Offshore Cage Research Articles

Effects of fasting on golden pompano Trachinotus ovatus: Physiological and biochemical responses

In practice, golden pompano (Trachinotus ovatus) reared in offshore cages may experience short-term fasting during extreme weather conditions, yet their physiological and biochemical responses remain poorly understood. To investigate the responses of this species to fasting, golden pompano weighing 138.0 ± 2.1 g were deprived of food for 0, 7, 14, 21 and 28 days, followed by assessments of body mass, somatic parameters, proximate composition, muscle glycogen, intestinal digestive enzymes, muscle amino acid and fatty acid profiles, nutritional value, and muscle texture and water holding capacity. Lower condition factor, hepatosomatic index, viscerosomatic index, hepatic glycogen, and intestinal activities of amylase, lipase and trypsin were found in the fasted fish than in the non-fasted fish, while a sharp decline in these parameters occurred on the first week of fasting. Fresh mass, dry mass, whole body and muscle contents of crude protein and lipid tended to decrease with prolonged fasting, while no statistical differences were found in these parameters between fish fasted for 7 days and the non-fasted fish. Furthermore, the decline rate of whole body crude lipid was consistently higher than that of whole body crude protein throughout the different stages of the 28-day fasting period, with the exception of the second week of fasting. No statistical differences were found in the total essential amino acids (∑EAA), non-essential amino acids (∑NEAA), ratio of ∑EAA to∑NEAA, chemical score, amino acid score, and essential amino acid index in the fasted fish compared to the non-fasted fish of group 0d. Fasting altered the muscle profile of SFA, MUFA and PUFA, sometimes reducing muscle springiness (groups 7d and 14d) and hardness (group 21d). Compared to non-fasted fish, fish fasted for 7 and 14 days exhibited statistically lower or equal drip loss, water loss rate, storage losses, and frozen exudate rate, whereas higher cooked meat rate. The above results indicate that during the 28-day fasting period, the visceral fat and hepatic glycogen are initially metabolized, followed by body proteins and lipids, to maintain the normal metabolism in fasted fish. Fasting has beneficial effects on the nutritional value of amino acids and fatty acids in muscle, although it modifies the muscle SFA, MUFA and PUFA composition and sometimes has negative effects on muscle texture. Considering the balance between body weight loss and flesh quality improvement, the duration of fasting for cultured golden pompano prior to harvesting should not exceed 14 days.

Transcriptome analysis of large yellow croaker (Larimichthys crocea) at different growth rates.

The unsynchronized growth of the large yellow croaker (Larimichthys crocea), which impacts growth efficiency, poses a challenge for aquaculture practitioners. In our study, juvenile stocks of large yellow croaker were sorted by size after being cultured in offshore cages for 4 months. Subsequently, individuals from both the fast-growing (FG) and slow-growing (SG) groups were sampled for analysis. High-throughput RNA-Seq was employed to identify genes and pathways that are differentially expressed during varying growth rates, which could suggest potential physiological mechanisms that influence growth rate. Our transcriptome analysis identified 382 differentially expressed genes (DEGs), comprising 145 upregulated and 237 downregulated genes in comparison to the SG group. GO and KEGG enrichment analyses indicated that these DEGs are predominantly involved in signal transduction and biochemical metabolic pathways. Quantitative PCR (qPCR) results demonstrated that cat, fasn, idh1, pgd, fgf19, igf2, and fads2 exhibited higher expression levels, whereas gadd45b and gadd45g showed lower expression compared to the slow-growing group. In conclusion, the differential growth rates of large yellow croaker are intricately associated with cellular proliferation, metabolic rates of the organism, and immune regulation. These findings offer novel insights into the molecular mechanisms and regulatory aspects of growth in large yellow croaker and enhance our understanding of growth-related genes.

