Farming fish in the sea will not nourish the world

Environmental, economic, and social sustainability in aquaculture: the aquaculture performance indicators

Aquaculture is a rapidly growing food production technology, but there are significant concerns related to its environmental impact and adverse social effects. We examine aquaculture outcomes in a three pillars of sustainability framework by analyzing data collected using the Aquaculture Performance Indicators. Using this approach, comparable data has been collected for 57 aquaculture systems worldwide on 88 metrics that measure social, economic, or environmental outcomes. We first examine the relationships among the three pillars of sustainability and then analyze performance in the three pillars by technology and species. The results show that economic, social, and environmental outcomes are, on average, mutually reinforced in global aquaculture systems. However, the analysis also shows significant variation in the degree of sustainability in different aquaculture systems, and weak performance of some production systems in some dimensions provides opportunity for innovative policy measures and investment to further align sustainability objectives.

Short term decreases in salinity, combined with the right choice of species, can allow for a more nutritious sea lettuce lipid profile

The sea lettuce Ulva spp is becoming an increasingly important macroalgae for aquaculture. Sea lettuce can be grown on- and off-shore, displays high growth rates, and its biomass possesses attractive nutritional benefits. Among those are their fatty acids (FA) and lipid profiles, rich in omega 3 Polyunsaturated Fatty Acids (PUFAs) as well as bioactive lipids. In order to tailor those properties for food applications, we explored the use of a short-term (seven days) low salinity treatment to modulate the lipid profile of two species of Ulva. We found large quantitative differences between species, and while a low-salinity treatment negatively affected growth, Ulva australis' lipid profile was positively impacted. Total FA particularly ɷ-3 PUFAs, increased three-fold, as well as most polar lipid species including known bioactive compounds. This study highlights profound differences between species and describes a simple method to increase the nutritional properties of Ulva biomass for food applications.

Wild fish consumption can balance nutrient retention in farmed fish

Wild fish used as aquafeeds could be redirected towards human consumption to support sustainable marine resource use. Here we use mass-balance fish-in/fish-out ratio approaches to assess nutrient retention in salmon farming and identify scenarios that provide more nutrient-rich food to people. Using data on Norway's salmon farms, our study revealed that six of nine dietary nutrients had higher yields in wild fish used for feeds, such as anchovies and mackerel, than in farmed salmon production. Reallocating one-third of food-grade wild feed fish towards direct human consumption would increase seafood production, while also retaining by-products for use as aquafeeds, thus maximizing nutrient utilization of marine resources.

Microplastics in water, feed and tissues of European seabass reared in a recirculation aquaculture system (RAS)

Plastic particles (PLs) are ubiquitous in aquatic ecosystems and aquaculture production is susceptible to contamination from external or endogenous sources. This study investigated PL presence in water, fish feed and body sites of 55 European seabass produced in a recirculating aquaculture system (RAS). Fish morphometric parameters and health status biomarkers were determined. A total of 372 PLs were recovered from water (37.2 PL/L), 118 PLs from feed (3.9 PL/g), and 422 from seabass (0.7 PL/g fish; all body sites analysed). All 55 specimens had PLs in at least two of the four body sites analysed. Concentrations were higher in the gastrointestinal tract (GIT; 1.0 PL/g) and gills (0.8 PL/g) than in the liver (0.8 PL/g) and muscle (0.4 PL/g). PL concentration in GIT was significantly higher than in muscle. Black, blue, and transparent fibres made of man-made cellulose/rayon and polyethylene terephthalate were the most common PLs in water and seabass, while black fragments of phenoxy resin were the most common in feed. The levels of polymers linked to RAS components (polyethylene, polypropylene, and polyvinyl chloride) were low suggesting a limited contribution to the overall PL levels found in water and/or fish. The mean PL size recovered from GIT (930 μm) and gills (1047 μm) was significantly larger than those found in the liver (647 μm) and dorsal muscle (425 μm). Considering all body sites, PLs bioconcentrated in seabass (BCF_Fish >1) but their bioaccumulation did not occur (BAF_Fish <1). No significant differences were observed in oxidative stress biomarkers between fish with low (<7) and high (≥7) PL numbers. These findings suggest that fish produced in RAS are mainly exposed to MPs through water and feed. Further monitoring under commercial conditions and risk assessment are warranted to identify potential threats to fish and human health and define mitigating measures.

