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The commercial viability of walleye (Sander vitreus) as an aquaculture species requires that walleye gametes are available year‐round so that multiple cohorts of walleye can be brought to market throughout the year. This study aimed to apply photothermal manipulations to three groups of walleye broodstock to induce out‐of‐season spawning and obtain a year‐round supply of fertilized walleye eggs. We manipulated photothermal regimes for three groups of broodstock to induce spawning in February (early), April (in‐season), and July (late‐season). In autumn, water temperatures were chilled to 8°C in all treatments. The duration of the chill period varied for each treatment with the early, in‐season, and late treatments remaining chilled for 6, 18, and 30 weeks, respectively, before being warmed to induce spawning. Fecundity was significantly lower for late‐season broodstock. Egg size and gonadosomatic index were significantly smaller in the early‐season treatment. Fertilization success was similar for early and in‐season treatments but was 0% for eggs from the late‐season treatment. Larval survival was significantly lower for walleye from early‐season broodstock. Our results suggest that early out‐of‐season spawning for walleye is possible but comes with tradeoffs of smaller egg size and lower larval survival. [ABSTRACT FROM AUTHOR]

Aquaculture has expanded rapidly over the past half century and has surpassed capture fisheries as a source of seafood globally. However, most of the aquaculture production growth has occurred in developing countries. Despite early leadership in the global aquaculture industry, most developed countries have played only a minor role in the Blue Revolution. This paper examines the potential for developed nations to increase aquaculture production using recirculating aquaculture system (RAS) based production. The United States is used as a case study to highlight potential benefits associated with RAS-based production for developed country producers. The paper examines potential marketing and production benefits associated with RAS-based production in developed countries and evaluates the potential for RAS to avoid some regulatory and social opposition obstacles that have hindered other forms of aquaculture in developed countries. [ABSTRACT FROM AUTHOR]

The effect of different feed rations on RAS-based pikeperch juveniles' growth parameters was studied. Juvenile pikeperch were reared in three separate experiments (I, II, and III) at a temperature of 24 °C with initial body weights of the fish at 1.3, 9.4, and 25.6 g, respectively. Four applied feed rations increased by 0.5% in each experiment: 3.0, 3.5, 4.0, and 4.5% of body weight per day (BW day−1) in experiment I; 2.0, 2.5, 3.0, and 3.5% BW day−1 in experiment II; 1.0, 1.5, 2.0, and 2.5% BW day−1 in experiment III. Each experiment in triplicates lasted 28 days. The fish were reared in tanks with working volumes of 1.0 m3 each. All experiments were performed in the same recirculating aquaculture system. The stocking density in experiments I, II, and III was 800, 400, and 200 individuals per tank, respectively. The results of experiment I showed the highest specific growth rate (SGR), weight gain (WG), and biomass gain at the feed ration of 4.5% BW day−1 (P < 0.05). In experiment II, feed ration from 2.5 to 3.5% BW day−1 showed the highest final weight (P < 0.05). In experimental III, feed ration of 2.0 and 2.5% BW day−1 showed the highest final weight, SGR, and WG (P < 0.05). Only in experiment III, based on SGR and WG, second-order polynomial regression showed that the optimal feed ration for pikeperch was 2.35–2.39% BW day−1. [ABSTRACT FROM AUTHOR]

Since reef-building corals rely on both heterotrophy and endosymbiotic dinoflagellate autotrophy to meet their metabolic needs, it is necessary to consider both food supply and light levels, respectively, when optimizing their cultivation ex situ. Herein nubbins of the model reef coral Pocillopora acuta cultured in recirculating aquaculture systems at photosynthetically active radiation levels of 370 or 670 μmol quanta m−2 s−1 were fed Artemia nauplii at concentrations of either 33 or 78 individuals mL−1 in a separate feeding tank for 6 hr in the dark thrice weekly. A subset of nubbins was experimentally wounded at the outset of the 84-day experiment to assess recovery, and 100% fully healed within 2–4 weeks. All cultured corals survived, and unwounded corals (1) grew at a specific growth rate approaching 0.5% day−1 and (2) demonstrated a mean total linear extension of 0.2% day−1 (~6–8 cm year−1); these are far higher than growth rates normally documented in situ. In the feeding tank, corals tolerated nitrate levels up to 25 mg L−1, but once concentrations reached 50 mg L−1 by day 84, tissue necrosis began to occur in nubbins of one tank. This highlights the importance of feeding in separate tanks during long-term culture of corals, and bio-filtration could reduce the possibility of organic matter accumulation in future coral culture studies. [ABSTRACT FROM AUTHOR]

To assess the impact of different substrates in a recirculating water system on the immune response and antioxidant capacity of Babylonia areolata, we conducted a comparative analysis of the transcriptomes and antioxidant performance of the digestive glands in three substrate environments (sand—S group, ceramic granules—C group, and PVC breeding nest—P group). Transcriptome results revealed that the S group and P group exhibited the highest number of differentially expressed genes (DEGs), with a total of 2218 DEGs, including 928 upregulated and 1290 downregulated DEGs. The C group and P group had 1055 DEGs in common, with 316 upregulated and 739 downregulated DEGs. The C group and S group had the fewest DEGs, with 521 in total, including 303 upregulated and 218 downregulated DEGs. GO enrichment analysis showed that in the S vs P group, terms such as catalytic activity, membrane part, and cellular process were enriched with 287, 262, and 180 DEGs, respectively. In the C vs P group, binding, cellular process, and cell part were enriched with 146, 135, and 127 DEGs, respectively. In the C vs S group, catalytic activity, membrane part, and metabolic process were enriched with 90, 83, and 59 DEGs, respectively. Kegg enrichment analysis revealed significant changes in immune-related pathways in the S vs P group, including lysosome, phagosome, and leukocyte transendothelial migration, with 30, 13, and 10 enriched DEGs, respectively. In the C vs P group, phagosome, drug metabolism—other enzymes, and N-Glycan biosynthesis showed significant changes in immune-related pathways, with 9, 6, and 4 enriched DEGs, respectively. In the C vs S group, lysosome, PPAR signaling pathway, and fatty acid degradation exhibited significant changes in immune-related pathways, with 8, 4, and 3 enriched DEGs, respectively. Regarding antioxidant capacity, the S group showed significantly higher total T-AOC than the other experimental groups, while CAT, SOD, POD, and AKP were lower than in the C and P groups. The ACP level in the Sand group was not significantly different from the P group but significantly lower than the C group. In conclusion, substrate environments significantly influence the immune-related genes and key antioxidant enzyme activities in B. areolata. [ABSTRACT FROM AUTHOR]

