Aquaculture Sites Research Articles

Genetic evidence for seasonal consumption of monkfish (Lophius spp.) and salmonids (Salmo spp.) by gray seals

AbstractRecoveries of gray seal (Halichoerus grypus) populations across their eastern Atlantic distribution have led to a steady increase in seal‐fishery interactions. Fishers have estimated depredation of salmonids (Salmo spp.) and monkfish (Lophius spp.) as high as 40% and 59% respectively in Ireland. However, empirical evidence for the consumption of these species has been extremely limited due to diagnostic hard part remains not being found in scats or stomach samples. We applied species‐specific primers and tested for the presence of monkfish and salmonids in gray seal diet genetically using quantitative polymerase chain reaction (qPCR) on scats. Monkfish occurred in 29.7% of sampled scats, while salmonids occurred in 12.7%. Seasonal and regional variability in occurrence were noted for both species, likely related to the migratory behavior of the prey species and proximity of seal haul‐outs to aquaculture sites. Traditional hard part analysis of scats, including scats that tested positive for monkfish and salmonid DNA, failed to find any evidence of either species. This study provides important empirical evidence for the consumption of these species in Ireland that can inform management.

Fishery spatial plans and effort displacement in the eastern Ionian Sea: A bioeconomic modelling

The management of fisheries requires well-planned approaches that consider the socio-ecological costs and benefits of management options while minimising conflicts among fishing practices. We developed a framework to anticipate the cost-effectiveness of several fisheries management options, including space-time closures, gear selectivity improvements, and fishing effort reduction of eastern Ionian Sea fisheries. We also examined to what extent these fisheries could be influenced by placing new aquaculture sites into specific areas. We used a dynamic space-time model considering the effect of possible fishing effort displacement on alternative marine areas. A fine-scale distribution of 6 species of high commercial importance, for the eastern Ionian fisheries (central Mediterranean), was used together with the fishing effort distribution of trawlers, purse-seines, and small-scale fisheries to track the implications on several bio-economic indicators. The study revealed that the stocks and the fisheries economics benefited from a 10% reduction in fishing effort for all fishery sectors, while the unwanted fish catch was slightly higher. Thus, although there are notable advantages, this management option is not sufficient to support an EU regulatory framework aiming to promote more selective fishing practices and mitigate unwanted catches. However, we showed that the protection of juveniles, by imposing selectivity improvements or space-time closures on trawlers, slightly reduced the unwanted catch. Nevertheless, the benefit for the majority of stocks and fisheries economics, during the five-year simulation period, was limited. In the case of space-time closures, this is attributed to the offset due to the fishing effort displacement towards other areas. While the benefit on fish populations by improving trawl selectivity, it depends on the species. Finally, the establishment of new aquaculture units could lead to a slight re-allocation of fishing effort along the border of the new sites without substantially affecting the profit of small-scale fisheries. Such findings are useful for fisheries management and broader spatial planning in the Ionian Sea. They will provide insight to policymakers and different fishing sectors, thus enabling a more transparent and participatory decision–making process.

Identification of Suitable Aquaculture Sites Using Large-Scale Land Use and Land Cover Maps Factoring the Prevailing Regulatory Frameworks: A Case Study from India

Identification of a suitable site is a crucial step for the sustainability of an aquaculture venture. This study shows a framework for identifying areas suitable for freshwater and brackishwater aquaculture in India while integrating the governing regulations. Land use and land cover (LULC) maps at 1:10,000 scale derived from high-resolution imagery were used as base maps, along with allied layers. Site selection criteria were identified through review. Multi-criteria evaluation technique was used to select the technically suitable sites. Coastal regulation zone and coastal aquaculture authority guidelines, which form the regulatory framework governing brackishwater aquaculture in India, were spatially applied on the technically suitable sites to locate sites complying with regulations. The analysis was carried out using layers in the vector geographical information system format. The study was done in one coastal block each from two coastal states along the east coast of India, viz. Odisha and Tamil Nadu. The study identified areas suitable for brackishwater aquaculture in the selected blocks of Odisha (Ersama block: 86 ha) and Tamil Nadu (Pattukottai block: 343 ha). Areas suitable for freshwater aquaculture in Ersama and Pattukottai were 4286 ha and 6265 ha, respectively, while the areas suitable for freshwater aquaculture with interventions, in the respective blocks, were 487 ha and 2467 ha. In context of scarce land availability for aquaculture and stringent laws governing it, we demonstrate utility of large-scale LULC maps for identifying sites suitable for freshwater and brackishwater aquaculture, through a multi-criteria approach.