Exploring the underlying mechanisms of enteritis impact on golden pompano (Trachinotus ovatus) through multi-omics analysis

Enteritis posed a significant health challenge to golden pompano (Trachinotus ovatus) populations. In this research, a comprehensive multi-omics strategy was implemented to elucidate the pathogenesis of enteritis by comparing both healthy and affected golden pompano. Histologically, enteritis was characterized by villi adhesion and increased clustering after inflammation. Analysis of the intestinal microbiota revealed a significant increase (P < 0.05) in the abundance of specific bacterial strains, including Photobacterium and Salinivibrio, in diseased fish compared to the healthy group. Metabolomic analysis identified 5479 altered metabolites, with significant impacts on terpenoid and polyketide metabolism, as well as lipid metabolism (P < 0.05). Additionally, the concentrations of several compounds such as calcitetrol, vitamin D2, arachidonic acid, and linoleic acid were significantly reduced in the intestines of diseased fish post-enteritis (P < 0.05), with the detection of harmful substances such as Efonidipine. In transcriptomic profiling, enteritis induced 68 upregulated and 73 downregulated genes, predominantly affecting steroid hormone receptor activity (P < 0.05). KEGG pathway enrichment analysis highlighted upregulation of SQLE and CYP51 in steroidogenesis, while the HSV-1 associated MHC1 gene exhibited significant downregulation. Integration of multi-omics results suggested a potential pathogenic mechanism: enteritis may have resulted from concurrent infection of harmful bacteria, specifically Photobacterium and Salinivibrio, along with HSV-1. Efonidipine production within the intestinal tract may have blocked certain calcium ion channels, leading to downregulation of MHC1 gene expression and reduced extracellular immune recognition. Upregulation of SQLE and CYP51 genes stimulated steroid hormone synthesis within cells, which, upon binding to G protein-coupled receptors, influenced calcium ion transport, inhibited immune activation reactions, and further reduced intracellular synthesis of anti-inflammatory substances like arachidonic acid. Ultimately, this cascade led to inflammation progression, weakened intestinal peristalsis, and villi adhesion. This study utilized multi-level omics detection to investigate the pathological symptoms of enteritis and proposed a plausible pathogenic mechanism, providing innovative insights into enteritis verification and treatment in offshore cage culture of golden pompano.

Ecological implications of unintentional aquaculture escapees: an overview of risks, remediation strategies and knowledge gaps in the aquaculture sector of India and riparian East African countries

The global expansion of aquaculture has driven significant technological advancements, including raceways, Integrated Multitrophic Aquaculture (IMTA) and marine offshore cages. However, unregulated aquaculture escapees pose a severe threat to aquatic biodiversity, acting as a potential time bomb for the entire ecosystem. Addressing this issue requires a comprehensive understanding of the impact of unintentional escapees on aquatic ecosystems, particularly in India and riparian East African countries (Kenya, Uganda, and Tanzania). Using an exploratory research design drawing from various peer-reviewed sources, this study outlines the dynamic growth of aquaculture in these countries, identifies high-impact escape incidents, and correlates risks and remedies with global cases, especially in regions such as Norway, Scotland, Ireland, Colombia, and the United States, where serious incidents of aquaculture escapees have been reported. The research categorizes aquaculture development trends, discusses mechanisms of escapee impact, proposes remedies, assesses methods and inferential strength, and highlights gaps in the existing literature. The study revealed complex ecological shifts caused by aquaculture escapees from invasive non-native fish species, affecting predation, competition, and genetic diversity. Escaped fish from aquaculture facilities pose a significant threat to aquatic biodiversity, especially in the study regions. The escalating risk of unintentional escapes was highlighted in India and three East African countries. To mitigate this, the study proposes integrating escapee management into national fisheries systems, amending fisheries laws, holding fish farmers accountable for aquaculture system failure, and developing comprehensive regulations for non-native species in aquaculture within the study regions. It is recommended to standardize the planning for aquaculture facilities and implement emergency plans, training, local mobilization and further research on the impact thresholds of aquaculture escapees in the study regions. Ecological education in aquaculture communities and the recognition of the role of translational scientists are crucial for the dissemination of knowledge. Urgent government action is needed to address unreported aquaculture escapes, preventing further ecosystem degradation and ensuring global aquaculture sustainability.

Re-evaluation of certain aspects of the EFSA Scientific Opinion of April 2010 on risk assessment of parasites in fishery products, based on new scientific data. Part 1: ToRs1-3.

