Oyster Production Research Articles

Stark differences in spatial gradients of Eastern oyster (Crassostrea virginica) productivity in two Florida, USA, estuaries

The eastern oyster (Crassostrea virginica) is a foundation species in U.S. Atlantic and Gulf coast estuaries because of its numerous ecosystem services and importance to local fisheries. Concerns about the persistence and sustainable harvesting of oysters in the state of Florida is growing due to environmental factors (e.g., increased predation, salinity, and disease) and increased harvesting pressure. Thus, we need to understand which estuary locations are best suited for conservation or restoration efforts. Here, we use a combination of field experiments and modeling to assess the potential oyster productivity at sites throughout two estuaries at the same latitude but in different ocean basins: Apalachicola Bay (Gulf of Mexico coast) and the Guana Tolomato Matanzas National Estuarine Research Reserve (GTM, Atlantic coast). Our population model used the per-recruit approach from fisheries science, allowing us to combine field data on growth and mortality to estimate productivity (measured as lifetime spawning output) in an elegant way, without requiring assumptions about unknown larval supply processes. Subtidal Apalachicola Bay oysters exhibit an expected pattern, with greater productivity in the inner estuary nearer the river mouth and predation reducing productivity in the seaward direction. In contrast, intertidal GTM oysters do not exhibit strong spatial gradients, with little effect of predators and slightly higher productivity near the river mouth; intertidal oysters in Apalachicola exhibited similar productivity and lack of predator effect. We attribute these differences in oyster productivity to differences in tidal exposure, the predator community, and hydrology of oyster reefs at the two study sites. Thus, we would give diverging recommendations for spatial prioritization of restoration and conservation efforts. Additionally, these results lead us to caution against generalized statements about spatial patterns of oyster productivity within estuaries without consideration of the predation context.

Strategies to improve the postharvest management of flat oyster (Ostrea edulis) from aquaculture using the short-term storage and package in an innovative closed-circuit system.

This study aimed to improve postharvest management of flat oysters reared in a longline system in the mid Adriatic Sea, using short-term storage and package in an innovative closed-circuit system. For the trial, 870 oysters were employed, divided into three experimental groups (A, B, and C), N=270 oysters each group, whereas the remaining 60 oysters were used for the 2 controls. Each group differed in relation to the time spent in the depuration tank and the time of packaging: group A was packed and immediately transferred to the cell; group B was depurated in a tank for 48h, then packed and transferred to the cell; group C was depurated in a tank for 48h and then packed, depurated for another 24h and transferred to a cell. Samples of each group were sampled at different times of permanence in cell (t0) up until 12 days (t12) for biomorphometric, sensorial, nutritional, and microbiological analysis. Although the nutritional and sensorial quality of the oysters was more pronounced in group A, B and C groups also showed good results. In these two groups, thanks to the use of the modern water recirculation system the quality and safety of oysters was improved by reducing the presence of sludge and eliminating fecal contaminants completely than A treatment and seawater control. These results were also confirmed by the tank control, where a more extended depuration period positively influenced the same parameters emphasizing the importance of the adequate depuration processes in oyster production.

Deep Learning-Based Oyster Packaging System

With the deepening understanding of the nutritional value of oysters by consumers, oysters as high-quality seafood are gradually entering the market. Raw edible oyster production lines mainly rely on manual sorting and packaging, which hinders the improvement of oyster packaging efficiency and quality, and it is easy to cause secondary oyster pollution and cross-contamination, which results in the waste of oysters. To enhance the production efficiency, technical level, and hygiene safety of the raw aquatic products production line, this study proposes and constructs a deep learning-based oyster packaging system. The system achieves intelligence and automation of the oyster packaging production line by integrating the deep learning algorithm, machine vision technology, and mechanical arm control technology. The oyster visual perception model is established by deep learning object detection techniques to realize fast and real-time detection of oysters. Using a simple online real-time tracking (SORT) algorithm, the grasping position of the oyster can be predicted, which enables dynamic grasping. Utilizing mechanical arm control technology, an automatic oyster packaging production line was designed and constructed to realize the automated grasping and packaging of raw edible oysters, which improves the efficiency and quality of oyster packaging. System tests showed that the absolute error in oyster pose estimation was less than 7 mm, which allowed the mechanical claw to consistently grasp and transport oysters. The static grasping and packing of a single oyster took about 7.8 s, and the success rate of grasping was 94.44%. The success rate of grasping under different transportation speeds was above 68%.

