Expansion Of Aquaculture Research Articles

Construction of a novel environmentally-friendly long-term antifouling coating with a double-layer structure regulated by phenylmethyl silicone oil and verification of the static antifouling performance of the coating

The expansion of nuclear power, marine aquaculture, and maritime transportation has highlighted the need for effective antifouling strategies to address biofouling, which poses economic and environmental challenges. Traditional antifouling coatings, including toxic coatings (TCs) and fouling-release coatings based hydrophobicity polydimethylsiloxane (PDMS), often result in issues such as high environmental toxicity and limited effectiveness under static conditions. This study addresses these limitations by developing a novel double-layer coatings (DLCs) system that combines a phenyl silicone oil (PSO)-infused fouling-release coatings based PDMS top layer with a TC base layer. Methods used in this study include surface, mechanical and antifouling property analyses, as well as assessments of copper ion (CuⅡ) release rates. Key findings reveal that the bacterial removal rates of DLCs with 4 % PSO before and after 180 days of immersion were 60.00 % and 87.50 %, respectively. The antibacterial performance of the DLCs increased with the PSO content. The static average release rate of Copper ions (RtCuII) from DLCs with 4 % PSO at 180 days was 12.62 μg⋅cm-2⋅d-1. PSO significantly regulates CuⅡ release, improving static antifouling performance and reducing environmental impact. The leaching of PSO creates a slippery surface layer, enhancing fouling-release properties; and increased PSO content promotes greater CuⅡ release control and long-term antifouling effectiveness.This DLC approach provides a sustainable antifouling solution with enhanced durability and environmental benefits, offering significant improvements over conventional antifouling methods.

Establishment and mechanism of thioacetamide-induced hepatopancreas injury model in red swamp crayfish Procambarus clarkii

The red swamp crayfish (Procambarus clarkii), widely farmed in China, frequently suffers from hepatopancreatic diseases due to the expansion and environmental degradation of aquaculture. Hepatopancreatic injury models are essential for studying disease mechanisms and treatments, yet few exist for crustaceans. This study aims to establish a hepatopancreatic injury model in P. clarkii using the hepatotoxic compound thioacetamide (TAA) and investigate the underlying damage mechanisms. P. clarkii were intramuscularly injected with TAA at concentrations of 0.2, 0.4, and 0.8 mg/g and observed at 6, 12, 24, and 48 h. The results showed that TAA at 0.2–0.8 mg/g significantly affected hepatopancreatic function and oxidative stress-related enzymes in P. clarkii. However, only 0.8 mg/g TAA produced a time-dependent damage effect suitable for a hepatopancreatic injury model. Histopathological analysis revealed that P. clarkii injected with 0.8 mg/g TAA exhibited key model features, including R cell adhesion and swelling, hepatic tubule rupture, and numerous small vacuoles. Therefore, 0.8 mg/g TAA intramuscular injection can effectively establish a hepatopancreatic injury model in P. clarkii. Transcriptomic and metabolomic analyses revealed that metabolic disruptions in energy, amino acid, lipid, and nucleotide pathways are central to TAA-induced hepatopancreatic injury in P. clarkii. CYP2L1X1, CYP2U1lX1, and CYP2D14l are likely key contributors to the hepatopancreatic injury induced by TAA in P. clarkii. The results of this study will provide support for further research on the mechanisms of hepatopancreatic diseases in freshwater crayfish and the development of preventive and therapeutic drugs.

Long-Term Variations in Habitat Use of Humpback Dolphins Due to Anthropogenic Activities in Western Pearl River Estuary

Marine mammals near coastlines are highly vulnerable to human activities like rapid industrialisation, port construction, and sea reclamation, which can alter their habitat use. This study examines changes in the habitat use of Indo-Pacific humpback dolphins in the western Pearl River Estuary (WPRE) by employing a kernel density estimation model that considers physical barriers. Sighting records from systematic surveys in 2007–2008 and 2019–2020, along with remote sensing data, were used to analyse changes in shorelines and areas affected by maritime projects since 1973. Approximately 552.98 km2 of water was permanently lost to reclamation between 1973 and 2020. In 2007–2008, dolphins preferred natural shorelines, while reclamation drove them away from artificial ones. By 2019–2020, their core habitat had decreased by two-thirds, with some areas disappearing, likely due to aquaculture expansion. These results highlight the importance of adopting improved environmental assessment methodologies in the planning and regulation of aquaculture activities in the WPRE to better protect the dolphin habitat.

