Mariculture Systems Research Articles

Immune response of the Almaco jack (Seriola rivoliana) against the infestation with Neobenedenia sp. in three cultivated temperatures.

The Almaco jack (Seriola rivoliana) is a marine fish maintained in mariculture systems and frequently infested by monogenean parasites like Neobenedenia sp. Severe infestations can lead to high mortalities and economic losses for farmers. This study evaluated the effects of temperature on the immune response on Almaco jack infested with Neobenedenia sp. We exposed infested fishes at temperatures of 20°C, 24°C, and 30°C for 20days and took samples of different tissues at the beginning of the experiment, and after 3 and 20days. The tissues considered were the skin, thymus, cephalic kidney, and spleen to evaluate the relative gene expression of different genes: Hsp70, IgM, IL-1β, IL-10, and MyD88. Our results showed an increase in IL-1β gene expression in the skin after 20days of infestation but no significant effect of temperature on gene expression, despite increases in infestation rates with temperature. Therefore, relative genetic expression was controlled by the number of parasites and the days post-infestation. These results show that the parasite infestation induced a local response in the skin, but that temperature has an indirect effect on the immune system of Almaco jack.

Leveraging marine biotechnology for an All-Atlantic sustainable blue economy

Despite the lack of research, development, and innovation funds, especially in South Atlantic countries, the Atlantic is suited to supporting a sustainable marine bioeconomy. Novel low-carbon mariculture systems can provide food security, new drugs, and climate mitigation. We suggest how to develop this sustainable marine bioeconomy across the entire Atlantic.

Deciphering variations in the surficial bacterial compositions and functional profiles in the intersection between North and South Yellow Sea

The coastal ocean systems play paramount role in the nutrient biogeochemistry because of its interconnected environment. To gain a novel insight into coupling relationships between bacterial community, functioning properties and nutrient metabolism, we conducted analysis on the patterns and driving factors of planktonic bacterial functional community across subsurface water of marine ranching near the Yellow Sea in both summer and winter. Illumina HiSeq Sequencing and a corresponding set of biogeochemical data were used to assess distribution patterns of taxa, adaptive mechanism and metabolic function. Results demonstrated that Proteobacteria, Cyanobacteria, Actinobacteriota and Bacteroidota were dominant phyla both in summer and winter. Taxonomic profiles related to nutrient variation were found to be highly correlated with Dissolved Oxygen (DO) and Chlorophyll fluorescence (FLUO), and distinct diversity differences were also found between summer and winter samples. Functional activity in summer associated with the relative abundance of phototrophy and photoautotrophy were the highest in the subsurface water, while in winter the dominant functional properties were mainly include chemoheterotrophy and aerobic_ chemoheterotrophy. A significant difference related to functional activity between summer and winter, mainly representing ligninolysis and iron_respiration. In general, our study provides a framework for understanding the relative importance of environmental factors, temperature variation and nutrient availability in shaping the metabolic processes of aquatic microorganisms, particularly in ocean mariculture systems.

The occurrence of pollutants in organisms and water of inland mariculture systems: Shrimp aquaculture is a procession of Microplastics accumulation

Microplastics (MPs) pollution in the ocean was widely concerned, but the current study on MPs pollution in the mariculture system is relatively lacking. This study researched the MPs pollution characteristics in water and shrimp at different stages of the pond and industrial aquaculture. The study shows that in the same aquaculture stage, MPs abundance in shrimp and water in pond aquaculture mode is higher than that in industrial aquaculture mode. The MPs pollution characteristics in shrimp and water show significant consistency. The hazard index of MPs in pond water and industrial models are 122 (Level Ⅲ) and 540 (Level Ⅲ), respectively, indicating that industrial aquaculture models may suffer from more severe MPs stress. The aquaculture period and mode significantly affected the MPs abundance of water and shrimp, but there was no interaction between the aquaculture period and mode. MPs abundance in shrimp show a significant relationship with the length of crustacean and weight. This study further enhanced the understanding of MPs pollution of water and organisms in different aquaculture modes at different stages, and warned MPs is widely spread in mariculture systems.