Background: In this study, we investigated the effects of swimming activity and feed restriction on digestion and antioxidant enzyme activities in juvenile rainbow trout (average body weight of 26.54 ± 0.36 g). Methods: The stomach, liver and kidney tissues were obtained from four distinct groups: the static water group (fish were kept in static water and fed to satiation), the feeding restricted group (fish were kept in static water with a 25% feed restriction), the swimming exercised group (fish were forced to swimming at a flow rate of 1 Body Length per second (BL/s)) and the swimming exercised‐feed restricted group (subjected to swimming exercise at a 1 BL/s flow rate along with a 25% feed restriction). We determined the levels of glutathione, lipid peroxidation and the activities of catalase, superoxide dismutase, glutathione peroxidase, glutathione reductase, glucose‐6‐phosphate dehydrogenase and lactate dehydrogenase, as well as the presence of reactive oxygen species in the tissues obtained from the fish. Additionally, the activities of pepsin, protease, lipase and arginase in these tissues were measured. Results: Swimming activity and feed restriction showed different effects on the enzyme activities of the fish in the experimental groups. Conclusion: It can be concluded that proper nutrition and exercise positively influence the antioxidant system and enzyme activities in fish, reducing the formation of free radicals. This situation is likely to contribute to the fish's development. [ABSTRACT FROM AUTHOR]

Biofloc technology (BFT) has gained increased interest as a potential low-cost and environmentally friendly method for sustainable aquaculture development. However, the addition of external organic carbon source and the increased aeration needed to promote biofloc formation could be a limitation of this technology. The integration of microalgae on the BFT has the potential to improve the overall efficiency of the method, since microalgae can photosynthetically assimilate nitrogen (ammonia, nitrate, and nitrite) without the requirement of external organic carbon addition. In this work, BFT was supplemented with microalgae Nannochloris sp. isolated and adapted in BFT, while four different C/N ratios (0:1, 5:1, 10:1, and 15:1) were applied in artificial aquaculture wastewater to investigate the nitrogen removal efficiency under reduced external organic carbon addition and to assess the nutritional value of the produced biomass. The present study demonstrated that microalgal integration into a biofloc system led to an efficient ammonia removal and repression of nitrite formation at a lower C/N ratio of 5:1 compared to optimum 15:1 of the series consisting of biofloc only. At the optimum levels of C/N, protein content was not changed (around 37%); however, the incorporation of microalgae into the biofloc resulted in a significant decrease of protein digestibility. Lipid content was also decreased (from approx. 16 to 11%) in the series with incorporated microalgae with less unsaturated fatty acids composition. Microbial diversity was altered in the different series examined, while bacterial and eukaryotic communities participating in the nitrogen cycle and degradation of complex organic compounds were discussed. [ABSTRACT FROM AUTHOR]

Depuration is a proven pre-harvest procedure that eliminates off-flavor from Atlantic salmon produced in recirculating aquaculture systems. However, applied research indicates that depurating salmon lose weight while fasting, which reduces farmgate revenue. Low-ration feeding was therefore evaluated as a method to mitigate weight loss while depurating 3–4 kg Atlantic salmon. Salmon implanted with passive-integrated-transponders were weighed, exposed to concentrated geosmin (GSM) and 2-methylisoborneol (MIB), and stocked in eight pre-disinfected partial reuse systems. Feed was either offered for 4 days or withheld entirely (n = 4) during a 6-day depuration period. Salmon from both treatments rapidly eliminated GSM and MIB, but slightly lower levels remained in fish that were fed (P <.05). Fed and fasted salmon lost 0.3 and 1.1% of their initial body weight, respectively (P <.05). Under the conditions of this study, feeding Atlantic salmon during depuration minimized weight loss without negatively impacting off-flavor elimination. [ABSTRACT FROM AUTHOR]

In intelligent feeding recirculating aquaculture system, accurately estimating fish population and density is pivotal for management practices and survival rate assessments. However, challenges arise due to mutual occlusion among fish, rapid movement, and complex breeding environments. Traditional object detection methods based on convolutional neural networks (CNN) often fall short in fully addressing the detection demands for fish schools, especially for distant and small targets. In this regard, we introduce a detection framework dubbed FCFormer (Fish Count Transformer). Specifically, the Twins-SVT backbone network is employed first to extract global features of fish schools. To further enhance feature extraction, especially in the fusion of features at different levels, a Bi-FPN aggregation network model with a CAM Count module is incorporated (BiCC). The CAM module aids in focusing more on critical region features, thus rendering feature fusion more cohesive and effective. Furthermore, to precisely predict density maps and elevate the accuracy of fish counting, we devised an adaptive feature fusion regression head: CRMHead. This approach not only optimizes the feature fusion process but also ensures superior counting precision. Experimental results shown that the proposed FCFormer network achieves an accuracy of 97.06%, with a mean absolute error (MAE) of 6.37 and a root mean square error (MSE) of 8.69. Compared to the Twins transformer, there's a 2.02% improvement, outperforming other transformer-based architectures like CCTrans and DM&lowbar;Count. The presented FCFormer algorithm can be effectively applied to fish density detection in intelligent feeding recirculating aquaculture system, offering valuable input for the development of intelligent breeding management systems. [ABSTRACT FROM AUTHOR]

Floating treatment wetland (FTW) as a wastewater processing technology in recirculating aquaculture systems (RAS) of catfish is considered to be effective in eliminating the pollutant load of nitrogen, phosphorous, and organic matter. This research aims to reduce the concentration of pollutant loads and obtain an effective ratio between the volume of the FTW and the total water volume of the catfish RAS. The FTW system uses Vetiveria zizanoides grown on floating media and equipped with an aerator in the bottom layer of the pond. Several FTW volume ratios were used to determine an FTW system that is effective in reducing pollutant loads according to the mass balance concept. This approach was conducted to maintain acceptable water quality in catfish cultivation ponds. The study results showed that most pollutant load concentrations decreased in all ponds. The largest removal percentage included the parameters TAN, COD, TSS, TP, nitrate, phosphate, and TN, namely 88.54%, 66.17%, 85.68%, 91.30%, 83.85%, 61.46%, and 44.68%, respectively. The effective ratio between the volume of the FTW processing system and the total water volume of 0.543with an age group of fish of 9-12 weeks was able to eliminate the pollutant loads from catfish pond wastewater. [ABSTRACT FROM AUTHOR]

Abstract The commercial viability of walleye (Sander vitreus) as an aquaculture species requires that walleye gametes are available year‐round so that multiple cohorts of walleye can be brought to market throughout the year. This study aimed to apply photothermal manipulations to three groups of walleye broodstock to induce out‐of‐season spawning and obtain a year‐round supply of fertilized walleye eggs. We manipulated photothermal regimes for three groups of broodstock to induce spawning in February (early), April (in‐season), and July (late‐season). In autumn, water temperatures were chilled to 8°C in all treatments. The duration of the chill period varied for each treatment with the early, in‐season, and late treatments remaining chilled for 6, 18, and 30 weeks, respectively, before being warmed to induce spawning. Fecundity was significantly lower for late‐season broodstock. Egg size and gonadosomatic index were significantly smaller in the early‐season treatment. Fertilization success was similar for early and in‐season treatments but was 0% for eggs from the late‐season treatment. Larval survival was significantly lower for walleye from early‐season broodstock. Our results suggest that early out‐of‐season spawning for walleye is possible but comes with tradeoffs of smaller egg size and lower larval survival.