Rethinking Freshwater Cage Aquaculture: A Case in Ghana

Lakes around the world, including Ghana’s Lake Volta, are facing insidious threats from pollutants due to high dependency on aquatic ecosystems. Cage aquaculture is expanding across Africa because of its potential to address food insecurity, provide livelihoods, and boost local economies. However, the uncontrolled expansion of cage aquaculture can have significant negative impacts on water resources, including environmental footprints that threaten biodiversity. Given the intensification of cage aquaculture for tilapia farming on Lake Volta, we advocate for a transition to inland-integrated aquaculture systems that promote circularity. Strengthening stakeholder collaboration is essential for enhancing competence in mapping inland aquaculture areas, identifying eco-friendly alternatives and reinforcing aquaculture regulations, with particular emphasis on cage culture on Lake Volta. These strategies can reduce the pressures imposed by tilapia cage farms on the lake while promoting best management practices. Additionally, capacity building must be an ongoing process to address knowledge gaps, including the development of effective preparedness plans executed during emergencies. The ongoing pollution from illegal mining in the Black Volta River, a tributary of Lake Volta, along with endemic diseases in the lake, further compounds fish health and welfare issues. This underscores the urgent need to implement inland transition strategies to protect the lake, mitigate disease spread, and ensure safe fish food production.

Local perceptions of marine conservation aquaculture for the restoration of native Atlantic salmon (Salmo salar) in Downeast, Maine

The entities responsible for the management of the endangered Gulf of Maine Distinct Population Segment of Atlantic salmon (Salmo salar) have partnered with a commercial aquaculture company to apply a novel conservation aquaculture program. This effort marks a major shift in management and has garnered mixed public reactions. Recent expansion of aquaculture in Maine has been a point of controversy as people and systems grapple with the social, environmental, and legal aspects of this burgeoning industry. Still, the use of aquaculture for conservation has shown some promise. In 2021, a questionnaire was administered to 850 households (response rate 27 %) in Maine via the Drop-off and Pick-up method. We examined differences and similarities in attitudes, beliefs, and knowledge about Atlantic salmon, hatcheries, and aquaculture between property owners in the town where the proposed net pens would be located (Cutler; n=73), and those in neighboring towns (n=152). The Potential for Conflict Index (PCI2) was used to examine differences between the groups. Both groups held similar positive attitudes toward Atlantic salmon, endangered species conservation, freshwater hatcheries, and both commercial and conservation aquaculture. Both groups believe that “Atlantic salmon should be protected,” and that freshwater hatcheries and marine conservation aquaculture “should be used for conservation.” However, Cutler residents had less consensus and supported the use of freshwater hatcheries and marine conservation aquaculture less than other respondents. Community concerns have stalled efforts to move the project forward. Our research indicates there are several social concepts which may help to explain localized opposition to the project.

Searching for sea lice: surveillance to assess environmental infection pressures to model and inform sea lice infestation management

The expansion and development of sustainable salmon aquaculture requires research, innovation and, where necessary, regulation to manage environmental impacts. Sea lice are a key concern for marine salmonid fish aquaculture as these parasites adversely affect farmed and wild salmonids. Reducing the risk of harmful infestation levels requires appropriate data to support modelling and inform adaptive management processes. Throughout their life cycle, sea lice occur as either planktonic larvae or as ectoparasites on farmed, wild or sentinel fish host populations. Limited resources require surveillance methodologies and strategies for these stages to be optimized to obtain data that meet the specific needs of control. In this review we assess the different surveillance strategies available to inform the appropriate management of sea lice impacts on wild salmonids. We advocate modelling as the most effective way to use surveillance data, with subsequent model improvements informed by the continued input of collected data. A feedback loop is proposed of identifying/collecting empirical data to improve models, which in turn will direct more focused surveillance for future data collection and so drive adaptive management processes. In the future, surveillance monitoring, as part of an adaptive management regime in Scotland, should build on existing links between stakeholders and policy makers, and use both models and data to help the sustainable development of the aquaculture industry.