Physical carrying capacity of a potential aquaculture site in the Mediterranean: the case of Sigacik Bay, Turkey.

The aim of the present study was to evaluate physical carrying capacity of a potential cage aquaculture site near a Cittaslow area in the northern part of the Mediterranean (Sigacik Bay, Turkey). Developing tools for timely management of marine aquaculture facilities are important to minimize harmful influences of fish farming. The physical carrying capacity was estimated by mathematical formulations previously developed for the same area, using data of topographical characteristics of the site, production capacities, and leased area information of fish farms in total. Based on the findings of the present study, estimated physical carrying capacity of the potential aquaculture site with a total area of 38.9 ha near the Cittaslow residential area of "Sigacik Bay" was found as 27,694 tons of fish production which is more than 2-fold of the present production level that is around 11,800 tons in the area. Therefore, it might be concluded from a physical point of view that the production level of the present cage farms in Sigacik Bay is below risk levels.

Temporal and Spatial Variations of the Biochemical Composition of Phytoplankton and Potential Food Material (FM) in Jaran Bay, South Korea

Food material (FM) derived from biochemical components (e.g., proteins, lipids, and carbohydrates) of phytoplankton can provide important quantitative and qualitative information of the food available to filter-feeding animals. The main objective of this study was to observe the seasonal and spatial variations of the biochemical compositions of phytoplankton and to identify the major controlling factors of FM as a primary food source in Jaran Bay, a large shellfish aquaculture site in South Korea. Based on monthly sampling conducted during 2016, significant monthly variations in the depth-integrated concentrations of major inorganic nutrients and chlorophyll a within the euphotic water column and a predominance (49.9 ± 18.7%) of micro-sized phytoplankton (>20 μm) were observed in Jaran Bay. Carbohydrates were the dominant biochemical component (51.8 ± 8.7%), followed by lipids (27.3 ± 3.8%) and proteins (20.9 ± 7.4%), during the study period. The biochemical compositions and average monthly FM levels (411.7 ± 93.0 mg m−3) in Jaran Bay were not consistent among different bays in the southern coastal region of South Korea, possibly due to differences in controlling factors, such as environmental and biological factors. According to the results from multiple linear regression, the variations in FM could be explained by the relatively large phytoplankton and the P* (PO43− − 1/16 × NO3−) and NH4+ concentrations in Jaran Bay. The macromolecular compositions and FM, as alternatives food source materials, should be monitored in Jaran Bay due to recent changes in nutrient concentrations and phytoplankton communities.

Functional trait-based layers - an aquaculture siting tool for the Mediterranean Sea

Aquaculture, the current fastest-growing food sector, is one of the major opportunities that could be reaped to cope with the increased demand for proteins from the sea and simultaneously generate economic growth while ensuring sustainable use of natural resources. The number of tools and approaches suggested to promote the selection of suitable areas - focusing mostly on the management of potential conflicting uses at sea - is rapidly increasing. However, to date, there is a lack of information regarding spatial planning according to a trait-based approach encompassing the functional and biological data of farmed species; a gap that may lead to selecting unsuitable areas for farming. To fill this gap, our study builds on a functional trait-based mechanistic approach based on the Dynamic Energy Budget (DEB) theory allowing to generated species and site-specific predictions of aquaculture performances and the related environmental impact. We applied this approach to a commercial species farmed in the Mediterranean Sea, namely, the European seabass (Dicentrarchus labrax). We used three seeding sizes (1.5, 2, 2.5 g) to run model simulations and answer a crucial question for farm management, i.e. the selection of the best seeding size. A sensitivity analysis coupled with our simulations allowed to spatially represent the performance growth and environmental impact per seeding size across Mediterranean countries. The accuracy of the model's outcome was strengthened by using high-resolution satellite data over a wide area of investigation (c.a. 302,000 km2). The novel informative obtained layers combine both the modelling of aquaculture performance and related environmental impact to fill a lacking perspective within both AZAs (Allocated Zones for Aquaculture) and AZEs (Allowable Zones of Effect) concepts. Our approach allowed discriminating the best zones for European sea bass aquaculture at country level for each of the tested seeding sizes. High-resolution predictions of aquaculture performances and impact were provided for each of the nineteen Mediterranean coastal countries, zooming at Exclusive Economic Zone scale (EEZ). We highlighted pole-ward negative patterns with the best values in the Southern basin; Libya, Tunisia and Egypt in particular. Our spatial contextualization - through high resolution mapped outcomes - represents an effective and salient tool for stakeholders and policy makers, based on the translation of complex computational modelling results into easy-to-read maps. The highlighted patterns may provide scientific evidence for proactive capacity-building programmes at country level in the future.