The Probiotic Bacillus hwajinpoensis Colonizes the Digestive System of Crassostrea gigas Larvae and Protects Them from Vibrio alginolyticus Infection.

The Pacific oyster Crassostrea gigas is one of the most important cultured marine species around the world. Production of Pacific oysters in China has depended primarily on hatchery produced seeds since 2016, with the successful introduction and development of triploid oysters. However, the seed supply of Pacific oysters is threatened by recurring mass mortality events in recent years. Vibriosis is the most commonly encountered disease associated with intensive oyster culture in hatcheries and nurseries. Vibrio alginolyticus and Bacillus hwajinpoensis were the two strains with pathogenic and probiotic effects, respectively, identified during the Pacific oyster larvae production. To monitor their colonization process in Pacific oyster larvae, green fluorescent protein (GFP) and red fluorescent protein (RFP) were labeled to the pathogenic V. alginolyticus and the probiotic B. hwajinpoensis stain, respectively. The pathogenic and probiotic effects of the two strains during the colonization process were then assessed. Stabile expression of GFP and RFP were observed in corresponding stains, and the capabilities of growth, biofilm formation and in vitro adhesion of GFP- and RFP- tagged stains were not significantly different from those of the wild-type strains. Usage of probiotics of 105 CFU/mL significantly inhibited the growth of pathogenic V. alginolyticus and reduced the mortality of D-sharped larvae. Both the pathogenic and probiotic strains employed a similar route to enter and colonize the oyster larvae, which indicates that competing with pathogens for binding and spreading sites were one of the mechanisms of B. hwajinpoensis to provide the probiotic effects to oyster larvae. In summary, employment of fluorescence-tagged pathogenic and probiotic strains simultaneously provides us with an excellent bioassay model to investigate the potential mechanisms of probiotics.

Relative importance of phenotypic plasticity and carryover effects in response to small salinity shifts during oyster aquaculture production

Variability of water conditions in coastal environments could affect oyster aquaculture production through three main environmental-tolerance mechanisms: phenotypic plasticity, within-generation carryover effects, and selective mortality. Aquaculture production of eastern oyster, Crassostrea virginica, larvae occurs on weekly timescales in Virginia, with variations in salinity experienced by subsequent larval cohorts. The present study examined the relative importance of within-generation carryover effects – phenotypic changes during a previous life stage that impact a later stage – and phenotypic plasticity in shaping the performance of juvenile oysters after an experience of small differences in salinity (< 2 salinity units) during the larval stage. Genetic diversity was also assessed to rule out large shifts in allele frequencies, or loss of diversity, that would suggest observed effects were the result of selective mortality rather than carryover effects or phenotypic plasticity. Larval oysters were reared through settlement and metamorphosis under two salinities (thirteen and fifteen) that represent small differences between consecutive spawns in a hatchery. Juveniles were then raised in situ in two Virginia tributaries of the lower Chesapeake Bay, the York and Rappahannock rivers. Oyster production occurs within these two tributaries under distinct salinity conditions, with the Rappahannock tending to be of lower salinity. Metrics of survival, growth, oxidative stress, and condition index were compared to assess phenotypic plasticity and within-generation carryover effects. Juvenile oyster survival and physiology correlated with in situ environmental conditions rather than previous larval salinity experience. Specifically, juvenile oysters raised in the Rappahannock River had greater survival (13%), shell length (14%), condition index (38%), and dry tissue weight (78%) than those raised in the York River, regardless of larval salinity. Rappahannock River oysters also had 20% lower total antioxidant capacity than York River oysters. Genetic diversity remained high with no large shifts in allelic frequencies that would suggest non-random loss of alleles attributable to selection. Our results suggest that small salinity differences experienced in shellfish hatcheries 48 h after fertilization likely do not impact juvenile oyster performance during grow-out; rather, phenotypic plasticity likely underpins juvenile oyster performance during the transition from hatchery to farms. The importance of phenotypic plasticity presents another reason why farm site selection is critical to the performance and success of aquaculture product. Future studies are needed to further identify whether larval responses to salinity conditions are dependent on additional environmentally relevant conditions like temperature or the timing of exposure post-fertilization to better understand the relative importance of phenotypic plasticity, within-generation carryover effects, and selective mortality within oyster aquaculture.