Surveillance data published since 2010, although limited, showed that there is no evidence of zoonotic parasite infection in market quality Atlantic salmon, marine rainbow trout, gilthead seabream, turbot, meagre, Atlantic halibut, common carp and European catfish. No studies were found for greater amberjack, brown trout, African catfish, European eel and pikeperch. Anisakis pegreffii, A. simplex (s. s.) and Cryptocotyle lingua were found in European seabass, Atlantic bluefin tuna and/or cod, and Pseudamphistomum truncatum and Paracoenogonimus ovatus in tench, produced in open offshore cages or flow-through ponds or tanks. It is almost certain that fish produced in closed recirculating aquaculture systems (RAS) or flow-through facilities with filtered water intake and exclusively fed heat-treated feed are free of zoonotic parasites. Since the last EFSA opinion, the UV-press and artificial digestion methods have been developed into ISO standards to detect parasites in fish, while new UV-scanning, optical, molecular and OMICs technologies and methodologies have been developed for the detection, visualisation, isolation and/or identification of zoonotic parasites in fish. Freezing and heating continue to be the most efficient methods to kill parasites in fishery products. High-pressure processing may be suitable for some specific products. Pulsed electric field is a promising technology although further development is needed. Ultrasound treatments were not effective. Traditional dry salting of anchovies successfully inactivated Anisakis. Studies on other traditional processes - air-drying and double salting (brine salting plus dry salting) - suggest that anisakids are successfully inactivated, but more data covering these and other parasites in more fish species and products is required to determine if these processes are always effective. Marinade combinations with anchovies have not effectively inactivated anisakids. Natural products, essential oils and plant extracts, may kill parasites but safety and organoleptic data are lacking. Advanced processing techniques for intelligent gutting and trimming are being developed to remove parasites from fish.

Evaluation of the green development efficiency of marine fish culture in China

Green development efficiency (GDE) is an important criterion for measuring the level of green development. GDE considers not only economic development efficiency but also environmental costs. In China, marine fish culture, as one of the pillar industries of mariculture, promotes green development and industrial transformation and upgradation. Based on data from the field surveys of marine fish farmers (2017–2019) and the China Fishery Statistical Yearbook (2018–2020), this study establishes an evaluation index system and uses the super-slack-based measure model (Super-SBM) to evaluate the GDE of marine fish culture. The results show that the average GDE of marine fish culture in China was 0.9529, which was in an inefficient state. As for culture species, golden pompano (Trachinotus ovatus) and cobia (Rachycentron canadum) were the two species farmed in an efficient state, with a GDE of 1.2107 and 1.0659, respectively. Regarding culture modes, green modes (offshore cage aquaculture, industrial recirculating aquaculture, and engineering pond aquaculture) were in an efficient state, with a GDE of 1.2310, 1.0827, and 1.0401, respectively. Traditional modes (industrial flow-through aquaculture, ordinary cage aquaculture, and ordinary pond aquaculture) were in an inefficient state, with their GDE being 0.9884, 0.8746, and 0.8248, respectively. Green modes have higher GDE than traditional modes. In contrast, the production and culture areas of green modes were less than those of traditional modes because the profits of the same species in green modes were lower than those in traditional modes. The results of this study present an objective assessment of the GDE of marine fish culture in China and provide valuable insights for analyzing the mechanisms to improve the GDE of marine fish culture.

The male and female genomes of golden pompano (Trachinotus ovatus) provide insights into the sex chromosome evolution and rapid growth