Rhamnolipid-assisted solid-phase denitrification process for enhanced nitrate removal of recirculating mariculture system water

Solid-phase denitrification (SPD) is a promising approach for treating recirculating mariculture systems (RMS) water, but its relatively slow nitrate removal rate presents a challenge. This study, for the first time, investigates the enhanced nitrate removal in the SPD process by rhamnolipid (RL) addition. The enhancement by RL addition (20 and 40 mg L−1) was significant and largely persisted even after RL dosing was stopped. Specifically, the nitrate removal in RL-assisted SPD reactors was enhanced by 1.7–2.6 and 1.9–2.1 times for influent NO3−-N concentrations of 100 and 200 mg L−1, respectively. The enhancement was attributed to the improved biofilm formation, as indicated by the increased contents of biomass and extracellular polymeric substances. Moreover, the abundances of denitrification and biofilm formation functional bacteria (Pseudomonas and Denitromonas) also increased. RL addition increased abundances of functional genes involved in carbon degradation and nitrate removal. The denitrification and assimilatory nitrate reduction pathways achieved nitrate removal together. Therefore, RL-assisted SPD presents a novel strategy for treating nitrate-rich RMS water.

Nitrogen removal capability and mechanism of a novel heterotrophic nitrification–aerobic denitrification bacterium Halomonas sp. DN3

Recently, the functional microorganisms capable of eliminating nitrogenous waste have been applied in mariculture systems. As a potential candidate for treating mariculture wastewater, strain DN3 eliminated 100% of ammonia and nitrate and 96.61%–100% of nitrite within 72 h, when single nitrogen sources at concentrations of 0–50 mg/L. Strain DN3 also exhibited the efficient removal performance of mixed-form nitrogen (ammonia, nitrate, and nitrite) at salinity 30 ‰, C/N ratio 20, and 180 rpm. The nitrogen assimilation pathway dominated inorganic nitrogen metabolism, with less nitrogen (14.23%-25.02% of TN) lost into the air via nitrification and denitrification, based on nitrogen balance analysis. Moreover, the bacterial nitrification pathway was explored by enzymatic assays and inhibition assays. These complex nitrogen assimilation and dissimilation processes were further revealed by bacterial genome analysis. These results provide important insight into nitrogen metabolism of Halomonas sp. and theoretical support for treating mariculture wastewater with strain DN3.

Study on the Treatment of Simulated Recirculating Mariculture Wastewater by Thiosulfate-Based Autotrophic Denitrification

In this study, a sulfur-based autotrophic denitrifying filter (SADF) was developed for the purpose of removing nitrate from simulated recirculating mariculture wastewater. Results showed that over 90% of the nitrate could be effectively eliminated by utilizing thiosulfate as the electron donor, with a molar ratio of thiosulfate-S to nitrate molar ratio of 2:1 or greater. Additional batch tests confirmed that thiosulfate was a suitable sulfur source for nitrate removal even without prior accumulation of the biomass to nitrite. Excess thiosulfate had a minor impact on N-removal efficiency, so an external sulfur source was not required for nitrate removal, however, it could still help to reduce nitrate accumulation and water replacement to some extent. High-throughput sequencing results illustrated that Thiomicrospira and Thioalkalivibrio were the dominant autotrophic denitrifying genera in the SADF, while Thiomicrospira was more significantly affected in the case of insufficient sulfur sources. As the issue of nitrate accumulation in the mariculture recirculating system has been resolved, only a small amount of water needs to be added to the system daily. Therefore, the thiosulfate-based SADF process has the potential to be implemented for nitrate removal in mariculture systems, which could present a promising sustainable solution to the nitrate pollution issue.