Comparative Description and Analysis of Oyster Aquaculture in Selected Atlantic Regions: Production, Market Dynamics, and Consumption Patterns

In the face of an increasing world population and a subsequent need for an increase in sustainable and healthy food production, low trophic species, such as oysters, emerge as a promising alternative. However, regional variations in oyster production techniques, market dynamics, and consumption patterns create challenges for both the global and local industry’s growth. In this study, a descriptive qualitative analysis of oyster markets across seven Atlantic regions was carried out. The Pacific oyster (Crassostrea gigas) was found to be farmed in most Atlantic regions except the US but is classified as invasive in Sweden and potentially invasive in South Africa. Other farmed and/or harvested species include native species (C. gasar and C. rhizophorae) in Brazil, the American cupped oyster (C. virginica) in the US, and the European flat oyster (Ostrea edulis) in France, Sweden, and the US. In Irish farms, Pacific oysters are primarily for export to European markets. The marine aquaculture sectors of Sweden, South Africa, and Namibia, as well as Brazil’s farming for C. gasar, were found to be underdeveloped. This study also observed a variation in licensing, property rights, and regulatory frameworks. Financial challenges for small businesses, ecological implications of seed production techniques, biosecurity risks, and public health considerations are emphasized as critical areas for attention. This study offers valuable insights into the selected markets and can serve as a useful resource for policymakers, aquaculture practitioners, and stakeholders in optimizing global shellfish industry strategies.

Efficient preparation of oyster hydrolysate with aroma and umami coexistence derived from ultrasonic pretreatment assisted enzymatic hydrolysis

In the study, an efficient protease Neutrase®-Flavourzyme® (NF) was screened to prepare the umami-aroma flavor oyster hydrolysate. The effect of protease and ultrasonic pretreatment (UP) assisted by the optimal protease on the flavor substances was investigated. The results demonstrated that the optimal UP-NF (450 W) showed a higher amino acid nitrogen content of 0.34 g/100 mL compared to the NF, and 19 major aroma compounds including octanal, decanal, nonanal, benzaldehyde, 2-undecanone, and 1-octen-3-ol were obtained. Additionally, the free amino acid and fatty acid spectrum indicated that the formation of flavor compounds was primarily due to the oxidation of linoleic and linolenic acids and the degradation of amino acids. Furthermore, taste analysis proved that increased umami and saltiness resulted from the accelerated release of Glu, Asp and 5′-IMP. Overall, UP-NF proved to be an effective method for producing umami-aroma flavor, facilitating further processing of oyster products for the application.

