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[Extract] Aquaculture selective breeding programs employ a closed nucleus mating strategy whereby animals displaying sought-after characteristics are mated to produce next generation offspring with increased pre-valence of desirable phenotypes. Offspring exhibiting high genetic merit for favorable traits are then usually chosen as candidate parents for the subsequent breeding cycle. The selective breeding process is replicated each succeeding generation in order to accumulate genetic gain within the breeding population. The long term success of these closed breeding systems is dependent on a number of factors: including, the heritability of a trait, the intensity of selection, the additive genetic variance observed in the founding population, and the amount of additive genetic variance maintained over subsequent generations (Falconer et al., 1996; Loughnan et al., 2016). If breeding practices are not properly managed, the number of animals with high relatedness will increase (Gjedrem and Baranski, 2009b), leading to a substantial loss of genetic diversity over subsequent generations (Pante et al.,2001). The maintenance of genetic diversity is critical to accommodate current and future changes in production environments, and if left unchecked, it can lead to inbreeding through increased homozygosity and deleterious fitness consequences associated with inbreeding depression (Pante et al., 2001). This loss of genetic diversity can also hamper progress within the selective breeding program as it limits the amount of genetic variance available for selection (Falconer, 1960).

Aquaculture has experienced a burgeoning growth worldwide in the last decade resulting in nearly 50% of seafood originating from aquaculture farms. However, there are less studies on the utilization of the manure produced by aquatic organisms in comparison to warm-blooded livestock. Aquaponics offers more efficient utilization of nutrients and can reduce the operational costs in aquaculture. This paper presents the results of a study to identify the optimal settings to digest fish manure through a microbial-assisted aerobic bioprocess, using endogenous heterotrophic and nitrifying bacteria. The effects of pH (5.5, 6.0 and 6.5), temperature (30, 35 and 40 °C) and duration (1–30 days) on kinetics of nitrogen mineralization were investigated and compared to a control bioreactor (carried out without pH adjustment). The mineralization dynamics for all pH-controlled bioreactors revealed that only ammonification occurred. No nitrification was observed for all three-temperature conditions and throughout the entire bioprocessing period. The mineralization process in the control bioreactor, on the other hand, followed the typical non-inhibited nitrogen mineralization (i.e., release of ammonium followed by oxidation into nitrate). However, nitrate was only observed at temperatures

Geosmin (GSM) and 2-methylisoborneol (MIB) are secondary metabolites of cyanobacteria that are often present in recirculating aquaculture systems (RAS) and are problematic, even at low (ng L−1) concentrations, due to their taste and odor effects on water and accumulation in the lipid tissue of fish. Removal of these compounds is difficult due to their extremely low concentrations and advanced treatment technologies, such as advanced oxidation processes (AOPs) have to be employed. In this study, a novel AOP consisting of immobilized TiO2 in a UV reactor was tested at bench scale for removal of GSM and MIB in both batch and continuous flow modes. Batch reactor application at a full-scale RAS resulted in average GSM and MIB removal efficiencies of 61% and 72%, respectively, with a 6 h treatment time. No significant removal of GSM and MIB was observed in continuous flow mode, most likely due to both lower residence time and low initial concentrations of both compounds. No negative effects were observed on downstream biological wastewater treatment processes, indicating that the proposed UV-TiO2 process can be safely integrated into RAS.