IntroductionGolden pompano (Trachinotus ovatus) is economically significant important for offshore cage aquaculture in China and Southeast Asian countries. Lack of high-quality genomic data and accurate gene annotations greatly restricts its genetic breeding progress. ObjectivesTo decode the mechanisms of sex determination and rapid growth in golden pompano and facilitate the sex- and growth-aimed genetic breeding. MethodsGenome assemblies of male and female golden pompano were generated using Illumina, PacBio, BioNano, genetic maps and Hi-C sequencing data. Genomic comparisons, whole genome re-sequencing of 202 F1 individuals, QTL mapping and gonadal transcriptomes were used to analyze the sex determining region, sex chromosome evolution, SNP loci, and growth candidate genes. Zebrafish model was used to investigate the functions of growth candidate gene. ResultsFemale (644.45 Mb) and male (652.12 Mb) genomes of golden pompano were assembled and annotated at the chromosome level. Both genomes are highly conserved and no new or highly differentiated sex chromosomes occur. A 3.5 Mb sex determining region on LG15 was identified, where Hsd17b1, Micall2 and Lmx1a were putative candidates for sex determination. Three SNP loci significantly linked to growth were pinpointed, and a growth-linked gene gpsstr1 was identified by locus BSNP1369 (G → C, 17489695, Chr23). Loss of sstr1a (homologue of gpsstr1) in zebrafish caused growth retardation. ConclusionThis study provides insights into sex chromosome evolution, sex determination and rapid growth of golden pompano.

욕지도 외해가두리 양식장의 참다랑어(Thunnus orientalis) 양식 사업성 비교분석

This study aimed to analyze the feasibility of T. orientalis offshore aquaculture production performance in Yokjido located in Tongyeong, Korea. Based on the collected biological, costs and market price data, the results indicated that under the same conditions of analyzing economic feasibility. At the social discount rate of 4.5% applied to public corporations and quasi-governmental organizations, 2,000 caught and imported T. orientalis were sold at a survival rate of 60%, respectively, at an individual weight of 30 kg to KRW 40,000/kg, thereby the financial feasibility of T. orientalis offshore cage culture was analyzed. The net present value (NPV) of caught bluefin tuna was 1,858,952 thousand won, and the corresponding internal rate of return (IRR) was 17.6%. In the case of imported, the net present value (NPV) was -1,157,227 thousand won, and the corresponding internal rate of return (IRR) was -4.2%. As a result of estimating the net present value (NPV) and internal rate of return (IRR) using the cash flows (including depreciation) generated for 10 years in units of the business period (1year). For the caught juvenile, NPV showed a positive value and IRR exceeded the social discount rate of 4.5%. On the other hand, in the case of imported, NPV had a negative value and IRR was less than 4.5% of the social discount rate. Therefore, it was found that there is a business possibility to cultivate T. orientalis with juvenile caught at the offshore farm in Yokjido has business potential.

A Review of Unmanned System Technologies with Its Application to Aquaculture Farm Monitoring and Management

This paper aims to provide an overview of the capabilities of unmanned systems to monitor and manage aquaculture farms that support precision aquaculture using the Internet of Things. The locations of aquaculture farms are diverse, which is a big challenge on accessibility. For offshore fish cages, there is a difficulty and risk in the continuous monitoring considering the presence of waves, water currents, and other underwater environmental factors. Aquaculture farm management and surveillance operations require collecting data on water quality, water pollutants, water temperature, fish behavior, and current/wave velocity, which requires tremendous labor cost, and effort. Unmanned vehicle technologies provide greater efficiency and accuracy to execute these functions. They are even capable of cage detection and illegal fishing surveillance when equipped with sensors and other technologies. Additionally, to provide a more large-scale scope, this document explores the capacity of unmanned vehicles as a communication gateway to facilitate offshore cages equipped with robust, low-cost sensors capable of underwater and in-air wireless connectivity. The capabilities of existing commercial systems, the Internet of Things, and artificial intelligence combined with drones are also presented to provide a precise aquaculture framework.

Wave Analysis for Offshore Aquaculture Projects: A Case Study for the Eastern Mediterranean Sea

The investigation of wave climate is of primary concern for the successful implementation of offshore aquaculture systems as waves can cause significant loads on them. Up until now, site selection and design (or selection) of offshore cage system structures on extended sea areas do not seem to follow any specific guidelines. This paper presents a novel methodology for the identification of favorable sites for offshore aquaculture development in an extended sea area based on two important technical factors: (i) the detailed characterization of the wave climate, and (ii) the water depth. Long-term statistics of the significant wave height, peak wave period, and wave steepness are estimated on an annual and monthly temporal scale, along with variability measures. Extreme value analysis is applied to estimate the design values and associated return periods of the significant wave height; structures should be designed based on this data, to avoid partial or total failure. The Eastern Mediterranean Sea is selected as a case study, and long-term time series of wave spectral parameters from the ERA5 dataset are utilized. Based on the obtained results, the most favorable areas for offshore aquaculture installations have been identified.

