Aquaculture Development Research Articles

Understanding tilapia mortalities and fish health management in Lake Volta: a systematic approach

Unusual fish mortalities in aquaculture threaten global food security and carry significant socio-economic burdens. In 2018, Nile tilapia (Oreochromis niloticus) suffered unusual patterns of mortalities, attributed to disease-causing agents in Lake Volta cage aquaculture. In recent times, disease investigations have shifted from single to consideration of multiple factors to understand the puzzling range of causal risk factors. This study therefore aimed at expanding on tilapia mortality risk factors, while documenting fish health and Lake Volta management practices for sustainable aquaculture. We interviewed relevant aquaculture stakeholders operating on Lake Volta and conducted thematic analysis on their responses to map out mortality risk factors and management practices. The identified risk factors were conceptualized in established models of causation web and Social-Ecological System to explain the practical significance of the findings. The results showed that the risk factors of tilapia mortalities are a combination of pathogens and non-infectious factors mediated by weak law enforcement. The results further suggested mortality reinforcing mechanisms through the horizontal transmission of pathogens, namely, Streptococcus agalactiae and Infectious Spleen and Kidney Necrosis Virus. Moreover, the recognition of weak enforcement as a possible factor reinforcing human activities is a non-infectious route that can be deleterious to fish health. Health management practices comprised phytotherapy, vaccination, heat shock treatment, biological controls, and best husbandry practices. Lake management involves creating a waterfront buffer of 85.34 m, surveillance, and executing the framework guiding aquaculture development on the Lake. The findings are suggestive of complementary quantitative studies that augment the qualitative evidence herein. Such follow up studies can disclose precise mortality risk factors to inform policy directives and effective remedial strategies that can secure fish and lake health.

Comparative assessment of Chinese mitten crab aquaculture in China: Spatiotemporal changes and trade-offs

The increasing human demand for high-quality animal protein has provided impetus for the development of aquaculture. Chinese mitten crab (Eriocheir sinensis) is a catadromous species rapidly being cultured in China but scientific literature documenting its life cycle environmental and economic consequences remains scarce. This study aims to address this gap by examining the spatio-temporal evolution of crab aquaculture in China since the 2000s and evaluating the environmental and economic characteristics along its life-cycle stages: megalopa, juvenile crab, and adult crab cultivation. The geostatistical analysis shows a more dispersed pattern of crab aquaculture nationally as crab grows, with coastal provinces that have brackish water for megalopa cultivation but wider spatial coverage for juvenile and adult crab cultivation. Our findings reveal that the production of 1 ton of live-weight crab results in 7.65 ton of CO2 equivalent of greenhouse gas emissions, surpassing previous estimates for finfish fish production by approximately 50%. Most environmental pressures occur during the adult crab cultivation stage, with significant contributions from upstream processes such as electricity and feed production. By comparing between different production systems, our study shows that crab aquaculture in lake systems performs better than pond systems in terms of most global environmental impact categories and economic considerations. This work contributes to the existing literature by elucidating the spatio-temporal changes of crab aquaculture boom in China and constructing a representative life cycle data pool that broadens the benchmark knowledge on its environmental and economic characteristics. We highlight the trade-offs between environmental and economic performance as well as the balance between global and local environmental impacts to promote sustainable growth in the aquaculture industry.

The probiotic roles of Lactiplantibacillus plantarum E2 as a dietary supplement in growth promotion and disease resistance of juvenile large yellow croaker (Larimichthys crocea)

Bacterial diseases are the most important limiting factors for the development of large yellow croaker aquaculture. Probiotics are considered to be a promising alternative approach for the control of bacterial diseases in aquaculture. However, the studies on probiotics used in farmed large yellow croakers were very limited. In this study, we isolated and identified a Lactiplantibacillus plantarum E2 from the intestinal tract of large yellow croaker. L. plantarum E2 showed significant antibacterial activities against several aquaculture pathogenic bacteria, intestinal environmental tolerance, and biosafety. After 7 weeks of feeding, the E2 supplementation of dietary significantly improved the growth and the survival rates of large yellow croakers after Pseudomonas plecoglossicida PQLYC4 challenge. Further analysis showed that E2 effectively improved the intestinal integrity, and increased the intestinal α-amylase, trypsin and lipase activities. Moreover, the E2 supplementation also significantly suppressed the mRNA expression of IL-10 and increased the mRNA expression of IL-1β, IL-12α, IL-17D, IFN-γ, and TNF-α-R. Gut microbiota analysis showed that E2 significantly affected gut microbial community composition by decreasing the relative abundance of Sphingomonas and increasing the relative abundance of Lactobacillus and Pseudomonas. Finally, E2 could improve resistance of large yellow croaker against P. plecoglossicida PQLYC4 infection. Therefore, our findings showed that L. plantarum E2 has potential application as a probiotic in large yellow croaker, which may provide a new strategy of preventing and controlling bacterial diseases in this species.