In addition to environmental factors, particle size can interfere with the nitrification process because smaller flocs are less efficient in terms of ammonia and nitrite oxidation. The objective of the present study was to evaluate, in three experiments, the effect of the biofloc size on the nitrification process during the production of the white shrimp Litopenaeus vannamei in a BFT system. In all experiments, 1% of biofloc inoculum from production tanks was used. Water samples were taken to photograph and measure the flocs. Measurements of temperature, salinity, nitrogen compounds and total suspended solids were also carried out in the experiments. In experiment 1, the flocs were separated by sifting the water through mesh nets of 50, 150 and 300 μm in size. In addition, there was a control treatment with integral flocs. In experiment 2, the bioflocs were separated into 300 and 600 μm size classes and were compared with an integral control. Experiment 3 aimed to evaluate the nitrification process in treatments with flocs smaller than 150 μm, in flocs without handling (Control), and in the treatment where flocs were partially filtered in a 50 μm mesh for five days. This treatment resulted in a reduction in the particle size; however, when the meshes were later removed, and the biofloc size increased again. Different from our original hypothesis, the results of these three experiments indicate that the size of the biofloc, as well as the amount of total suspended solids, do not affect the nitrification process in the BFT system. However, all treatments that included manipulation through sifting showed a delay or a decrease in the nitrification activity. Thus, it is likely that, more than the particle size or floc abundance, the rupture of the floc structure affects the distribution and interaction of nitrifying bacteria with reflections in the nitrification process.

Reducing dependency on environmentally unsustainable formulated feeds, most of which include limited reserves of fishmeal as a protein source, is a priority for the aquaculture industry, particularly for intensive culture systems. One approach is to increase nitrogen reuse within the system by feeding nitrogen-rich aquaculture effluent to deposit feeders, thereby closing the aquaculture nitrogen-loop. This study, for the first time and on a laboratory-scale, has reared juveniles of the sea cucumber Holothuria scabra at high densities solely on particulate organic waste from a commercial-scale land-based abalone recirculating aquaculture system. Furthermore, growth rates and biomass yields were increased significantly by adjusting the effluent C:N from 5:1 to 20:1 by adding exogenous organic carbon sources (glucose, starch and cellulose), so fuelling accelerated heterotrophic bacterial production within the redox-stratified tank sediment. Sea cucumber juveniles reared solely on effluent had a biomass density of 711 g m−2 after four months whereas animals reared on starch-amended effluent (the best performing treatment) had a final density of 1011 g m−2. Further optimisation of this approach could increase biomass yields and pave the way for the commercial cultivation of deposit feeding animals on waste streams, thus contributing to more environmentally sustainable aquaculture. Here, the nitrogen that originated from fishmeal is not lost through the discharge of aquaculture effluent; rather, it is immobilised into single cell biomass that is up-cycled into high-value secondary biomass. We demonstrate that sea cucumbers can be produced at high density through the manipulation of the C:N ratio of aquaculture effluent.

Maintaining low concentrations of nitrogen compounds in aquaculture water is a key requirement for a recirculating aquaculture system (RAS), due to the potential detrimental effects of ammonia or nitrate on fish growth and metabolic activities. Herein, a microbial fuel cell (MFC) was investigated to accomplish the removal of either nitrate or ammonia from real RAS water (with simulated daily nitrate/ammonium accumulation) while generating electricity, via aerobic nitrification in the cathode, electricity/concentration driven transport across anion exchange membrane, and subsequent heterotrophic denitrification in the anode chamber. The experiment went through two stages, nitrate removal (Stage I) and ammonia removal (Stage II). In Stage I when daily nitrate addition was performed to mimic nitrate accumulation (0.050 kg NO3−-N m−3 NCC d−1, NCC: net cathodic chamber volume) in the MFC cathode, a stable current density of 12.48 A m−3 could be achieved with a 73.3% nitrate removal and 91.3% COD removal at the end of day 15. To better mimic ammonium accumulation in the RAS effluent without a biofilter, daily ammonium addition (0.050 kg NH4+-N m−3 NCC d−1) was performed in the cathode in Stage II. The MFC system achieved a total inorganic nitrogen removal rate of 0.051 kg N m−3 NCC d−1, and a COD removal efficiency of 91.8% with a current density of 74.00 A m−3. A preliminary analysis of energy balance indicated that the proposed MFC could potentially achieve energy-positive RAS water treatment with a net energy production of 7.50 × 10−3 kWh m−3 treated RAS water or 0.145 ± 0.031 kWh kg−1 removed nitrogen. The results of this study indicate that MFCs have a potential to treat RAS water with simultaneous energy recovery.