Evaluating the growth potential of a typical bivalve-seaweed integrated mariculture system - a numerical study of Sungo Bay, China

A biophysical model was used to study bivalve-seaweed integrated culture in Sungo Bay, a typical intensive longline mariculture site in China. Based on this model, the observed variations in pelagic variables and growth of cultivated species were reasonably reproduced. The results showed that the nutrients carried by water exchange were more than sufficient to support the growth of kelp, while the growth of oysters was mainly supported by the local accumulation of phytoplankton, and the majority of scallop's food was supplied by water exchange. A reduction of water exchange would lead to a decrease in the quality of scallops, whereas the growth of oysters would be promoted. Considering the interactions among species and areas, the growth potential of mariculture in Sungo Bay was evaluated. From an area-scale perspective, mariculture in specific areas has certain growth potential. From a bay-scale perspective, the seeding density in the bay should be reduced. In addition, a precise assessment of growth potential should be a tradeoff between seeding density and water exchange. Although further improvement is needed, this model is an effective tool to assist with the management of spatially heterogeneous aquaculture systems, and similar approaches can be applied to other aquaculture sites.

Improving quantification of bivalve larvae in mixed plankton samples using qPCR: A case study on Mytilus edulis

Problems sourcing spat from naturally occurring seed beds for relay has been the main underlying limiting factor in mussel aquaculture over recent years. Attempts to address this issue require a better understanding of mussel larval patterns during the initial planktonic phase prior to settlement. A crucial step in progressing the detection and prediction of larval travel is the accurate identification of mussel larvae within environmental samples in conjunction with hydrodynamic patterns. This requires unambiguous, high throughput methods for the discrimination between larvae of morphologically-similar bivalve species. Presently methodologies require direct microscopic observation with accuracy based on taxonomic skills, techniques which are impractical for large-scale larval movement studies. Species-specific polymerase chain-reaction (PCR) presents a powerful alternative method for species detection. In addition, the technique allows for the collection of quantitative real-time PCR data which can be used for inter sample comparisons of relative larval abundance.In this study Blue mussel Mytilus edulis D-stage larvae were used to compare and optimise DNA extraction methods and to examine the quantitative potential of species-specific qPCR targeting the polyphenolic adhesive protein involved in byssal thread production. Molecular data were used to create a predictive model which could be employed to determine larval numbers from real-time data. Assays were then used to estimate M. edulis abundance in vertical–tow plankton samples collected from a trial aquaculture site off the North Wales coast.This method offers a more effective means of temporal and spatial larval pattern analysis which will improve the tracking and predictive capabilities of seed supply hydrodynamic models used for dispersal and population connectivity predictions.

