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Abstract: Five potential relaxant chemicals were evaluated: 2-phenoxyethanol, menthol crystals, benzocaine, MS-222, and magnesium chloride to induce relaxation in the queen conch for cultured pearl production. S. gigas were exposed to each chemical and were observed continuously for 30 min. Conch were placed on the bottom of the container with the aperture facing upwards (i.e., in an inverted position). When conch returned to their ‘normal’ position, they were turned facing upwards again. This process continued until conch were unable to return to their normal position. Only 30 g L−1 magnesium chloride induced adequate relaxation in S. gigas to attempt pearl seeding. Conch exposed to all other treatments, except 0.25 g L−1 menthol, showed a strong ‘kicking’ (escape) reaction during the initial 2 min to 7 min of exposure. After such reaction, conch retracted into their shells and within the 30 min exposure period they showed no signs of relaxation. Conch exposed to 0.25 g L−1 menthol did not attempt to right but slowly retracted into their shells and did not show signs of relaxation. Conch can be relaxed in 20 min with magnesium chloride. They showed an extended mantle, a relaxed foot and a slow response to physical manipulation. [Copyright &y& Elsevier]

As an innovative approach to fisheries, marine ranching is subtly transforming the development patterns of coastal cities through the enhancement of fisheries, the professional transition of fishermen, and the restoration of the marine environment. Utilizing the entropy method and the staggered difference-in-differences (DID) method, this paper calculated the high-quality development index (HQDI) of 53 coastal cities from 2010 to 2021 and assessed the influence degree of marine ranching on coastal cities' HQDI. The key findings were as follows. Firstly, marine ranching generally improved the HQDI of coastal cities. Coastal cities with national marine ranching demonstration zones achieved an average increase of approximately 0.83 % in their HQDI compared to those without. Secondly, through the effect of carbon emission reduction, marine ranching contributed to an average increase of approximately 0.84 % in the HQDI. However, the green technology innovation and industrial structure upgrading effects have yet to materialize. Thirdly, this impact varied among coastal cities. When the number of marine ranching exceeded three, the average increase of HQDI was approximately 1.82 %. This effect was pronounced in higher-tier cities, with first-tier cities experiencing an average increase of 1.26 %, second-tier cities an average increase of 1.19 %, and third-tier cities an average increase of 2.18 %. Furthermore, this effect was significant in northern coastal cities, where the average increase was approximately 0.98 %. In coastal cities with low levels of manpower and material resources, this effect was also pronounced, with the HQDI increasing by an average of about 1.01 % and 0.98 %, respectively. Lastly, the spatial econometric analysis revealed a positive spatial spillover effect. This paper evaluated the effectiveness of China's recent marine ranching construction, providing a theoretical and empirical foundation for authorities to formulate targeted policies and measures. • The impact of marine ranching on high-quality development of coastal cities is examined. • Economic and societal aspects of aquaculture are figured out. • The carbon reduction effect of aquaculture is found out. • Entropy method and a staggered difference-in-differences model are used. • The micro data of 53 coastal cities are collected. [ABSTRACT FROM AUTHOR]

Trace elements are essential nutrients for aquatic organisms. Aquatic species rely primarily on external sources (diet and the environment) for trace mineral nutrition. Trace element bioavailability differs among species and is influenced by the forms of minerals (organic or inorganic) and environmental factors. Rotifers that belong to the Brachionus genus play a significant role in aquaculture operations (by serving as live feed source for marine larval rearing) and are also important in ecological studies with regard to aquatic ecosystems. Rotifers engage in cyclical parthenogenesis, enabling rapid population expansion through asexual reproduction and the formation of resting eggs via sexual reproduction. The generation of resting egg facilitates long-term preservation and enables a consistent supply of rotifers. Rotifers are often subjected to trace element conditions through indirect trophic transfer or direct exposure in rearing systems or fields. The nutritional and toxicological effects of essential trace elements, such as iron, zinc, selenium, and copper in rotifers have been studied. While we identified species-specific modifications in reproductive patterns and metabolic activities, such as inhibited or enhanced sexual reproduction in different rotifers, with distinct responses in neutral lipid accumulation in reproductive organs and oxidative defenses within the Brachionus plicatilis species complex under iron and zinc exposure. Accordingly, we hypothesized that specific trace elements function as nutrients for growth and essential metabolisms, while also controlling the transition of rotifer reproductive patterns. To strengthen our understanding, this paper presented a systematic literature review on the effects of various essential trace elements, especially iron, zinc, selenium, and copper on the reproduction of rotifers. We elucidated the mechanisms from multiple perspectives, including behavior, biochemical, and genetic. This review also discussed aspects of their influence on phytoplankton–zooplankton–larval interactions, given the importance of trace elements in the aquatic food web. Finally, we outlined the regulatory effects of trace elements on intra- and interspecific responses from individual and population ecological viewpoints, and the ecophysiological significance of interactions with other elements and environmental factors. Understanding the interactions of rotifers with trace elements and the mechanisms underlying species-specific responses provides valuable insights into rotifer culture management and contributes to improved aquaculture practices. [Display omitted] • Trace elements may control the transition of reproductive patterns in rotifers. • Trace elements affect rotifer behavior, energy, and antioxidant metabolism. • Responses to trace elements reflect the interactions with environmental factors. • Trace element exposure has a long-term effect on aquatic ecosystem homeostasis. [ABSTRACT FROM AUTHOR]