Long-term water quality model in aquaculture based on dilated convolution feature fusion and interactive learning

The prediction of water quality parameters is of great significance for maintaining water stability and controlling marine environments. However, due to the temporal nature of water quality parameters and the influence of surrounding changeable environments, water quality is characterized by complex nonlinearity and instability. In current prediction research, there are many training parameters and poor generalization ability, and its prediction accuracy cannot be guaranteed. Thus, this paper proposes a network model called Feature Fusion Interactive learning network (FFINet) based on dilated convolution feature fusion and interactive learning. FFINet is composed of the SCFINet module and TCINet module in parallel, and the two modules accept the same original sequence. The SCFINet module captures the local features of the sequence through feature fusion and proposes interactive learning to extract the trend, periodicity and irregularity information of the subsequence. The TCINet module uses expansion convolution to capture the long-term dependencies of sequences and uses interactive learning to compensate for information loss during separation, can process sequences simultaneously in parallel mode, and can retain irregular information of sequences. The model adds a dual residual connection to weaken the problem of model gradient vanishing, and each layer outputs sequences of the same length to be added as input to the lower layer. Dissolved oxygen concentration experiments are conducted at multiple marine ranches, and the results of the proposed model are compared with those of other deep learning models, showing that FFINet has better prediction performance than existing approaches. This paper provides important theoretical guidance for sustainable aquaculture development.

Application of GIS and fuzzy sets to small-scale site suitability assessment for extensive brackish water aquaculture

ABSTRACT The rapid expansion of extensive brackish water aquaculture (BA) in Indonesia has created an urgent need to develop effective and reliable methods to evaluate and select sites suitable for aquaculture development. The lack of supporting spatial data at appropriate scales has limited the application of GIS-based multi-criteria evaluation methods (MCEs) in Indonesia. This study presents alternative fuzzy-based Geographic Information System (GIS) methods to evaluate and select sites suitable for extensive brackish water aquaculture. This study successfully produced fuzzy set maps from a water availability sub-model, a land conversion sub-model and a green belt buffer zone sub-model. With grades of membership, the fuzzy set maps provide smooth class boundary representation, which creates more options for decision-making than a map classified with crisp logic. Combining these sub-models produced an overall site suitability map at the scale of 1:50,000 for the study region. This final suitability map effectively excluded more than 95% of the unsuitable area for BA. This broad-scale site suitability assessment approach is a helpful planning tool to promote Indonesia’s sustainable development of extensive brackish water aquaculture. It identifies possible conflicts in land uses and considers conservation issues early in the planning process. The output can be used to scope research areas for more detailed investigations in countries where BA is a vital livelihood.

Reproductive studies on the carpet clam Paphia textile (Paratapes textilis) (Gmelin 1791) (Family: Veneridae): a guide of aquaculture management along the Egyptian coasts of the Red Sea and Suez Canal

BackgroundMost aquatic biota's reproductive biology and life cycle are essential to the sustainable management and development of coastal ecosystems and aquaculture. The bivalve Paphia textile (Gmelin 1791), also known as Paratapes textilis, has an economic value in Indo-Pacific waters, including the Red Sea and the Suez Canal lakes, the Egyptian coasts. However, P. textile suffers from extensive fishing and exploitation.AimThe present work aims to study the Paphia textile's reproductive cycle on the Egyptian coasts of the Red Sea for the first time. It helps to manage and develop the coastal ecosystems and aquaculture.MethodologySamples were collected monthly from two saline lakes in the Suez Gulf from December 2019 to November 2020. As part of the comprehensive research study, sex ratio, condition index, sexuality, histological analysis of gonads, shell size, and gonad index were used to investigate the reproductive cycle.ResultsThe results reveal a male-biased sex ratio, possibly due to anthropogenic stressors. The Paphia textile is dioecious. No hermaphrodite cases were observed in the studied specimens. The condition index in winter and spring indicates periods dominated by mature individuals. Five reproductive maturity stages were assigned for both P. textile males and females. Due to the simultaneous development of several developmental stages monthly throughout the sampling year, warm water may be responsible for non-sequential gametogenic cycles. As measured environmental parameters correlate with maturity stages, temperature, salinity, and chlorophyll a play important role in gonad growth. The size at first sexual maturity at which 50% of the Paphia textile population reached maturity ranged from 28.60 to 31.50 mm for females, and between 31.70 and 34.10 mm for males. As the gonad index increases during the ripe stages, this index decreases during the resting, spawning, and spent phases.ConclusionsThe findings suggest the most suitable temperature for aquaculture spawning is between 20 °C and 30 °C in subtropical waters. Fishing should generally be prohibited at sizes less than 28.60 mm for better management and sustainability of this valuable aquatic resource on the Egyptian coasts of the Red Sea.