Molecular identification of a novel antimicrobial peptide in giant Triton snail Charonia tritonis: mRNA profiles for tissues and its potential antibacterial activity

Antimicrobial peptides (AMPs) play an important role in innate immunity against microorganisms. AMPs is an effective antibacterial agent, and the chances of causing pathogens to develop is very low. However, there is little information about AMPs in the giant Triton snail Charonia tritonis. In this research, an antimicrobial peptide gene (termed Ct-20534) was identified in C. tritonis. The open reading frame of Ct-20534 is 381 bp in size and it encodes a basic peptide precursor containing 126 amino acids. Ct-20534 gene was found to be expressed in all five tissues examined by real-time fluorescence quantitative PCR (qPCR), but the highest expression was found in the proboscis. This is the first report that antibacterial peptides have been found in C. tritonis, and it has been proved that Ct-20534 has antibacterial activity against Gram-positive bacteria and Gram-negative bacteria, among which the activity of Staphylococcus aureus is most significantly inhibited, this suggests that the newly discovered antimicrobial peptides in C. tritonis may play an important role in the immune system and bacterial resistance of C. tritonis. This study presents the discovery of a newly identified antibacterial peptide from C. tritonis, with its structural properties fully characterized and potent antibacterial activity confirmed. The results provide essential fundamental data for the development of preventive and therapeutic measures against aquatic animal diseases, which in turn can promote the sustainable and stable growth of the aquaculture industry and create economic benefits. Additionally, this research lays the foundation for future development of novel anti-infective drugs.

Small pelagic fish supply abundant and affordable micronutrients to low- and middle-income countries

Wild-caught fish provide an irreplaceable source of essential nutrients in food-insecure places. Fishers catch thousands of species, yet the diversity of aquatic foods is often categorized homogeneously as 'fish', obscuring an understanding of which species supply affordable, nutritious and abundant food. Here, we use catch, economic and nutrient data on 2,348 species to identify the most affordable and nutritious fish in 39 low- and middle-income countries. We find that a 100 g portion of fish cost between 10 and 30% of the cheapest daily diet, with small pelagic fish (herring, sardine, anchovy) being the cheapest nutritious fish in 72% of countries. In sub-Saharan Africa, where nutrient deficiencies are rising, <20% of small pelagic catch would meet recommended dietary fish intakes for all children (6 months to 4 years old) living near to water bodies. Nutrition-sensitive policies that ensure local supplies and promote consumption of wild-caught fish could help address nutrient deficiencies in vulnerable populations.

On the wrong track: Sustainable and low-emission blue food diets to mitigate climate change

Seafood and other aquatic food (blue food) are often advocated as sustainable protein sources crucial to meeting global food demand. Consumption choices allow citizens to take actions that reduce the environmental burden of food production and tackle the climate crisis. Here we used a high-resolution Spanish national-level dataset collected from 12,500 households between 1999 and 2021 as a study case to assess trends in blue food consumption concerning sources, types and stressors resulting from their production. By aggregating species groups according to source, we found an overall reduction in the consumption of most wild species. For farmed species, we found a pronounced increase in the consumption of carnivorous fish and an overall decrease in low trophic-level species consumption, such as bivalves. Using published studies, we estimated greenhouse gases, nitrogen, and phosphorus emissions to assess trends in environmental footprint. Low performance was associated with the consumption of high trophic-level species intensively farmed in distant regions, such as carnivorous fish, due to high stressor emissions related to their production and transport. Across all groups, consumption of locally farmed bivalves conduced to the lowest stressor emissions, providing an example of ‘net-zero' blue food. Our analysis identified historical trends in the environmental footprint of blue food consumption and consumers' choices that promote environmentally sustainable diets. It also highlights vast differences in the ecological footprint associated with the consumption of aquaculture-sourced protein. Based on our assessment, we recommend refocusing consumption patterns toward farmed species with small environmental footprints, such as locally produced low trophic-level species, and implementing policies that increase consumers' environmental awareness and minimize food production systems' footprints. Considering global blue food demand is predicted to nearly double by mid-century, consumers' choices can significantly impact sustainable production practices and mitigate climate change.