Impact of floating platforms on the limnological aspects of hydropower plant reservoirs

Floating platforms at the hydropower plant reservoirs are attractive sites for aquaculture, fishing and other recreational activities. However, the unregulated construction of these platforms may negatively affect the fauna, flora and water quality of reservoirs. Thus, this study aimed to evaluate the impact of floating platforms on the limnological aspects of Nova Ponte hydropower plant reservoirs at the Center-West of Minas Gerais State of Brazil. The obtained data were analyzed using the correlation and regression analysis. Dissolved oxygen, biochemical oxygen demand, chemical oxygen demand, total coliforms and thermotolerant bacteria were plotted against the density of floating platforms. The density of platforms significantly (p-value > 0.05) impacted the analyzed limnological aspects of reservoirs. Based on the present results, 4 floating platforms/km2 (1 platform per 25 hectares) of surface water should be the maximum density in order to avoid the deterioration of water quality of reservoirs. With 4 platforms/km2, the expected values in fishing period were estimated to be 5.4 mg/L for biochemical oxygen demand, 375 most probable number per 100 mL of sample for thermotolerant bacteria and 6.1 mg/L for chemical oxygen demand. In fishing-ban period, the expected values were estimated to be 4.1 mg/L for dissolved oxygen, 3.4 mg/L for biochemical oxygen demand, 379 most probable number per 100 mL of sample for thermotolerant bacteria and 4.2 mg/L for chemical oxygen demand. This finding provides important base-line information which could help policy makers to take effective measurements for the appropriate management of surface water resources.

Sustainable Growth, Resource Rent and Taxes in Aquaculture

Global aquaculture represents an opportunity for sustainable growth in supply of healthy food and private and public income, but also has environmental footprints and thus requires a balanced policy approach by governments. Salmon aquaculture has until recently experienced rapid growth, and periods of high profitability. In all producer countries, salmon aquaculture is subject to different regulations that indirectly restrict output at the firm level and may restrict global supply in the short run. The sector has become a candidate for extraordinary taxation in Norway, and a tax regime which is unique in the context of global food production is under consideration. An argument is that society allocates sea locations to salmon firms for free, and that these provide economic returns well above normal returns to capital due to the number of sites being limited, both in Norway and globally. To this end, this paper uses a panel data set to analyze patterns of productive performance and profitability in Norwegian salmon aquaculture to analyze whether these patters suggest economic rents or infra-marginal profits. We find significant variations in productive and economic performance over time and across firms, a variability that is inconsistent with a claim that all the economic profits are a resource rent generated by a natural resource in the form of limited aquaculture sites. Our results suggest that infra-marginal profits are important part of total profits in the salmon aquaculture sector.

Spatial differences in growth rate and nutrient mitigation of two co-cultivated, extractive species: The blue mussel (Mytilus edulis) and the kelp (Saccharina latissima)

Cultivation of extractive species, such as bivalves and seaweeds, provides opportunities for food production while removing excess nutrients in eutrophic coastal waters. However, to optimize these ecosystem services, selecting aquaculture sites that affect growth and nutrient uptake is important. In a transplant experiment we assessed spatial growth patterns of the blue mussel Mytilus edulis and the kelp Saccharina latissima, which were used to estimate nutrient removal. Optimal locations for growth and nutrient extraction differed, mussels grew better in relatively sheltered inner coastal areas, whereas seaweed growth increased in outer more exposed coastal areas. Estimates of mitigatory capacity indicated that under the best available conditions, mussels remove approximately 700 kg N and 6600 kg C ha−1yr−1, whereas seaweed removes approximately 100 kg N and 1000 kg C ha−1yr−1. We identified the importance of site selection for the overall capacity of two extractive species (bivalves and seaweeds) in order to synergistically maximise their growth and nutrient mitigation.

Native predator limits the capacity of an invasive seastar to exploit a food-rich habitat

Biodiverse ecosystems are sometimes inherently resistant to invasion, but environmental change can facilitate invasion by disturbing natural communities and providing resources that are underutilised by native species. In such cases, sufficiently abundant native predators may help to limit invasive population growth. We studied native and invasive seastars feeding under two mussel aquaculture sites in south-east Australia, to determine whether food-rich farm habitats are likely to be reproductive hotspots for the invasive seastar (Asterias amurensis) and whether the larger native seastar (Coscinasterias muricata) reduces the value of the farms for the invader. We found that invaders were not significantly more abundant inside the farms, despite individuals residing within the farms having higher body condition metrics and reproductive investment than those outside. By contrast, the native seastar was 25 × more abundant inside the two farms than outside. We observed several intraguild predation events and an absence of small invaders at the farms despite reports of high larval recruitment to these environments, consistent with some level of biotic control by the native predator. A laboratory choice experiment showed that invaders were strongly attracted to mussels except when the native predator was present. Together, these findings indicate that a combination of predation and predator evasion may play a role in reducing the value of food-rich anthropogenic habitats for this invasive species.