Aquaculture in Africa: Current Status and Conjectural Assessing of Potential of its Coastline (Land Side) for Aquaculture in Future

In 2020, Africa (except Egypt and Nigeria) had about 400 thousand tonnes of products by aquaculture. But, hypothetical studies show that this amount can be increased to 1,500 thousand tonnes if 1% of the length of the African coastline is dedicated to aquaculture. It is sufficient for one serving of protein food for 5 billion people (300 g raw aquatic product for one serving). The results of this research are hypothetical and differ from the existing reality, but these data show that African coasts have a high potential for aquaculture development. Countries that are developed in the field of aquaculture ought to help Africa in the development of the aquaculture industry.

Recent Developments in Aquaculture and Future Prospects: A Comprehensive Review

In the pursuit of promoting sustainable aquaculture production, numerous cutting-edge technologies have emerged in recent years. The utilization of effective microbes (EM) in managing water quality, the implementation of biofloc technology, aquamimicry, the inclusion of Black Soldier Fly (BSF) as an additional protein source, the use of triploidy and polyploidy, vaccines, probiotics, and prebiotics, the integration of Internet of Things (IoT) for monitoring water quality in the farm operation, the practice of monosex culture, and the application of neo-female techniques are all being employed in aquaculture operations. The advancements in these cutting-edge technologies have been focused on promoting sustainable aquaculture production, mitigating the risk of disease outbreaks, enhancing crop yields, and contributing to eco-friendly environmental initiatives. This review paper highlights the cutting-edge technologies that have emerged in the field of aquaculture in recent years, up until the present time, with a focus on advancements in fish nutrition. The advancements in aquaculture technology have been instrumental in promoting the achievement of sustainable development goals, particularly SDG-1 (no poverty) and SDG-2 (zero hunger). These goals are aimed at reducing poverty and eliminating hunger by utilizing the enhanced aquaculture production facilitated by the latest technological innovations. In the arena of aquaculture, this review paper has the potential to nourish the minds of aquaculturists and aquafarmers with a bountiful feast of knowledge. It unveils the latest technologies and developments in the realm of aquaculture, serving as a nutritious resource that can enhance the operation of cultures and promote a fruitful increase in production in the not-so-distant future.

Ferulic acid alleviates carp brain damage and growth inhibition caused by avermectin by modulating the Nrf2/Keap1 and NF-κB signaling pathways

The increasing concern over environmental pollution caused by the pesticide avermectin used in aquaculture has attracted significant attention. The use of avermectin, a neurotoxic pesticide, in aquatic environments leads to toxic effects on non-target organisms, particularly causing harm to fish. The phenolic compound ferulic acid possesses excellent anti-inflammatory and antioxidant capabilities. This study was conducted by establishing a chronic exposure experiment to avermectin, proposes the use of ferulic acid as a dietary additive to protect the carp brain from damage caused by exposure to avermectin. Furthermore, it investigates the anti-inflammatory and antioxidant effects of ferulic acid in the carp brain under chronic exposure to avermectin. The experimental results demonstrate that ferulic acid can alleviate brain tissue inflammation and oxidative stress by modulating the Nrf2/Keap1 and NF-κB signaling pathways. It protects the carp brain from chronic avermectin-induced damage, preserves the integrity of the carp blood-brain barrier, enhances the levels of feeding factors, and thereby alleviates carp growth inhibition. These findings provide new therapeutic strategies and a theoretical foundation for the sustainable development of carp aquaculture.