Depuration of live oysters to reduce Vibrio parahaemolyticus and Vibrio vulnificus: A review of ecology and processing parameters

Consumption of raw oysters, whether wild-caught or aquacultured, may increase health risks for humans. Vibrio vulnificus and Vibrio parahaemolyticus are two potentially pathogenic bacteria that can be concentrated in oysters during filter feeding. As Vibrio abundance increases in coastal waters worldwide, ingesting raw oysters contaminated with V. vulnificus and V. parahaemolyticus can possibly result in human illness and death in susceptible individuals. Depuration is a postharvest processing method that maintains oyster viability while they filter clean salt water that either continuously flows through a holding tank or is recirculated and replenished periodically. This process can reduce endogenous bacteria, including coliforms, thus providing a safer, live oyster product for human consumption; however, depuration of Vibrios has presented challenges. When considering the difficulty of removing endogenous Vibrios in oysters, a more standardized framework of effective depuration parameters is needed. Understanding Vibrio ecology and its relation to certain depuration parameters could help optimize the process for the reduction of Vibrio. In the past, researchers have manipulated key depuration parameters like depuration processing time, water salinity, water temperature, and water flow rate and explored the use of processing additives to enhance disinfection in oysters. In summation, depuration processing from 4 to 6 days, low temperature, high salinity, and flowing water effectively reduced V. vulnificus and V. parahaemolyticus in live oysters. This review aims to emphasize trends among the results of these past works and provide suggestions for future oyster depuration studies.

Prospects of Low Trophic Marine Aquaculture Contributing to Food Security in a Net Zero-Carbon World

To limit compromising the integrity of the planet, a shift is needed towards food production with low environmental impacts and low carbon footprint. How to put such transformative change towards sustainable food production whilst ensuring food security into practice remains a challenge and will require transdisciplinary approaches. Combining expertise from natural- and social sciences as well as industry perspectives, an alternative vision for the future in the marine realm is proposed. This vision includes moving towards aquaculture mainly of low trophic marine (LTM) species. Such shift may enable a blue transformation that can support a sustainable blue economy. It includes a whole new perspective and proactive development of policy-making which considers, among others, the context-specific nature of allocation of marine space and societal acceptance of new developments, over and above the decarbonization of food production, vis á vis reducing regulatory barriers for the industry for LTM whilst acknowledging the complexities of upscaling and outscaling. This needs to be supported by transdisciplinary research co-produced with consumers and wider public, as a blue transformation towards accelerating LTM aquaculture opportunities in a net zero-carbon world can only occur by considering the demands of society.

More Than Fish—Framing Aquatic Animals within Sustainable Food Systems

Aquatic animals are diverse in terms of species, but also in terms of production systems, the people involved, and the benefits achieved. In this concept piece, we draw on literature to outline how the diversity of aquatic animals, their production, and their consumption all influence their impact within the food system. Built on evidence from an array of reductionist and non-reductionist literature, we suggest that food systems researchers and policymakers adapt current methods and theoretical frameworks to appropriately contextualise aquatic animals in broader food systems. We do this through combining current understandings of food systems theory, value chain, livelihoods, nutritional outcomes, and planetary boundaries thinking. We make several claims around understanding the role of aquatic animals in terms of nutritional output and environmental impacts. We suggest a need to consider: (1) the diversity of species and production methods; (2) variable definitions of an “edible yield”; (3) circular economy principles and the impacts of co-products, and effects beyond nutrient provision; (4) role of aquatic animals in the overall diet; (5) contextual effects of preservation, preparation, cooking, and consumer choices; (6) globalised nature of aquatic animal trade across the value chain; and (7) that aquatic animals are produced from a continuum, rather than a dichotomy, of aquaculture or fisheries. We conclude by proposing a new framework that involves cohesive interdisciplinary discussions around aquatic animal foods and their role in the broader food system.