Critical connectivity thresholds and the role of temperature in parasite metapopulations

Managing the spread of parasite populations is a ubiquitous challenge for managers of natural and farmed systems. A specific current example are “sea lice”, parasitic marine organisms that live on both wild and farmed Salmon sp., posing a persistent challenge to aquaculture operations in high latitude countries. Lice reproduce with pelagic larvae that spread in the water column, meaning that fish farm sites are connected to one another as a result of their relative location and the response of the organism to the environment. Much work has investigated population connectivity for specific systems, using computational models that link the physical and biological processes affecting larval transport. However, although probability and frequency of dispersal events may be calculated, the specific implications for outbreaks on sites is not entirely clear. We therefore used population models to describe the stage-structured dynamics of connected sea lice population networks, with the goal of establishing the critical connection strength (probability of successful dispersal) for occurrence of an outbreak. Our initial investigation deals with the case of “self-infection” of a single isolated population. Vital rates of life-cycle stages respond to temperature, and as a consequence so does critical connectivity. A dispersal success probability of around 0.01 is required for sea lice population development at the optimal temperature, although this is dependent on parameterisation. The analysis is extended to networks of sites interacting via dispersal, and we show how fallow sites can lead to substantial reductions in population growth rates. Our results provide an important, and to date, missing component in assessment of the environmental impact of marine aquaculture sites. They provide a basis upon which site operators and regional planners can appraise specific developments in the context of their surroundings, and may provide a means for future development of adaptive management strategies.

Behavioural responses to predators in Mediterranean mussels (Mytilus galloprovincialis) are unaffected by elevated pCO2

Ocean acidification is expected to affect marine organisms in the near future. Furthermore, abrupt short-term fluctuations in seawater pCO2 characteristic of near-shore coastal regions and high-density aquaculture sites currently have the potential to influence organismal and community functioning by altering animal behaviour. While anti-predator responses in fishes exposed to elevated pCO2 are well documented, such responses in benthic marine invertebrates are poorly studied. We used high frequency, non-invasive biosensors to test whether or not short term (3-week) exposure to elevated pCO2 could impact behavioural responses to the threat of predation in adult Mediterranean mussels from Galicia on the northwestern coast of Spain. Predator alarm cues (crushed conspecifics) resulted in a prolonged (1 h) reduction in the degree of valve opening (−20%) but had no clear effect on overall valve movement activity, while elevated pCO2 did not affect either response. Our results add to the increasing body of evidence suggesting that the effects of end-of-century pCO2 levels on marine animal behaviour are likely weak. Nonetheless, longer-term exposures spanning multiple generations are needed to better understand how ocean acidification might impact behavioural responses to predation in marine bivalves.

Gut Microbiota of Five Sympatrically Farmed Marine Fish Species in the Aegean Sea.

In this study, we hypothesized that sympatrically grown farmed fish, i.e. fish which experience similar environmental conditions and nutritionally similar diets, would have more convergent gut microbiota. Using a "common garden" approach, we identified the core microbiota and bacterial community structure differences between five fish species farmed in the same aquaculture site on the west coast of the Aegean Sea, Greece. The investigated individuals were at similar developmental stages and reared in adjacent (< 50 m) aquaculture cages; each cage had 15 kg fish m-3. The diets were nutritionally similar to support optimal growth for each fish species. DNA from the midgut of 3-6 individuals per fish species was extracted and sequenced for the V3-V4 region of the bacterial 16S rRNA. Only 3.9% of the total 181 operational taxonomic units (OTUs) were shared among all fish. Between 5 and 74 OTUs were unique to each fish species. Each of the investigated fish species had a distinct profile of dominant OTUs, i.e. cumulative relative abundance of ≥ 80%. Co-occurrence network analysis for each fish species showed that all networks were strongly dominated by positive correlations between the abundances of their OTUs. However, each fish species had different network characteristics suggesting the differential significance of the OTUs in each of the five fish species midgut. The results of the present study may provide evidence that adult fish farmed in the Mediterranean Sea have a rather divergent and species-specific gut microbiota profile, which are shaped independently of the similar environmental conditions under which they grow.