Energy and imported trout egg subsidies hold a pivotal role for Iranian trout farms. They aim to decrease production costs, yet their impact on the profit efficiency of farms remains dubious. The first objective of this paper is to assess how the current subsidy scheme affects the profit efficiency of hatchery and propagation trout farms in Mazandaran, Iran. We examine several subsidy reform scenarios to enhance profit efficiency as a second objective. Standard profit efficiency (SPE) is used to acquire the efficiency of the trout farms using data envelopment analysis. Results show that the majority of farms are inefficient and highly dependent on subsidies. Comparing farms with high efficiency against those with low efficiency as a third aim of research highlights the importance of farms holding a propagation license, engaging in vertical integration, achieving adult trout production surpassing 81 t, and maintaining a fish total feed consumption to trout production ratio below 0.74. Findings from reformation scenarios reveal 1) redirecting the current subsidy towards purchasing the extruder machines for fish feed production, 2) transferring funds to subsidize electricity based on the farm's electricity consumption, and 3) opting for the production of genetically modified eggs gives higher SPE. Reformation can also reduce the burden on public funds and dependency on importation. • Hatchery and propagation of Iranian trout farms are heavily dependent on subsidies. • The allocation of subsidies leads to enhanced standard profit efficiency (SPE). • Removing electricity and trout egg import subsidies notably reduces SPE compared to diesel fuel subsidy elimination. • Introducing reform options to modify the current subsidy regime could improve SPE. • Funding extruder machines, paying trout farms for electricity, and using genetically modified eggs all boost SPE. [ABSTRACT FROM AUTHOR]

This paper examines whether commercialisation improves productivity in small-scale aquaculture. An empirical understanding of the commercialisation-productivity nexus remains underdeveloped yet crucial for shaping policies aimed at the sustainable development of the sector. This is particularly pertinent in developing countries, where productive capacity and market access are hindered by resource constraints and underdeveloped infrastructure. We address this knowledge gap by using a representative sample of small-scale, subsistence-oriented fish farmers collected through multistage sampling from three major aquaculture districts (Dzongkhags) in Bhutan. We employ data envelopment analysis and bootstrap regression techniques to estimate how the productivity levels of small-scale famers are associated with the extent of commercialisation in post-harvest fish sales. We find that commercialisation significantly improves productivity ⸺ specifically, a 10-percentage point increase in fish sales enhances the technical efficiency and capacity utilisation rate of fish farmers by 3.1 and 1.4 percentage points, respectively. Our results suggest that even small-scale, subsistence-oriented farmers, whose main livelihood is not fish farming, are incentivised to operate more efficiently when they have enhanced marketing opportunities. Our study indicates that aggregate fish production in Bhutan could be increased substantially by leveraging this productivity-commercialisation nexus, without expanding the fishpond's area or investing in more advanced technologies. • Does commercialization motivate fish farmers to enhance their productivity? • Aquaculture production in Bhutan is small-scale and subsistence oriented, with limited market access. • We show that a 10 % increase in fish sales is associated with a 1.4 to 3.1 % increase in farm-level productivity. • Such productivity improvements can substantially increase the national fish output with existing technologies and fish ponds. • Subsistence-oriented farmers are incentivized to operate more efficiently when they have enhanced marketing opportunities. [ABSTRACT FROM AUTHOR]

The widespread use of antibiotics against aquaculture diseases also triggers the emergence of immunosuppression, antibiotic residues, antibiotic resistance genes, and environmental damage in cultured fish globally, thus resulting in the banning of many antibiotics. As a safer and more effective antibacterial product, the probiotic Clostridium butyricum (C. butyricum) has been increasingly used as additives in aquaculture to overcome the abuse of antibiotics and to promote fish health and their productivity. To date, studies in fish culture focus on the beneficial effects of C. butyricum on growth performance, antioxidant properties, intestinal microbiota, intestinal immune and health, and disease resistance. Therefore, C. butyricum is likely to become a potential alternative to antibiotics for prevention of enteric pathogen infection and related diseases. This paper systematically reviews the latest research and application progress of probiotic C. butyricum strains in fish culture. The focus of this review is a discussion of the beneficial effects of C. butyricum on diverse fish species, specifically the underlying mechanisms of C. butyricum in promoting growth, and improving disease resistance and the associated immune response. To realize large-scale application in the aquaculture industry, it is essential to conduct further investigation of the interrelationships between the C. butyricum and the immune system of the host, and the C. butyricum -triggered signaling pathways to secure the trials further. [Display omitted] • The mechanisms of Clostridium butyricum in the host immune system were summarized. • The beneficial effects of Clostridium butyricum on fish farming were analyzed. • The safety of Clostridium butyricum in fish farming was evaluated. [ABSTRACT FROM AUTHOR]