Effects of Chinese herbal medicines on growth performance, intestinal flora, immunity and serum metabolites of hybrid grouper (Epinephelus fuscoguttatus♀×Epinephelus lanceolatu♂).

The immunomodulatory roles of Chinese herbal Medicine (CHM) in aquatic animals have been well-recorded. However, how CHM impacts the intestinal microbiota and serum metabolism is not fully understood. In this study, the effects of different additive levels of CHM on the growth performance, immunity, intestinal flora and serum metabolism of hybrid grouper (♀Epinephelus fuscoguttatus×♂Epinephelus lanceolatu) were investigated. The addition of 0.5%, 1.0%, 1.5% and 2.0% Chinese herbal medicine compound to feed could significantly improve the weight gain rate (WGR), specific growth rate (SGR) and survival rate (SR) of grouper, reduced feed coefficient, while had no significant difference on morphometric parameter. The most significant improvement for the parameters above was observed in 1.5% group. Different addition levels of CHM could also significantly enhance the activities of ACP, AKP, SOD, CAT and LZM in serum. Accordingly, the supplementation of CHM significantly induced up-regulation of immune genes such as IL-8, IL-1β, TNF-α, Nrf2, Lzm in the liver, spleen and head kidney of grouper, improved the resistance of grouper to V. harveyi as well. The intestinal flora analysis showed that at the phylum level, the main dominant species of intestinal microorganisms were Firmicutes, Proteobacteria, Bacteroidota, Actinobacteriota, Gemmatimonadota, Desulfobacterota, Fusobacteriota and Myxococcota. At the genus level, the high abundance was Lactobacillus, Streptococcus, Bacteroides, Escherichia, Romboutsia, Sphingomonas and Muribaculaceae. The abundance of probiotics (such as Lachnospiraceae, Lactobacillaceae, Streptococcaceae, etc) in CHM-supplement groups were higher (highest in 1.5% group) compared with control group. Moreover, a total of 11 common differential metabolic pathways were screened by LC-MS metabolism analysis of serum, they were Neuroactive ligand-receptor interaction, Purine metabolism, Linoleic acid, Glycerophospholipid metabolism, Taurine and hypotaurine metabolism, Arginine and proline metabolism, ABC transporters, Aminoacyl-tRNA biosynthesis, Arachidonic acid metabolism, Drug metabolism-cytochrome P450, alpha-Linolenic acid metabolism. Also, three common differential metabolites (PI(20:4(5Z,8Z,11Z,14Z)/18:1(11Z)), PC(20:3(8Z,11Z,14Z)/22:1(13Z)), PC(22:0/20:4(5Z,8Z,11Z,14Z)) associated with intestinal health, growth and disease resistance was found. These data will contributes to a comprehensive understand for the regulatory roles of CHM on fish, which is also beneficial for the disease control and sustainable development of aquaculture.

Uridine alleviates high-carbohydrate diet-induced metabolic syndromes by activating sirt1/AMPK signaling pathway and promoting glycogen synthesis in Nile tilapia (Oreochromis niloticus).

Carbohydrates have a protein sparing effect, but long-term feeding of a high-carbohydrate diet (HCD) leads to metabolic disorders due to the limited utilization efficiency of carbohydrates in fish. How to mitigate the negative effects induced by HCD is crucial for the rapid development of aquaculture. Uridine is a pyrimidine nucleoside that plays a vital role in regulating lipid and glucose metabolism, but whether uridine can alleviate metabolic syndromes induced by HCD remains unknown. In this study, a total of 480 Nile tilapia (Oreochromis niloticus) (average initial weight 5.02±0.03g) were fed with 4 diets, including a control diet (CON), HCD, HCD+500mg/kg uridine (HCUL) and HCD+5,000mg/kg uridine (HCUH), for 8 weeks. The results showed that addition of uridine decreased hepatic lipid, serum glucose, triglyceride and cholesterol (P<0.05). Further analysis indicated that higher concentration of uridine activated the sirtuin1 (sirt1)/adenosine 5-monophosphate-activated protein kinase (AMPK) signaling pathway to increase lipid catabolism and glycolysis while decreasing lipogenesis (P<0.05). Besides, uridine increased the activity of glycogen synthesis-related enzymes (P<0.05). This study suggested that uridine could alleviate HCD-induced metabolic syndrome by activating the sirt1/AMPK signaling pathway and promoting glycogen synthesis. This finding reveals the function of uridine in fish metabolism and facilitates the development of new additives in aquatic feeds.