The role of policy in supporting alternative marine farming methods: A case study of seafloor ranching in Australia

Recent attention to the ecosystem service-generating potential of marine aquaculture (mariculture) indicates that there is substantial opportunity for marine farming to optimise practices that benefit both production and nature. One strategy for augmenting sustainability within the mariculture industry is to develop more diverse farming practices and culture species that can operate within existing ocean space constraints, contribute to ecological and conservation objectives, and assuage negative public sentiment towards mariculture. While this strategy has the potential to expand mariculture's sustainability, the implementation of these alternative culture approaches will likely depend on whether the management frameworks that regulate the industry have the authority and the capacity to enable farming innovations and encourage investment in diverse mariculture systems. Using Australia and seafloor ranching of molluscs as a case study, we explore the suitability of existing policy and legislation to support novel farming methods. We find that the policy frameworks differ across States in terms of their applicability (both implicit and explicit) to seafloor ranching activities, with substantial gaps regarding the siting and building of farming infrastructure. In the context of these results, we discuss potential strategies for leveraging existing policy and management frameworks to meet the needs of seafloor ranching and identify operational stages where new, targeted policy could be particularly impactful. Our case study offers practical insights to policymakers in Australia and other countries and regions seeking to support innovations in culture methods with a greater potential for sustainability.

A novel decision-support system for augmenting sustainable lobster production through comparison of mariculture systems at increasing stages of technological development

In the face of depleting wild stocks of lobster globally, mariculture is widely viewed as a technology for enhancing production, resource efficiency, economics, and effective management of dwindling stocks while supporting livelihood security. We used a novel multi-stage experimental strategy followed by robust non-linear growth model simulations for establishing a Decision-Support System (DSS) to foster sustainable and cleaner production practices in lobster mariculture. The strategies explored in the first stage, which dealt with rearing lobsters in sea cages at increasing levels of technological development, significantly enhanced lobster production and thus, culture system productivity 5.9 times over unsustainable conventional systems. Growth performance, feed utilization, and survivability of lobsters were found to be significantly ameliorated in culture setup-3 (P ≤ 0.01), which was the most technologically advanced setup. In the second stage, non-linear models were fit to growth curves, and the best-fit models were used for the prediction of lobster biological metrics in the mariculture systems. These predictions were then validated using in-situ allometric traits. The DSS thus developed can effectively aid decision-making to optimize culture duration, stock condition, feed optimization, and harvest size to maximise economic returns from lobster mariculture while ensuring sustainability.

Sustainable intensification of small-scale mariculture systems: Farm-level insights from the coastal regions of India

This study undertakes a comprehensive assessment of selected mariculture enterprises in the coastal regions of India, centered on long-term sustainability as the key focus. This is juxtaposed against India's ambitious blue economy targets and policy thrust that pin on the expansion of mariculture as a promising avenue for enhancing marine fish production. Farm-level, region-specific, techno-economic, and socio-cultural factors associated with, and conditional on, sustainable intensification of mariculture-based production systems are examined in detail. The Principles-Criteria-Indicators (PCI) approach is used to establish the linkage between identified farm-level indicators and various dimensions of sustainability. While the selected enterprises were assessed to be technically and economically viable in general, glaring gaps were evident on key indicators of sustainability such as the legitimacy of access over water bodies, use of quality seed and feed, institutional credit access, market access, and fair marketing practices, optimal stocking density, mechanization, use of renewable energy, adoption of environmental-friendly culture practices, farm surveillance, crew safety, and social protection. This indicates the need for taking proactive measures to ensure the long-term sustainability of mariculture, particularly in the initial stages of establishment when such interventions are easy to adopt. Based on the insights obtained from the analysis, a broad set of strategies, policy options, and institutional interventions critical to scaling-up coastal mariculture enterprises along the east and west coasts of India are presented.

Evaluating the influence of environmental variables on the length-weight relationship and prediction modelling in flathead grey mullet, Mugil cephalus Linnaeus, 1758.