Population growth increases wastewater production, enhances environmental concerns, and increases wastewater treatment costs. This study aimed to use Anodonta cygnea (freshwater mussels) exposed to some water pollution in a closed cycle to treat wastewater by consuming harmful or undesirable pollutants in water. The results demonstrated that mussels eliminated all microalgae, reduced organic pollutant concentration (chemical oxygen demand removal rate 40% faster than lacked mussels tank), and removed some water hardening minerals such as Calcium (Ca) (more than 77%) and Nickel (Ni) as heavy metal (more than 78%), confirming that freshwater mussels could be helpful in the wastewater treatment cycle. The method can be used as the practical implementation of setting up a semi-natural system for the decentralized wastewater purification relying on the recruitment of mussels. The method also suggests a favorable and eco-friendly treatment mechanism to remove chemical oxygen demand, chemical elements, biological pollutions, and microorganisms.

Biofouling causes major functional and economic problems for aquaculture due to their settlement and subsequent growth on fish-cage netting. As biofouling management is an economic and environmental issue, feasible management practices are clearly required to balance industries and environmental requirements. The most frequent way to control biofouling in aquaculture is by applying Cu-based antifouling paints on fish nets to prevent the undesired growth of biofouling. The most important fish species employed in marine fish farming are cultivated with knotted nylon and ultra-high-molecular-weight polyethylene (UW-polyethylene) nettings. In this study, we examined the effects of two commercial Cu coatings and two manufactured net materials (nylon and UW-polyethylene) on biofouling biomass, community structure, Cu bioaccumulation and the metal composition of fouling assemblages in order to provide farmers with a tool to help reduce the environmental impact of the biocide employed for coating nets. The MDS ordination of the samples coated with both paints on nylon and UW-polyethylene nets showed a gradual modification of community structure associated with rising Cu concentrations. The PCA analysis indicated that the ordination of trace element composition of biofouling varied between concentrations and nets in both paints. The experiments revealed that the fouling biomass decreased following negative exponential regression with an increasing Cu concentration. The increase in fouling biomass with reduced Cu bioaccumulation was greater in nylon than in UW-polyethylene nets. In the nylon nets, the median bioaccumulation on nets (CuF-50) rose with an 0.75- to 0.82-fold increase in the basal biomass. Conversely, biomass increased 0.50- to 0.63-fold the basal or minimum fouling biomass with a full antifouling paint concentration (B0) when CuF-50was calculated in the UW-polyethylene nets. These results suggest that similar reductions in bioaccumulated Cu in both nets could be achieved without sacrificing excessive fouling biomass increases.

Minimizing ammonium is one of the most important concerns in the practice of aquaculture. Chemoautotrophic bacterial nitrification (CBN) and heterotrophic bacterial assimilation (HBA) are the two main ammonium pathways in aquaculture water under light-limited conditions. CBN oxidizes ammonia–nitrogen (NH4+-N) to nitrite–nitrogen (NO2−-N) and finally to nitrate–nitrogen (NO3−-N), and this is the primary strategy employed in recirculating aquaculture systems using fixed-cell bioreactors. Zero-exchange management systems based on HBA and biofloc technology have been developed referred as biofloc aquaculture systems. HBA is encouraged in biofloc aquaculture systems by increasing the C/N ratio. However, NO3−-N build-up was found in many studies examining these systems, with CBN proposed as the responsible mechanism and documenting the factors leading to the occurrence of the CBN process. This paper examines the relative importance of CBN and HBA in biofloc aquaculture systems. A mechanism is proposed and future study aimed at mediating NH4+-N pathways in biofloc aquaculture systems is recommended.

Hydraulic retention time (HRT) is one of the most critical operational parameters for solid-phase denitrification. The effect of HRT on solid-phase denitrification reactors (DR) packed with corrugated paperboard was investigated in recirculating aquaculture systems (RAS). Denitrification efficiencies of DR were 81.21–85.05% at HRTs of 0.5–2.0 h. The optimal HRT for denitrification was 2.0 h with a rate of 14.81 mg/(L substrate day). HRT significantly affected the bacterial community structure in DR by changing the population dynamics of the dominant bacteria and denitrifying functional bacteria such as Rhizobiaceae, Desulfovibrionaceae, and Arcobacteraceae. Moreover, the HRT of the DR showed a significant effect on the bacterial community in the nitrification reactor and culture water. Reducing HRT can promote the growth of total bacteria in the DR. However, it revealed a limiting effect on the abundance of key genes of the nitrogen cycle, including the amoA, nirK and nosZ. Under the condition of short HRT, the DR can also achieve a good denitrification effect, which provides feasible management measures for nitrogen removal in RAS.

