Aquaculture Farms Research Articles

Identifying macroplastic pathobiomes and antibiotic resistance in a subtropical fish farm

Macroplastics are ubiquitous in aquaculture ecosystems. However, to date the potential role of plastics as a support for bacterial biofilm that can include potential human pathogenic bacteria (PHPB) and antibiotic-resistant bacteria (ARB) has been largely overlooked. In this study, we used a combination of metabarcoding and standard antibiotic susceptibility testing to study the pathobiome and resistome of macroplastics, fish guts and the environment in a marine aquaculture farm in Mauritius. Aquaculture macroplastics were found to be higher in PHPB, dominated by the Vibrionaceae family (0.34 % of the total community), compared with environmental samples. Moreover, isolates from aquaculture plastics showed higher significant multiple antibiotic resistance (MAR) compared to non-plastic samples of seawater, sediment and fish guts. These results suggest that plastics act as a reservoir and fomite of PHPB and ARB in aquaculture, potentially threatening the health of farmed fish and human consumers.

Inapparent decrease in phytoplankton biomass accompanied by significant size composition succession in the shellfish aquaculture farm in the western Taiwan strait

We conducted an annual monthly sampling in the aquaculture areas of Lianjiang and Zhangpu, Fujian province, in the west coast of the Taiwan Strait, to gain insight into the effects of shellfish aquaculture on total phytoplankton biomass and its distribution in phytoplankton size fractions. We observed that the total chlorophyll-a (TChl-a) concentration was higher in Zhangpu (annual mean 2.690 ± 2.375 μg/L) than in Lianjiang (annual mean 1.700 ± 1.500 μg/L) and that Lianjiang had a high N/P ratio during the study, which may have been the main reason for the differences in phytoplankton biomass between the two shellfish aquaculture areas. The response of phytoplankton to shellfish aquaculture was different in the northern versus southern areas. During the aquaculture period of Lianjiang, the TChl-a concentration of surface water was approximately 14% lower than that of bottom water, and such a decreasing trend of Chl-a concentration was consistently present in micro-, nano-, and pico-size fractions. Phytoplankton depletion was not observed during investigation in Zhangpu, which showed highly variable in environmental factors. The contribution of pico-sized Chl-a to TChl-a is evaluated by shellfish aquaculture to some extent in Lianjiang. The shift from the dominance of nano-phytoplankton to the dominance of micro- phytoplankton and pico-phytoplankton was caused mainly by seasonal variation in environmental conditions. In complex marine environments, the distribution of phytoplankton biomass in phytoplankton size fractions showed no significant response to shellfish aquaculture.

Nutritional Fish Diseases in Aquaculture: A Human Health Hazard or Mythical Theory: An Overview

To consume or not to consume farmed fish diagnosed with nutritional disorders within an aquaculture culture system is a question that resonates with fisheries and aquaculture experts worldwide. Proper fish health management in aquaculture should be a critical area of concern for all fish farmers. It has become a fundamental requirement for achieving sustainable aquaculture production. However, many fish farmers, particularly in developing countries lack knowledge about nutritional fish diseases and how to effectively manage them on the farm. Like human health, farmed fish’s health in aquaculture systems should be a daily priority for fish farmers. Nutritional fish diseases are often overlooked by the majority of fish farmers, even at the commercial level. Most Fish farmers may not realize that nutritional disease prevention can be achieved through the use of well-formulated fish feeds that meet all the nutritional requirements for fish growth. Additionally, maintaining good water quality and implementing best management practices are essential to ensure that the fish stock remains healthy in the culture system. Since different fish species have varying nutritional dietary requirements, it is important to formulate the right nutritional diet based on the specific fish species being cultured. Fish feeds should contain the necessary nutrients to ensure opportunistic disease resistance. Furthermore, fish farmers should be familiar with early diagnosis techniques for nutritional fish disease disorders. This ensures that the harvested fish reaching the market does not raise concerns about the quality and safety of farmed fish products. Failure to diagnose nutritional disorders associated with poor feeds and diets can create doubts in the rapidly growing aquaculture industry. Therefore, this review aims to explore the nutritional requirements of farmed fish species, the impact of nutritional deficiencies on human and public health, the causes of nutritional disorders, and viable therapies for managing these diseases in farmed fish. The data for this review article were collected from various secondary sources, including internationally reputable peer-reviewed articles, conference proceedings reports, internet searches, and more. The findings highlight the importance of providing aquaculture farmers with essential information on fish nutrition-related disease control, as nutritional diseases have been found to be detrimental to fish health and public health. Moreover, many farmed fish affected by nutritional disorders have entered the global fish market, raising questions about their impact on human health. Therefore, it is crucial for fish farmers to prioritize early diagnosis of nutritional fish diseases to ensure the safety of farmed fish in the market and maintain consumer confidence in farmed fish globally. The study recommends further research into the potentially lethal effects of different nutritional fish diseases, particularly when consumed in large quantities and to the environment especially when dead fish is discarded in the backwaters of an aquatic ecosystem.