Optimization of plastic polymers for shellfish aquaculture infrastructures: in situ antifouling performance assessment

Biofouling poses a significant challenge to bivalve aquaculture affecting both the target culture and/or the immersed infrastructure. In suspended bivalve cultures (e.g., oysters and scallops), biofouling accumulation leads to additional labor demands and increased costs for the maintenance of underwater structures. Given that the inherent properties of materials used in farming infrastructure influence the formation of fouling communities, evaluating how these materials perform under diverse environmental conditions can help the industry select the most effective materials for preventing or minimizing biofouling growth. This study evaluates the impact of aquaculture material and environmental conditions on biofouling, focusing on two commonly used plastic polymers in marine aquaculture: polyamide (PA) and high-density polyethylene (PE). Both untreated and color-additive treated polymers were tested for their response to fouling development. Performance was gauged by total fouling wet weight and the extent of fouling-induced mesh occlusion. Experimental panels were deployed for 4 months (from May to September 2021) in estuarine (oyster farm) and marine (port) environments on the northern coast of Portugal. The marine sites exhibited greater fouling species diversity, while higher biofouling loads were found in the subtidal estuarine area. Within 3 months, complete mesh occlusion occurred mainly due to colonial hydroids (Obelia dichotoma) in the subtidal site. In contrast, panels deployed in the intertidal estuarine area had lower fouling biomass and mesh occlusion. Notably, significant differences between polymer types and treatments were only evident in the estuarine intertidal area, with long air exposure during low tide. White panels outperformed orange ones in fouling biomass, and PA panels outperformed PE panels in mesh occlusion. These differences were attributed to the settlement and growth of the acorn barnacle Austrominius modestus, known to favor dark-colored and less hydrophilic surfaces. Considering that oyster production in intertidal areas is one of the most important aquaculture industries globally, these findings offer valuable insights into material selection and characteristics that can mitigate fouling loads and their associated impacts. These results could also be relevant for other forms of bivalve aquaculture where infrastructure-related biofouling presents a challenge.

Genetic improvement of oysters: Current status, challenges, and prospects

AbstractOysters are one of the most commercially important shellfish species and have been cultured for thousands of years. Oyster aquaculture supports the major aquaculture industries in many countries. Over the last few decades, the oyster breeding and aquaculture industries have developed rapidly to meet the continually growing demand. Many researchers have made significant efforts toward the genetic improvement of commercially important traits in oysters. Some strains with fast‐growing, disease‐resistant, and stable shell‐colours have been developed through selective breeding. Some hybrid varieties have been developed by crossing different geographical populations or cultivated strains. Several hybrids exhibit considerable genetic variation and improved productive performance. Additionally, polyploid induction technologies have been applied in the oyster aquaculture industry, which provides a useful tool for performance improvement and genetic containment of cultured stocks. At present, the development of molecular breeding also provides a great opportunity for oyster genetic improvement. These advances in oyster breeding have improved the quality of oysters, brought great economic benefits, and been conducive to the sustainability of oyster production. Nonetheless, there are still some limitations and obstacles in oyster breeding, such as infectious diseases, summer mortality, conservation of germplasm resources, environmental contamination, and climate change. The present review provides an overview of the current status, challenges, and prospects in oyster breeding.

Evaluating the influence of cage motion on the growth and shell characteristics of oysters (Crassostrea virginica) among several gear types

An influx of new oyster culture gear provides growers with an expanded ability to grow oysters throughout the water column. Each gear type is exposed to a different regime of physical forces, which is thought to affect oyster production differently; however, there is a poor understanding of the physical conditions inside cages and how they influence the production rate and quality of oysters. A greater understanding of the fundamental relationships between cage motion, oyster growth, and shell shape could help to improve the efficiency of off-bottom oyster production. Such understanding is critical for tailoring gear selection and tuning gear performance to suit grower needs. To address this void, cage motion, internal oyster movement, and oyster growth among three common cultivation methods (Virginia-style bottom cages, Seapa® long-line baskets, and floating cages) were monitored over a single growing season to clarify the role of the physical environment on oyster performance (shell and tissue growth). The averages and variance in motion among each cultivation method were noticeably different, which resulted in significant differences in the growth rate and quality of oysters they produced. Movement of the floating cages and long-line baskets could largely be explained by wind waves generated from a single direction in the field (r2 = 0.49, r2 = 0.36, respectively), while bottom cage movement was far less affected by wind waves. The changes in physical conditions inside each cultivation method demonstrated a trade-off between shell growth rate (a metric of time to market) and shell and meat quality (representative of crop value). These results can help inform growers wishing to strategically adopt cultivation methods that are most aligned with their production goals.