The allocation of zones for aquaculture development is a strategic problem as it involves long-term outcomes and many stakeholders with competing interests. Resource planners require tools to support such complex allocation decisions, but these are either lacking or with serious limitations. This paper presents an approach that improves the traditional method of developing aquaculture zoning model. Four scenario narratives describing potential development pathways for aquaculture in Nigeria were used to guide the model development, from selection of suitability factors to evaluation of alternatives. The modelling objective was to identify a suitable location for zoning small-to-medium scale commercial pond catfish production in Nigeria. So, a GIS-based multi-criteria evaluation (MCE) was used to produce a suitability map, from which five alternative zones were extracted. These zones were then compared using three sustainability criteria that were designed based on future uncertainties highlighted by the four scenarios. Results show that 4 of the 5 zones are concentrated in the north-eastern part of Nigeria, while the other one occurred in the north-west. Furthermore, this study found two top-ranking zones that can be selected in all the scenarios, meaning the two zones with the most potential to support the sustainable development of small-to-medium scale aquaculture in Nigeria. As these two were almost tied in ranking, sensitivity analyses across the scenarios revealed the most stable zone to changes in the criteria scores. These findings can be used to inform aquaculture expansion policy in Nigeria and integrate the activity into wider land use planning. Overall, the new approach advances the traditional method of developing GIS-based MCE models for aquaculture zoning, as it generates options and relevant information to facilitate strategic decision-making. • Aquaculture zoning is a strategic problem requiring comprehensive tools. • Traditional suitability models for aquaculture planning not equipped to evaluate outputs. • New modelling approach developed, considering uncertainties in long-term planning. • Approach enhances decision support for zoning implementation. [ABSTRACT FROM AUTHOR]

As the importance of aquaculture increases, the scale and benefits of aquaculture are continuously emphasized. To achieve stable, efficient and high-precision detection instead of manual labor, we have adopted a UAV combined with artificial intelligence approach by improving the YOLOv8 model, and realizes the real-time detection of dead fish in the aquaculture by transmitting the frames captured by the UAV back to the server for computation in real time. The experimental results show that the improved model achieves an accuracy of 95.6 %, a recall of 95.2 %, a mAP 50 of 98.1 %, and a MAP50–95 of 67.5 % on the dataset constructed in this paper, which are 5.4 %, 22.8 %, 12.6 %, and 10.52 % higher than the original model, respectively. As a result, the accuracy of recognizing small dead fish targets in the view of UAV aerial photography has been greatly improved, and can be applied to the detection under different water surface shooting conditions. In addition, the UAV detection method proposed in this study can be combined with other schemes and applied to unmanned management of aquaculture and fisheries to detect problems in aquaculture in a timely and accurate manner. • Real-time dead fish detection using the UAV. • Detection of small dead fish targets using an improved Yolov8 models. • Accuracy of dead fish identification was 95.6 %. • Help to find dead fish in time to avoid the spread of disease and economic losses. [ABSTRACT FROM AUTHOR]

In aquaculture, analyzing the swimming behavior of micropterus salmoides using multi-object tracking technology is a crucial non-contact method for obtaining data and assessing vitality. However, existing approaches suffer from high false detection and target loss rates due to issues like occlusion between individuals and their variable body shapes. Therefore, this paper proposes a novel multi-object tracking model (Yolo-AWD + CBT) for accurate and real-time tracking of micropterus salmoides swimming behavior. Our method improves upon the Yolov8n backbone network feature extraction module by incorporating an Adaptive Weight Downsampling (AWD) module to address the loss of feature information during downsampling in the original network. To tackle the challenge of variable body shapes during swimming, we replace the original loss function with XIOU, enhancing the network's ability to localize targets. For the tracking algorithm, we introduce trajectory confidence information into ByteTrack, thus improving the tracking accuracy of micropterus salmoides during swimming. Experimental results on object detection and multi-object tracking datasets demonstrate that our proposed model (Yolo-AWD + CBT) achieves a 1.07 % and 5.4 % improvement in P and (AP 50 : 95). In terms of tracking performance, compared to the original model, HOTA increases by 6.25 %, MOTA by 3.15 %, and IDsw decreases by 58.33 %, resulting in swimming behavior data errors within the range of −7 % to +3 %. These results indicate that our proposed multi-object tracking method can effectively track multiple targets in various scenarios and accurately capture micropterus salmoides swimming behavior data, providing technical support for non-contact vitality analysis. • A novel multi-object tracking approach for efficient fish swimming behavior analysis. • Improving YOLOv8 object detection performance with AWD and XIOU. • Extended kalman filter and track confidence for enhanced trajectory matching. [ABSTRACT FROM AUTHOR]

Addressing the challenge of insufficient underwater marine life images leading to diminished accuracy in existing target recognition models, this paper introduces Random Vector Functional Link (RVFL), a suitable model for small sample training, to reduce the dependency of traditional visual recognition models on data volume by replacing the Softmax classifier in the Faster Region-Based Convolutional Neural Network (R-CNN) model. The RVFL network assigns random weights to enhance the model's adaptability to diverse data distributions, thereby improving its generalization performance. Furthermore, the RVFL model incorporates multiple nonlinear activation functions, thereby enhancing the neural network's representational capacity for high-dimensional data. The application of the proposed model to the task of marine fish small sample target recognition demonstrates its effectiveness in mitigating the low accuracy issue caused by data scarcity. It significantly improved recognition accuracy and offered new insights into addressing underwater small sample image recognition challenges. • Introduced the Random Vector Functional Link network to enhance Faster R-CNN performance for underwater fish recognition. • Validated the model's robustness, showing enhanced performance even with varying dataset sizes and types. • Achieved higher accuracy in multi-sample environments, despite the increased complexity of multiple fish species. [ABSTRACT FROM AUTHOR]