Effects of different water quality regulators on growth performance, immunologic function, and domestic water quality of GIFT tilapia.

Water quality regulation is widely recognized as a highly effective strategy for disease prevention in the field of aquaculture, and it holds significant potential for the development of sustainable aquaculture. Herein, four water quality regulators, including potassium monopersulfate (KMPS), tetrakis hydroxymethyl phosphonium sulfate (THPS), bacillus subtilis (BS), and chitosan (CS), were added to the culture water of Oreochromis niloticus (GIFT tilapia) every seven days. Subsequently, the effects of these four water quality regulators on GIFT tilapia were comprehensively evaluated by measuring the water quality index of daily growth-related performance and immune indexes of GIFT tilapia. The findings indicated that implementing the four water quality regulators resulted in a decrease in the content of ammonia nitrogen, active phosphate, nitrite, total organic carbon (TOC), and chemical oxygen demand (COD) in the water. Additionally, these regulators were found to maintain dissolved oxygen (DO) levels and pH of the water effectively. Furthermore, using these regulators demonstrated positive effects on various physiological parameters of GIFT tilapia, including improvements in final body weight, weight gain rate (WGR), specific growth rate (SGR), condition factor (CF), feed conversion ratio (FCR), spleen index (SI), hepato-somatic index (HSI), immune cell count, the activity of antioxidant-related enzymes (Nitric oxide, NO and Superoxide dismutase, SOD), and mRNA expression levels of immunity-related factors (Tumor Necrosis Factor-alpha, TNF-α and Interleukin-1 beta, IL-1β) in the liver and spleen. Notably, the most significant improvements were observed in the groups treated with the BS and CS water quality regulators. Moreover, BS and CS groups exhibited significantly higher serum levels of albumin (ALB) and total protein (TP) (P < 0.05), whereas the other indicators showed no significant difference (P > 0.05) compared to the control group. However, the KMPS and THPS groups of GIFT tilapia exhibited significantly higher serum levels of aspartate aminotransferase (AST), alanine transaminase (ALT), creatinine (CRE) and blood urea nitrogen (BUN) (P < 0.05), whereas they exhibited significantly decreased HSI (P < 0.05). In addition, the partially pathological observations revealed the presence of cell vacuolation, nuclear shrinkage, and pyknosis within the liver. In conclusion, these four water quality regulators, mainly BS and CS, could improve the growth performance and immunity of GIFT tilapia to varying degrees by regulating the water quality and then further increasing the expression levels of immune-related factors or the activity of antioxidant-related enzymes of GIFT tilapia. On the contrary, the prolonged use of KMPS and THPS may gradually diminish their growth-enhancing properties and potentially hinder the growth of GIFT tilapia.

Assessing sustainable performance of aquatic species using multiple footprints for comprehensive dietary advice

Aquaculture has become an important source of food, providing an alternative to wild fisheries and terrestrial food. However, the environmental impacts of aquaculture can vary greatly, and it is essential to understand the relationship between the nutrition provided by aquatic species and their multiple environmental footprints for targeted dietary advice and sustainable development of aquaculture. In this study, we examined 49 aquatic species or taxa divided into eight groups, considering ten nutrients and five environmental impacts for Chinese aquaculture. The results showed that species varied widely in their nutritional values and environmental impacts, with mussel, razor clam, marine bass, flounder and snapper being the most recommended for sustainable performance (sustainability score Si > 1.60). In contrast, tilapia performed poorly (Si = 0.11) in both nutritional score and environmental impacts, thus should not be promoted in dietary advice. Results of spatial analysis showed that Qinghai (Si = 1.06) and Tibet (Si = 0.75) had the highest sustainable development level for freshwater aquaculture, while there were large differences in marine aquaculture among coastal provinces (the highest Si in Zhejiang was 1.42, and the lowest Si in Guangxi was 0.56) and the sustainable performance of all coastal provinces is reduced to varying degrees when freshwater aquaculture and marine aquaculture are considered comprehensively. Increasing the proportion of high sustainable performance species is an effective way to improve the sustainability score in most provinces, particularly coastal ones. We suggest that the proportion of species production should be adjusted, and the cultivation of species with high sustainable performance should be prioritized. This study provides an initial assessment of the sustainability of aquatic food by combining nutrition and multiple environmental impacts for Chinese aquaculture.