Study on milky haemolymph diseases infection in wild and cultured of spiny lobster, Panulirus homarus in Indonesia

Milky Haemolymph Disease in Spiny Lobster (MHD-SL) is the most pathogenic diseases in spiny lobster (Panulirus homarus). Research on MHD-SL infection has not been undertaken in Indonesia. Therefore, present study aims to determine the infection of MHD-SL lobster. In 2016 a total of 240 lobsters for 30 each both from wild and cultured sample were collected from four locations (Candi Kusuma Bay of Bali Island, Gerupuk, Awang, and Telong-Elong Bays of Lombok Island) and in 2019, 50 lobster samples were collected for artificial infection study. While in January 2020, another 40 lobsters were collected from 2 different sites of culture (coastal and offshore cages) within Telong Elong Bay to determine infection of MHD-SL and for transmission study. The MHD-SL diseased was first check by clinical sign and confirmed by PCR-DNA molecular with specific primer of 254 bp. An experimental infection of MHD-SL was carried out by injection and cohabitation. The result showed that infected MHD-SL lobster shows inactive, loose appetite to eat, reddish and white colour of abdomen then moribund and all positive by PCR test. MHD-SL was found only in cultured lobster on the cages located at coastal water and no in the cages located at offshore within Telong-Elong Bay. In the experiment of artificial infection, either by injection or cohabitation, shows clinical sign of MHD-SL appeared at 8 days and all died after 14 days for both treatments. The present study approved that MHD-SL is pathogenic agent belonged to Rickettsia-like bacterium and infection occurred by horizontal transmission.

Storm damage risk assessment for offshore cage culture

This study establishes a practical methodology for storm damage risk assessment and zoning for offshore cage culture by superimposing the vulnerability theory onto hydrodynamic modeling. The peak significant wave height is statistically correlated to the normalized fatigue load criteria at specified loading cycles to classify the destruction duration and damage state during storm events. The yield damage of the flotation pipe under cyclical wave oscillations was identified as the major failure mechanism of the sea cage. The structural failure risk would significantly decrease to 4.5-m waves, which is much lower than the manufacturing standard due to cumulative damage in a relatively short operation time. The wave-circulation model was applied to hindcast 112 high-impact typhoon scenarios in the study area for the return period analysis of the storm wave field. The damage risk distribution of the cage culture was mapped across the landscape to increase storm strength according to the vulnerability classification. The effectiveness of island shielding was explicitly revealed, and the leeward side was overall less risky as the return period increased, with the safe area shrinking inshore. For extreme conditions over a 100-year return period, the shield performance of leeward bays varied significantly due to the shoreline profile differences. Some existing cage deployment locations are at-risk relative to the structural resistance capability, whereas other unrecognized areas might be suitable for cage culture. These findings imply the necessity of storm risk assessment before proactive prevention measures and deployment zoning. The methodology may also be adapted to storm risk predictions for other facilities in the coastal ocean.

Study on the Coexistence of Offshore Wind Farms and Cage Culture

In this study, a hydrodynamic model was used that includes the effects of wave–current interactions to simulate the wave and current patterns before and after offshore wind turbine installation in western Taiwan. By simulating the waves and currents after the offshore wind turbine was established, the waves and currents caused by the wind turbine were seen to have a limited range of influence, which is probably within an area about four to five times the size of the diameter (12–15 m) of the foundation structure. Overall, the analysis of the simulation results of the wave and current patterns after the offshore wind turbines were established shows that the underwater foundation only affected the local area near the pile structure. The wind farm (code E) of the research case can be equipped with about 720 cage cultures; if this is extended to other wind farms in the western sea area, it should be possible to produce economic-scale farming operations such as offshore wind power and fisheries. However, this study did not consider the future operation of the entire offshore wind farm. If the operation and maintenance of offshore wind farms are not affected, and if the consent of the developer is obtained, it should be possible to use this method to provide economically large-scale farming areas as a mutually beneficial method for offshore wind power generation and fisheries.