Since reef-building corals rely on both heterotrophy and endosymbiotic dinoflagellate autotrophy to meet their metabolic needs, it is necessary to consider both food supply and light levels, respectively, when optimizing their cultivation ex situ. Herein nubbins of the model reef coral Pocillopora acuta cultured in recirculating aquaculture systems at photosynthetically active radiation levels of 370 or 670 μmol quanta m−2 s−1 were fed Artemia nauplii at concentrations of either 33 or 78 individuals mL−1 in a separate feeding tank for 6 hr in the dark thrice weekly. A subset of nubbins was experimentally wounded at the outset of the 84-day experiment to assess recovery, and 100% fully healed within 2–4 weeks. All cultured corals survived, and unwounded corals (1) grew at a specific growth rate approaching 0.5% day−1 and (2) demonstrated a mean total linear extension of 0.2% day−1 (~6–8 cm year−1); these are far higher than growth rates normally documented in situ. In the feeding tank, corals tolerated nitrate levels up to 25 mg L−1, but once concentrations reached 50 mg L−1 by day 84, tissue necrosis began to occur in nubbins of one tank. This highlights the importance of feeding in separate tanks during long-term culture of corals, and bio-filtration could reduce the possibility of organic matter accumulation in future coral culture studies.

Constant and proper mixing of water in fish farms is essential for creating maximum uniformity, minimizing stagnant areas, properly distributing oxygen, and removing solid waste from the bottom of the ponds. The effect of the inflow installation mode and inflow momentum force in octagonal ponds was examined on the hydrodynamic flow mixing by laboratory modeling. For this purpose, the inflow was analyzed in three modes with angles of 90, 60, and 30° and the inflowing force at four levels with values of 0.004, 0.009, 0.013, and 0.018 N by the residence time distribution curve and hydraulic efficiency of octagonal ponds. The laboratory modeling results revealed that the inflow at the 90° mode for all four-momentum forces does not form an eddy current and short circuit in the pond's flow, as the result of which the hydraulic efficiency of the pond falls in the weak range. To improve the hydraulic efficiency of the pond, the inflow was installed at 60 and 30° modes; the results demonstrated 2.68 and 3.26 times higher efficiency than the 90° mode. Moreover, for all three inflow installation modes, the hydraulic efficiency had an inverse relationship with the inflow momentum force.

Abstract A reliable and cost‐effective source of fingerlings is essential for the successful commercial aquaculture of black sea bass. This study aimed to determine the effects of nursery tank stocking densities on the growth performance, feed efficiency, survival, tolerance to shipping, and biochemical quality of juvenile black sea bass. In two experiments, different stocking densities were compared for black sea bass at different stages of development. In Experiment 1, intermediate stage juveniles (1.27 g mean wt) were stocked at densities of 4.5 and 6.5 fish per liter of tank volume. Growth performance and biochemical quality were similar between the two density treatments. In Experiment 2, early post‐metamorphic stage juveniles (mean wt. = 0.524 g) were compared using the same stocking densities. While the fish reared at 4.5 fish/L were slightly larger, there were no significant differences in growth performance or biochemical quality between the density treatments. After both experiments, the fingerlings from each density treatment showed high survival rates under acute crowding and simulated shipping conditions. The study demonstrates that high NT densities of 4.5 and 6.5 fish/L did not negatively impact the growth performance and quality of black sea bass fingerlings, providing transport‐ready fingerlings in a relatively short period.

In recirculating aquaculture systems, cultivated fsh cannot incorporate all the phosphate contained in the feed. Excess phosphate ends up in the culture water and in the sludge produced. If the sludge cannot be valorised directly in agriculture, a chemical recovery as concentrated phosphate is an interesting option to help closing the phosphorus cycle. This study investigates the extent to which accumulated phosphorus can be recovered by acid re-dissolution with subsequent precipitation on sludge from two diferent recirculating aquaculture systems cultivating African Catfsh (Clarias gariepinus). Acid treatment could increase the ratio of dissolved phosphorus available for subsequent precipitation by 53% for extensive and by 61% for intensive fsh farming. With the consecutive precipitation in total up to 86% of the phosphorus from the sludge could be recovered. Phosphorus re-dissolution with citric acid requires the highest amount of acid per g dry matter as well as of sodium hydroxide for subsequent precipitation. Sulfuric and nitric acids have comparably lower demands. [ABSTRACT FROM AUTHOR]

A reliable and cost‐effective source of fingerlings is essential for the successful commercial aquaculture of black sea bass. This study aimed to determine the effects of nursery tank stocking densities on the growth performance, feed efficiency, survival, tolerance to shipping, and biochemical quality of juvenile black sea bass. In two experiments, different stocking densities were compared for black sea bass at different stages of development. In Experiment 1, intermediate stage juveniles (1.27 g mean wt) were stocked at densities of 4.5 and 6.5 fish per liter of tank volume. Growth performance and biochemical quality were similar between the two density treatments. In Experiment 2, early post‐metamorphic stage juveniles (mean wt. = 0.524 g) were compared using the same stocking densities. While the fish reared at 4.5 fish/L were slightly larger, there were no significant differences in growth performance or biochemical quality between the density treatments. After both experiments, the fingerlings from each density treatment showed high survival rates under acute crowding and simulated shipping conditions. The study demonstrates that high NT densities of 4.5 and 6.5 fish/L did not negatively impact the growth performance and quality of black sea bass fingerlings, providing transport‐ready fingerlings in a relatively short period. [ABSTRACT FROM AUTHOR]

Abstract Background In this study, we investigated the effects of swimming activity and feed restriction on digestion and antioxidant enzyme activities in juvenile rainbow trout (average body weight of 26.54 ± 0.36 g). Methods The stomach, liver and kidney tissues were obtained from four distinct groups: the static water group (fish were kept in static water and fed to satiation), the feeding restricted group (fish were kept in static water with a 25% feed restriction), the swimming exercised group (fish were forced to swimming at a flow rate of 1 Body Length per second (BL/s)) and the swimming exercised‐feed restricted group (subjected to swimming exercise at a 1 BL/s flow rate along with a 25% feed restriction). We determined the levels of glutathione, lipid peroxidation and the activities of catalase, superoxide dismutase, glutathione peroxidase, glutathione reductase, glucose‐6‐phosphate dehydrogenase and lactate dehydrogenase, as well as the presence of reactive oxygen species in the tissues obtained from the fish. Additionally, the activities of pepsin, protease, lipase and arginase in these tissues were measured. Results Swimming activity and feed restriction showed different effects on the enzyme activities of the fish in the experimental groups. Conclusion It can be concluded that proper nutrition and exercise positively influence the antioxidant system and enzyme activities in fish, reducing the formation of free radicals. This situation is likely to contribute to the fish's development.