Boldness, activity, and aggression: Insights from a large-scale study in Baltic salmon (Salmo salar L).

Atlantic salmon (Salmo salar) display high levels of agonistic behavior in aquaculture farms, resulting in fin damage and chronic stress. Aggression affects fish growth and performance negatively, and presents a serious welfare problem. Indeed, it would be beneficial to identify, separate or exclude overly aggressive individuals. Research on behavioral syndromes suggests that aggressive behavior may correlate with other behavioral traits, such as boldness and locomotory activity. We aimed to develop a high-throughput method to quantify and predict aggressive behavior of individual parr in hatchery-reared Baltic salmon (Salmo salar L.). We screened approximately 2000 parr in open field (OF) and mirror image stimulation (MIS) tests. We extracted seven variables from video tracking software for each minute of the tests; distance moved and duration moving (activity), the duration in and number of entries to the center of the arena (boldness), the distance moved in and duration spent in the area adjacent to the mirror during the MIS test (aggressiveness) and head direction (lateralization). To investigate the relationship between activity, boldness and aggression we first correlated the first six variables to one another. Second, we assigned individuals to high, medium, low or zero aggression groups based on the MIS test and quantified activity and boldness in each group. Third, we analyzed whether the fish viewed the mirror with the left or right eye. Our results show that medium and low aggressive fish were the most active, while highly aggressive fish showed average activity. Aggressive groups did not differ in boldness. Activity and boldness were positively correlated. Finally, we detected a preference for fish to view the mirror with the left eye. We conclude that aggressiveness cannot be predicted from the results of the OF test alone but that the MIS test can be used for large-scale individual aggression profiling of juvenile salmon.

Emergence of Decapod iridescent virus 1 in cultured shrimp from Taiwan in 2020.

This study was to identify and characterize Decapod iridescent virus 1 (DIV1) in the outbreaks reported in two whiteleg shrimp farms and one black tiger shrimp farm located in northern Taiwan in 2020. The histopathology, electron microscopy and polymerase chain reaction (PCR) specific for the DIV1 were used to identify the virus, and the phylogenetic analysis was performed by comparing the major capsid protein gene fragment of DIV1s from Taiwan with reference sequences of the family Iridoviridae. DIV1 was identified by diagnostic PCR and caused mild mortality (20%) in cultured Penaeus monodon and high mortality (100%) in cultured whiteleg shrimp. Cultured P. monodon was first found to be infected with DIV1 through natural route of infection. Histopathological examination showed dark-eosinophilic cytoplasmic inclusions in the degenerative cells of targeted hematopoietic tissues. For electron microscopy, a non-enveloped virus particle was observed from homogenates of mixed target organs through negative staining with a diameter of 112±2nm. Nucleotide sequences of DIV1 isolates from the Taiwanese outbreak are 100% identical to those from the PRC. Based on the clinical evidence, mortality rates, histopathology, electron microscopy examinations and phylogenetic analysis, it is believed that DIV1 is the causative agent of the outbreak. This is the first report of DIV1 in cultured shrimp in Taiwan. The emergence of DIV1 signals a warning to shrimp aquaculture farmers worldwide.