The integration of bioremediation systems is one of the most promising techniques to mitigate the environmental impact of aquaculture effluents. Also, it allows nutrient recycling, production diversification, and the creation of high-value by-products. In marine aquaculture, where the implementation of salt-tolerant extractive species is essential, halophyte plants have demonstrated to be optimal candidates for bioremediation of saline aquaculture wastewater. This study aimed to evaluate for the first time the efficiency of Sarcocornia neei (Lag.), a halophyte plant with high adaptability, salinity tolerance and growth potential when irrigated with seawater, in removing nutrients from marine fish aquaculture wastewater and artificial effluents. Two experiments were carried out. In the first one, the growth rate, removal of inorganic nutrients, and accumulation of organic compounds in deep-water hydroponics and sand-substrate systems were evaluated in artificial effluents with different nitrogen and phosphate loads during 70 days. In the second, due to the better performance achieved by S. neei in deep-water systems, its nitrogen removal efficiency and productivity rates were evaluated in deep-water aquaponics with marine aquaculture wastewater and artificial effluents at higher nitrogen loads during 61 days. The highest productivity rates achieved by S. neei (14.41 ± 0.78 kg m−2) were obtained in deep-water culture units, reaching 100% plant survival, suggesting that this species is more suitable for its implementation in this type of system. Significant total ammonia nitrogen removal rates were obtained by the plants, achieving a maximum in sand-substrate systems (0.68 ± 0.41 g m−2 day−1). The results of nitrate removal rates obtained by S. neei (11.25 ± 31.38 g m−2 day−1) make this species an ideal potential candidate for the removal of this compound present in marine RAS effluents. Accumulation of organic compounds was corroborated by obtaining a significant increase (p These results indicated that S. neei is a good candidate for its use as a biofilter for marine aquaculture wastewater. Further investigations should be done to analyze possible influences on growth rates and nutrient removal efficiency by adding essential micronutrients, adjusting effluent salinity, and implementing different plant densities. Also, further studies could be interesting to determine the feasibility of long-term integration of a bioremediation system with S. neei associated with marine aquaculture effluents, approaching its application to industrial-scale production systems.

The oxygen demand, acidification potential, and waste loads of carbon dioxide, nitrogen, and phosphorus from feed were determined for production of channel catfish Ictalurus punctatus, tilapia Oreochromis spp., Atlantic salmon Salmo salar, rainbow trout Oncorhynchus mykiss, and whiteleg shrimp Litopenaeus vannamei. Loads of these variables in culture systems (system loads) at typical FCRs ranged from 1090 to 1500 kg t− 1 for feed oxygen demand, 270–440 kg t− 1 for acidification potential, 1186–1885 kg t− 1 for carbon dioxide, 35.9–63.5 kg t− 1 for nitrogen, and 6.1–15.9 kg t− 1 for phosphorus. Using these estimates as representative of feed-based aquaculture and literature data on the proportions of system waste loads typically discharged to the environment (environmental loads), the approximate amounts of waste generated globally by feed-based aquaculture were estimated to be small in comparison to estimates of global anthropogenic waste. Nevertheless, aquaculture should lessen its environmental waste load, and the benefit of improving FCR in reducing waste load was illustrated. Statement of relevance This research will be important in efforts to assess the pollution potential of aquaculture facilities. This will be especially important for aquaculture certification efforts.