Key Performance Indicators of Common Carp (Cyprinus carpio L.) Wintering in a Pond and RAS under Different Feeding Schemes

Overwintering impacts common carp performance, yet the nature of changes is not known. The aim of the study was to compare the zootechnical and key performance indicators (KPI) of Cyprinus carpio wintering in a pond with no supplementary feeding (MCF), in a Recirculating Aquaculture System (RAS) fed typical (30% of protein and 8% of fat) carp diet (AFC), and in a RAS fed high protein (42%) and fat (12%) diet (ABF). The analysis showed that ABF fish had the highest final body weight and the Fulton’s condition factor, as well as the lowest food conversion rate compared with AFC and MCF fish. Histomorphological assessment revealed that MCF fish had thinner skin layers, a depleted population of mucous cells in skin, an excessive interlamellar mass in the gills, and no supranuclear vacuoles in the intestine compared to fish from RAS. At the molecular level, higher transcript levels of il-1β and il-6 transcripts were found in the gills of MCF than in fish from RAS. The transcript level of the intestinal muc5b was the highest in ABF fish. Relative expression of il-1β and il-6 in gills were presumably the highest due to lamellar fusions in MCF fish. Described KPIs may assist carp production to ensure sustainability and food security in the European Union.

Aquaculture Site Selection of Oncorhynchus Mykiss (Rainbow Trout) in Markazi Province Using GIS-Based MCDM

The production of seafood, particularly in areas far from coastlines, makes aquaculture an optional farming alternative. Case research from the semi-arid Markazi province, Iran, is examined as a viable aquaculture location for Oncorhynchus mykiss (rainbow trout). ArcGIS Version 10.6.1 and Super Decision Version 3.2 software are utilized for the zoning and assessment of criteria maps. All criteria, i.e., sub-criteria and limitations, were gathered through the academic literature, qualitative interviews via expert opinion, national data, and guidelines. By imposing constraints on the premier aquatic potential map, the final map of the aquaculture potential of Markazi province was obtained. The results indicated that 40.79% of Markazi province has a high potential for aquaculture development. According to the sensitivity analysis, changes in criterion value (i.e., increase or decrease) in weight corresponded with the rate of change. Aquaculture development would require large-scale investment and make Markazi province a major seafood producer in the region.

Transcriptional Signatures of Immune, Neural, and Endocrine Functions in the Brain and Kidney of Rainbow Trout (Oncorhynchus mykiss) in Response to Aeromonas salmonicida Infection

Rainbow trout (Oncorhynchus mykiss) serves as one of the most important commercial fish with an annual production of around 800,000 tonnes. However, infectious diseases, such as furunculosis caused by Aeromonas salmonicida infection, results in great economic loss in trout culture. The brain and kidney are two important organs associated with “sickness behaviors” and immunomodulation in response to disease. Therefore, we worked with 60 trout and investigated transcriptional responses and enrichment pathways between healthy and infected trout. We observed that furunculosis resulted in the activation of toll-like receptors with neuroinflammation and neural dysfunction in the brain, which might cause the “sickness behaviors” of infected trout including anorexia and lethargy. We also showed the salmonid-specific whole genome duplication contributed to duplicated colony stimulating factor 1 (csf-1) paralogs, which play an important role in modulating brain immunomodulation. Enrichment analyses of kidneys showed up-regulated immunomodulation and down-regulated neural functions, suggesting an immune-neural interaction between the brain and kidney. Moreover, the kidney endocrine network was activated in response to A. salmonicida infection, further convincing the communications between endocrine and immune systems in regulating internal homeostasis. Our study provided a foundation for pathophysiological responses of the brain and kidney in response to furunculosis and potentially offered a reference for generating disease-resistant trout strains.

Opportunities and challenges for upscaled global bivalve seafood production

Slow growth in the bivalve mariculture sector results from production inefficiencies, food safety concerns, limited availability of convenience products and low consumer demand. Here we assess whether bivalves could meet mass-market seafood demand across the bivalve value chain. We explore how bivalve production could become more efficient, strategies for increasing edible meat yield and how food safety could be improved through food processing technologies and new depuration innovations. Finally, we examine barriers to consumer uptake, such as food allergen prevalence and bivalve preparation challenges, highlighting that appealing and convenient bivalve food products could provide consumers with nutritious and sustainable seafood options-and contribute positively to global food systems.