Nursery upweller type has minimal impact on subsequent grow-out of Eastern oysters (Crassostrea virginica)

Demand for oysters in the premium half-shell market drives the need for research to optimize and improve oyster aquaculture production methods. After setting, oysters are typically maintained in nursery upwellers that provide nutrients and oxygen while removing waste. They remain in the nursery until they are large enough to be deployed in aquaculture gear. Land-based upweller systems include silo and bottle upwellers, with bottles requiring less space and maintenance. However, it is unknown if upweller type influences oyster growth, shape, or survival after field deployment. This study reared Eastern oysters, Crassostrea virginica, to 2 mm in silo or bottle upwellers and deployed them to floating bags for a six-week grow-out period. Oysters were sampled initially, then size graded, counted, and redeployed every two weeks. Changes in growth parameters, quality ratios, survival, and hinge backbend deformity prevalence were determined after six weeks. Initially, silo-reared oysters were larger than those reared in bottles, likely due to the need for flow rate optimization and/or the tumbling action that breaks the fragile growing edge of the shell. Despite these initial differences, there were minimal size differences between upweller types after six weeks of growth in the field. There were no significant differences in survival, hinge backbend abnormality prevalence, or size class distribution between upweller types. These results indicate that upweller choice has minimal impact on the grow-out phase of oyster production and both systems are acceptable for Eastern oyster production in the northern Gulf of Mexico.

Hatchery seed production of flat oysters from the Mar Menor lagoon

The Mar Menor lagoon (SE Spain) suffers a severe eutrophication process aggravated since the collapse of the lagoon in 2016. Together with it, the populations of the flat oyster Ostrea edulis have been decimated in the lagoon, but also in the European seas, where the species and the habitats provided by it have mainly disappeared. The Mar Menor Oyster Initiative’s main objectives are gaining knowledge on the nutrient extraction capability of the Mar Menor flat oyster and developing the required tools for restoration and bioextraction actions. The project RemediOS, within the framework of the Mar Menor Oyster Initiative, aims to obtain flat oyster seed using the decimated local broodstock to provide the initiative with an oyster population to work with. The present work describes the results of the first attempt of Mar Menor local broodstock reproduction in captivity. Larvae produced in the hatchery accounted for 57.5 million, of which 11.8 million were cultured and 0.68 million survived to settlement and metamorphosis.

Cooperation and cheating orchestrate Vibrio assemblages and polymicrobial synergy in oysters infected with OsHV-1 virus.

Polymicrobial infections threaten the health of humans and animals but remain understudied in natural systems. We recently described the Pacific Oyster Mortality Syndrome (POMS), a polymicrobial disease affecting oyster production worldwide. In the French Atlantic coast, the disease involves coinfection with ostreid herpesvirus 1 (OsHV-1) and virulent Vibrio. However, it is unknown whether consistent Vibrio populations are associated with POMS in different regions, how Vibrio contribute to POMS, and how they interact with OsHV-1 during pathogenesis. By connecting field-based approaches in a Mediterranean ecosystem, laboratory infection assays and functional genomics, we uncovered a web of interdependencies that shape the structure and function of the POMS pathobiota. We show that Vibrio harveyi and Vibrio rotiferianus are predominant in OsHV-1-diseased oysters and that OsHV-1 drives the partition of the Vibrio community observed in the field. However only V. harveyi synergizes with OsHV-1 by promoting mutual growth and accelerating oyster death. V. harveyi shows high-virulence potential and dampens oyster cellular defenses through a type 3 secretion system, making oysters a more favorable niche for microbe colonization. In addition, V. harveyi produces a key siderophore called vibrioferrin. This important resource promotes the growth of V. rotiferianus, which cooccurs with V. harveyi in diseased oysters, and behaves as a cheater by benefiting from V. harveyi metabolite sharing. Our data show that cooperative behaviors contribute to synergy between bacterial and viral coinfecting partners. Additional cheating behaviors further shape the polymicrobial consortium. Controlling cooperative behaviors or countering their effects opens avenues for mitigating polymicrobial diseases.