The world’s best practices in the development of aquaculture in the framework of the implementation of projects for the multipurpose use of the infrastructure of the fuel and energy complex

The article discusses the current international experience of integrating various aquaculture projects into the infrastructure of the fuel and energy complex. Against the background of the active growth in the production of aquaculture products, there is a tendency for the multipurpose use of energy sector facilities (oil platforms, wind farms, etc.) to obtain valuable aquaculture products both during their operation and after the completion of the project period of use. The specifics of the production and assortment of aquaculture facilities and farming methods in different regions of the world have been identified, which determined the features of the integration of aquaculture into fuel and energy facilities. The most common and has been used for many decades in many countries of the world is the cultivation of aquaculture facilities on the recycled water of thermal power plants and reservoirs of hydroelectric power plants. In the European region, there is an active use of offshore platforms for the extraction of hydrocarbons with simultaneous agricultural, aquaculture, scientific activities and the production of electricity through the installation of wind and wave turbines. Oxygen and hydrogen production is organized on some platforms. In North America, projects of hybrid systems “food-energy-water” are being developed using aquavoltaics technology, which allows maintaining the aquatic environment in optimal condition. Fish farming is combined with the cultivation of crustaceans and shellfish, oil platforms are often repurposed into artificial reefs. A patented project of an integrated floating system consisting of four vertical-axial wind turbines connected to a single system with a solar battery and a floating base for the placement of aquaculture facilities is being implemented in Asia. The development of such projects, in addition to the pronounced positive economic effect, also contributes to improving the level of food security of the regions. The use of engineering structures and other infrastructure facilities as new locations and substrates for the cultivation and free habitat of various hydrobionts can significantly reduce the negative impact of the fuel and energy industry on the environment.

Efficient breeding and growth advantage of all-male population in Lanzhou catfish (Silurus lanzhouensis)

Sex is one of the most valuable traits for aquaculture fish with distinct sexual dimorphisms, and breeding of monosexual populations improves aquaculture efficiency. Lanzhou catfish (Silurus lanzhouensis) with XX/XY sex determination system is an endemic fish in the Yellow River of China and exhibits sexual growth dimorphism. Here, we tracked the body weight, length and width of Lanzhou catfish and found out that males displayed faster growth performance than females from 3 months post fertilization, accompanied by sexually dimorphic expression of growth hormone/insulin-like growth factor (GH/IGF) axis genes. Subsequently, we performed genetic analyses in the self-fertilized family obtained from a hermaphrodite individual. Similar to the artificial gynogenetic family, the offspring of the self-fertilized family had significant higher genetic homozygosity and similarity than that of the sexually reproduced family. More importantly, we used the YY male obtained by self-fertilization to mate with two XX female individuals and reproduced an all-male population with XY sex chromosomes, saving one generation time (3 years) and avoiding estradiol treatment compared with the conventional way of all-male population production. And the all-male population showed an obvious growth advantage over the normal population with both sexes, facilitating the development of catfish aquaculture.

Bacillus indicus and Bacillus subtilis as alternative health and colouration promoters to synthetic astaxanthin in cyprinid aquaculture species

One of the largest challenges for the sustainable development of global aquaculture is the threat of infectious diseases. Preventative strategies that reduce antibiotic use are required to ensure fish health, minimise infectious diseases and subsequent pharmaceutical interventions. Recent strategies involve health-promoting feed supplements, such as astaxanthin and probiotic bacteria. Astaxanthin, a widely used carotenoid, offers colouration and antioxidant properties that can improve fish growth and fish survival when challenged with a pathogen. Probiotics can provide fish with a range of health benefits ranging from enhanced feed digestion, synthesis of vitamins, boost of innate immune response and active defence against potential pathogens.In this study, we tested if novel probiotic blends (Bacillus subtilis and/or Bacillus indicus) can be used as alternative health and/or colouration supplements to astaxanthin in two cyprinid species, mirror carp (Cyprinus carpio) and Red Comet goldfish (Carassius auratus auratus). Using experimental feed trials and 16S rRNA microbial profiling, the impact of the probiotic on fish growth and microbial community within the distal gastrointestinal tract was assessed. In addition, in mirror carp, blood samples were tested for immunology and haematological parameters, while in goldfish colouration of the skin was analysed.Mirror carp fed astaxanthin showed significantly increased growth whereas B. substilis /B.indicus supplementation had non-significant effects on growth performance. Our results provide the first insights into how the supplementation of astaxanthin changes the microbial composition in cyprinid species. In mirror carp, astaxanthin and the probiotic blend induce a significant shift in gut microbial communities. Mirror carp fed B. substilis/ B.indicus showed several indices of potential microbial and health benefits such as increased diversity, an abundance of potentially beneficial bacteria and enhancement of the phagocytic activity and creatinine blood levels. However, no effect on colouration, growth or the microbial community was found in goldfish, highlighting substantial species-specific differences in response to probiotics, in two closely related cyprinid species. Further research into the efficacy and site of colonization of supplemented bacteria in fish gastrointestinal tracts, and the mechanisms underlying the observed shifts in the host microbiota, is required to fully understand species-specific responses to probiotic supplementation.