Evaluating a Suitable Aquaculture Site Selection Model for Cobia (Rachycentron canadum) during Extreme Events in the Inner Bay of the Penghu Islands, Taiwan

Despite numerous studies on the effect of a cold weather disaster on fisheries in 2008, no operational systems have been developed to monitor the threat of such an event to mariculturists in the Penghu Islands (PHI) region of Taiwan. The present study employed a suitable aquaculture site selection map of the inner bay of the PHI to reduce aquaculture losses and mortality rates of cobia (Rachycentron canadum) during extreme events. Daily marine environmental data, including sea surface temperature (SST), chlorophyll-a concentration (chl-a), and wind speed in the winter, were collected. An extreme event was defined as a period of over 11 days in a month of strong winds (&gt;6 m/s). Four parameters in the PHI inner bay, including SST, cold-water intrusion days, chl-a, and offshore distance to the PHI coastline, were used to evaluate suitable aquaculture sites for cobia culture. The results indicated that La Niña events could not be used as a factor to detect cold-water intrusion events and select suitable aquaculture sites in the PHI. The evaluated suitable aquaculture site selection map, obtained using an arithmetic mean model and a geometric mean model, revealed that the avoidance sites during extreme events were concentrated in the northern and northwestern PHI. Suitable areas were concentrated in the southeastern areas. We further suggested that commercial cobia aquaculture operations in the PHI inner bay could be moved to the suitable sites in southeastern PHI during extreme events.

Phytoplankton Dynamics in the Middle Adriatic Estuary, with a Focus on the Potentially Toxic Genus Pseudo-nitzschia

The Krka River estuary is a karstic, permanently stratified estuary due to the strong freshwater inflow. It is a special environment in which to study the phytoplankton community, especially because this area is an important aquaculture site. Among other potentially toxic phytoplankton species, the diatom genus Pseudo-nitzschia occurs frequently and is a potential source of domoic acid (DA), causing shellfish toxicity and human intoxication. The main objective was to examine the dynamics of the phytoplankton community and, in particular, the genus Pseudo-nitzschia in the upper part of the Krka estuary, through monthly sampling over two years. The phytoplankton community was analysed using light microscopy and scanning electron microscopy to determine the diversity of Pseudo-nitzschia species and characterise the environmental parameters associated with a high abundance of Pseudo-nitzschia species. Seven Pseudo-nitzschia species were identified in the investigation, with higher frequencies and abundances in the less variable layer, at a 7 m depth. Blooms of Pseudo-nitzschia were noted in the late summer/early autumn, dominated by P. delicatissima/arenysensis. Winter assemblages were characterised by P. pseudodelicatissima/cuspidata, P. calliantha, and P. subfraudulenta, and were associated with domoic acid occurrence in shellfish.

Parameterising resuspension in aquaculture waste deposition modelling

Sustainable expansion of global aquaculture depends on a thorough understanding of environmental impacts. Open-water culture operations produce waste food and faeces, the benthic impacts of which are a focus of regulation. Seabed interactions of wastes are complex, depending on current velocity, seabed substrate and waste material characteristics. The accuracy achieved in modelling intensity and spatial extent of impacts is contingent upon the representation of this interaction and its implications for resuspension. We used benthic flumes to study resuspension processes at 11 salmon aquaculture sites, covering a range of sediment types. Erosion rates and critical entrainment stress were computed at the cage edge and between 100 and 500 m away, characterising seabed erodibility in highly impacted and less impacted sediments. Heavily impacted cage-edge sediments had an erosion threshold (mean 0.02 N m-2) that was an order of magnitude lower, and markedly less heterogeneous, than that of nearby less impacted sediments (mean across sites 0.19 N m-2). This likely reflects a seabed which was smothered by waste material close to the depositional centre. Further out, the covering of waste material is less continuous, thinner, and more admixed with underlying sediments. Bed erosion rates were found to be a linear function of excess stress. The results provide important information on how benthic flumes can be deployed to collect spatial and temporal data for parameterisation of erosion and entrainment processes in numerical waste transport simulation models such as DEPOMOD, and the comparatively large field-based dataset should contribute to the goal of allowing a more realistic representation of particulate waste in these models.