Fish stocks that are grown under diverse environmental conditions have different biometric relationships and growth patterns. The biometric length-weight relationship (LWR) is an essential fishery assessment tool, as fish growth is continuous and depends on genetic and environmental factors. The present study attempts to understand the LWR of the flathead grey mullet, Mugil cephalus Linnaeus, 1758, from different locations. The study area encompassed its distribution in the wild across freshwater location (one), coastal habitats (eight locations), and estuaries (six locations) in India to determine the relationship between various environmental parameters. Specimens (n = 476) of M. cephalus were collected from commercial catches and the length and weight of individual specimens were recorded. Monthly data from the study locations were extracted for nine environmental variables from the datasets downloaded from the Physical Oceanography Distributed Active Archive Center (PO.DAAC) and the Copernicus Marine Environment Monitoring Service (CMEMS) over 16 years (2002 to 2017) on the Geographical Information System platform. The parameters of the LWR, intercept 'a' and slope or regression coefficient 'b', varied from 0.005321 to 0.22182 and 2.235 to 3.173, respectively. The condition factor ranged from 0.92 to 1.41. The partial least squares (PLS) score scatter plot matrix indicated differences in the environmental variables between the locations. PLS analysis of the regression coefficient and environment parameters revealed that certain environment variables viz., sea surface temperature, salinity, dissolved oxygen, nitrate, and phosphate, played a positive role. However, chlorophyll, pH, silicate, and iron played a negative role in influencing weight growth across various locations. The results revealed that the M. cephalus specimens from three locations, Mandapam, Karwar, and Ratnagiri, possessed significantly higher fitness to their environment than those from the other six locations. The PLS model can be used to predict weight growth under the various environmental conditions of different ecosystems. The three identified locations are useful sites for the mariculture of this species considering their growth performance, the environmental variables, and their interactions. The results of this study will improve the management and conservation of exploited stocks in regions affected by climate change. Our results will also aid in making environment clearance decisions for coastal development projects and will improve the efficiency of mariculture systems.

Application of modified clay in intensive mariculture pond: Impacts on nutrients and phytoplankton

Nutrients and phytoplankton associated with mariculture development are important concerns globally, as they can significantly impact water quality and aquaculture yield. Currently, there is still insufficient information regarding the variations in nutrients and phytoplankton community of intensive mariculture systems, and effective treatment is lacking. Here, based on consecutive daily monitoring of two Litopenaeus vannamei ponds from July to October, the dynamic variations in nutrients and phytoplankton were elucidated. In addition, modified clay (MC) method was adopted to regulate the nutrients and phytoplankton community. The temporal variations in organic and inorganic nutrients presented fluctuating upward trends. Notably, organic nutrients were the dominant species, with average proportions of TON/P in TN/P were as high as 75.29% and 87.36%, respectively. Furthermore, a marked increase in the ratios of dinoflagellates to diatoms abundance were also observed in the control pond, concurrently with dominant organic nutrients, ascending N/P ratio and decreasing Si/N and Si/P ratios. In the MC-regulated pond, MC reduced the contents of both organic and inorganic nutrients. Furthermore, a distinct change pattern of dominant phytoplankton community occurred, with green algae becoming the most abundant phytoplankton in the MC-regulated pond. This study can provide new insights into an effective treatment for managing water quality and maintaining sustainable mariculture development.

Physiology, metabolism, antibiotic resistance, and genetic diversity of Harveyi clade bacteria isolated from coastal mariculture system in China in the last two decades

Vibrio bacteria, particularly members of the Harveyi clade, are the most important pathogens of aquatic organisms that cause significant economic losses in the world. It is difficult to provide specific data on taxa of the Harveyi clade for biological research and prevention strategies. Therefore, we conducted an extensive phenotypic and antibiotic resistance study, as well as phylogenetic and molecular typing of 192 isolates of the Harveyi clade collection from 2000 to 2020 with a typical interannual difference from a coastal area in China. The isolates had a significant interspecific genetic and antibiotic resistance diversity. Based on the multilocus sequence analysis (MLSA) of housekeeping genes (gyrB, pyrH, recA, and atpA), 192 Harveyi clade isolates were rapidly and accurately classified into 10 species. The population of these isolates was composed of 95 sequence types (STs), of which 92 STs were newly identified, indicating a high degree of genetic diversity. ST327 ranked first, accounting for 11.5% of the total number of isolates (22 out of 192), followed by ST215 with 6.25%, while 63 STs included single isolates. At the metabolic level, the physiological and biochemical experiments revealed that all the Harveyi clade isolates were positive for oxidase and negative for melibiose. The isolates showed a varied tolerance to 11 antibiotics. No isolates were resistant to neomycin. The percentages of sulfadimidine-resistant strains (61 out of 192), sulfadiazine (44 out of 192), sulfamonomethoxine (44 out of 192), sulfamethoxazole (33 out of 192), thiamphenicol (34 out of 192), ciprofloxacin (52 out of 192), and enrofloxacin (31 out of 192) were 31.77%, 22.92%, 22.92%, 17.19%, 17.71%, 27.08%, and 16.15%, respectively. A proportion of 61.8% of the isolates presented a multiple antibiotic resistance index (MARI) lower than 0.1, indicating that the risk of antibiotic resistance transmission of most of the Harveyi clade is low in mariculture systems in China. These results provide substantial data to support further studies on the identification and genetic and metabolic diversity of Harveyi clade isolates in mariculture systems in China.