Influence of various carbon and nitrogen ratios in a jaggery-based biofloc rearing system on the Asian stinging catfish Heteropneustes fossilis

Biofloc technology (BFT) is becoming popular in aquaculture. As the human population has rapidly increased, so has the demand for protein, driving the expansion of aquaculture. The increased use of aqua medicines in aquaculture has led to resistant microbes. BFT offers a promising, eco-friendly solution by promoting beneficial microbes to improve fish health and reduce chemical use, supporting the industry's long-term sustainability. BFT recycles waste without water exchange by maintaining an optimal carbon-nitrogen (C:N) ratio and adding an external carbon source, which promotes the growth of heterotrophic bacteria and other essential microbes that absorb ammonia from feed and waste, forming beneficial microbial aggregates. This study evaluated the effects of various C:N ratios in a jaggery-based BFT system on water quality, growth, feed efficiency, and the well-being of Heteropneustes fossilis. A completely randomized design with triplicates (2.33 kg/m³ in 1500 L tanks) was used to compare a control group without biofloc to three BFT treatments with C:N ratios of 8:1 (CN8), 12:1 (CN12), and 16:1 (CN16) over 180 days. Daily feeding was conducted at 5–2 % of the fish's body weight (initial weight of 5.0±0.5 g). Higher C:N ratios were linked to reduced dissolved oxygen, ammonia, and nitrite levels, alongside increased total suspended solids, floc volume, and heterotrophic bacteria counts, while the CN12 had the highest levels of beneficial microbes (Firmicutes and Actinobacteria), leading to superior fish growth, survival, and biomass compared to CN8 and CN16. The CN12 also showed better stress response, hematology, immunity, and antioxidant properties. Histologically, fish in CN12 and CN8 had healthier liver and intestines compared to CN16 and control. The results suggest that a C:N ratio of 12:1 was optimal for biofloc systems used in cultivating H. fossilis, enhancing both microbial growth and water quality.

Which Novel Ingredient Should be Considered the “Holy Grail” for Sustainable Production of Finfish Aquafeeds?

ABSTRACTThe immense production of fishmeal and fish oil is dramatically intensifying the severe state of pelagic fisheries overexploitation. The latter in conjunction with the increasing demand for low‐cost protein‐rich food supply prompt aquaculture to employ new practice. Several novel dietary ingredients are currently under evaluation for potential incorporation in aquafeeds in an effort to shift the aquaculture sector toward a more sustainable and economic production. The present review aims to summarize the existing findings regarding the effects of studied alternatives to fishmeal and fish oil on the most valuable and commercially produced marine (Sparus aurata and Dicentrarchus labrax) and freshwater (Salmo salar and Oncorhynchus mykiss) finfish species in European aquaculture. Alternative protein sources, including macroalage (marine plants), krill (marine fishery), insects (terrestrial), terrestrial animal by‐products (processed/rendered), and single cell ingredient (biotechnology), are discussed for their efficiency in promoting the growth and the welfare of both fry and adult cultured finfish species. Applicability of these ingredients is reviewed in terms of nutrient composition, dietary inclusion level, performance output, digestibility, and health benefits. In addition, a meta‐analysis was conducted based on data from peer‐reviewed scientific publications in order to assess whether novel ingredients meet the dietary protein (amino acid) and lipid requirements of finfishes. Aquafeed reformulation strategies should ensure the recommended daily nutritional requirements and additionally indicate the meta‐analysis alternatives, such as microalgae, which are deficient in essential amino acids. The sustainable expansion of aquaculture is on the horizon, but which novel ingredients may be regarded as the key drivers to its establishment?

Research progress on the application of Clostridium butyricum in shrimp aquaculture

In recent years, with the continuous expansion of aquaculture and the vigorous development of the aquaculture industry, the breeding environment and diseases have become increasingly prominent, and the quality and output of aquaculture products have been affected to a certain extent, which has become one of the important factors restricting the development of aquaculture industry. Clostridium butyricum is a kind of clostridium bacillus, a gram-positive bacterium, strictly anaerobic, which can form spores and produce short-chain fatty acids, biofuel compounds, and biomaterial precursors such as H2, butanol, and 1,3-propanediol in the process of fermenting carbohydrates and sugars. This article reviews the isolation, identification, main biological functions, and mechanism of C. butyricum in the gastrointestinal tract of aquatic animals and summarizes the role of C. butyricum in improving the growth performance, digestibility, survival, immune response, disease resistance, and intestinal structure, as well as regulating the intestinal symbiotic microbiota and metabolic disorders of aquatic animals. To provide insights into the key research directions of C. butyricum in shrimp aquaculture in the future, including research on the relationship between C. butyricum and the host immune system and the possibility of using C. butyricum as an antibiotic substitute for disease prevention and treatment, this study aims to provide a reference for the comprehensive utilization of C. butyricum in shrimp aquaculture and promote the high-quality development of the shrimp aquaculture industry.