This paper explores the perspectives surrounding digital technology adoption in rainbow trout farming in Ontario, Canada. While digital transformation can help support and meet the growth needs of the fishery and aquaculture industries, few studies explore digital technology adoption in aquaculture and even fewer consider the diverse perspectives of various actors in this context. We aim to fill this gap by examining the viewpoints of key rainbow trout farming stakeholders, such as producers, researchers, and technology providers, regarding adopting digital technologies. This study, which is unique in the Ontario context, employed Q methodology to explore the perspectives of different actors using the extended theory of planned behaviour as a framework. We performed the Q-sort procedure using Qualtrics, providing 23 actors with 27 statements on a scale from strongly agree to strongly disagree. Q-factor analysis in PQ-method software identified three distinct discourses. Discourse 1 highlights skilled employees and data-related concerns, Discourse 2 emphasises understanding the complexity and costs associated with digital technologies, and Discourse 3 emphasises financial assistance and perceived value, focusing on attitude and perceived behavioural control. Interestingly, the three discourses were represented by various groups of actors, and not all respondents from the same sector shared the same perception. The findings of this study contribute to the limited scientific research on digital technology adoption in rainbow trout farming, which can inform strategic policy decisions. • The rainbow trout industry in Ontario lacks research on digital adoption. • We address a gap in stakeholder opinions on aquaculture digital technology adoption using Q-methodology. • Uncovers three distinct discourses: skilled workforce & data concerns, complexity & cost awareness, and financial aid & perceived value. • Discourses not confined to specific roles, highlighting diverse perspectives within groups. [ABSTRACT FROM AUTHOR]

To gain a comprehensive understanding of cultivating microalgae for lipid and fatty acid production with high CO 2 , this study conducted a meta-analysis based on 757 data sets from 51 papers for the first time. The findings show that high CO 2 concentrations (0.1–30%) generally promote microalgal growth, whereas extreme high CO 2 levels (30–50%) usually exhibit negative effects. High CO 2 levels (0.1–30%) also commonly stimulate cellular lipid accumulation. Therefore, high CO 2 levels (0.1–50%) increase lipid productivity of both freshwater and marine microalgae, particular for Chlorophytina. These elevated CO 2 levels (0.1–30%) reduce saturated fatty acid content of microalgae but enhance the content of unsaturated and polyunsaturated fatty acids, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Advanced molecular editing techniques, e.g., CRISPR-Cas9, can be utilized to improve microalgal tolerance to flue gases that contain hazardous compounds while condition optimalization for maximal use of CO 2 in the production of microalgae with high lipid content should also be conducted in future. This research provides crucial insights for designing and optimizing microalgae cultivation with high CO 2 to produce lipid and fatty acids. • Higher CO 2 concentrations commonly promote microalgal growth and lipid accumulation. • High CO 2 levels increase lipid productivity of both freshwater and marine microalgae. • High CO 2 levels reduce saturated fatty acid content of microalgae. • Unsaturated fatty acid content of microalgae is stimulated by high CO 2. • Content of EPA and DHA is promoted by high CO 2 , particularly for marine microalgae. [ABSTRACT FROM AUTHOR]

Interest and engagement in aquaculture has been increasing in recent years to meet aquatic resource demands, and much attention has been directed to growing seaweed in the United States. However, research and regulatory environments have not kept pace with its growth, leading to challenges to expanding the industry, and in many cases, these developments may be ahead of available peer-reviewed literature, resulting in a dearth of information from industry participants about their needs and perspectives. The results of the first survey of industry members and those adjacent to the US domestic seaweed aquaculture industry are presented. Presenting contributions of participants throughout the supply chain from seaweed seed string producers through to processors and culinary professionals, and including regulators and researchers. A total of 268 respondents responded to the needs assessment survey, with engagement from fourteen states, primarily representing the U.S. northeast and west coasts. Results describe a wide differential in levels of industry engagement and development across states with Maine providing an example of a well-developed industry, and others just beginning to develop seaweed growing permits and infrastructure. Respondents were asked to identify challenges which were then categorized as: (1) production systems (32%); (2) market opportunities, including both supply and demand (26%); (3) regulations (26%); and (4) post-harvest opportunities and infrastructure (i.e., processing facilities) (16%). Considering these challenges collectively, a holistic approach to scaling up the industry is needed to address challenges throughout the supply chain and across states. The paper concludes with recommendations for policy makers, regulators, extension professionals and researchers to assist this nascent industry in scaling up domestically by working to facilitate information transfer across states and roles within the industry to increase capacity at various levels of the supply chain, address remaining scientific questions, and move toward a regulatory framework for an inter-state (or domestic) industry. • Seaweed aquaculture is garnering much attention in the United States as a sustainable food source and use of aquatic resources, yet research and regulations have not kept pace with its growth. The first needs assessment of US domestic seaweed aquaculture industry members and those adjacent to the industry is presented and discussed. • Levels of engagement and industry development differ drastically across states and though some lessons can be transferred between states where the industry is further developed and those at earlier stages of development, differences between states may present different types of challenges. • Scaling up the industry overall necessitates coordinated efforts at the federal level on certain issues, especially from a regulatory perspective. • Industry-wide challenges were identified by participants throughout the value chain, suggesting that participants approach the industry from a holistic perspective. • Policy makers, regulators, extension professionals and researchers to assist this nascent industry in scaling up, domestically, by facilitating information transfer within the industry to increase capacity and move toward a regulatory framework for a cross-state industry. [ABSTRACT FROM AUTHOR]