Assessing the economic impacts of severe skeletal anomalies in Mediterranean hatcheries culturing seabream and seabass

AbstractThe economic impact of skeletal anomalies in aquaculture farming is a significant issue for the industry, as deformed fish are frequently discarded because of their low survival rate and a variety of other disadvantages, including increased costs, consumer distrust of aquaculture products, and ethical concerns. The goal of this article is to propose a method for calculating the direct costs of severe skeletal anomalies in typical Mediterranean seabream and seabass aquaculture hatcheries using a deterministic static model programmed in MATLAB that simulates their annual operation. Our findings suggest that larger hatcheries experience higher direct costs associated with severe skeletal anomalies but have better financial stability and significantly higher expected profits. Mean results indicate that the annual economic losses of severe skeletal anomalies for seabream and seabass Mediterranean aquaculture are 22.88 million euros per year for a scenario of low severe skeletal anomalies, 65.34 million euros per year for a scenario of medium severe skeletal anomalies, and 115.98 million euros per year for a scenario of high severe skeletal anomalies. Furthermore, some options for increasing the financial stability of the hatcheries are to increase the sale price of fingerlings, reduce the feed conversion ratio, and reduce the feed unit cost.

The structure, conduct, and performance of the hatchery segment of the aquaculture value chain in Bangladesh

IntroductionSeed production has experienced significant growth in Bangladesh over the last decade, driven by the increasing number of hatcheries. The hatchery segment plays a crucial role in the overall growth and development of aquaculture in the country. Understanding its structure, conduct and performance is essential for assessing its impact on the productivity and profitability of aquaculture farms. However, there is a limited number of methodologically rigorous studies focusing on the hatchery segment in Bangladesh. The study aimed to fill the gap in the exiting literature by conducting a methodologically analysis of the hatchery segment of aquaculture value chain in Bangladesh.MethodsThis study was conducted in seven of the main aquaculture producing districts in southern Bangladesh. A comprehensive structured survey was conducted between May and August 2022 with 66 enterprises, including 42 carp+catfish, 16 tilapia, and 8 crustacean hatcheries.Results and discussionThe major findings and their implications are as follows. (1) The number of hatcheries increased by 15% over the past decade, with a 27% increase in fish hatcheries and a 47% decrease in crustacean hatcheries. (2) Carp and tiger shrimp were the most commonly produced fish and crustacean seeds, contributing 67% and 99% of volume and 66% and 97% of sales value, respectively. (3) The hatcheries were family-owned and operated enterprise, and generated a total 2,491 full time equivalent (FTE) jobs. (4) Hatcheries used 86% of their broodstock annually and replaced them regularly for improving quality and avoiding inbreeding. (5) 18% of hatcheries reported facing diseases and/or water quality problems, but mean economic loss was only 0.71% of seed sales value, which is a low level of loss and waste. (6) Average annual net profit margin was relatively modest, averaging 54% of the gross revenue, which suggests the existence of competitive seed production and marketing. The results showed that the hatchery segment in southern Bangladesh appears to be dynamic, well developed, efficient, and relatively competitive.

Monthly distribution of lipophilic marine biotoxins and associated microalgae in the South Sea Coast of Korea throughout 2021

