimicrobial resistance and adverse health outcomes. This review examines the widespread use of antibiotics in aquaculture, highlighting key challenges such as the lack of reliable data on antibiotic consumption in many regions as well as variability in regulatory enforcement. While strict regulations in European countries help to mitigate risks, the growing, often unregulated use of antibiotics in low- and middle-income countries exacerbates concerns over food safety. This paper provides an in-depth analysis of global regulatory frameworks and the impact of antibiotic residues on public health, and it offers recommendations for improving the monitoring, regulation, and responsible use of antibiotics in aquaculture in order to ensure safer food products from farmed fish. It contributes to a deeper understanding of the global scope of antibiotic misuse in aquaculture and points to an urgent need for more effective management practices.

In the immediate vicinity of a slaughterhouse, a fishpond was built that uses treated wastewater from the slaughterhouse, and in this way integrates a new value chain in the form of purification and use of slaughterhouse wastewater in an aquaculture production system. The negative aspect of such integrated production systems is the concern related to the safety of fish meat produced in these systems. The aim of this research was to determine the activity level of Cs-137, K-40, Ra-226, Th-232, and Na-22 in water, sediment, and carp harvested from a pond that received purified water from a slaughterhouse. All samples were collected in spring and in autumn. The activity concentrations of selected radionuclides were determined by gamma spectrometry (HPG-e detector). The activity of K-40 in water samples ranged from 8.4 to 15.6 Bq L⁻¹. The specific activity concentrations of the Ra-226 in water samples ranged between 1.02 ± 0.11 and 2.76 ± 0.49 Bq kg⁻¹. The results of the activity of natural radionuclides (Bq kg⁻¹) in the sediment samples were in the following ranges: 440–629 for K-40, 10.7–15 for Th-232, 20.2–44.4 for Ra-226, and 1.08–2.04 for Na-22, with average values of 531.75, 12.3, 32.97, and 1.75, for K-40, Th-232, Ra-226, and Na-22, respectively. The average content of Th-232 (12.3 Bq kg⁻¹) did not exceed the world UNSCEAR average value of 45, while the average content of Ra-226 (32.97 Bq kg⁻¹) slightly exceeded the UNSCEAR value of 32 Bq kg⁻¹. The K-40 concentration activity of 531.75 Bq kg⁻¹ was much higher than the UNSCEAR weighted average value of 420 Bq kg⁻¹. In the fish samples, natural radionuclide Na-22 was detected only in autumn (2.74 ± 0.32 Bq kg⁻¹). Results of Cs-137 and Th-232 concentrations were below the method detection limit in all samples, ˂0.5 Bq kg⁻¹ and ˂2 Bq kg⁻¹, respectively. The activity of K-40 was in the range from 121 to 160 Bq kg⁻¹. The activity concentrations of the Ra-226 in carp samples ranged between 9.5 and 54.4 Bq kg⁻¹. The results indicate that consumption of fish meat obtained from this integrated system does not pose a significant health concern in the case of the usual consumption rate that is typical for the population of Serbia. Almost no statistically significant seasonal variations were observed.

Vibrio species are widely distributed and can be potentially pathogenic to aquatic organisms. In this study, we isolated Vibrio spp. from environmental samples (seawater, sediment, and fish swabs) collected over a three-year period from a fish farm in Mali Ston Bay in the Adriatic Sea, Croatia, and assess their distribution. A total of 48 seawater samples and 12 sediment samples, as well as gill and skin swabs from 110 farmed European seabass, were analysed for the presence of Vibrio. Vibrio strains were identified to the species level by MALDI TOF MS. The analysis revealed that V. alginolyticus was the predominant species in European seabass, followed by V. anguillarum. V. alginolyticus was isolated from the sediments, along with V. gigantis and V. pomeroyi, while V. chagasii, V. cyclitrophicus, V. fortis, V. gigantis, V. harveyi, V. pelagius, and V. pomeroyi were isolated from seawater. V. anguillarum was isolated only twice during two different spring seasons, once from a diseased sea bass and the second time from a healthy sea bass. We analysed these two isolates and found that they differ both genetically and in terms of resistance to antibiotics. Our results confirm the seasonality of vibriosis incidence and the presence of the pathogenic V. anguillarum, which increases the risk of vibriosis.

The study investigates feeding habits of thermophilic species and species with subtropical affinity in the fishing catch in the Bay of Medulin (northeastern Adriatic Sea), and contributes to the knowledge about their presence in recently extended distributional range. In our methodology, the presence of the Seriola dumerili, Sphyraena sphyraena, Lichia amia, Coryphaena hippurus, Caranx crysos, Pomatomus saltatrix, and incidence of Trachinotus ovatus is recorded. A total of 220 specimens are captured during 2017, 2018 and 2019. A dietary assessment is performed, and the index of relative importance IRI was calculated for each prey category. Diet overlap is calculated using Schoener’s index, based on IRI. The principal diet of C. hippurus included Sardina pilchardus and Loligo vulgaris. Pomatomus saltatrix consumed species from the Sparidae family and T. ovatus crustaceans from the Mysidacea family. Different species from genus Atherina are represented important foods for L. amia, S. dumerili and S. sphyraena. Diets of significant importance for L. amia included fishes from the family Sparidae, for S. sphyraena from the Carangidae family, and S. dumerili from the Clupeidae and Muliidae families. Our analysis of diet overlap is based on IRI suggests no diet overlap between analysed fish species from Medulin Bay, and that these species utilise differing trophic niches.

Vibrio spp. have an important role in biogeochemical cycles; some species are disease agents for aquatic animals and/or humans. Predicting population dynamics of Vibrio spp. in natural environments is crucial to predicting how the future conditions will affect the dynamics of these bacteria. The majority of existing Vibrio spp. population growth models were developed in controlled environments, and their applicability to natural environments is unknown. We collected all available functional models from the literature, and distilled them into 28 variants using unified nomenclature. Next, we assessed their ability to predict Vibrio spp. abundance using two new and five already published longitudinal datasets on Vibrio abundance in four different habitat types. Results demonstrate that, while the models were able to predict Vibrio spp. abundance to an extent, the predictions were not reliable. Models often underperformed, especially in environments under significant anthropogenic influence such as aquaculture and urban coastal habitats. We discuss implications and limitations of our analysis, and suggest research priorities; in particular, we advocate for measuring and modeling organic matter.

This study examined culturable skin microbiota that was associated with farmed European seabass (Dicentrarchus labrax). Healthy European seabass were sampled during summer commercial harvest from one conventional fish farm where antibiotics are used, and from another practicing a certified antibiotic-free fish aquaculture. Physicochemical and microbiological analysis of seawater and sediment were performed, as well as determination of culturable bacteria, including Vibrio, from skin swabs of European seabass and seawater and sediment at both farms. Samples were processed for isolation of bacteria and their characterization by molecular and antibiotic susceptibility tests. In both fish farms, most of the bacteria that were identified in the skin belonged to the genera Pseudomonas and Vibrio. Some of the microbiota that were identified are known to be pathogenic to fish: V.alginolyticus, V. anguillarum, and V. harveyi. Vibrio strains showed higher resistance to certain antibiotics compared to previous studies. This study provides, for the first time, information on the culturable skin bacteria that is associated with healthy European seabass under culture conditions with and without the use of antibiotics. This information will be useful in assessing how changes in culturable microbiota may affect the health of farmed European seabass, indicating a potential problem for fish health management during disease outbreaks.