Both population and economic development are driving the rapid adoption of aquaculture development worldwide. The unique attributes of the intensive factory recirculating aquaculture system, including high density, low pollution, and high efficiency, have made this system an important avenue for aquaculture transformation and improvement, and this fits the current concept of green development in aquaculture. Flow patterns are an important environmental factor in the recirculating water aquaculture systems, with this parameter directly affecting the growth and welfare of fish within the system. However, it is also worth noting that the presence and movement of the fish also affect the construction of the system flow pattern. This study presents a comprehensive analysis of the effects of flow field conditions in recirculating aquaculture systems on different fish species, including the effects of flow rate on the growth and development, physiological indicators, and survival rates of commonly cultured fish, as well as the effects of other hydrodynamic conditions, such as circulating water and circulating water exchange rates, on fish behavior. The effects of fish and their locomotor behavior on hydrodynamic conditions and performance in culture ponds are also discussed, including the effects on turbulence intensity, flow-field flow patterns, and water mixing in these systems. The methods used to study the effect of fish movement on the flow field characteristics of any system can be broadly categorized into real measurement methods and numerical studies, where the real measurement methods include the visualization of research objects using the particle image velocimetry (PIV), acoustic Doppler velocimetry (ADV), and rhodamine water tracer fluorescence method. In contrast, numerical studies primarily rely on the application of the computational fluid dynamics (CFD) method. The advantages and disadvantages of both approaches are evaluated in this study. Our evaluations include a discussion of the common problems with the current system for constructing the circulating water aquaculture systems in industry, such as neglecting the flow field construction, lack of cross-disciplinary research, poor regularity, and repeatability of research, and suggest that a systematic experimental program should be established in combination with refined numerical simulation methods to facilitate the development of more accurate complex models. The aim of this study was to clarify the design of hydrodynamic conditions in these aquaculture systems in order to promote the development of better circulating water aquaculture systems for the industry in the hope of improving both the fish and water balance.

The economic feasibility for captive breeding of marine ornamental fish in small spaces is poorly known, especially when considering threatened species. The present study analyzed the economic feasibility for producing Yellow Neon Goby (Elacatinus figaro) (vulnerable) in urban aquaculture systems through different production scenarios: pessimistic, normal, and optimistic, at sales prices of US$ 5.71, US$ 7.62, and US$ 9.52/unit. The financial analysis pointed the total cost of production per animal available to marine ornamental fish trade was between US$ 3.99 and R$ 8.03, with labor and rent as the main expenses. Six of the nine observed schemes showed profitability, including under loss conditions of an entire cycle. The net present value (NPV 8%) reached US$ 83,256 (negative value, unfeasible) until US$ 230,122 (positive value, viable), with profitable conditions presenting an internal rate of return (IRR) ranging from 10.87 to 97.84% and return on capital observed from the first to the sixth year of activity. In addition to the sustainable potential for biodiversity conservation, these results expressed reinforce urban ornamental aquaculture as a profitable instrument for public policy in socioeconomic development at large urban centers and their peripheral regions. [ABSTRACT FROM AUTHOR]

The paper discusses the current prognoses of aquaculture development worldwide putting an emphasis on its effect on the environment and the issue of the protection of water reservoirs in different countries. Water consumption in diversified aquaculture systems is presented herein as well as the characteristics of the mechanical and biological water treatment methods in fish farms, with particular attention paid to the recirculating water systems. New aquaculture technologies using post-production waters are presented. The paper provides a discussion on the contribution of aquaculture to the global greenhouse gas emissions and the means of limiting this emission. The effect of climate change on aquatic ecosystems is presented in the context of the changes of the aquaculture production profile. The paper includes a brief presentation of the methods of mitigating the changes with respect to contamination of aquatic ecosystems as well as climate change. Reducing the water footprint can be achieved through selective breeding, species diversification and implementation of more technologically advanced aquaculture systems such as: integrated multi-trophic aquaculture, aquaponics and recirculation systems in aquaculture. The need for certification of fish farms with water recirculation systems is justified in the paper. The issues addressed herein are summarised and the main areas for extending the research promoting preservation of aquatic ecosystems in aquaculture are presented.

Large rainbow trout marketed as steelhead are gaining considerable attention for production in recirculating aquaculture systems (RAS). Diploid and triploid trout with varying genetics are available from several commercial suppliers; however, the performance and processing metrics of these lines have not been compared when raised in freshwater RAS. Current data on these outcomes could support more accurate cost and profitability estimates for potential RAS projects and optimize operation for existing farms. Accordingly, the objective of this study was to quantify performance metrics, processing yield, and fillet composition of six all-female rainbow trout lines (three diploid and three triploid) exposed to an artificial winter (12:12 light: dark at 40 g (Artificial Winter Photoperiod; AWP)) or continuous, 24-h light (No Winter Photoperiod; NWP) grown in a semi-commercial scale freshwater RAS to 3.5 kg. Overall, growth was impacted by line, ploidy, and artificial winter photoperiod. Diploid and AWP trout were smaller than triploids and NWP trout at stocking and 500 g. Mean diploid and triploid weight was similar at larger sizes (>1 kg); however, triploid performance compared to diploids varied by commercial supplier. Mortality was lower in lines from commercial supplier 1 than lines from commercial supplier 2 and the United States Department of Agriculture (14.4 ± 0.8 vs 27.5 ± 2.0 and 29.8 ± 4.3%, respectively). Head-on gutted and skin-on fillet yields were related with larger fish weight. Mature prevalence in diploids may have led to differences observed between diploids and triploids in fillet lipid (10.9 ± 0.8 vs 13.3 ± 0.6%) and moisture (67.0 ± 0.6 vs 65.1 ± 0.4%). The results provide guidance for rainbow trout RAS producers to make informed decisions on optimal harvest size targets and tailor their rainbow trout line or ploidy selection to those harvest sizes.

Abstract Production of Atlantic salmon smolts in recirculation aquaculture systems (RAS) is growing, and novel production protocols using continuous light in RAS are being implemented in the industry. In the present study, Atlantic Salmon parr were exposed to either a traditional protocol (short‐day winter signal [12:12 L:D] for 6 weeks) or to continuous light. Both photoperiods were applied in freshwater (FW) and brackish water RAS. Salmon from all treatments were transferred to seawater pens at 200 and 600 g and grown until slaughter size. A control group was smoltified with a 6‐week short‐day winter signal and kept in FW until sea transfer at 100 g. Continuous light gave a higher growth rate in RAS but reduced feed intake and growth and increased feed conversion ratio during the first 8 weeks in seawater. However, at slaughter, fish exposed to continuous light was bigger than fish given a winter signal because of the higher growth rate in RAS. Slaughter weight was lowest in fish transferred to sea at 600 g, despite having the highest day‐degree sum during their life span. The best performing group was the control group transferred at 100 g. All treatments handled transfer to seawater and survival and maturation were not affected by the treatments in RAS. The immune status was examined with a multigene expression assay on BioMark HD platform from parr stage to 5–7 months after seawater transfer. Overall, there was no significant effect of photoperiod or salinity on the expression of the selected immune genes. In sum, the results from this study indicate that using continuous light in RAS may have negative effects on performance shortly after transfer in fish transferred to sea at 200 g, whereas at 600 g, all treatments had reduced growth after transfer irrespective of treatment in RAS.