Compound climate risks threaten aquatic food system benefits

Aquatic foods from marine and freshwater systems are critical to the nutrition, health, livelihoods, economies and cultures of billions of people worldwide, but climate-related hazards may compromise their ability to provide these benefits. Here, we estimate national-level aquatic food system climate risk using an integrative food systems approach that connects climate hazards impacting marine and freshwater capture fisheries and aquaculture to their contributions to sustainable food system outcomes. We show that without mitigation, climate hazards pose high risks to nutritional, social, economic and environmental outcomes worldwide-especially for wild-capture fisheries in Africa, South and Southeast Asia, and Small Island Developing States. For countries projected to experience compound climate risks, reducing societal vulnerabilities can lower climate risk by margins similar to meeting Paris Agreement mitigation targets. System-level interventions addressing dimensions such as governance, gender equity and poverty are needed to enhance aquatic and terrestrial food system resilience and provide investments with large co-benefits towards meeting the Sustainable Development Goals.

Characteristics and Dynamics of the Freshwater Fish Market in Chengdu, China

The drivers and characteristics of trends in aquatic product consumption are a crucial component of fish food system sustainability. The Chinese market for aquatic products is the largest in the world, yet little has been published on the characteristics of the freshwater fish market. This Paper draws on interviews with key informants to understand the social characteristics of the freshwater fish market in Chengdu, Sichuan province. Price, food safety and quality, freshness and local culinary traditions are important influences on patterns of freshwater fish consumption. However, imported species such as pangasius and branded products are increasing in popularity, indicative of changes in the Chengdu freshwater fish market and the Chinese market for aquatic products more generally.

Identifying Policy Best-Practices to Support the Contribution of Aquatic Foods to Food and Nutrition Security

The relationship between aquatic foods and food nutrition and security is increasingly recognised in policy and practice, yet many governance instruments do not acknowledge or support this important connection. The most effective policy approaches to support the link between these sectors, or 'best practices' are currently unknown. We reviewed relevant governance instruments from multiple countries to identify how these instruments linked fisheries, aquaculture and food security and nutrition, including the policy framing and evidence of political commitment. Of the documents connecting the sectors (65%), the majority did so in the context of developing the fisheries/aquaculture sector to increase aquatic food availability and/or access (51%), followed by developing the fisheries/aquaculture sector as a livelihoods approach to indirectly improve food security (33%), for example, through income generation. Sectoral links established in the context of nutrition-sensitive approaches to fisheries and aquaculture were less common (5%). Almost one third (29%) of instruments supported the connection between aquatic foods and food security and nutrition across three or more different contexts relevant to food security or food systems, while 12% indicated a very high level of commitment. We recommend some key attributes for future policy development to help build coherence between sectors and to help frame coherent food system-based policies.

Blue Economy and Blue Activities: Opportunities, Challenges, and Recommendations for The Bahamas

Following the global shutdown of tourism at the onset of the COVID-19 pandemic, small island developing states such as The Bahamas had their economies immobilized due to their heavy dependence on the industry. Beyond economic recovery in a post COVID-19 paradigm, the blue economy, blue growth, and associated activities offer pathways for a more resilient economy and is well-suited for The Bahamas. This paper suggests conduits for economic development using a traditional strength, coastal and marine tourism, in conjunction with the emerging fields of ocean renewable energy, offshore aquaculture, marine biotechnology, and bioprospecting. The interlinkages between each activity are discussed. Knowledge gaps in offshore aquaculture, ocean renewable energy, marine biotechnology, and marine environment monitoring are identified. In each sector case, strategic and tactical decision-making can be achieved through the exploitation of ocean numerical modeling and observations, and consequently should be invested in and developed alongside the requisite computational resources. Blue growth is encouraged, but instances of blue injustice are also highlighted. Crucially, pursuing blue economy activities should be given top national priority for economic recovery and prosperity.