Motivators and impediments to mushroom commercialisation in Ghana: Implication for policymakers, development partners and extension agents

Waste (organic waste) management is a major challenge for urban and peri-urban areas all over the world. This is because landfilling raises greenhouse gas emissions, whereas indiscriminate refuse dumping wastes valuable nutrients and energy that are still present in the refuse. Fungi, such as mushrooms, have the unique ability to decompose and transform obstinate organic substances into protein. The government, private sector, and foreign development partners in Ghana's Greater Accra region have invested in mushroom (oyster) production to boost commercialization for economic development. However, commercialization remains low, and significant income gains from mushroom commercialization have yet to be realised. Psychosocial factors are imperative for agricultural commercialization because they create a thriving environment and incentive for agricultural commercialization in general, and mushroom commercialization in specific. To determine the motivations and impediments to mushroom commercialization, we used a questionnaire to survey 153 oyster mushroom producers censused from the Ga East and the Adentan municipalities in the Greater Accra region. The data was analyzed using Principal Component Analysis (PCA), means and standard deviations. Our results showed three [3] motivators: social awareness, economic value, and market incentives, and three [3] impediments: institutional and personal weakness, market uncertainty, and value chain challenges. The major motivators to mushroom commercialization are social awareness (M = 3.94) and economic value (M = 3.93) whereas the major impediments comprised market uncertainty (M = 3.59) and institutional and personal weaknesses (M = 3.29). We recommend that policy effort to create enabling institutional environment and social awareness of mushroom coupled with development partners' and extension agents' effort to train farmers on mushroom production management are key to enhancing commercial mushroom production in Ghana.NB: M=Mean

Factors that facilitate or limit the development of bivalve mollusk aquaculture in BCS, Mexico: The small-scale producers’ perspective

Aquaculture is the activity with the highest economic growth in the fishing sector worldwide. This activity in Baja California Sur (BCS) Mexico is at a key moment due recent upturn in production and the number of operating organizations; regarding bivalve mollusks culture (the livelihood of hundreds of families), but they are unable to stabilize their production. The purpose of this research was to determine the factors that limit/favor the development of the activity, in order to propose strategic actions to improve the situation. For this, through a survey, a political, economic, social and technological, ecological, and legal analysis (PESTEL) were integrated. Among the results stands out that 88% of the companies started activity less than a decade ago, with a higher rate of company creation in the last four years. The producer’s profile shows that they come mainly from fishing and agricultural activities, and two-thirds only have primary or secondary education. As a relevant weakness, only 22% of companies have social security for workers and their families. Environmental conditions, climate, water quality, and high product consumption stand out as favorable aspects. Among the limitations are the shortage of seeds, deficient infrastructure, marketing problems, and lack of financing programs. Within the political factors, producers demand the ordering of the sector. We conclude the need to improve government support programs, seed production, innovation process, productive and commercial articulation, crop diversification, and strengthening of the BCS oyster product network.

Vibrio aestuarianus clade A and clade B isolates are associated with Pacific oyster (Magallana gigas) disease outbreaks across Ireland.