Cost of effluent treatment, water quality maintenance and feeds constitute most of aquaculture's operational costs, and influence its sustainability. The present study examined the effectiveness of periphyton for biofiltration of mariculture effluents. Marine periphyton was allowed to spontaneously develop on a plastic net substrate, in experimental bioreactors that were fed with effluents from fish mariculture ponds. Biomass development and nutrient uptake were followed over four seasons. Attention was given to the orientation and area of the net substrate, season and additional operational factors. The highest specific growth rate (SGR) of 27% day− 1 was measured during the second week of periphyton growth in the summer. Mean daily periphyton production rates in the spring and autumn were 2.4 and 1.8 g (ash-free dry weight) m− 2 day− 1, respectively. The vertical orientation of the net substrate was overall advantageous over the horizontal orientation. Increasing the substrate area of vertically oriented nets in the biofilter increased the removal efficiency of total ammonia nitrogen (TAN) up to 80%, and allowed more biomass production in the biofilter. Multiple polynomial regression models suggest strong effect of biomass weight and effluent retention time on the removal efficiency of TAN and dissolved inorganic nitrogen (DIN). The removal rates of TAN and DIN in these experiments were between 0.11 and 1.2 g N m− 2 (substrate area) day− 1 for periphyton at the age of 7 and 42 days, respectively. Marine periphyton seems to be a simple, low cost and sustainable component, which can perform biofiltration/rehabilitation of water quality and potentially serve as feed for fish and shrimp.

Biofilters composed of Ulva or periphyton reveal great potential in removal of excess nitrogen in mariculture effluent while producing protein-rich edible biomass. However, TAN depletion is requisite to improve nitrate removal performance. In the current study we compared the contribution of Ulva fasciata and periphyton in removal of nitrogen, particularly in the form of nitrate, from fishpond effluent. For this purpose, we integrated U. fasciata or periphyton as a secondary biofilter downstream to a primary U. fasciata biofilter, and measured growth and nutrient removal performance in each of these two-step biofilters and in their constitutuent biofiltration units. The upstream U. fasciata biofilters removed nearly all TAN from fishpond effluent, leaving less than 5 μM of TAN but excess NO3-N in the effluent leaving these biofilters for the downstream biofilters. The downstream U. fasciata biofilter removed 76% of NO3-N from its inlet water. While this was about three times more efficient than its periphyton counterpart, the periphyton's specific removal rate of this nutrient (1.5 g NO3-N g−1 DW d−1) was much faster than that of U. fasciata. Overall, integration of two sequenced U. fasciata biofilters (‘Ulva-Ulva’) yielded more biomass and removed more nitrogen than the Ulva-periphyton biofilter (removing 25 vs. 18 g N wk.−1, respectively). Despite the differences in N removal rate and efficiency, the protein level in upstream U. fasciata and downstream periphyton was relatively similar (~25% DW), while somewhat lower in the downstream U. fasciata. Results of the current study favour the two-step U. fasciata biofilter, but periphyton's faster specific removal of NO3-N and its contribution to oxygen generation should not exclude further improvement of this technology.

A high-rate nitrogen removal process is required to maintain the water quality in aquaculture tanks used to produce high-density fish populations in recirculating aquaculture systems. In this study, a combined pilot-scale system of down-flow hanging sponge (DHS) reactors and upflow sludge blanket (USB) reactors was applied as a nitrogen removal system for a longtooth grouper Epinephelus bruneus recirculating aquaculture system. The DHS reactors demonstrated high total ammonium nitrogen (TAN) removal efficiencies and the TAN concentration in the aquaculture tank was maintained at 0.32 ± 0.12 mg-N·L−1. The USB reactor fed with sodium acetate acted as a denitrification unit and adjusted the pH through denitrification reaction. All E. bruneus survived the entire experimental period and the daily weight gain rate of 0.6%·day−1 was comparable to that in marine aquaculture. This result shows that the DHS-USB system to be a novel applicable system for nitrogen removal processes in recirculating aquaculture systems and further study at a large scale should be recommended.