Abstract Land‐based Atlantic salmon, Salmo salar, grow‐out facilities utilize depuration to remediate off‐flavor. Water used in this process is either discharged or repurposed as supply water in recirculating aquaculture systems (RAS). Both approaches require an understanding of water quality and waste production for water treatment decisions and compliance with pollution discharge standards; however, these data were lacking. Therefore, a study was carried out to characterize these parameters. To begin, 311 salmon (5–6 kg) originally cultured in freshwater RAS were stocked at 100 kg/m3 in an 18 m3 depuration tank. Feed was withheld 1 day before transfer and throughout the 7‐day study period. Hours after stocking, total suspended solids (TSS), total phosphorus (TP), and total ammonia nitrogen (TAN) levels spiked, and concentrations declined thereafter. Delta TSS and TP were negligible by the end of the trial; however, TAN plateaued, indicating that salmon began to catabolize somatic tissue in the absence of feeding. Geosmin and 2‐methylisoboreol levels in water and fish were low throughout the study. This research indicates that residual waste production occurs while depurating Atlantic salmon. Procedural refinements and recommendations were gleaned including locality for introducing depuration system water within RAS and extension of the feed withholding period before depuration.

The paper discusses the current prognoses of aquaculture development worldwide putting an emphasis on its effect on the environment and the issue of the protection of water reservoirs in different countries. Water consumption in diversified aquaculture systems is presented herein as well as the characteristics of the mechanical and biological water treatment methods in fish farms, with particular attention paid to the recirculating water systems. New aquaculture technologies using post-production waters are presented. The paper provides a discussion on the contribution of aquaculture to the global greenhouse gas emissions and the means of limiting this emission. The effect of climate change on aquatic ecosystems is presented in the context of the changes of the aquaculture production profile. The paper includes a brief presentation of the methods of mitigating the changes with respect to contamination of aquatic ecosystems as well as climate change. Reducing the water footprint can be achieved through selective breeding, species diversification and implementation of more technologically advanced aquaculture systems such as: integrated multi-trophic aquaculture, aquaponics and recirculation systems in aquaculture. The need for certification of fish farms with water recirculation systems is justified in the paper. The issues addressed herein are summarised and the main areas for extending the research promoting preservation of aquatic ecosystems in aquaculture are presented. [ABSTRACT FROM AUTHOR]

Land‐based Atlantic salmon, Salmo salar, grow‐out facilities utilize depuration to remediate off‐flavor. Water used in this process is either discharged or repurposed as supply water in recirculating aquaculture systems (RAS). Both approaches require an understanding of water quality and waste production for water treatment decisions and compliance with pollution discharge standards; however, these data were lacking. Therefore, a study was carried out to characterize these parameters. To begin, 311 salmon (5–6 kg) originally cultured in freshwater RAS were stocked at 100 kg/m3 in an 18 m3 depuration tank. Feed was withheld 1 day before transfer and throughout the 7‐day study period. Hours after stocking, total suspended solids (TSS), total phosphorus (TP), and total ammonia nitrogen (TAN) levels spiked, and concentrations declined thereafter. Delta TSS and TP were negligible by the end of the trial; however, TAN plateaued, indicating that salmon began to catabolize somatic tissue in the absence of feeding. Geosmin and 2‐methylisoboreol levels in water and fish were low throughout the study. This research indicates that residual waste production occurs while depurating Atlantic salmon. Procedural refinements and recommendations were gleaned including locality for introducing depuration system water within RAS and extension of the feed withholding period before depuration. [ABSTRACT FROM AUTHOR]

Production of Atlantic salmon smolts in recirculation aquaculture systems (RAS) is growing, and novel production protocols using continuous light in RAS are being implemented in the industry. In the present study, Atlantic Salmon parr were exposed to either a traditional protocol (short‐day winter signal [12:12 L:D] for 6 weeks) or to continuous light. Both photoperiods were applied in freshwater (FW) and brackish water RAS. Salmon from all treatments were transferred to seawater pens at 200 and 600 g and grown until slaughter size. A control group was smoltified with a 6‐week short‐day winter signal and kept in FW until sea transfer at 100 g. Continuous light gave a higher growth rate in RAS but reduced feed intake and growth and increased feed conversion ratio during the first 8 weeks in seawater. However, at slaughter, fish exposed to continuous light was bigger than fish given a winter signal because of the higher growth rate in RAS. Slaughter weight was lowest in fish transferred to sea at 600 g, despite having the highest day‐degree sum during their life span. The best performing group was the control group transferred at 100 g. All treatments handled transfer to seawater and survival and maturation were not affected by the treatments in RAS. The immune status was examined with a multigene expression assay on BioMark HD platform from parr stage to 5–7 months after seawater transfer. Overall, there was no significant effect of photoperiod or salinity on the expression of the selected immune genes. In sum, the results from this study indicate that using continuous light in RAS may have negative effects on performance shortly after transfer in fish transferred to sea at 200 g, whereas at 600 g, all treatments had reduced growth after transfer irrespective of treatment in RAS. [ABSTRACT FROM AUTHOR]

Biofloc technology involves the manipulation of the culture system's carbon: nitrogen ratio to promote bacterial community growth to convert toxic nitrogenous wastes and organics into functional microbial protein; this protein can then be used as a food source and mediate water quality. Biofloc systems have several advantages, which include improved biosecurity, feed conversion, water use efficiency, and nutrient processing. Analyzing the nutritional value and the relationship between high production of aquacultural practices using biofloc is essential. Many studies have demonstrated that biofloc increases the growth of aquatic species by acting as a food source or providing bioactive compounds. Other than this, the beneficial micro-organisms in biofloc systems contain compounds such as organic acids that could resist the growth of pathogenic microbes. They will also serve as a natural probiotic and increase the immunity and survival of fish and shrimp. This technology could be useful for further integration within many aspects of aquaculture production when microbial interactions are considered. However, future studies must fully understand the principles and mechanisms behind the benefits of interactions between biofloc and cultured fish and crustacean species. [ABSTRACT FROM AUTHOR]

Shrimp is the most popular seafood in the United States; its production plays an important role in the aquaculture industry. However, shrimp farming causes various environment impacts that must be mitigated to ensure the sustainability of shrimp production. This study performed a life cycle assessment (LCA) on two US‐based and one Vietnam‐based shrimp production chains from cradle to US market covering three farming systems and eight shrimp feed formulae. Midpoint environmental impacts including terrestrial acidification, freshwater eutrophication, and global warming were determined. For the intensive production chain (IPC), feed production was identified as the main contributor to the terrestrial acidification potential (TAP) and global warming potential (GWP), and its freshwater eutrophication potential (FEP) was dominated by shrimp farming. Poultry by‐product and fish meals were the feed ingredients contributing high TAP and GWP. However, soybean, wheat, and corn gluten meals produced higher FEP; hence, substituting plant‐based proteins for animal‐based ones in shrimp feeds did not all have positive environmental consequences. Shrimp farming was the hotspot of all the environmental impacts of the semi‐intensive production chain (SPC) and extensive production chain (EPC), except for the TAP of the EPC. Among the three production chains, the IPC had the highest FEP due to the on‐farm discharge of phosphorus‐containing wastewater, and the SPC caused the highest TAP because of the intensive uses of electricity and fertilizers for pond cultivation. Although the EPC was most sustainable in terms of TAP and FEP, open farming in mangrove areas produced the highest GWP owing to land transformation. This LCA study is expected to serve as US shrimp farmers' decision‐making guidelines to adapt farming practices with lower environmental footprint. [ABSTRACT FROM AUTHOR]