Gross yield driving the mass fluxes of fishery drugs: Evidence of occurrence from full aquaculture cycle in lower Yangtze River Basin

Expanding aquaculture has generated pollutants like fishery drugs in wastewater, which affects the aquatic environments and hinders sustainable development of aquaculture. To evaluate the occurrence, mass fluxes and production factors of fishery drugs in aquaculture, full-aquaculture-cycle monitoring in finfish and crustacean wastewater was conducted in the lower Yangtze River Basin, and 28 pesticides and 15 antibiotics were detected. The results showed that individual fishery drugs varied from ppt to ppb levels. Among them, sulfonamides were dominant with a mean concentration of 105.95 ± 4.13 ng·L−1 in finfish aquacultural wastewater, and insecticides were prevailing in crustacean aquacultural wastewater with a content of 146.56 ± 0.66 ng·L−1. Since the susceptibility to finfish disease determined the aquaculture practice, there were significant differences between two types of aquacultural wastewater. Finfish aquacultural wastewater contained more drugs and reached peak earlier in rapid-growth period, yet crustacean aquacultural wastewater peaked at the harvest period, to prevent against disease. Meanwhile, higher ecological risk, especially for florfenicol, were found in finfish wastewater. With 6 production factors from Good Aquaculture Practice, the gross yield was the most influential factor of drug mass flux, explaining 98 % variance by stepwise regression. Apart from increasing concentrations of fishery drugs in wastewater, regional high-yield aquaculture also significantly impacted the corresponding mass flux. As estimated by linear regression, 1.63 tons of target drugs would be discharged by 1 Mt. aquatic products, and 7.77 tons were discharged from aquaculture in the lower Yangtze River Basin in 2021. This is the first report to quantify mass fluxes of fishery drugs and to highlight gross yield as the most influential factor, which provides guidance for the supervision and regulation of sustainable aquaculture.

Governing sociocultural sustainability through standards: Evidence from aquaculture eco-certification schemes

Nonstate certifying authorities have long used standards as a governance instrument to improve sociocultural sustainability in the aquaculture sector. However, studies document that sociocultural sustainability has been marginalized in aquaculture certification standards. Against this background, I explore the purview of the sociocultural “principles” embodied in standards to improve sociocultural sustainability in aquaculture development. Although the burgeoning scholarship underscores the coverage of sociocultural indicators in aquaculture certification standards, there is limited research on what principles are included in standards to advance sociocultural sustainability in aquaculture. To address this question, I draw on one of the four dimensions of the “full-spectrum” sustainability framework (FSF), namely, the sociocultural dimension, to compare the extent to which such principles correspond to the FSF. Using the interpretive method, I examine six standards of five transnational aquaculture eco-certification schemes. I argue that standards overwhelmingly underscore issues concerning health and well-being, whereas the emphasis on improving producers' ethical practices and resolving burning issues that profoundly affect indigenous peoples and local communities is comparatively fragile. I further contend that the Naturland, Global Good Agricultural Practice, and Friend of the Sea's (FOS) aquaculture certification standards are weaker than the Aquaculture Stewardship Council and Global Aquaculture Alliance standards, and the FOS standard is the weakest in terms of addressing sociocultural sustainability. I conclude that the exclusion of, and negligible attention to, crucial sociocultural issues can potentially undermine the vision of standards to ensure and govern sociocultural sustainability in aquaculture, thereby providing a rationale for improving certification standards.