Bacteria from the family Vibrionaceae have been implicated in mass mortalities of farmed Pacific oysters (Magallana gigas) in multiple countries, leading to substantial impairment of growth in the sector. In Ireland there has been concern that Vibrio have been involved in serious summer outbreaks. There is evidence that Vibrio aestuarianus is increasingly becoming the main pathogen of concern for the Pacific oyster industry in Ireland. While bacteria belonging to the Vibrio splendidus clade are also detected frequently in mortality episodes, their role in the outbreaks of summer mortality is not well understood. To identify and characterize strains involved in these outbreaks, 43 Vibrio isolates were recovered from Pacific oyster summer mass mortality episodes in Ireland from 2008 to 2015 and these were whole-genome sequenced. Among these, 25 were found to be V. aestuarianus (implicated in disease) and 18 were members of the V. splendidus species complex (role in disease undetermined). Two distinct clades of V. aestuarianus - clade A and clade B - were found that had previously been described as circulating within French oyster culture. The high degree of similarity between the Irish and French V. aestuarianus isolates points to translocation of the pathogen between Europe's two major oyster-producing countries, probably via trade in spat and other age classes. V. splendidus isolates were more diverse, but the data reveal a single clone of this species that has spread across oyster farms in Ireland. This underscores that Vibrio could be transmitted readily across oyster farms. The presence of V. aestuarianus clades A and B in not only France but also Ireland adds weight to growing concern that this pathogen is spreading and impacting Pacific oyster production within Europe.

Ostreid herpesvirus-1 microvariant surveillance in Pacific oysters (Magallana gigas, Thunberg, 1793) in Australia in 2011.

To demonstrate that OsHV-1 microvariant was limited to the known infected areas in New South Wales at the time of the survey in 2011. A 2-stage survey to demonstrate probability of infection at 2% design prevalence within oyster growing regions and to detect at least one infected region (4% design prevalence) with 95% confidence. Magallana gigas in nominated oyster growing regions in New South Wales, South Australia and Tasmania as approved by the Aquatic Consultative Committee on Emergency Animal Diseases and documented in a national surveillance plan. Field sampling for active surveillance and laboratory selection of appropriate tissues using methods to minimize potential for cross contamination. Published methods for qPCR and conventional PCR for OsHV-1 microvariant. Stochastic analysis of survey results to demonstrate probability of detection in the areas tested. OsHV-1 microvariant was not detected in a total 4121 samples according to the case definition developed for the survey. However, in NSW a screening qPCR for OsHV-1 detected 13 samples that reacted. These samples were negative at 2 laboratories in the qPCR and conventional PCR assays used in the case definition for the survey. We concluded that oyster production areas of Australia outside the infected area in NSW met the criteria for self-declaration of freedom at the time of the survey in 2011. This activity illustrated achievements in surveillance for an emerging emergency animal pathogen where epidemiological and test validation data were limited, but where data was required to inform the emergency disease response. It also illustrated the challenges faced by investigators in interpreting surveillance results using tests with limited validation. It was guided by and has informed improvements in surveillance and emergency disease preparedness.

Evaluation of green development in mariculture: The case of Chinese oyster aquaculture

Green development, which is to achieve economic growth and environmental improvement under the principle of harmony between people and nature, has become the mainstream of the world economy, and green development assessment of the industry is becoming increasingly urgent to achieve sustainable development goals. Combining the concept of green development and the characteristics of the mariculture industry, this study establishes a mariculture evaluation system of “yield & area + green economy + green progress”. Firstly, yield and area data are analyzed separately to reflect the green production of mariculture. Secondly, the evaluation index assesses the green growth of the industry in terms of green economy and green progress, the indices are constructed using the calculated relative indicators, weighted using the average of entropy and CRITIC, and the scores are converted into percentages using the efficacy coefficient method. Thirdly, apply the obstacle degree model to analyze the impact of each indicator, so as to identify the key factors affecting the score, and put forward targeted suggestions for improvement. Then, the evaluation system is applied to compare the green development levels of oyster aquaculture in six major regions in China. The results show that the trend of oyster aquaculture areas in China from 2011 to 2020 is largely influenced by local government policies, and the increase in yield has a positive effect in reducing carbon dioxide concentration and purifying seawater quality, but the disposal of waste by-products has become a serious problem for the development of the industry. Fujian has the highest overall evaluation score, benefiting from the largest domestic market share, while other regions have different strengths in terms of aquaculture technology promotion, yield growth, or oyster production levels. The factors that hinder the green development of each region vary, including low economic income, excessive area growth, and industrial inattention. In a word, Chinese oyster aquaculture needs to pay special attention to the problem of high production and low efficiency brought about by rapid expansion.