Aquaculture plays a crucial role in meeting the growing demand for seafood worldwide. However, the sustainability of aquaculture practices faces challenges from environmental pollutants and toxins. Traditional methods of assessing aquatic toxicity often rely on whole organism tests, which can be time-consuming, expensive, and ethically challenging. In recent years, the utilization of fish cell lines as in-vitro testing models in aquaculture toxicology has emerged as a promising alternative approach. Fish cell lines offer several advantages, including cost-effectiveness, scalability, and reduced ethical concerns. This review paper provides an overview of the implementation of fish cell lines in aquaculture toxicology, focusing on their applications in assessing the toxicity of environmental contaminants, mechanistic studies, and biomarker discovery. Furthermore, we discuss the advantages and limitations of fish cell lines compared to traditional whole organism tests explore challenges and future perspectives for integrating fish cell lines into regulatory frameworks. Overall, the integration of fish cell lines into aquaculture toxicology holds great promise for enhancing the sustainability and safety of aquaculture practices in the face of increasing environmental pressures. [Display omitted] • Fish cell lines are valuable tools for screening contaminant toxicity. • Fish cell lines offer insights into toxic mechanisms of contaminants. • Fish cell lines could be key to unlocking sustainable aquaculture practices. [ABSTRACT FROM AUTHOR]

Open-net finfish farms require monitoring to manage fish welfare and to mitigate risk for diseases and parasites which could threaten wild fish populations. In salmonid farming the ectoparasite copepod sea lice Lepeophtheirus salmonis (Caligidae) is a major concern. This paper's novel contribution is the application of sampling statistics to determine the number of sea lice which should be sampled per pen so as to report the abundance of sea lice with a given accuracy. It does so considering the different statistical distributions which occur at high- and low prevalence of sea lice and combines these considerations to guide the reader towards counting a number of sea lice which would be more inline with other statistical applications. Existing pen sampling routines are analysed and the sampling error is quantified. These findings need to be taken into account when sampling protocols for sea lice are designed as it is especially important for fish welfare. • The error in sample averages for common sea lice counting regimes is quantified. • Comprehensive sample estimates of sea lice abundance in finfish farming are provided. • Implications would improve welfare standards of salmonid farming. [ABSTRACT FROM AUTHOR]

Abstract Monitoring an aquatic environment in aquaculture is usually carried out by controlling its physicochemical and biological parameters. The global state of the process is evaluated though the individual conditions shown in each parameter. However, the correlation structure in the data, caused by interdependence between these parameters, provides relevant information which must be controlled. Thus, the complex structure of the data requires a multivariate control method to explore both the individual and interactive effects of the environmental parameters. To achieve this goal, this paper presents a statistical method based on a Multivariate Exponentially Moving Average (MEWMA) chart to monitor the multivariate structure of an aquatic environment in aquaculture, especially in a crop of tilapia in Mozambique. The results show that the adjusted MEWMA chart is more consistent when controlling the conformity and stability of environmental parameters. Therefore, it can be considered an efficient statistical method to monitor an aquatic environment in aquaculture. Highlights • This paper presents a multivariate methodology to monitor the aquatic environment in tilapia (oreochomis mossambicus) crop tanks. • It was consisted a real study in the company Aquapesca de Moçambique • The data were analyzed through a MEWMA model in order to exploit relevant information of the process concerning the state of the aquatic environment. [ABSTRACT FROM AUTHOR]

Abstract This paper introduces a special issue of Aquaculture that brings together the largest collection of research on aquaculture value chains compiled to date, comprising 19 individual papers and this introductory review. The introduction identifies five themes emerging from research on aquaculture value chains in the special issue, namely: multi-polarity, diversity and scale, dynamics of transformation, performance and equity, and technical and institutional innovation. Contrary to much research to date, the papers addressing these themes show how the expansion of aquaculture has resulted highly diverse configurations of production for consumption in the global South. Collectively, the papers highlight the need for greater attention to neglected value chain segments and categories of actor, modes of production, regulation, and innovation, and patterns of access to benefits. The papers synthesized also affirm the need for more rigorous and diverse future value chain research to illuminate the aquaculture sector's ongoing development, and contribute to the sustainable expansion as an increasingly important component of the global food system. Highlights • Synthesis of five core themes on aquaculture value chain research. • Aquaculture value chains not as global as commonly thought. • Diverse configurations of aquaculture production, trade and consumption in global South. • Diverse approaches and methodologies for aquaculture value chain research available. • Research focus needed on value chains in context of wider global food system. [ABSTRACT FROM AUTHOR]

This paper adopts the stochastic frontier model with flexible risk to analyze production risk, technical efficiency and its determinants of fish farms in four regions of Ghana including Greater Accra, Volta, Western and Ashanti regions. The study employs a two year panel data from 320 farms making a total of 640 observation through a random selection. The findings demonstrates that the translog model is best fit for the mean output function, whilst the input variables: hired labour, family labour, fingerlings, feed and other cost are identified to positively influence fish farm output at an increasing returns to scale. The paper also finds that feed and other cost are risk increasing inputs, whilst hired labour, family labour and fingerlings are identified to be risk decreasing inputs. The estimated average technical efficiency score of 0.74 shows that efficiency is compromised when the production technology is modeled without the flexible risk property which gave a score of 0.87. Additionally, the results show that age 2 , experience, pond area, gender, pond type and fish farming education significantly influence technical efficiency of farmers. This paper also highlights that technical efficiency of fish farms in the study area improved over time. In conclusion, the paper notes that on the average, 26% of potential output is lost due to technical inefficiency and production risk and given the present state of technology and input level, the possibility of enhancing production can be achieved by reducing technical inefficiency by 26% through adoption of practices of the best fish farm, whilst taking production risk into consideration. [ABSTRACT FROM AUTHOR]