The optimal water flow in fish breeding tanks is one of the crucial elements necessary for the well-being and proper growth of fish, such as salmon or trout. Considering the round tanks and the uneven distribution of water-flow velocity, ensuring a nearly optimal flow is an important task that may be performed using various sensors installed to monitor the water flow. Nevertheless, observing the rapid development of video analysis methods and considering the increasing availability of relatively cheap cameras, the use of video feedback has become an interesting alternative that limits the number of sensors inside the water tanks in accordance with the requirements of fish breeders. In this paper, an analysis of the use of optical flow algorithms for this purpose is performed and an estimation method based on their features is proposed. The results of the flow estimation using the proposed method are verified experimentally and compared with the measurement results obtained using the professional water-flow meter, demonstrating a high correlation, exceeding 0.9, confirming the proposed solution as a good alternative in comparison to the use of expensive sensors and meters. [ABSTRACT FROM AUTHOR]

Recirculating aquaculture systems offer sustainable fish production but face challenges related to ammonia levels. Ammonia, particularly the un-ionized fraction, NH3, can negatively impact fish growth and health. Traditional ammonia estimation methods, including offline analyses and affordable, yet inaccurate, in-situ measurements, lack the ability to provide reliable real-time insights. Data assimilation combines simulation models and in-situ measurements to provide more accurate estimations. In this study, we demonstrate a novel approach using data assimilation to enhance real-time ammonia estimation in RAS. First, ammonia dynamics are described by forming equations that constitute a simulation model, based on the feeding amounts and the biofilter removal rate parameters. Then, an extended Kalman filter is presented and customized to integrate the simulation model and total ammonia nitrogen measurements for estimating NH3, NH4+, and biofilter parameters. We validated our method through synthetic and laboratory case studies and demonstrated its superior estimation capability as compared to in situ measurements or simulation models. Furthermore, improved ammonia estimation led to improved current and future fish weight estimations, which can be essential for reliable RAS management. The proposed approach facilitates wider adoption of DA in challenging estimations in aquaculture. • Data Assimilation (DA) was applied in an aquaculture setup. • A method for ammonia estimation in RAS using DA was introduced. • DA outperformed ammonia estimations by either simulations or measurements. • Improving ammonia estimation enhanced fish weight estimations. • DA has the potential to reliably provide complex aquaculture estimates. [ABSTRACT FROM AUTHOR]

In this case study, the high densities of fish in the rearing facility make an easy transfer and multiplication of specific pathogens. The limited space in which the fish are forced to live is itself a factor that overstates adaption mechanisms and can lead to the weakening of resistance to diseases. The authors presents the main parasitosis of cyprinids registered during the first period in closed recirculating aquaculture system after the transfer from open aquaculture system. These are represented by: spring viraemia of carp, ligulosis, lernaeosis, bothriocephalosis, saprolegniosis during the experimentation period of six weeks in a closed system. Results of this study shows the relationship between environmental factors and parasitosis development and the characteristics of the diseases registered in urban Recirculating Aquaculture Systems from epidemiology, pathology, etiology and diagnostics points of view. In conclusion, biosecurity measures must be applied in any kind of aquaculture activity and fish health must be monitored continuously so any treatments to be appropriate and applied as efficiently as possible.

Prokaryotic interactions in recirculating aquaculture systems (RAS) environmental communities may play a crucial role in driving their functional potential. However, these interactions are often neglected. The aim of this work is to detect prokaryotic interactions in a Solea senegalensis RAS, through the definition of relevant taxa and cluster identification using co-variance and co-occurrence tools. Amplicon sequence variants (ASV) were obtained from the water, tank biofilm, and biofilters of two systems, pre-ongrowing and weaning, and the study focuses on two microbial target groups, the potentially pathogenic and the nitrifying prokaryotes. No significant negative correlations were found with any target ASVs, indicating a mostly cooperative environment. As expected, ammonia oxidizing bacteria (Nitrosomonas) and archaea (Candidatus Nitrosopumilus) were found to be positively interacting with the nitrite oxidizing bacteria Nitrospira. However, no interactions were found between them, and results hint at a niche differentiation based on ammonia competition. Nitrospira also showed subcommunities with no ammonia oxidizing archaea or ammonia oxidizing bacteria correlations, hinting at a separate functional role of complete ammonia oxidation to nitrate for some Nitrospira ASVs. Two taxa commonly associated with pathogenic outbreaks, Tenacibaculum and Vibrio, had a significant positive correlation in one of the systems. With no outbreaks reported, this association may prove relevant in disease preventions and to improve outbreak predictions. Future studies may further elucidate this interaction, as cumulative evidence is still needed to better understand this correlation.

The constant reuse of waters in recirculating aquaculture systems (RAS) together with the continuous addition of organic matter from fish degradation components, faeces and non-consumed feed promote the accumulation of dissolved organic matter (DOM), particularly of fulvic acids (FA), leading to the yellow discoloration of their waters. The accumulation of these acids in RAS can have potential effects on its water quality, and consequently fish health and welfare. Thus, the characterization of FA is paramount for improving water quality, and subsequently fish productivity in RAS. In this study, a non-targeted analysis by quadrupole time-of-flight mass spectrometry (QTOF-MS) was used to characterize the recirculating aquaculture systems fulvic acids (RASFA) and then compare their molecular fingerprints with actual reference standards of fulvic acids (FA) (Suwannee River; SRFA, Elliott soil; ESFA and Pahokee Peat; PPFA) purchased from the International Humic Substance Society (IHSS). The results of this study demonstrated the applicability of QTOF-MS as a rapid and comprehensive screening technique to characterize the FA fraction of DOM from RAS and to monitor differences in their molecular fingerprints when compared with other FA samples (SRFA, ESFA and PPFA). The QTOF-MS data from SRFA and ESFA standards matched the list of formulas obtained by 17 high-resolution mass spectrometry (HRMS) instruments with 90 and 76% accuracy, respectively, which guaranteed the power of QTOF-MS without the need for further coupling to liquid chromatography (LC). RASFA was found to be rich in low- and high-oxygen unsaturated classes of compounds (lowOC: 61.73% and highOC: 19.28%) and was similar in composition to SRFA. On the contrary, the ESFA and PPFA soil standards consisted mainly of aliphatic compounds (36.77 and 55.74%, respectively) and differed significantly in composition from the RASFA and SRFA water samples. RASFA matched with 66% of the elemental compositions obtained from the DOM of makeup waters analyzed in a previous experiment, indicating freshwater and seawater origins with a high fraction of terrestrial-derived organic matter (Tanimoto score: 0.53 between RASFA and SRFA). The unique information obtained from the molecular-level analysis of FA samples by QTOF-MS highlights the importance of this technique to characterize and compare FA from different origins rendering it possible to track the FA compositional changes along the water treatment processes of RAS. To our knowledge, this is the first study that characterizes the molecular fingerprints of the RASFA by QTOF-MS and compares them with the available FA reference standards from IHSS. [ABSTRACT FROM AUTHOR]