The increasing influence of oyster farming on sedimentary organic matter in a semi-closed subtropical bay

Oyster farming activities play a pivotal role in the biogeochemical cycles of coastal marine ecosystems, particularly in terms of sedimentary carbon cycling. To gain deep insights into the influence of expanding oyster culture on the sedimentary carbon cycle, surface sediments were collected from the Maowei Sea, which is the largest oyster farming bay in south China, based on six filed surveys between July 2010 and December 2022. The sediment samples were analyzed for total organic carbon (TOC), total nitrogen (TN), stable carbon and nitrogen isotopes (δ13C and δ15N) to evaluate the inter-annual variations in the source contribution to sedimentary organic matter (SOM). The results revealed that the average contents of sedimentary TOC and TN were 0.67 ± 0.41 % and 0.06 ± 0.03 %, respectively. Fluctuations in the C/N molar ratios ranged from 5.8 to 23.6, with an average of 12.6 ± 2.9, indicating a significant terrestrial input contribution to SOM in the study area. Furthermore, the integration of stable isotope analysis and Bayesian mixing model demonstrated a gradual increase in the mean proportion of shellfish biodeposition to SOM, from 12.0 ± 5.6 % in July 2010 to 21.1 ± 7.3 % in December 2022, consistent with the progressive expansion of oyster aquaculture along this coastal area, thereby emphasizing the substantial influence of oyster farming on SOM composition. With the anticipated expansion of oyster farming scale and production in the future, shellfish biodeposition is expected to assume a more important role in shaping SOM dynamics and sedimentary organic carbon cycling in coastal waters. Overall, this study provided an important perspective for better assessing the impact of expanding mariculture scale on coastal biogeochemical cycles, thereby making valuable contributions to future policy formulation concerning mariculture and ecological conservation.

Aquacultural source of nitrous oxide revealed by nitrogen isotopes

The rapid expansion of coastal aquaculture has led to an increase in the coverage of aquaculture ponds, where intense feed-derived nitrogen is causing significant emissions of nitrous oxide (N2O). Multiple N2O production pathways and the relative importance of water column vs. sedimentary production in aquaculture ponds remain uncertain. Clarifying these pathways is vital for sustainable aquaculture development. Using 15N-labeled dissolved inorganic nitrogen, the pathways and rates of N2O production in subtropical aquaculture ponds located in south China, cultivating whiteleg shrimp, Japanese seabass, and giant river prawn, were successfully characterized. Total N2O production rates ranged from 6 to 70 µmol-N m−2 d−1, with the shrimp pond exhibiting the highest total N2O production rates, followed by ponds for seabass and prawn. These differences are primarily due to varying feed amounts causing differences in dissolved nutrients in water column and sediment. Particularly, nutrient and organic matter accumulation at the surface sediment stimulated N2O production. The oxygenated sediment on a centimeter scale could produce substantially more N2O compared to the water column above on a meter scale. Partial denitrification, i.e., nitrate and nitrite reduction to N2O, was more important (> 60 %) for N2O production in aquaculture ponds. The availability of nitrite is likely a major factor driving partial denitrification for both sedimentary and water column N2O production.

Habitat selection of non‐breeding American black ducks in an urban estuary

AbstractShellfish aquaculture is a globally expanding industry, including in urban estuaries that support non‐breeding waterfowl. The effects of shellfish aquaculture on the spatial distribution of non‐breeding waterfowl, however, are poorly understood and depend on the ecology of waterfowl and cultivated shellfish species. We investigated how proximity to shellfish aquaculture influenced habitat selection and movement patterns of American black ducks (Anas rubripes) during the non‐breeding season (~Oct–May) in 2020–2023 in Rhode Island, USA. The extent to which proximity to aquaculture influenced habitat selection of black ducks depended on factors specific to individuals' primary non‐breeding sites, although proximity to aquaculture did not have biologically meaningful influences on black duck movement rates across all sites. Black ducks across sites consistently selected for areas better suited for aquaculture (i.e., areas of potential future development) relative to areas poorly suited for aquaculture (i.e., areas less likely to be developed). The continued expansion of aquaculture into preferred black duck habitats will increase black duck interactions with aquaculture and therefore should be considered in the decision‐making process for siting future aquaculture leases. Future studies should quantify the extent to which continued expansion of aquaculture in those preferred coastal habitats directly influences black ducks.