Composition and distribution of bacterial communities and antibiotic resistance genes in fish of four mariculture systems

Fish-related antibiotic resistance genes (ARGs) have attracted attention for their potentially harmful effects on food safety and human health through the food chain transfer. However, the potential factors affecting these ARGs have not been fully explored. In this study, ARGs and bacterial communities in the fish gut, mucosal skin, and gill filaments in fish were comprehensively evaluated in four different mariculture systems formed by hybrid grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂), Gracilaria bailinae, and Litopenaeus vannamei using different combinations. The results showed that 9 ARGs were detected in the gut and mucosal skin and 6 ARGs in the gill filaments. The detection rate of aphA1 was the highest, and the abundance was 1.91 × 10−3 - 6.30 × 10−2 copies per 16 S rRNA gene. Transposase gene (tnpA-04) was detected in all samples with the abundance of 3.57 × 10−3 - 3.59 × 10−2 copies per 16 S rRNA gene, and was strongly correlated with multiple ARGs (e.g., aphA1, tet(34), mphA-02). Proteobacteria, Deinococcus-Thermus, Firmicutes, and Bacteroidetes were the dominant phyla in the four mariculture systems, accounting for 65.1%–96.2% of the total bacterial community. Notably, the high relative abundance of Stenotrophomonas, a potential human pathogen, was elevated by 20.5% in the hybrid grouper gut in the monoculture system. In addition, variation partitioning analysis (VPA) showed that the difference in bacterial communities between mariculture systems was the main driving factor of ARGs distribution differences in hybrid groupers. This study provides a new comprehensive understanding of the characterization of fish-related ARGs contamination in different mariculture systems and facilitates the assessment of potential risks of ARGs and pathogen taxa to human health.

Effects of integrated multi-trophic aquaculture on microbial communities, antibiotic resistance genes, and cultured species: A case study of four mariculture systems

Aquaculture is an important protein source in many countries, including China. Integrated multitrophic aquaculture (IMTA) is widely used to reduce the environmental pressure of aquaculture and to increase profits. However, effects of IMTA on host immune and metabolic responses, the dynamics of bacterial communities, and antibiotic resistance genes (ARGs) are relatively understudied. In this study, the IMTA mariculture systems with different combinations of the hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂), the whiteleg shrimp (Litopenaeus vannamei), and the alga (Gracilaria bailinae) were constructed to evaluate the effects of different culture systems on the aquatic environment and cultured species during the initial stage of aquaculture. Results showed that G. bailinae could effectively remove inorganic nutrients accumulated in water, which in turn significantly promoted growth and enhanced non-specific immunity and glycolipid metabolism in the hybrid grouper. Although ARGs were present throughout the culture process, the relative abundance of ARGs in three of the four culture systems decreased with culture time. This was especially the case in the monoculture and the fish-algal IMTA systems, indicating that these aquaculture systems had a scavenging effect on ARGs in the environment. Correlation and network analyses indicated that ARGs were not significantly correlated with environmental factors but were closely related to bacterial communities. Approximately 25 bacterial groups of Bacteroidetes and Proteobacteria were significantly correlated with ARGs, including aminoglycoside, beta-lactamase, chloramphenicol, and multidrug resistance genes. Moreover, tnpA-07, a transposase gene, indirectly affected ARGs through its interaction with Acteroidetes and Proteobacteria. This study provides insights into further optimizing culture methods and controlling the spread and ecological risk of ARGs in IMTA systems.