Aquaculture farms have been established along the South Sea Coast of Korea, supplying most of the seafood consumed domestically. However, annual harmful algal blooms pose a potential threat to seafood safety. This study aimed to determine the spatial and seasonal distributions of 12 lipophilic marine biotoxins (LMTs) in phytoplankton and mussels in the region in 2021. Solid-phase adsorption toxin tracking (SPATT) was used to monitor the cumulative compositions of LMTs in seawater. LMT concentrations were also determined in twelve commercially available species of domestic shellfish to evaluate the potential risks to human health. Gonyaulux spinifera and Dinophysis acuminata, causative microalgae of yessotoxins (YTXs) and pectenotoxins (PTXs), respectively, showed high densities in the region from May to July. This period corresponded to high LMT concentrations in phytoplankton and mussels. Phytoplankton mainly contained PTX-2 and homo-YTX, with a maximum concentration of 2300 ng g−1 wet weight (ww) in May. In contrast, mussels mainly contained homo-YTX and YTX, with a maximum concentration of 1300 ng g−1 ww in July. LMTs-producing microalgae showed low densities and concentrations after July, whereas mussels accumulated toxins until September. In the SPATT sampler, more diverse LMTs were detected than in seawater, phytoplankton, and mussels. For example, dinophysistoxin-1 and azaspiracid-2 were detected only in SPATT. YTXs were detected in domestic seafood samples, including mussels, red scallops, and pen shells, but the concentrations were below the European Food Safety Agency recommended standard of 3.75 mg YTX-eq. kg−1. Moreover, the hazard quotient was less than 100 in all scenarios, indicating that the human health risk was not significant. This study provides valuable data on monthly distribution patterns of LMTs in the South Sea Coast of Korea and can serve as baseline data for future management policies of marine biotoxins.

Replacement of dietary fish meal by fermented soybean meal improves growth, energy metabolism, and innate immune response in Penaeus vannamei Boone, 1931 (Decapoda: Dendrobranchiata: Penaeidae)

Abstract Fishmeal (FM) is considered a preferred source of protein for aquatic feed due to its good palatability and digestibility, a balanced amino acid profile, and a low level of anti-nutritional factors (ANFs). Shortage of FM supply and increases in price, however, are major challenges faced by feed producers and aquaculture farmers. Fermented soybean meal (FSBM) has been proposed to partially replace FM because of its high nutritional value and low cost. The optimal FSBM concentration for substituting FM and effects of FSBM substitution on growth performance, energy metabolism, and immune response nevertheless remain unclear. We evaluated the effects of shrimp diets containing FSBM at 0% (FM), 25% (FSBM25), 50% (FSBM50), 75% (FSBM75), and 100% (FSBM100) on the shrimp Penaeus vannameiBoone, 1931. FSBM50 led to a significantly higher weight gain (postlarvae 1927.36 ± 46.64%, young juveniles 237.00 ± 8.25%, and juveniles 153.96 ± 2.18%) than the other experimental and control diets in different stages of the shrimp. The FM group consumed less oxygen than the experimental diet groups. FSBM75 and FSBM100 led to a significantly higher ammonia-N excretion than FM, FSBM25, and FBSM50. All experimental diet groups exhibited a significantly higher O:N ratio (8.3 ± 0.8–9.4 ± 1.7) than the FM group (7.1 ± 0.2). Shrimp fed with FSBM25- and FSBM50-containing diets exhibited an increased total hemocyte count, and FSBM25, FBSM50, and FSBM100 led to a significantly higher superoxide anion production than FSBM75 and FM. FSBM substitution in shrimp diets resulted in a significantly higher phagocytic activity than the FM diet, suggesting that FSBM substitution improves the cell-mediated immune response in shrimps. In challenge trials with white spot syndrome virus (WSSV), all experimental diets led to a higher survival rate than the FM diet, and in Vibrio parahaemolyticus challenge trials, FSBM50 led to a higher survival rate than the other experimental and control diets, indicating that FSBM substitution in shrimp diets could improve the defense capacity of shrimps against WSSV and V. parahaemolyticus.