Replacement of fishmeal with a microbial single-cell protein induced enteropathy and poor growth outcomes in barramundi (Lates calcarifer) fry.

Fish meal (FM) replacement is essential for the sustainable expansion of aquaculture. This study focussed on the feasibility of replacing FM with a single-cell protein (SCP) derived from methanotrophic bacteria (Methylococcus capsulatus, Bath) in barramundi fry (Lates calcarifer). Three isonitrogenous and isoenergetic diets were formulated with 0%, 6.4% and 12.9% inclusion of the SCP, replacing FM by 0%, 25% and 50%. Barramundi fry (initial body weight 2.5 ± 0.1 g) were fed experimental diets for 21 days to assess growth performance, gut microbiome composition and gut histopathology. Our findings revealed that both levels of SCP inclusion induced detrimental effects in barramundi fry, including impaired growth and reduced survival compared with the control group (66.7% and 71.7% survival in diets replacing FM with SCP by 25% and 50%, respectively; p < .05). Both dietary treatments presented mild necrotizing enteritis with subepithelial oedema and accumulation of PAS positive, diastase resistant droplets within hepatocytes (ceroid hepatopathy) and pancreatic atrophy. Microbiome analysis revealed a marked shift in the gut microbial community with the expansion of potential opportunistic bacteria in the genus Aeromonas. Reduced overall performance in the highest inclusion level (50% SCP) was primarily associated with reduced feed intake, likely related to palatability issues, albeit pathological changes observed in gut and liver may also play a role. Our study highlights the importance of meticulous optimization of SCP inclusion levels in aquafeed formulations, and the need for species and life-stage specific assessments to ensure the health and welfare of fish in sustainable aquaculture practices.

Small water body significantly contributes to nitrous oxide emissions in China's aquaculture

Aquaculture systems are expected to act as potential hotspots for nitrous oxide (N2O) emissions, largely attributed to substantial nutrient loading from aquafeed applications. However, the specific patterns and contributions of N2O fluxes from these systems to the global emissions inventory are not well characterized due to limited data. This study investigates the patterns of N2O flux across 127 freshwater systems in China to elucidate the role of aquaculture ponds and lakes/reservoirs in landscape N2O emission. Our findings show that the average N2O flux from aquaculture ponds was 3.63 times higher (28.73 μg N2O m−2 h−1) than that from non-aquaculture ponds. Additionally, the average N2O flux from aquaculture lakes/reservoirs (15.65 μg N2O m−2 h−1) increased 3.05 times compared to non-aquaculture lakes/reservoirs. The transition from non-aquaculture to aquaculture practices has resulted in a net annual increase of 7589 ± 2409 Mg N2O emissions in China's freshwater systems from 2003 to 2022, equivalent to 20% of total N2O emissions from China's inland water. Particularly, the robust negative regression relationship between N2O emission intensity and water area suggests that small ponds are hotspots of N2O emissions, a result of both elevated nutrient concentrations and more vigorous biogeochemical cycles. This indicates that N2O emissions from smaller aquaculture ponds are larger per unit area compared to equivalent larger water bodies. Our findings highlight that N2O emissions from aquaculture systems can not be proxied by those from natural water bodies, especially small water bodies exhibiting significant but largely unquantified N2O emissions. In the context of the rapid global expansion of aquaculture, this underscores the critical need to integrate aquaculture into global assessments of inland water N2O emissions to advance towards a low-carbon future.