Application of multi-omics combined with bioinformatics techniques to assess salinity stress response and tolerance mechanisms of Pacific oyster (Crassostrea gigas) during depuration.

Depuration is a vital stage to ensure the safety of oyster consumption, and salinity had a great impact on the environmental adaptability of oysters, but the underlying molecular mechanism was poorly understood during depuration stage. Here, Crassostrea gigas was depurated for 72h at different salinity (26, 29, 32, 35, 38g/L, corresponding to ±20%, ±10% salinity fluctuation away from oyster's production area) and then analyzed by using transcriptome, proteome, and metabolome combined with bioinformatics techniques. The transcriptome showed that the salinity stress led to 3185 differentially expressed genes and mainly enriched in amino acid metabolism, carbohydrate metabolism, lipid metabolism, etc. A total of 464 differentially expressed proteins were screened by the proteome, and the number of up-regulated expression proteins was less than the down-regulated, indicating that the salinity stress would affect the regulation of metabolism and immunity in oysters. 248 metabolites significantly changed in response to depuration salinity stress in oysters, including phosphate organic acids and their derivatives, lipids, etc. The results of integrated omics analysis indicated that the depuration salinity stress induced abnormal metabolism of the citrate cycle (TCA cycle), lipid metabolism, glycolysis, nucleotide metabolism, ribosome, ATP-binding cassette (ABC) transport pathway, etc. By contrast with Pro-depuration, more radical responses were observed in the S38 group. Based on the results, we suggested that the 10% salinity fluctuation was suitable for oyster depuration and the combination of multi-omics analysis could provide a new perspective for the analysis of the mechanism changes.

Transcriptome profiling explores the immune defence mechanism of triploid Pacific oyster (Crassostrea gigas) blood against Vibrio alginolyticus based on protein interaction networks.

Triploid oysters have provided the oyster industry with many benefits, such as fast growth rates, meat quality improvement, and increased oyster production and economic benefits, since the first report on triploid oysters was published. The development of polyploid technology has remarkably increased the output of triploid oysters to meet the increasing demand of consumers for Crassostrea gigas in the past decades. At present, research on triploid oyster has mainly focused on breeding and growth, but studies on the immunity of triploid oysters are limited. According to recent reports, Vibrio alginolyticus is a highly virulent strain that can cause disease and death in shellfish, shrimp, as well as serious economic losses. V. alginolyticus may be a reason why oysters die during summer. Therefore, using V. alginolyticus to explore the resistance and immune defense mechanisms of triploid oysters against pathogens presents practical significance. Transcriptome analysis of gene expression was performed in triploid C. gigas at 12 and 48h after infection with V. alginolyticus, and the respective 2257 and 191 differentially expressed genes (DEGs) were identified. The results of GO and KEGG enrichment analyses showed that multiple significantly enriched GO terms and KEGG signaling pathways are associated with immunity. A protein-protein interaction network was constructed to investigate the interaction relationship of immune-related genes. Finally, we verified the expression situation of 16 key genes using quantitative RT-PCR. This study is the first to use the PPI network in exploring the immune defense mechanism of triploid C. gigas blood to fill the gap in the immune mechanism of triploid oysters and other mollusks, and provide valuable reference for future triploid farming and pathogen prevention and control.