Uptake of the the government of Thailand's three national certification standards for shrimp aquaculture (CoC, GAP and GAP-7401) has remained limited. Using the Devil's Triangle framework, which highlights tradeoffs between accessibility, credibility and improvement, this paper examines the Thai government's rationale for developing these national certification standards, and compares this rationale with farmers' perceptions surrounding standard compliance. The findings demonstrate that different groups of farmers experience different tradeoffs between accessibility, credibility and improvement under each of the three standards. The paper concludes that improved coordination of these national certification standards could promote credible and inclusive step-wise improvement pathways for the Thai shrimp industry as a whole. [ABSTRACT FROM AUTHOR]

This paper examines how value chain coordination affects the ability of aquaculture producers to engage in eco-certification. Through a comparison of global salmon and shrimp value chains, it is argued that production risks and producer capacity are key determinants in the type of chain coordination adopted by lead firms. The results challenge global value chain governance theory by indicating that it is hierarchical (or vertically integrated) forms of coordination that are associated with high capabilities and low risk rather than market forms of coordination. It is also shown that eco-certification is more likely to be adopted in value chains with more engaged forms of coordination. This in turn means that eco-certification is a far less ‘hands off’ form of regulation than widely thought. The paper concludes that for certification to engage producers operating under market forms of chain coordination new arrangements are needed that can respond to challenges of improving producer capability and production risk. Statement of relevance By understanding the role of risk and producer capability this paper contributes to improving the application and impact of eco-certification in global aquaculture production. [ABSTRACT FROM AUTHOR]

The coastal cod fishery in Southern Norway has experienced a significant decline over the last decades. Recreational fishing for cod in the eastern part of the country is currently banned. Fisheries managers have adopted a variety of strategies to sustain the populations for resource users. Aquaculture-based fisheries enhancement has been considered as an alternative intervention to rebuild overexploited cod stock or to improve the opportunity for marine fishing. However, there has been a debate regarding its ecological and social effectiveness among stakeholders. In this paper, we conducted an online contingent valuation survey aiming to understand stakeholders' perceptions and attitude towards restocking of hatchery-produced juveniles as a potential restoration approach to rebuild depleted coastal cod populations and their willingness to pay for the implementation of such an enhancement program in southern Norway. Results indicate that the public has a positive perception to the potential restocking program. The average Willingness-To-Pay (WTP), e.g. fishing license fee, is approximately 175 NOK and 693 NOK if all of the respondents, and only counting those who are willing to, contribute. The introduction of a minimum fishing license fee of 175 NOK (approximately 17€) would cover the cost of production of over 20 million juvenile cod of appropriate size for release. Age of the respondents, the frequency of their fishing trips, and their perception of the decline of coastal cod were the main drivers for the WTP contribution while the amount of the WTP was strongly correlated to targeting particular species, educational level, and place of residence. Considering the critical situation of the coastal cod populations in southern Norway, together with the significant advances in cod rearing techniques, in fish tagging technology and the maturation of fisheries enhancement as science, and the positive stakeholders' perceptions and attitudes towards such an aquaculture-based enhancement program revealed from this study, it may be the time to re-evaluate the potential integration of a holistic cod restocking program within Norwegian coastal zone management. • Cod is an important food source and recreational fishing is highly valued in Agder. • Local stakeholders' have a positive attitude towards restocking coastal cod. • Respondents are willing to pay 175 NOK (≈ 17 €) on average for juvenile production. • A fishing license fee of 175 NOK would allow the release of over 20 million juveniles. [ABSTRACT FROM AUTHOR]

Villorita cyprinoides (Gray, 1825) also called the Indian black clam is a native species from the Indian peninsula directly related to the livelihood of many beneficiaries. The wild population of this Cyrenid clam is confronted with substantial challenges, including various climatic stressors and anthropogenic pressures such as overfishing and habitat destruction. A balance between capture fisheries and aquaculture through the development of hatchery technology is inevitable for ensuring the sustainable use of resources. The declining population of V. cyprinoides underscores the urgency of standardizing breeding protocols and implementing proper farming practices to foster a sustainable black clam fishery, given that Villorita is a potential candidate species for aquaculture. This paper describes the first successful induced spawning of the clam with successful rearing of larvae up to the umboned veliger stage and evaluates the efficacy of induced spawning through combined physical and chemical stimuli. Furthermore, our study employs eDNA metabarcoding to analyze plankton dynamics in waters from native clam beds. This sheds light on the potential microalgal dietary preferences of the species, which can be valuable in preparing diets for larval development and aquaculture in the future. • The first successful report on induced spawning in Villorita cyprinoides was achieved through physical and chemical stimuli. • Induced spawning indicated, V. cyprinoides as a potential candidate species for aquaculture with streamlined protocols. • Statistical analyses showed a significant correlation between physical stimuli and spawning. • eDNA metabarcoding revealed the dominant biota in the natural bed of black clams during peak breeding season. • The effective implementation of NGS provides initial insights into the advancements of artificial diet formulation. [ABSTRACT FROM AUTHOR]