Gilthead sea bream (Sparus aurata) was raised in six individual recirculating aquaculture systems (RAS) whose biofilters' performance was analyzed. Fish were fed with three different diets (a control diet, a fishmeal-based diet (FM), and a plant meal-based diet (VM)) and with three different feeding strategies (manual feeding to apparent satiation, automatic feeding with restricted ration, and auto-demand feeding). For every combination of diet and feeding strategy, the mean oxygen consumption, ammonia excretion, and ammonia removal rate were determined. Fish fed with the VM diet consumed the most oxygen (20.06 ± 1.80 gO2 consumed kg−1 day−1). There were significant differences in ammonia excretion depending on the protein content and protein efficiency of the diet, as well as depending on feeding strategy, which in turn affected ammonia removal rates. Fish fed by auto-demand feeders led to the highest mean ammonia removal rate (0.10 gN-TAN removed m−2 biofiltration area day−1), while not leading to peaks of high ammonia concentration in water, which preserve fish welfare and growth. [ABSTRACT FROM AUTHOR]

• Economic model predictive control deployed for recirculating aquaculture systems. • Economics of biomass growth and utility use computed by mechanistic process model. • Moving horizon estimator generates controller feedback and uncertain parameters. • Trout case study shows economic and batch time improvements over tracking control. • Estimators results in little performance degradation over full information cases. This study presents a novel economical operation scheme for recirculating aquaculture systems (RASs). The proposed approach is comprised of a moving horizon estimator and an economic model predictive controller (EMPC), which, respectively, provide the necessary feedback for the EMPC and make economically optimal decisions for the RAS. The scheme is enabled by a mechanistic RAS model, which is coupled with an objective function that jointly optimizes the economics of aquatic biomass growth and utility expenditure. The proposed scheme is tested on a rainbow trout case study, whereby it is compared against the previous state-of-the-art control approach in aerator failure and temperature disturbance scenarios. In both test scenarios, EMPC scheme outperforms the previous state state-of-the-art controller in terms of process economics (up to 41 % improvement) as well as shorter batch times (up to 22 % shortening). Furthermore, the scheme is shown to be capable of estimating uncertain parameters with little error (generally in the order of 5 %) and negligible effect on economic performance when compared to cases with full measurement access and no uncertainty. The proposed scheme provides a new and automated way to ensure RASs operate with maximal productivity, thus further incentivizing sustainability and the uptake of this technology. [ABSTRACT FROM AUTHOR]

Aquaponic systems have potential to improve water and nutrient use efficiency compared to separately operated recirculating aquaculture systems (RAS) and hydroponic facilities. However, fish feeds are optimized for fish performance and low effluent nutrient discharge instead of integrated production of fish and plants, often leading to deficiencies of certain dissolved plant nutrients in RAS water. This study tested the effect of gradually replacing a blend of animal by-products (poultry by-product meal, catfish by-product meal, poultry blood meal) in a marine ingredient-free and entirely animal protein-based diet with a blend of common plant protein sources in four quasi-realistic isonitrogenous (42% crude protein) and isocaloric (20 MJ/kg) diets for African catfish on growth performance, body composition and nutrient release in dissolved and solid form into RAS water. Reducing the contribution of animal proteins to dietary protein from 100% over 75% and 50% to 25% resulted in the best biomass gain (%), feed conversion ratio (dry matter basis) and protein efficiency ratio for the 50% level, with differences, however, non-significant compared to the 100% and 75% level. At the 25% level, i.e. the highest level of plant protein inclusion, significant impairments regarding these growth indices as well as body ash, P and Ca were recorded compared to all other diets. No differences were observed for total dissolved 4 release per unit of feed between diets. Higher animal protein contribution lead to significantly higher release of dissolved P and Ca into RAS water, whereas increasing plant protein contribution caused significantly higher release of dissolved K, Mg and B. A mass balance of dietary nutrient fate revealed that N, P, K, S and Mg primarily ended up in fish biomass and in dissolved form in RAS water rather than in collected solids, while Ca, Fe, Mn, Zn and Cu predominantly ended up in solids and fish biomass rather than in dissolved form in RAS water. Modeling daily RAS water exchange rates needed to achieve the dissolved N concentration of a standard hydroponic nutrient solution on the basis of dissolved N release per unit of feed revealed that the entirely animal protein-based diet could reach 100%, 86% and 5% of the required dissolved N, P and K concentrations and that the diet with the highest plant protein inclusion could reach 100%, 14% and 15%, both at an exchange rate of 118 L/kg of feed/day. • Higher animal by-product inclusion in African catfish diets increases the release of dissolved P and Ca into RAS water. • Higher plant protein inclusion increases the release of dissolved K, Mg and B. • Best dissolved N:P and N:Ca ratios in RAS water for hydroponics were achieved at the highest animal protein inclusion. • Best dissolved N:K and N:Mg ratios in RAS water for hydroponics were achieved at the highest plant protein inclusion. • Results highlight the potential of specialized feeds to improve RAS water nutrient profiles for aquaponics while ensuring fish performance. [ABSTRACT FROM AUTHOR]

The present study compared the productivity and concentration of nutrients in the leaf tissue of lettuce (Lactuca sativa) in two production methods in aquaponics and the production of the same lettuce species in soil, using the sludge from the aquaponics system as a source of fertilization. The experimental setup contained an aquaponics system for rearing tilapia (Oreochromis niloticus) and growing lettuce with two rows of interdependent cultures. The two aquaponics cultivation methods were plants grown on floating rafts (floats) and substrates. Three treatments were used for the soil test: 1‐fertilization with aquaponic sludge, 2‐chemical fertilization (NPK) and 3‐control (without fertilization). The performance results of the culture and the composition of the leaf tissue were evaluated, comparing the phytotechnical parameters of the lettuce grown in the soil and in aquaponics. Cultivation cycles were also compared in each treatment. In aquaponics, lettuces grown in the float method showed higher leaf number (NL), leaf weight (FM) and dry weight (DM) when compared to the substrate method in both cycles. When comparing the same treatment between cycles, a greater NL, FM and DM were shown in the float method in the first cycle, and the opposite was shown in plants cultivated with the substrate method for the NL and FM parameters, with higher values in the second cycle. Vegetables grown in the float method accumulated higher concentrations of N, P, K and Zn in their leaf tissues in both cycles, showing greater absorption of nutrients in this method. In the production of lettuce in the soil, there were no differences in the parameters NF and length of the largest leaf (LL) in the first cycle between the sludge and NPK treatments. In the second cycle, higher values of LL and DM were recorded in the lettuce cultivated in the sludge treatment. The sludge applied to the soil can provide nutrient accumulation strategies and have a low release rate, influencing the nutrients taken by the plants. The aquaponics sludge can be used to fertilize lettuces in the soil without accumulating toxic levels of nutrients in the vegetable tissue, showing potential as a strategy to reuse nutrients in integrated production systems. [ABSTRACT FROM AUTHOR]