New species and new records of bryozoan species from fouling communities in the Madeira Archipelago (NE Atlantic)

Hull fouling is considered to be the most significant vector of introduction of marine non-indigenous species (NIS) in the Madeira Archipelago (NE Atlantic) because these islands provide a vital passage route for many ships. The transfer of species between boat hulls and artificial substrates in marinas is known to be high. Bryozoans are among the most common groups of marine invertebrates growing on this type of substrate. In recent years, significant advances have been made in our knowledge about the biodiversity of bryozoans in the Madeira Archipelago. Nonetheless, the currently recognized numbers remain far from reflecting the actual bryozoan species richness. In this context, we examine bryozoan samples stemming from NIS monitoring surveys on artificial substrates along the southern coast of the Madeira Archipelago, in four recreational marinas and in two offshore aquaculture farms. This has yielded new information about ten bryozoan species. Two of them, Crisia noronhai sp. nov. and Amathia maderensis sp. nov., are described for the first time, although at least the first one was previously recorded from Madeira but misidentified. Bugula ingens, Cradoscrupocellaria insularis, Scruparia ambigua, and Celleporaria brunnea are recorded for the first time in Madeira. Moreover, the material of C. brunnea was compared with the type, and a biometric analysis was performed with material from the Atlantic and Mediterranean. All samples identified as C. brunnea in both regions are the same species, and the variations described in the literature apparently reflect high intracolonial variability. Finally, we provide new information for the descriptions of 4 additional bryozoans, namely, Crisia sp. aff. elongata, Cradoscrupocellaria bertholletii, Scrupocaberea maderensis, and Tricellaria inopinata.

The Use of Kaolin as a Prophylactic Treatment to Prevent Columnaris Disease (Flavobacterium covae) in Commercial Baitfish and Sportfish Species.

Aquaculture farms in Arkansas, USA routinely battle columnaris disease caused by Flavobacterium covae. Columnaris is prevalent during stressful events such as feed training and when fish are stocked at high densities in holding vats before sale. Kaolin clay was effective in laboratory trials as a treatment for columnaris in catfish. As a result, fish farmers are interested in applying kaolin products but were hesitant as they feared that the high doses of kaolin clay in vats might negatively affect the gills and overall health of fish. Therefore, we evaluated potential clay concentrations that might be used to prophylactically treat fish in vats. The effects of low to excessively high doses (0, 1, 2, 4, or 8 g/L) of kaolin clay (AkuaProTM, Imerys, GA, USA) were evaluated using a 72 h bioassay conducted in static tanks using Micropterus salmoides, Pomoxis nigromaculatus, Lepomis macrochirus, Ictalurus punctatus, Notemigonus crysoleucas, and Pimephales promelas. Results of these trials revealed a 100% survival rate across all six fish species exposed to kaolin clay at concentrations of up to 8 g/L for 48 h (followed by a 24 h recovery period in clean water) with no adverse effects to eyes, skin, gastrointestinal tract, or liver histology noted at any treatment. In addition, Micropterus salmoides analyzed for heavy metals due to exposure to the clay indicated that concentrations did not differ from control fish.

Multidrug-resistant phenotypes among biofilm-producing staphylococcal isolates from farm-raised fish: a molecular scrutiny.

To describe the molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) isolates from farm-raised fish. Fish samples (n=180) collected from aquaculture farms in three major districts of Kerala, yielded 45 methicillin-resistant staphylococci (MRS) (25%) isolates. All of the isolates were resistant to tested beta-lactams, and 19 (42.22%) were resistant to flouroquinolones. According to the resistance profile of each isolate, 33 of 45 (73.33%) are identified as multidrug-resistant (MDR) isolates, with an average multiple antibiotic resistance (MAR) index of 0.41±0.09. Notably, virulence determinants such as classical enterotoxin (sea & seb), and SE-like toxin (seg & sei) genes co-existed with Antimicrobial Resistance Genes (ARGs) in isolates studied. Regardless of the isolates being strong biofilm producers, only 23 (51.1%) harbored icaA and icaD genes. The heterogeneity of MRSA (n=17) clones were evident as the species belonged to three major spa types (t345, t2526, and t1309) and sequence types (STs), viz., ST772, ST88, and ST672. The current study on molecular characterization of the MRS isolates sheds light on the preventive measures that need to be implemented to limit the spread of AMR pathogens in aquaculture.

Biofloc technology and immune response of penaeid shrimp: A meta-analysis and meta-regression.