In recent years, the rapid development of the large-scale aquaculture industry has generated substantial economic benefits, positioning it as one of the fastest-growing sectors in global agricultural production. However, improper management practices in aquaculture, including overfeeding, improper feed selection, antibiotic misuse, high stocking densities, inappropriate choice of aquaculture species, and improper discharge of aquaculture wastewater, have resulted in significant watershed pollution in agriculture and the wastage of valuable resources. To address these challenges, extensive research and application of wastewater treatment technologies have been conducted in large-scale aquaculture in China. This review provides an overview of current cases and applications of wastewater treatment in large-scale aquaculture in China, focusing on four common intensive wastewater treatment methods: constructed wetland treatment model, ecological ditch treatment model, Integrated Multi-trophic Aquaculture model, and recirculating aquaculture model. The constructed wetlands utilize plants and microorganisms to purify both organic and inorganic pollutants in water, while ecological ditches employ engineering measures such as sedimentation ponds, interception ditches, and aeration devices to achieve wastewater treatment. Additionally, other aquaculture models are highlighted, such as Integrated Multitrophic Aquaculture (IMTA), which emphasizes synergistic interactions between aquaculture species and the recycling of nutrients, and the Recirculating Aquaculture Systems (RAS), which utilize water circulation and treatment equipment for wastewater treatment. The consequences and benefits of these systems in pollution reduction are described. These treatment technologies have made significant progress, offering theoretical guidance for environmentally friendly aquaculture production and the maintenance of ecological stability in aquaculture water bodies. Each wastewater treatment model has a different function, target, and methodology. Finally, this paper proposes directions and recommendations for future pollution management in large-scale aquaculture in China, including strengthening technological research and development, the combined application of multiple treatment models, promoting industry collaboration, and achieving resource sharing. These efforts will contribute to further promoting the sustainable development of China's aquaculture industry and provide valuable experiences and references for other countries and regions. • CWs and ecological ditch use plants and microorganisms to purify wastewater. • IMTA maximizes species interactions for efficient nutrient cycling. • RAS uses equipment to remove pollutants from aquaculture water for recirculation. • Utilizing multiple purification modes can enhance wastewater treatment efficiency. [ABSTRACT FROM AUTHOR]

Nucleolar dominance is one of the epigenetic phenomena that refers to the dominance effect exhibited by the suppression of ribosomal RNA gene loci from one parent in heterozygous organisms. In this paper, the genetic and expression changes of 45S rRNA genes in different generations of the crucian carp-like homodiploid fish lineage (2nNCRC, F 1 , F 2 , F 3 , F 5) and the autotetraploid carp lineage (4nNC, F 1 -F 3) formed by distant hybridization of common carp (Cyprinus carpio , COC) (♀) × blunt snout bream (Megalobrama amblycephala , BSB) (♂) were mainly studied. The results showed that the nucleolar dominance patterns were different in different generations of the 2nNCRC lineage and the 4nNC lineage. In the different generations of the 2nNCRC lineage, 2nNCRC-F 1 (F 3 , F 5) exhibited the phenomenon of nucleolar dominance, while 2nNCRC-F 2 did not and expressed the mutant 45S rRNA. The establishment of the nucleolar dominance pattern presented a more complicated situation, which may be related to the inconsistent coping mechanism among different generations after suffering the effect of "genome shock" at the early stage of the formation of the 2nNCRC lineage. Among the different generations of the 4nNC lineage, 4nNC-F 2 existed the phenomenon of nucleolar dominance and expressed mutant 45S rRNA. However, 4nNC-F 1 (F 3) did not exist in the phenomenon of nucleolar dominance. The establishment of the nucleolar dominance pattern showed a process of instability-stability-instability, revealing the epigenetic instability of this lineage. This result may be related to the comprehensive effect caused by the continuous "genome shock" at the early stage of the formation of the 4nNC lineage, which can provide clues for further revealing the possible mechanism of occurrence and survival of polyploidization vertebrates. Moreover, this study found that the nucleolar dominance was biased towards BSB in the 2nNCRC lineage, while it was biased towards COC in the 4nNC lineage. The inconsistent results appeared in the different ploidy lineages formed by the same distant hybridization combination, which further verified that the dominance of transcription advantages species did not necessarily determine the biased characteristics of nucleolar dominance. Two lineages derived a mutant ITS1 sequence, which the mechanism may be related to some mechanisms triggered by the "genome shock" effect. This study will further fill a gap in studying nucleolar dominance in the early stage of the formation of homodiploid and polyploid vertebrates and provide important experimental data for studying fish epigenetics, which is of great significance in fish genetic breeding and biological evolution. • This paper fills a gap in the study of nucleolar dominance (ND) in homodiploids. • ND pattern of homodiploids is more complex than that of allodiploids. • This study reveals a more complex ND pattern in the autotetraploid species. • Transcription advantage species do not determine the biased feature of ND. [ABSTRACT FROM AUTHOR]