The impact of aquaculture economics expansion on marine water quality in the EU Region

Water scarcity is a growing condition caused by climate change and human activity, and it influences and interacts with other stressors in freshwater and marine ecosystems, such as chemical pollution. Aquaculture production has a significant impact on the EU27 region's water stress and water contamination discharge levels. Therefore, the primary goal of this research is to examine how the aquaculture industry affects water contamination discharge in European Union developed countries (EU14) and European Union developing countries (EU13) from 1990 to 2023. Since the dependent variable's error terms are correlated with the independent variables, the endogeneity problem was solved with the use of robust least squares (RLS), two-stage least squares (2SLS), and ordinary least squares (OLS) estimators, which produced the major findings. According to the precise effect sizes, the aquaculture industry and gross domestic product are more important in determining water contamination discharge in developed EU14 countries than in developing EU13 countries. The precise magnitudes of the effect demonstrate that, compared to EU14 developed countries, water contamination discharge in EU13 developing countries is mostly determined by the use of hydrocarbons. However, as the precise magnitudes of the three estimators demonstrate, governance is more important in EU14 developed countries than in EU13 developing countries when it comes to controlling water contamination discharge. The authors advise policymakers to give policies targeted at improving the aquaculture industry's efficiency and green development top priority, especially in EU13 developing countries with unplanned aquaculture expansion and inefficient aquaculture industry outgrowth. The authors advise policymakers in the EU14 developed countries to take actions targeted at improving governance efficiency top priority.

The structure and function of a coastal state aquaculture plan

Aquaculture contributes approximately half of all global aquatic food production and will be critical in addressing future seafood demand, including the United States (U.S.). Many states, territories, and countries are developing and updating aquaculture specific policy in an effort to plan for, and better manage the expansion of aquaculture in their territorial waters. The U.S. has considerable potential to sustainably expand aquaculture production, which has been a focus in both federal and state policy. State aquaculture plans have been used for over 40 years to help plan and coordinate aquaculture development, with a growing emphasis on sustainability. Here, we located and evaluated a set of coastal state aquaculture plans released in the last 25 years (N = 7) in an effort to provide resources to states and territories interested in this activity. We synthesized information from each plan to understand the support, motivation, writing process and entities involved, taxa and environments under consideration, key structural elements, and the types of recommendations provided. We found that coastal state aquaculture plans are often government or industry initiatives developed in partnership with other groups, including academia, government agencies, and tribal actors, as well as supported formally by executive or legislative branches. Plans were diverse but tended to described the vision for the future, provide recommendations, identify and incorporate cross-cutting concepts into the plans (e.g., best management practices and marine spatial plans), and highlight the need for the plan to be updated regularly. As states aim to expand aquaculture, understanding the structure and function of the tools used by states to inform policy formation will be important to help make future development plans more effective and efficient.

Using passive acoustic monitoring to assess the overlap between endemic endangered Hector's dolphin (Cephalorhynchus hectori hectori) and mussel farms in the Banks Peninsula Marine Mammal Sanctuary, New Zealand

Abstract Aquaculture has maintained a sustained growth trend over the last 50 years, worldwide and in Aotearoa New Zealand. This industry is known to have environmental consequences, such as impacts on benthos, water column and higher trophic levels. Some of these impacts have been thoroughly studied, while others, such as the effects on cetaceans, are not well understood. This study used passive acoustic monitoring (PAM) to assess, for the first time, the overlap between kūtai—New Zealand greenlipped mussel (Perna canaliculus)—farms and habitat use by endemic endangered Hector's dolphins (Cephalorhynchus hectori hectori) within the Banks Peninsula Marine Mammal Sanctuary. T‐PODs were deployed in six bays, three with mussel farms and three without, between 2018 and 2019. Occurrence of dolphins, expressed as ‘dolphin positive minutes per day’ (DPM/day), was modelled using generalized linear mixed models. Results showed a strong interaction between farm (presence/absence) and season (summer/winter), with fewer acoustic detections of dolphins in winter if farms were present. Furthermore, in bays with mussel farms, there were significantly more click train detections on the opposite side of the bay, compared to the side by the mussel farm. Considering that results from this study suggest potential displacement of the dolphins due to the mussel farms, the recommendation is a precautionary approach. Further expansion of aquaculture in Hector's dolphin habitat should be done carefully, taking into account their habitat use, and conducting intensive monitoring including a robust ‘before and after’ design prior to the establishment of new farms.

Review of current perspectives and future outlook on bacterial disease prevention through vaccination in Asian seabass (Lates calcarifer).