Biological flocs develop as heterogenious communities of detritus, heterotrophic and autotrophic bacteria, algae, fungi and a variety of other things through appropriate management of the carbon-nitrogen ratio in aquaculture farming systems. These microbial communities improve the water quality, reduce the concentrations of toxic inorganic species, and act as a source of food and immunostimulants. However, the information about their role as immunostimulants is widely variable. To obtain a clearer view of the situation, it is necessary to summarize the current literature on this topic through a quantitative review analysis: a meta-analysis. The present work aims to evaluate the effect of biofloc technology (BFT) implementation on culture water quality through meta-analysis, meta-regression, and correlation analysis. Pubmed, Science Direct, Scopus, and Google Scholar were searched from 2000 to 2022 on the influence of BFT on immunological parameters. Three hundred and thirty-four of the scientific articles used BFT for penaeid shrimp, but only 25 articles met the inclusion criterion of using BFT to evaluate its effect on the shrimp's immunity. The current analysis found that the use of BFT stimulates all the evaluated immunological parameters. Also, meta-regression with fixed data of study parameters showed that slow-release carbon sources, probiotics, and an estimated carbon/nitrogen ratio of 10 potentiated a larger effect on BFT immune stimulation. The meta-analysis demonstrated that the volumes of the settleable solids (SS) and the total suspended solids (TSS) are crucial for the effect of BFT on the shrimp immune system. When TSS was higher than 294mg/L, the respiratory metabolism of the shrimp was compromised. The analysis found evidence of publication biases, indicating that the data had to be interpreted carefully. Nonetheless, this meta-analysis shows that the data quality was sound and the approach used was appropriate; moreover, it also showed that BFT can be an environmentally friendly alternative culture method that enhances the shrimp's immune system.

Optimized Dissolved Oxygen Prediction Using Genetic Algorithm and Bagging Ensemble Learning for Smart Fish Farm

The field of aquaculture is one of the numerous scientific disciplines that benefit greatly from machine learning (ML). The amount of dissolved oxygen (DO), an important indicator of water quality in sustainable fish farming, affects the yield of aquatic production. It is essential to make DO projections in fishing ponds to carry out the process of artificial aeration. We present DO forecasts utilizing time series analysis based on data obtained from Hanwha Aqua Planet Jeju, located in South Korea. This information could form the basis of a data foundation for an early detection system and improved aquaculture farm management. This research presents a unique genetic algorithm called GA-XGCBXT bagging ensemble model based on genetic algorithms. This model is built on XGBoost, CatBoost, and Extra Trees. In order to select the most outstanding features, various methodologies that exhibit a strong association with the primary data were applied. The performance of the proposed model was evaluated by comparing it to actual sensor data that had been observed, both in the training and validation sets. The precise evaluation accuracy of the anticipated results of the recommended GA-XGCBXT model was determined using various performance indices. By utilizing the strategy we suggested, we acquired a root mean square error of 0.310. Our objective is to enhance the machine learning model for aquaculture so that academics and practitioners can employ applications for smart fish farming with complete reliability.

Hydrodynamic Modification in Channels Densely Populated with Aquaculture Farms

We predicted small-scale hydrodynamics, including the effect of the aquaculture farming infrastructure, for a region within the group of salmon farm concessions identified in the Chilean regulation as ACS-7. The geographical region corresponds to the Caucahue Channel, composed of two branches connected by a constriction on Caucahue Island, Inland Sea of Chiloe, Chilean Patagonia. The prediction methodology considers the interaction of a regional ocean model and a high-resolution local CFD model. The model prediction was validated using available data from ADCP. We find that the Caucahue Channel is characterized by a complex circulation and hydrodynamics, including an unstable shear flow, with meanders and turbulent structures, and retention zones. Results show the aquaculture infrastructure has a non-local hydrodynamic effect. Differences in horizontal and vertical velocity can be quite significant even far from aquaculture centers, reaching up to 300% and 170%, respectively, in simulations without taking its effects into account. The useful characteristics of this predictive approach and its potential use in particle tracking and species diffusion prediction allow for the use of projecting as a tool for strengthening the environmental and productive management of this industry.