Viral diversity and biogeochemical potential revealed in different prawn-culture sediments by virus-enriched metagenome analysis

As the most numerous biological entities on Earth, viruses affect the microbial dynamics, metabolism and biogeochemical cycles in the aquatic ecosystems. Viral diversity and functions in ocean have been relatively well studied, but our understanding of viruses in mariculture systems is limited. To fill this knowledge gap, we studied viral diversity and potential biogeochemical impacts of sediments from four different prawn-mariculture ecosystems (mono-culture of prawn and poly-culture of prawn with jellyfish, sea cucumber, and clam) using a metagenomic approach with prior virus-like particles (VLPs) separation. We found that the order Caudovirales was the predominant viral category and accounted for the most volume (78.39% of classified viruses). Sediment viruses were verified to have a high diversity by using the construct phylogenetic tree of terL gene, with three potential novel clades being identified. Meanwhile, compared with viruses inhabiting other ecosystems based on gene-sharing network, our results revealed that mariculture sediments harbored considerable unexplored viral diversity and that maricultural species were potentially important drivers of the viral community structure. Notably, viral auxiliary metabolic genes were identified and suggested that viruses influence carbon and sulfur cycling, as well as cofactors/vitamins and amino acid metabolism, which indirectly participate in biogeochemical cycling. Overall, our findings revealed the genomic diversity and ecological function of viral communities in prawn mariculture sediments, and suggested the role of viruses in microbial ecology and biogeochemistry.

Spatiotemporal dynamics and resource use efficiency in mariculture production: A case study in Southeastern China

The rapid expansion of marine aquaculture poses a big challenge for sustainable development. More efficient production strategies are necessary to ensure a sustainable mariculture sector, yet the potential of feasible production gains without further environmental impacts is largely unknown. This work took one of the biggest mariculture centers in China to analyze the spatiotemporal dynamics of mariculture products in 2003, 2010, and 2016, explore potential factors associated with resource use efficiency, and quantify the potential of these factors to increase regional production. The mariculture sector had a rapid expansion in 2003–2010 and accelerated product diversification in 2010–2016, with overall annual growth rates of 4.6%, 24.9%, 14.6%, 20.4%, 24.7%, and 8.7% in finfish (Larimichthys crocea and others), sea cucumber (Apostichopus japonicus), abalone (Haliotis spp.), laminaria (Laminaria japonica), gracilaria (Gracilaria spp.), and porphyra (Porphyra spp.) production, respectively. Resource use impacts were dominated by finfish production (over 90% of the total), but recent increases were mostly due to the farming of other products. Our study also identified several demographic (household size), socioeconomic (income per capita), technical (farming density, feed usage, and energy usage), and environmental (distance between farms and total nitrogen concentration) variables that were correlated with resource use efficiency. Simulations based on regression models suggested that changes in these factors could increase fish and seaweed production by at least 3%–18% and 2%–23%, respectively, without increasing resource use levels. Sustainable intensification of local mariculture systems could be achieved by enhancing the access to more efficient technology and financial capital, increasing the willingness of engagement in the sector, facilitating the transaction of sea use rights, reducing the amount of nutrient released in coastal areas, and including the heterogeneous effects of farm distances and water quality in marine spatial planning. Our results highlight the existing opportunities in policymaking for more sustainable food production systems and the management of coastal ecosystems in mariculture-dominated seascapes.

Occurrence and distribution of antibiotics and antibiotic resistance genes in the guts of shrimp from different coastal areas of China