Structural and molecular indices in common carp (Cyprinus carpio L.) fed n-3 PUFA enriched diet

Sustainable freshwater aquaculture has been recently gaining attention owing to the potential of nourishing the world. The study aimed to evaluate the influence of finishing diets on the activity of 21 genes involved in hepatic lipid metabolism and intestinal homeostasis, liver and intestine histology, and the level of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids in common carp fillets. We compared two experimental diets: control diet mimicking a commercial feed (CTRL) and a test diet (CB) fortified with EPA and DHA retrieved from salmon by-products. An additional control (eCTRL) from extensively cultured carps was investigated. The study revealed that the expression of seven hepatic genes, e.g., lipoprotein lipase and fatty acid synthase, and six intestinal genes e.g., claudin-3c and γ-glutamyl transpeptidase, was influenced specifically by the experimental diets and farming type. Fish from the eCTRL group had the smallest hepatocytes and the largest nuclei compared with CTRL and CB. No pathological signs were found in intestine samples. Additionally, the levels of EPA and DHA in fillets were significantly higher in fish receiving CB compared with CTRL and eCTRL. The use of fortified diets is a promising solution to produce freshwater species with enhanced nutritional value without compromising the safety of fillets.

A 20-year retrospective review of global aquaculture

The sustainability of aquaculture has been debated intensely since 2000, when a review on the net contribution of aquaculture to world fish supplies was published in Nature. This paper reviews the developments in global aquaculture from 1997 to 2017, incorporating all industry sub-sectors and highlighting the integration of aquaculture in the global food system. Inland aquaculture-especially in Asia-has contributed the most to global production volumes and food security. Major gains have also occurred in aquaculture feed efficiency and fish nutrition, lowering the fish-in-fish-out ratio for all fed species, although the dependence on marine ingredients persists and reliance on terrestrial ingredients has increased. The culture of both molluscs and seaweed is increasingly recognized for its ecosystem services; however, the quantification, valuation, and market development of these services remain rare. The potential for molluscs and seaweed to support global nutritional security is underexploited. Management of pathogens, parasites, and pests remains a sustainability challenge industry-wide, and the effects of climate change on aquaculture remain uncertain and difficult to validate. Pressure on the aquaculture industry to embrace comprehensive sustainability measures during this 20-year period have improved the governance, technology, siting, and management in many cases.

Structural and Functional Diversity among Five RING Finger Proteins from Carassius Auratus Herpesvirus (CaHV)

Carassius auratus herpesvirus (CaHV) has been identified as a high-virulence pathogenic virus that infects aquatic animals, but the key factor for virus–host interaction is still unclear. Five Really interesting new genes (RING) finger proteins (39L, 52L, 131R, 136L, and 143R) of CaHV were screened to determine structural diversity. RING finger proteins were also predicted in other known fish herpesviruses, with an arrangement and number similar to CaHV. We performed multifaceted analyses of the proteins, including protein sizes, skeleton structures, subcellular localizations, and ubiquitination activities, to determine their precise roles in virus–host interactions. The five proteins were overexpressed and detected different levels of ubiquitination activities, and 143R showed the highest activity. Then, the prokaryotic expressed and purified full-length proteins (131R and 136L), RING domain isolates (131R_12–43 and 136L_45–87), and RING domain-deleted mutants (131RΔ_12–43 and 136LΔ_45–87) were prepared to detect their activities through ubiquitination assays. The results indicate that both full-length proteins and their isolates have activities that catalyze ubiquitination, and the full-length proteins possess higher activity than the isolates, but RING domain-deleted mutants lose their activities. Furthermore, the activities of the five proteins were verified as E3 ubiquitin ligase activity, showing that the RING domains determine the ubiquitination activity. These proteins present different subcellular localization. RING domain-deleted mutants showed similar subcellular localization with their full-length proteins, and all the isolates diffused in whole cells. The current results indicate that the sequence outside the RING domain determines subcellular localization and the level of ubiquitination activity, suggesting that the RING finger proteins of fish herpesviruses might have diverse functions in virus–host interaction.