Suspended culture of Pinna rudis enhances survival and allows the development of a seasonal growth model for Mediterranean Pinnids

A two-year growth study of 80 Pinna rudis individuals was conducted in offshore cages in the western Mediterranean Sea. A Von Bertalanffy growth model was fitted to monthly measured data of 40 individuals (Group 1), whereas length-dry weight relationship was established with the other 40 individuals (Group 2). Oceanographic data were sampled bimonthly. The individuals showed the fastest growth reported for a bivalve (1.32 mm day−1). Temperature acted as the main factor controlling growth, which showed strong seasonality, but phytoplankton availability acted as a limiting factor during the warmest periods of year. These data will be useful to understand P. rudis ecology. Furthermore, the length-dry weight regression is proposed as a tool for captivity diet confection of the critically endangered species P. nobilis. Natural mortality was 0% during the study period.

Indoor Aquaria and Offshore Cages Bacterial Disease of Cultivated Giant Clam

Giant clam marine culture is commonly influenced by a wide variety of pathogenic bacteria including Vibrio species, resulting in high losses. The current study was organized to investigate the bacterial infections, in the Hurghada area, between the culture of Tridacna maxima and Tridacna gigas in indoor aquaria and offshore cages. Eighty samples of T. maxima and T. gigas in both indoor aquaria and offshore cages were collected for bacteriological analysis. Samples were taken from gills, gut, mantels, and gonads of Tridacna. The results showed reduced motion followed by loss of attractive color pattern with 25 % and 20 % mortality rate among indoor cultured T. maxima and T. gigas, respectively. About forty-six bacterial isolates were identified, using phenotypic and biochemical testing. Most of those isolates were Vibrio logei, V. harveyi, and unidentified Vibrio. The pathogenicity and virulence of V. logei seem high with a 30% mortality rate. The current study would provide useful information for better management of bacterial infections in T. maxima and T. gigas.

First evidence of fish nocardiosis in Mexico caused by Nocardia seriolae in farmed red drum (Sciaenops ocellatus, Linnaeus).

Between August and December 2013, the offshore cages of a commercial marine farm culturing red drum Sciaenops ocellatus in Campeche Bay Mexico were affected by an outbreak of an ulcerative granulomatous disease with up to 70% cumulative mortality. Thirty-one adults displaying open ulcers on the skin were submitted for diagnosis. At necropsy, multiple white-yellowish nodules (0.1-0.5cm in diameter) were present in all internal organs, where the kidney and the spleen were the most severely affected. Histopathology evinced typical systemic granulomatous formations. Gram and Ziehl-Neelsen stains on tissue imprints, bacterial swabs and tissue sections revealed Gram-positive, acid-fast, branching beaded long rod filamentous bacteria. Tissue samples resulted positive for nocardiosis with a Nocardia genus-specific nested PCR. Definite identification at the species level and taxonomic positioning of the fastidious pathogen were achieved through a specific Nocardia seriolae PCR and by sequencing the gyrB gene of pure isolates. After administration of antibiotics during fry production, a posterior follow-up monitoring (from 2014 to 2017) detected mild but recurrent outbreaks of the bacteria with no seasonality pattern. To the extent of our knowledge, this is the first report of piscine nocardiosis in Mexico and the first time this disease is detected in red drum.

First genomic prediction and genome-wide association for complex growth-related traits in Rock Bream (Oplegnathus fasciatus).