In Vietnam, pangasius farming has developed rapidly in the past decades, with the aquaculture of this particular fish species proving to be very beneficial for the local economy. However, the emergence and spread of the Covid-19 pandemic and the policy responses in slowing the spread of the virus have significantly impacted the sector. This paper investigates both the vulnerability and resilience of pangasius aquaculture by identifying the various impacts of the Covid-19 pandemic on Vietnam's pangasius sector and the subsequent responses of this sector towards the issues brought forward by it. In this paper, data collected from 195 pangasius farms in Vietnam are operationalized via binary and ordinal logistic regression in an attempt to reveal the factors affecting the sector's output and the factors driving farmers' responses in the context of insecurity caused by the Covid-19 pandemic. Since the emergence of the pandemic-induced shock on the pangasius sector, farmers have encountered difficulties regarding the sale of harvests and have been confronted with lower prices for pangasius products, with the sector reporting a reduction in the sales volume and the number of buyers, as well as farmers facing disruptions in logistics and input accessibility. As a response to the impacts of the pandemic, pangasius farmers resorted to a number of coping strategies including feeding pangasius less, reducing the farming scale, delaying harvesting, and/or releasing smaller sized fingerlings. Our regressions suggest that farms signing contracts with buyers are more resilient to the reduction in output price and the reduction in number of buyers but, on the other hand, these farms seem to be more severely impacted by the adverse impacts of reduced sales volume, higher feed price and difficulty to sell harvest compared to those without contracts. Furthermore, our findings suggest that farms selling products to export traders suffered more severely from the reduction in the price of pangasius products and in the number of buyers but, at the same time, these farms seemed to have fewer problems with the reduced sales volume and the increased feed price. Interestingly, our findings also suggest a cross-vulnerability with climate change, specifically with respect to the increase in feed price and the disruption in input logistics, hereby further increasing the vulnerability of pangasius farmers. • Pangasius farms display a differential vulnerability to Covid-19 related shocks. • Vulnerability is affected by farm and farmer characteristics. • Covid pandemic caused reduction in output price and number of buyers. • Feed prices have increased during the pandemic. • Pangasius farms responded by reducing farming scale and delaying harvesting. [ABSTRACT FROM AUTHOR]

The literature on late-stage larval and puerulus settlement of tropical spiny lobsters suggests that a broad range of visually-assessed variables may play a role in the selection of settlement substrates. These variables include light level, luminosity, degree of exposure, and the availability of edges, crevices and clefts. A fishery has developed in Indonesia, that captures pueruli for grow-out purposes, along the entire southern coastline from Java to Sumbawa. The present study builds on knowledge gained on the behaviour and substrate preferences of settling pueruli by examining aspects of collector design and substrate surface characteristics in regard to catch rates. A series of tank-based experiments were used to examine preferences for various attributes of collector materials, and preferred material characteristics were then tested in a field experiment to verify the laboratory results. In the tank experiment the most preferred substrate was cement bag paper, followed by insect mesh, weed netting, PVC rubber and cement bag plastic. Crevice angles of 10° and 20° were significantly preferred over 30°. The substrate level and other substrates had less influence on settlement. However, both the lunar phase and type of materials tested in the field had a significant effect on settlement. Significantly greater numbers of pueruli were caught at the time of the new moon than at other moon phases. Cement bag paper was the most preferred material in the field, followed by cement bag plastic, insect mesh, weed fabric, and PVC rubber. [ABSTRACT FROM AUTHOR]

The Thau lagoon, located at the South of France, provides 10% of the French pacific oyster Crassostrea gigas production. Despite this intensive shellfish production, the larval recruitment of this species within the Thau lagoon is still misunderstood and spat collection remains highly variable; as a consequence, shellfish farmers rely mostly on hatchery”s spat. The present study aimed to describe reproduction features of C. gigas within the Mediterranean, as well as to explore spawning triggers of this species. To achieve this goal, the reproduction cycle from gametogenesis to spawning was followed during two years in several locations within the Mediterranean Thau lagoon. The spawning behavior of C. gigas within the Thau lagoon appeared to be slightly different from the one of the Atlantic Coast, showing several spawning events from June to October. The minimal temperature for massive spawning was 23 °C, which is much higher than temperatures mentioned in the literature for this species. A strong relationship was found between phytoplankton communities and gametogenesis, the latter being improved by a higher diatom/dinoflagellate ratio. Temperature was insufficient alone to explain spawning, highlighting other potential triggers such as the moon or lightning strikes. We made the hypothesis of a hierarchy of events triggering spawning, encompassing locking, synchrony and intensifying triggers. Statement of relevance This paper is filling in a gap in the literature regarding to reproduction of C. gigas in the Thau lagoon, which is always associated to temperature. However, temperature may not be the only factor involved in oyster reproduction, that is what we tried to show in this paper. [ABSTRACT FROM AUTHOR]

India is the world's second largest producer of farmed fish, and the state of Andhra Pradesh (AP) is by far the most important producer of farmed fish in India. Freshwater aquaculture has boomed in AP since the late 1970s, first with carps, then pangasius catfish. Over this period fish pond area and farmed fish production grew from nothing to reach 142,000 ha and 1.5 million tons, respectively. Despite its scale and dramatic consequences, the boom has received little attention in the international literature. The present paper addresses this gap by analyzing changes in the structure and conduct of each segment of AP's freshwater aquaculture value chain during four distinct phases of development (incubation, take-off, maturation and modernization). This analysis reveals that aquaculture development in AP shares many characteristics with agricultural commodity booms elsewhere in Asia. The paper contributes to the literature on crop booms by: 1) characterizing Southern domestic demand for agricultural products as an important but overlooked driver of agrarian development, and; 2) identifying interlinked processes of innovation and transformation in off-farm segments of the supply chain as a central feature of crop booms. [ABSTRACT FROM AUTHOR]