Evaluating a microalga (Schizochytrium sp.) as an alternative to fish oil in fish-free feeds for sablefish (Anoplopoma fimbria)

Alternative feeds are critical for the sustainable expansion of the marine finfish aquaculture industry. The industry uses wild-caught forage fish as a primary ingredient in farmed fish feeds. Alternative ingredients are needed to safeguard fisheries' sustainability and future aquaculture development. While there have been successes in alternative feeds, it is necessary to improve the existing options and identify alternative ingredients with higher concentrations of omega-3 polyunsaturated fatty acids (PUFAs). This study was designed to test a microalga, Schizochytrium sp., as a feed ingredient for sablefish (Anoplopoma fimbria) using six test diets. There were two fish-ingredient control diets: +FM+FO, which contained both fishmeal and fish oil, and −FM+FO, which contained fish oil, but no fishmeal. The remaining four diets contained alternative lipids and were completely fish-free. FF Flax contained flax oil as the only lipid source replacing fish oil. FF LowSc, FF ModSc, and FF HighSc contained a low, moderate, and high level of Schizochytrium sp. to replace fish oil, with flax oil content decreasing as the microalga increased. After a 20-week trial, sablefish growth differed across the feed treatments, with fish fed the high microalga-inclusion diet (FF HighSc) performing similarly to fish fed the fish-ingredient controls. Fulton's K condition factor, dry feed intake (DFI), and lipid productive value (LPV) were also influenced by treatment. For the four fish-free diets, specific growth rate increased with increasing inclusion of Schizochytrium sp. in the feed. Fillet fatty acid profiles were similarly influenced by diet treatment, generally reflecting the fatty acid profiles of the feed. Total fillet PUFAs were higher in sablefish from the fish-free treatments than the control treatments, with DHA increasing with increasing inclusion of dietary Schizochytrium. In contrast, EPA was higher in fillets from both fish-ingredient control treatments compared to fillets from the fish-free treatments, yet EPA remained higher than expected in sablefish fed the fish-free diets. Histologic evaluation of sablefish distal intestine and liver demonstrated that the microalga-inclusion diets were well tolerated and did not cause histomorphological changes in the tissues. These results suggest Schizochytrium sp. can increase PUFA concentrations in fish fillets without compromising fish health and growth, making it a viable ingredient for alternative sablefish feeds.

California Sea Cucumber (Apostichopus californicus) Abundance and Movement on a Commercial Shellfish Aquaculture Farm

California sea cucumbers (Apostichopus californicus) are often abundant at oyster farms in British Columbia, Canada both on the suspended gear as juveniles and on the seafloor beneath them as a mixture of juveniles and adults. Their natural abundance, high value, and potential to mitigate benthic organic loading has led to an interest in their coculture with oysters. Whether farmed sea cucumbers ought to be contained to physically separate them from wild stocks is debated. The present three-year field study examined the movement of wild California sea cucumbers on/off an operational oyster farm (~3000 m2) to help inform future sea cucumber aquaculture development. Sea cucumber effects on organic loading, immigration to/emigration from the farm, and the efficacy of various containment-material mesh types and sizes were examined. Juvenile and adult sea cucumber densities on the farm steadily increased from the end of winter through the end of summer, likely due in large part to juveniles falling off the suspended oyster gear, which occurred at an average rate of ~780 ind d−1 (for the whole farm) in the summer months. The largest increase in abundance on the farm was observed between January and March/April, when the population increased by 100–350 ind d−1. Between late summer and early winter, sea cucumbers emigrated from the farm at a rate of 50–90 ind d−1, neither juvenile nor adult densities on the farm changing appreciably over the winter. The sea cucumber density showed a progressive decrease in the first 20 m from the farm, after which the animals were scarcely noticed. Apostichopus californicus did not significantly decrease sediment organics beneath the farm compared to a nearby control site, but such an effect may have been lost due to their seasonal feeding cycles and/or the presence of other benthic grazers that were not part of our exclusion trial. Overall, our findings suggest that the separation of farmed and wild California sea cucumbers on a shellfish farm can only be guaranteed through containment, given the dynamic immigration and emigration patterns of wild stocks. Through laboratory trials, we found that individuals of A. californicus were able to squeeze through mesh as small as 32% of their contracted width and could escape fenced areas (90 ± 4% escape from nylon fencing and 40 ± 8% escape from VexarTM fencing) unless the fencing extended above the water surface (where there was no escape from either type).