Rock Bream (Oplegnathus fasciatus) is an important aquaculture species for offshore cage aquaculture and fish stocking of marine ranching in East Asia. Genomic selection has the potential to expedite genetic gain for the key target traits of a breeding program, but has not yet been evaluated in Oplegnathus. The purposes of the present study were to explore the performance of genomic selection to improve breeding value accuracy through real data analyses using six statistical models and to carry out genome‐wide association studies (GWAS) to dissect the genetic architecture of economically vital growth‐related traits (body weight, total length, and body depth) in the O. fasciatus population. After quality control, genotypes for 16,162 SNPs were acquired for 455 fish. Heritability was estimated to be moderate for the three traits (0.38 for BW, 0.33 for TL, and 0.24 for BD), and results of GWAS indicated that the underlying genetic architecture was polygenic. Six statistic models (GBLUP, BayesA, BayesB, BayesC, Bayesian Ridge‐Regression, and Bayesian LASSO) showed similar performance for the predictability of genomic estimated breeding value (GEBV). The low SNP density (around 1 K selected SNP based on GWAS) is sufficient for accurate prediction on the breeding value for the three growth‐related traits in the current studied population, which will provide a good compromise between genotyping costs and predictability in such standard breeding populations advanced. These consequences illustrate that the employment of genomic selection in O. fasciatus breeding could provide advantages for the selection of breeding candidates to facilitate complex economic growth traits.

Comparison for ecological economic performance of Chinese sea perch (Lateolabrax Maculatus) under different aquaculture systems

Chinese sea perch (Lateolabrax Maculatus) is one of the main marine fish culture species in China, its green development has received increasing attention and its ecological economic study is rare. Based on field survey, this paper takes water pollution tax of China as conversion indicator for aquaculture eutrophication to simulate aquaculture waste fee for further analyzing the ecological impact of Chinese sea perch's aquaculture. For data analysis, data envelopment analysis model has been used. The comparison for Chinese sea perch's economic performance and ecological economic performance under its main aquaculture systems has been done. The results show that: 1. The simulated waste fee has no significant impact for the comparison. 2. Ranking for ecological economic performance's ecological economic, technical and scale efficiency is as follow: pond farming, offshore cage culture and cage culture. 3. Offshore cage culture is the only system presenting positive increase for ecological economic performance, which makes its aquaculture activity more sustainable than other systems. 4. The key point of green development is to maximize the ecological economic efficiency of main aquaculture systems. Thus, offshore cage culture is the most sustainable aquaculture system among China's current marine fish culture systems, and other systems need innovation for achieving the green development of China's aquaculture.

A case study on farmed European seabass and gilthead seabream in central Italy: The negligible parasitological risk of nematode larvae paves the way for the freezing derogation

Gilthead seabream and European seabass are among the most appreciated farmed fish species in the European Union. This case study analysed the self-control plan procedures adopted in an offshore cage farm in Central Italy to prevent anisakids infection, in the light of the Anisakis contamination pathways previously proposed for farmed Atlantic salmon (Salmo salar), and of the criteria recommended by the European Food Safety Authority. Moreover, the results of the visual parasitological examination conducted by the Food Business Operator, as part of the self-control plan, on 5% of the total specimens with commercial size (2016–2020 period) were also considered. Results show an extremely low to negligible risk for the introduction of ascaridoid larvae, confirming the absence of these parasites in farmed specimens of both species. However, few implementations to the self-control plan are suggested for obtaining the derogation to preventive freezing, as established by the European legislation. These include the parasitological examination of a statistically significant sample of the farmed specimens (commercial sizes) conducted by trained personnel, as well as of farmed specimens found dead or underdeveloped (runts) and of wild specimens of other species which may enter the cages. The proposed approach can be adapted by other farms by adjusting the sample size based on the production volume and risk categorization. The exemption from the preventive freezing would represent an additional market opportunity for Italian aquaculture plants.

Study on Detection Image Processing Method of Offshore Cage

The paper aims to test the integrity of offshore cages. In this paper, offshore robots are used to collect video images. Through preprocessing methods such as color space conversion and Retinex algorithm of fusion-oriented filtering, the color distortion of the image is improved and the edge information of the image is maintained, so that the collected cage image is better recognized and calculated by the computer. And the paper uses the Canny algorithm to accurately locate the edge of the image, so that the boundary information can be reflected in more detail. In this paper, the adaptive threshold segmentation algorithm combined with mathematical morphology processing method is used to segment the offshore cage image, and extract the skeleton of the decomposed image to realize the detection of the integrity of the offshore net. Finally, a ROV equipped with a camera was used to verify the proposed method in a wave-flow water tank, which confirmed the effectiveness of the method and optimized the integrity recognition and image processing of the cage.