Biofloc technology involves the manipulation of the culture system’s carbon: nitrogen ratio to promote bacterial community growth to convert toxic nitrogenous wastes and organics into functional microbial protein; this protein can then be used as a food source and mediate water quality. Biofloc systems have several advantages, which include improved biosecurity, feed conversion, water use efficiency, and nutrient processing. Analyzing the nutritional value and the relationship between high production of aquacultural practices using biofloc is essential. Many studies have demonstrated that biofloc increases the growth of aquatic species by acting as a food source or providing bioactive compounds. Other than this, the beneficial micro-organisms in biofloc systems contain compounds such as organic acids that could resist the growth of pathogenic microbes. They will also serve as a natural probiotic and increase the immunity and survival of fish and shrimp. This technology could be useful for further integration within many aspects of aquaculture production when microbial interactions are considered. However, future studies must fully understand the principles and mechanisms behind the benefits of interactions between biofloc and cultured fish and crustacean species.

The optimal water flow in fish breeding tanks is one of the crucial elements necessary for the well-being and proper growth of fish, such as salmon or trout. Considering the round tanks and the uneven distribution of water-flow velocity, ensuring a nearly optimal flow is an important task that may be performed using various sensors installed to monitor the water flow. Nevertheless, observing the rapid development of video analysis methods and considering the increasing availability of relatively cheap cameras, the use of video feedback has become an interesting alternative that limits the number of sensors inside the water tanks in accordance with the requirements of fish breeders. In this paper, an analysis of the use of optical flow algorithms for this purpose is performed and an estimation method based on their features is proposed. The results of the flow estimation using the proposed method are verified experimentally and compared with the measurement results obtained using the professional water-flow meter, demonstrating a high correlation, exceeding 0.9, confirming the proposed solution as a good alternative in comparison to the use of expensive sensors and meters.

Atlantic salmon aquaculture is undergoing an expansion of land-based recirculating aquaculture systems (RAS), especially for freshwater (FW) stages of production. Juvenile salmon undergo parr-smolt transformation, also known as smoltification and become pre-adapted to tolerate seawater (SW). One aspect requiring study is the development of microbial communities during this time, especially in RAS systems. Here we analyzed temporal changes in microbiome associated with the intestine in Atlantic salmon during smolt production in a commercial RAS production facility and followed the same cohort of fish post-seawater transfer (SWT), using 16S rRNA gene sequencing. Microbial diversity and richness showed an increase over time across FW production, but declined sharply and significantly 1-week post-SWT before re-establishing itself with a completely different community structure after 4 weeks. Core microbial taxa could be assigned to three distinct categories; (1) omnipresent, (2) salinity specific, or (3) transient. By including diet and water samples in the analyses, we classified true core taxa associated with the host, those associated with the diet, and transient cores associated with microbial communities in tank water. The rising trend observed in microbial richness in the water may be a consequence of a temporal increase in organic load while dominance of Vibrionaceae may be attributed to the higher temperatures maintained during RAS production and above average natural water temperatures post-SWT. Functional analysis suggests modulation of metabolic pathways post-SWT, but downstream impacts on fish growth and health in a commercial setting remain to be elucidated. A deeper understanding of the interplay between microbial composition and functionality can play a role in optimizing fish performance in tightly regulated RAS production.

The constant reuse of waters in recirculating aquaculture systems (RAS) together with the continuous addition of organic matter from fish degradation components, faeces and non-consumed feed promote the accumulation of dissolved organic matter (DOM), particularly of fulvic acids (FA), leading to the yellow discoloration of their waters. The accumulation of these acids in RAS can have potential effects on its water quality, and consequently fish health and welfare. Thus, the characterization of FA is paramount for improving water quality, and subsequently fish productivity in RAS. In this study, a non-targeted analysis by quadrupole time-of-flight mass spectrometry (QTOF-MS) was used to characterize the recirculating aquaculture systems fulvic acids (RASFA) and then compare their molecular fingerprints with actual reference standards of fulvic acids (FA) (Suwannee River; SRFA, Elliott soil; ESFA and Pahokee Peat; PPFA) purchased from the International Humic Substance Society (IHSS). The results of this study demonstrated the applicability of QTOF-MS as a rapid and comprehensive screening technique to characterize the FA fraction of DOM from RAS and to monitor differences in their molecular fingerprints when compared with other FA samples (SRFA, ESFA and PPFA). The QTOF-MS data from SRFA and ESFA standards matched the list of formulas obtained by 17 high-resolution mass spectrometry (HRMS) instruments with 90 and 76% accuracy, respectively, which guaranteed the power of QTOF-MS without the need for further coupling to liquid chromatography (LC). RASFA was found to be rich in low- and high-oxygen unsaturated classes of compounds (lowOC: 61.73% and highOC: 19.28%) and was similar in composition to SRFA. On the contrary, the ESFA and PPFA soil standards consisted mainly of aliphatic compounds (36.77 and 55.74%, respectively) and differed significantly in composition from the RASFA and SRFA water samples. RASFA matched with 66% of the elemental compositions obtained from the DOM of makeup waters analyzed in a previous experiment, indicating freshwater and seawater origins with a high fraction of terrestrial-derived organic matter (Tanimoto score: 0.53 between RASFA and SRFA). The unique information obtained from the molecular-level analysis of FA samples by QTOF-MS highlights the importance of this technique to characterize and compare FA from different origins rendering it possible to track the FA compositional changes along the water treatment processes of RAS. To our knowledge, this is the first study that characterizes the molecular fingerprints of the RASFA by QTOF-MS and compares them with the available FA reference standards from IHSS.

The potential for marine aquaculture development in the United States is significant and recent factors have highlighted the benefits of developing a shortened seafood supply chain to service domestic markets. Marine finfish in particular hold tremendous potential as technological advancements, improvements in production efficiencies, and market forces have aligned to create opportunities for growth within this sector of the aquaculture industry. Olive flounder, Paralichthys olivaceus, also commonly known as the Japanese flounder or hirame, is a candidate species for the U.S. aquaculture industry, which has a demonstrated track record of culture success and high market value. Although cultivation of the species is novel to the United States, olive flounder has been produced commercially for decades in other regions, notably Korea and Japan. With a number of favorable production characteristics, including a relatively short growout time compared with other flatfish species, an efficient food conversion ratio, and a well‐established market presence, the species has been shown to be commercially viable. This study examines the opportunities for olive flounder to be developed in the United States, while also discussing the potential for land‐based recirculating aquaculture systems culture of this species in coastal areas to provide increased resilience for working waterfront communities. [ABSTRACT FROM AUTHOR]