Application of tylosin antibiotics to olive flounder (Paralichthys olivaceus) infected with Streptococcus parauberis

BackgroundOlive flounder, Paralichthys olivaceus, is an economically important aquaculture species in Korea. Olive flounders have been heavily damaged by streptococcal infections every year and are treated with antibiotics. However, antibiotic abuse is causing the emergence of resistant strains, and to overcome this, research has shown that new antibiotics must be applied. Tylosin is a relatively safe antibiotic and has good activity against Gram-positive bacteria and mycoplasma. We studied the therapeutic effects and side effects of tylosin on Streptococcus parauberis-infected olive flounder.MethodsAfter artificial infection of olive flounder with S. parauberis SPOF18J3, an appropriate dose of tylosin was confirmed by intramuscular injection (I.M.) at 2.5, 5, 10, and 15 mg/kg, and oral administration at 10 and 20 mg/kg. After I.M. and oral administration dosing of tylosin, side effects were confirmed by serological analysis, histopathological analysis, and median lethal dose (LD50) analysis at both an appropriate concentration and a high concentration. Statistical analysis was performed using one-way analysis of variance (ANOVA) and Tukey’s test (p < 0.05).ResultsThe appropriate I.M. and oral administration concentration of tylosin administered to olive flounder infected with S. parauberis SPOF18J3 was found to be 10 mg/kg. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were showed not significantly different between the control group and the experimental groups. The histopathologic results showed mild inflammatory responses in muscle and tubular vacuolization and tubular atrophy appeared, but there were no significant differences between the groups. The LD50 was confirmed to be 461 mg/kg.ConclusionIn this study, an effective treatment method was provided by verifying the treatment effects and side effects of tylosin in olive flounder infected with S. parauberis, which can be applied directly to aquaculture sites. In addition, these results may be used as a reference for evaluation required upon request to obtain approval for tylosin antibiotics as fishery antibiotics in Korea. After approval, it is possible that a fishery disease manager will be able to prescribe and sell the antibiotic tylosin.

Profiling of bacterial assemblages in the marine cage farm environment, with implications on fish, human and ecosystem health

This research presents a comprehensive study of bacterial assemblages within the water column and in the surface sediments in the zone of two European sea bass cage farms. By the application of the high-throughput amplicon sequencing of 16S rRNA gene, and further implementing microbial ecology tools, a bacterial segment from cage culturing systems and their respective controls were analyzed, with special reference to potential impact on animal, human and environmental health. Samples of seawater and sediments were collected seasonally, at locations situated in the central and southern Adriatic Sea. Bacterial composition was significantly different in the seawater vs. sediment. No significant differences in alpha diversity in sediments were indicated between aquaculture and control sites, and it appears that it is not affected by farming practices. Control sediments have higher relative abundance of aerobic and facultative anaerobic bacteria, while aquaculture sediments are markedly anaerobic. Sediments largely contain functional groups for respiration of sulfate and sulfur compounds, though doubly more in aquaculture sites. Seasonal groupings of bacterial assemblages were confirmed in the seawater, with higher relative abundance of known aquaculture pathogens (except Photobacterium in the winter samples) detected in the winter and summer, opposed to other two seasons. Rare taxa were analyzed in the sediment and in the water column in the search for known fish pathogens, with five genera detected: Vibrio, Pseudomonas, Photobacterium, Tenacibaculum and Mycobacterium. Biomarkers important for the impact of aquaculture on the environment were identified, e.g. Blastopirullela, Sva0081, Suflurovum, Spirochaeta 2, etc., as well as human and fish potential pathogens: Vibrio ichtyoentery, V. harvey, Acinetobacter lwoffi, A. johnsonii, Clostridium perfringens, etc. Chemoheterotrophy has emerged as the dominant functional group in both environments. Regarding priorities for aquaculture microbial management, seawater seems to contain a higher percentage of taxa connected to health-related functional groups.