With the continuous increase in shrimp (Litopenaeus vannamei) aquaculture production, the widespread use of antibiotics as a means of preventing and treating diseases has adversely affected the environment, animal health and symbiotic microorganisms in gut environments. At the same time, antibiotic resistance genes (ARGs) are widespread in aquaculture and pose a great threat to aquatic organisms and humans. Therefore, in the present study, the occurrence and distribution of 17 antibiotics, ARGs and mobile genetic elements (MGEs) were detected in the guts of shrimp collected from 12 coastal regions of China. The results showed that sulfadiazine, ciprofloxacin and norfloxacin were detectable in the guts of L. vannamei at all sampling sites. Sul1, sul2, floR and intI-1 were also detected in the guts of L. vannamei at all sampling sites. The total relative abundances of ARGs and MGEs were significantly positively correlated according to Pearson correlation analysis. Sulfonamide resistance genes (sul1 and sul2) were significantly positively correlated with intI-1. These results indicated that MGEs could increase the risk of horizontal gene transfer of ARGs in a gut environment. MGEs are the most important factors promoting the spread of ARGs. Correlation analysis showed that sulfadiazine was significantly positively correlated with sul1 and sul2 and that fluoroquinolone antibiotics were significantly positively correlated with floR, indicating that antibiotics could induce the production of ARGs. Network analysis indicated that Iamia and Alkaliphilus species may harbor the most antibiotic resistance genes, and these bacteria were closely related to the proliferation and spread of ARGs in a gut environment. Antibiotic use and the spread of ARGs in mariculture systems may have negative effects on shrimp and human health. The use of antibiotics should be strictly regulated to control contaminants in mariculture systems, including pathogens and ARGs, thereby reducing potential risks to human health.

Environmental and economic assessment of mariculture systems using a high share of renewable energy sources

Increased demand for fish products has resulted in greater investment in and modernization of the aquaculture sector. These processes have led to higher energy needs of aquaculture farms globally, resulting in their greater environmental impact. Fossil fuel is the main power source in aquaculture, and its combustion generates a large amount of Greenhouse Gases (GHGs) and other emissions. This paper considers the use of renewable energy sources (RESs) in mariculture systems to ensure at the same time cost-effective and environmentally friendly powering options. This paper investigates an alternative solution which relocates the majority of equipment and tasks from a mariculture vessel to a barge to reduce the energy demands of the vessel and to significantly lessen emissions of the system. The solution includes the full electrification of the workboat and the installation of PV cells and a wind turbine onboard the barge, combined with a diesel generator in an integrated power system. A Life-Cycle Assessment (LCA) was performed to evaluate the considered power system configurations from an environmental point of view, while a Life-Cycle Cost Assessment (LCCA) was performed to evaluate the economic performance of the proposed solutions. The results of the implementation of RESs in the mariculture system indicate an emission reduction of about 20% and an increase in capital costs by 0.61%. Feed reduction and the use of electricity in an alternative mariculture farm design in Croatia increase profitability by 4% in most cases.

Projecting global mariculture production and adaptation pathways under climate change.

The sustainability of global seafood supply to meet increasing demand is facing several challenges, including increasing consumption levels due to a growing human population, fisheries resources over-exploitation and climate change. Whilst growth in seafood production from capture fisheries is limited, global mariculture production is expanding. However, climate change poses risks to the potential seafood production from mariculture. Here, we apply a global mariculture production model that accounts for changing ocean conditions, suitable marine area for farming, fishmeal and fish oil production, farmed species dietary demand, farmed fish price and global seafood demand to project mariculture production under two climate and socio-economic scenarios. We include 85 farmed marine fish and mollusc species, representing about 70% of all mariculture production in 2015. Results show positive global mariculture production changes by the mid and end of the 21st century relative to the 2000s under the SSP1-2.6scenario with an increase of 17%±5 and 33%±6, respectively. However, under the SSP5-8.5scenario, an increase of 8%±5 is projected, with production peaking by mid-century and declining by 16%±5 towards the end of the 21st century. More than 25% of mariculture-producing nations are projected to lose 40%-90% of their current mariculture production potential under SSP5-8.5 by mid-century. Projected impacts are mainly due to the direct ocean warming effects on farmed species and suitable marine areas, and the indirect impacts of changing availability of forage fishes supplies to produce aquafeed. Fishmeal replacement with alternative protein can lower climate impacts on a subset of finfish production. However, such adaptation measures do not apply to regions dominated by non-feed-based farming (i.e. molluscs) and regions losing substantial marine areas suitable for mariculture. Our study highlights the importance of strong mitigation efforts and the need for different climate adaptation options tailored to the diversity of mariculture systems, to support climate-resilient mariculture development.