Asian seabass, Lates calcarifer, is an important aquatic species in mariculture. Intensive farming of this species has faced episodes of bacterial diseases, including those due to vibriosis, scale drop, and muscle necrosis disease, big belly disease, photobacteriosis, columnaris, streptococcosis, aeromoniasis, and tenacibaculosis. Vaccination is one of the most efficient, non-antibiotic, and eco-friendly strategies for protecting fish against bacterial diseases, contributing to aquaculture expansion and ensuring food security. As of now, although numerous vaccines have undergone laboratory research, only one commercially available inactivated vaccine, suitable for both immersion and injection administration, is accessible for preventing Streptococcus iniae. Several key challenges in developing vaccines for Asian seabass must be addressed, such as the current limited understanding of immunological responses to vaccines, the costs associated with vaccine production, forms, and routes of vaccine application, and how to increase the adoption of vaccines by farmers. The future of vaccine development for the Asian seabass industry, therefore, is discussed with these key critical issues in mind. The focus is on improving our understanding of Asian seabass immunity, including maternal immunity, immunocompetence, and immune responses post-vaccination, as well as developing tools to assess vaccine effectiveness. The need for an alignment of fish vaccines with state-of-the-art vaccine technologies employed in human and terrestrial animal healthcare is also discussed. This review also discusses the necessity of providing locally-produced autogenous vaccines, especially for immersion and oral vaccines, to benefit small-scale fish farmers, and the potential benefits that might be extended through changes to current husbandry practices such as the vaccination of broodstock and earlier life stages of their off-spring.

Diversity, evolution, and emergence of fish viruses.

The production of aquatic animals has more than doubled over the last 50 years and is anticipated to continually increase. While fish are recognized as a valuable and sustainable source of nutrition, particularly in the context of human population growth and climate change, the rapid expansion of aquaculture coincides with the emergence of highly pathogenic viruses that often spread globally through aquacultural practices. Here, we provide an overview of the fish virome and its relevance for disease emergence, with a focus on the insights gained through metagenomic sequencing, noting potential areas for future study. In particular, we describe the diversity and evolution of fish viruses, for which the majority have no known disease associations, and demonstrate how viruses emerge in fish populations, most notably at an expanding domestic-wild interface. We also show how wild fish are a powerful and tractable model system to study virus ecology and evolution more broadly and can be used to identify the major factors that shape vertebrate viromes. Central to this is a process of virus-host co-divergence that proceeds over many millions of years, combined with ongoing cross-species virus transmission.

Cumulative assessment of Diplectanum spp. occurrence, prevalence, and pathological impact in Dicentrarchus labrax from varied Egyptian fish farms

Monogenean trematodes, particularly those belonging to the Diplectanidae family, are significant metazoan parasites with substantial implications for aquaculture expansion. This study, investigatied the occurrence, prevalence, and pathological impact of Diplectanum spp. in European seabass (Dicentrarchus labrax) across three distinct Egyptian fish farms. During 2021–2022, we sampled 1800 European seabass (Dicentrarchus labrax) from three Egyptian fish farms (600 fish per farm). Farms 1 and 2 used semi-intensive earthen pond systems, while Farm 3 utilized an intensive floating cage system. Employing Clinical, post-mortem, parasitological, and molecular examination technique. Pathological lesions were identified, including skin and gill discoloration, emaciation, and internal organ abnormalities. Seasonal prevalence exhibited significant variations between farms, with highest rates observed in spring and Farm 3 reached an overall peak prevalence of 84.67 %. Parasitological examination distinguished two Diplectanum species morphologically, while molecular techniques exhibited limited specificity. Histopathology unveiled damage to gill, liver, spleen, kidney, and intestine, attributed to Diplectanum haptors including inflammation and internal bleeding, potentially leading to secondary infections. Molecular identification via PCR targeting ITS and 28SrDNA genes, revealing similar band sizes for the two Diplectanum species, indicating limited intraspecific genetic diversity. The study emphasizes investigating parasitic infections' prevalence and impact in aquaculture, necessitating robust molecular techniques for species differentiation. This study underscores the importance of investigating the prevalence and impact of parasitic infections in aquaculture. It highlights the need for robust molecular techniques to differentiate species. By focusing on Diplectanum spp. infections in D. labrax, the study offers valuable insights into managing parasites in aquaculture effectively.