Türkiye'de Alabalık Üretimi, Fiyatı ve Sübvansiyon Arasındaki Nedensel İlişkinin Araştırılması

Although there have been trout subsidies in Türkiye for many years, the fact that trout production has been below expectations, especially in recent years, has led to the need to investigate the effects of the subsidies. Thus, the present study was conducted to estimate the long-run relationship among trout production, producer price, and subsidy in Türkiye. The time-series data covering 1984-2016 regarding trout production, sales prices, and subsidies were used. The Vector Error Correction Model (VECM) and Granger Causality Analysis were utilized to estimate the time-dependent causality relationship among the variables. The VECM results, which estimate the existence of a long-run relationship among the variables, revealed that 46.8% of the long-run deviations in the price and subsidy variables will be corrected in the next period. The analysis results indicated that sales prices affect trout production negatively in the long term. Granger causality analysis indicated that the prior period values of production and price variables were the reason for the changes in the subsidy variable. In the short-term VECM model, it was revealed that changes in production and prices positively affect the subsidy. A percent increase in production and price increased the subsidy amount by 1.79 and 3.14 percent, respectively. To increase trout production, the current subsidy policy should be revised to improve the infrastructure and capacity of aquaculture farms. Subsidies for the fishery sector should also be increased in real terms to achieve their objectives.

Antimicrobial Resistance, Virulence Properties and Genetic Diversity of Salmonella Typhimurium Recovered from Domestic and Imported Seafood.

The quantity of seafood imported and produced by domestic aquaculture farming has increased. Recently, it has been reported that multidrug-resistant (MDR) Salmonella Typhimurium may be associated with seafood. However, information is limited to the antimicrobial resistance, virulence properties, and genetic diversity of S. Typhimurium recovered from imported and domestic seafood. This study investigated the antimicrobial resistance, virulence properties, and genetic diversity of S. Typhimurium isolated from domestic and imported catfish, shrimp, and tilapia. A total of 127 isolates were tested for the presence of multidrug-resistance (MDR), virulence genes (invA, pagC, spvC, spvR), and genetic diversity using the Sensititre micro-broth dilution method, PCR, and pulsed-field gel electrophoresis (PFGE), respectively. All isolates were uniformly susceptible to six (amoxicillin/clavulanic acid, ceftiofur, ceftriaxone, imipenem, nitrofurantoin, and trimethoprim/sulfamethoxazole) of the 17 tested antimicrobials and genetically diverse. Fifty-three percent of the Salmonella isolates were resistant to at least one antimicrobial and 49% were multidrug resistant. Ninety-five percent of the isolates possessed the invA gene, 67% pagC, and 43% for both spvC, and spvR. The results suggest that S. Typhimurium recovered from seafood is frequently MDR, virulent, and have the ability to cause salmonellosis.

Seasonal Dynamics of Marine Bacterial Communities in Aquaculture Farms: The case of the Northern Ionian Coastal Ecosystem (Mediterranean Sea)

Coastal aquaculture systems are complex environments with multiple microbial interactions that affect fish health and productivity. High-throughput amplicon sequencing is a valuable tool for identifying such bacterial communities and investigating the relationship between bacterial diversity and sustainability in these systems. In the present study, the seasonal dynamics of marine bacterial communities were assessed, in terms of diversity and composition, in three marine aquaculture farms in the northern Ionian Sea (western Greece) and a distant control site unaffected by aquaculture activities, using 16S rRNA amplicon metabarcoding. Results revealed that Proteobacteria, Bacteroidota, Cyanobacteria, and Verrucomicrobiota were the dominant phyla in the bacterial communities. Alpha diversity was significantly lower in the aquaculture farms compared to the control site. Season was the major factor driving bacterial community fluctuations. Comparative analysis between seasons revealed the presence of differentially abundant amplicon sequence variants (ASVs) in all pairwise comparisons, with the majority of them belonging to the phyla Bacteroidota (families Flavobacteriaceae, Cryomorphaceae) and Proteobacteria (family Rhodobacteraceae). Our study provides the first detailed description of bacterial communities present in Greek coastal aquaculture farms using amplicon metabarcoding analysis and expands our understanding of the impact of seasonality and environmental variables on marine bacterial community diversity and composition.

Investigating the effects of fish effluents as organic fertilisers on onion (Allium cepa) yield, soil nutrients, and soil microbiome

Although waste waters from aquaculture farms, known as fish effluents, have been shown to be a viable source of nutrients for crop production, their use is not permitted in organic production under the current European regulatory framework, Council Regulation (EU) 2018/848. In contrast, the use of livestock manure as fertiliser is allowed and indeed encouraged. In this work we tested the effects of two types of fish effluents – filtered and unfiltered fish waters – from an aquaponic system on the yield of onions (Allium cepa) and the soil nutrients and microbiome, compared with a fertilisation regime using composted horse manure. Soil fertility was enhanced by the addition of fish effluents, in particular in the soil treated with unfiltered fish water or sludge, which resulted in the soil with the highest nitrate content. Fertilisation with fish water and aerobically treated fish sludge resulted in higher yields than the manure, performing the best in all growth and yield measurements. The bulb weight and bulb diameter in the onions fertilised with manure were 102.43 g ± 7.26 and 61 mm ± 2.05 respectively, the ones fertilised with filtered fish effluents were 126 g ± 6.64 and 66.52 mm ± 2.17, and the ones fertilised with filtered (fish water) and unfiltered (sludge) fish effluents were 133.32 g ± 6.86 and 67.66 mm ± 1.81. The horse manure significantly affected the microbial community structure of the soil, resulting in a higher species diversity compared with the fish effluents, with the most predominant genus types being Flavobacterium, Pseudarthrobacter, Sphingomonas, Massilia, Nitrososphaera, Pseudomonas and Nocardioides. However, the microbial activity in the soil with fish effluents was also significant, which indicates that the soil treated in this way can be considered a ‘living soil’, as required for organic certification in the EU. Overall, the results confirm the findings of previous studies on the effectiveness of fish effluents as fertilisers, and highlight the superior performance of fish effluents compared with a livestock manure, thus directly questioning the prohibition on using fish effluents in organic agriculture.

Triple-hurdle model analysis of aquaculture farmers’ multi-stage willingness to participate in green and healthy aquaculture actions in China: based on ecological cognition and environmental regulation perspectives

Implementing the action of green and healthy aquaculture is an important measure to ensure the stable and secure supply of crucial agricultural products and promote the green and high-quality development of the fishing industry in China. This article divides the willingness to participate in the green and healthy aquaculture actions (GHAAs) into three stages: whether to participate, mode of participation, and degree of participation based on the dynamic decision-making process of the farmers. Based on micro survey data of aquaculture households in Zhejiang Province, this paper applies the Triple-Hurdle model to analyze the effect of ecological cognition and environmental regulation on multi-stage participation willingness, with a particular emphasis on exploring the differences in participation willingness between two types of green aquaculture methods, traditional and emerging technologies. The results show that ecological cognition has a positive promoting effect on the willingness to participate in actions and the degree of willingness to participate in both types of technological methods, the constrained environmental regulation policies significantly positively affects the degree of willingness to participate in traditional technological methods, and the incentive environmental regulation policies significantly positively affects the willingness to choose emerging technological methods and its degree of willingness to participate. The analysis of the regulatory effect of environmental regulation shows that constrained regulation policies can enhance the willingness of high ecological cognition farmers to participate in actions, while incentive policies are helpful for high ecological cognition farmers’ adoption willingness of emerging green production technology. In addition, there are scale and intergenerational differences in the effects of ecological cognition and environmental regulation on farmers’ willingness to participate in actions.