In response to increasing demand for aquaculture products and strict new regulations on organic matter and nitrogen discharge, inland closed recirculating aquaculture systems (RASs) are being developed as a viable eco-sustainable alternative to traditional aquaculture (e.g. ponds, raceways and cages) because of their minimal environmental impact and controlled operation. Fish feed is virtually the only source of carbon and nitrogen to the system. It is estimated that 20 to 30% of the feed nitrogen and 50% of the feed carbon are assimilated or utilized by the fish, while the rest is released to the water. Understanding the fate and utilization of these elements can help optimize RAS efficiency and economics. The fate of carbon and nitrogen was studied by mass balance in a novel near-zero discharge ( 2 and the rest (5%) remained as nondegradable carbon in the UASB. Using the UASB can save up to 12% of the system's energy demands, both directly as energy (methane) input and indirectly by reducing the system's oxygen demand. Of the feed nitrogen, 29% was assimilated by the fish and bacteria in the nitrification reactor and 40–50% was removed in the denitrification reactor, of which 10–20% was removed by anammox. Lastly, ~ 20% of the nitrogen was removed in the UASB reactor, likely by precipitation. It was demonstrated that the system was operating at high stocking density, with almost complete nitrogen and carbon removal and energy recovery. Statement of relevance The fate of carbon and nitrogen was studied by mass balance in a novel near-zero discharge (

The accuracy and precision of different methods for detecting the endpoint of the total alkalinity titration and the typical accuracy and precision obtained for alkalinity analyses by a large sample of laboratories were investigated. The optimum, endpoint for total alkalinity titrations decreased from pH 5.0 at 10 mg l − 1 alkalinity to pH 4.2 for 300 mg l − 1 alkalinity or more. The appropriate color changes for bromocresol green-methyl red (BG-MR) and methyl orange (MO) indicators also varied with the initial total alkalinity of samples. Despite differences in pHs at endpoints for samples of different alkalinities, when the best endpoint pH, best color of BG-MR and MO, or the endpoint of methyl purple were used in titrations of standard solutions, there were few differences between measured alkalinities and standard alkalinities — the accuracy was better than ± 3 mg l − 1 . Results of spike and recovery tests on aquaculture pond water samples also revealed that an accuracy of ± 3 mg l − 1 alkalinity could be achieved on either unfiltered or filtered samples by all four methods of acceptable endpoint detection. Although precision of measurements could not be consistently maintained below ± 1 mg l − 1 , coefficients of variation for repeated measurements usually were less than 3% for all methods of endpoint detection. Nevertheless, this degree of precision was adequate to achieve good accuracy that is the major concern in water analysis. Variations in alkalinity measurement that could result from improper selection of endpoint pH (or color) were rather small — usually not more than ± 5 mg l − 1 . In an interlaboratory comparison of alkalinity determinations on standard solutions, most laboratories reported inaccurate alkalinities. These inaccuracies were greater than possible endpoint variations. The most likely sources of error contributing to poor results by the different laboratories were improperly standardized acid for alkalinity titrations, reliance on burets or other titrating devices with coarse calibrations, and use of excessively small sample volumes. Moreover, it was clear that most of the participating laboratories did not have a satisfactory method of quality control. Statement of relevance Alkalinity is important as a source of carbon for photosynthesis, as a buffer, and as a general index of productivity. Thus, it is often measured, but by several different methods of endpoint detection. This study provides useful information of the reliability of alkalinity analyses and recommends how to maintain acceptable precision and accuracy of the procedure.

The presence of high concentrations of ammonia, nitrite, and nitrate is a big challenge for the aquaculture industry to sustain fishery production, hence need to be treated in an economically feasible and environmentally friendly way. In the present study, a consortium of three bacterial isolates I4, I6, and I12, identified as Bacillus cereus, Bacillus amyloliquefaciens, and Pseudomonas stutzeri respectively, were assembled for the biodegradation of ammonia and nitrite in aquaculture wastewater. The consortium was employed as a bioaugmentation agent in tanks stocked with Oreochromis mossambicus fingerlings. During the experimental period of 15 days, under controlled conditions of temperature and light, the values of tested parameters were found to be increasing in both treatment and control tanks. The residual concentration of ammonia in the tanks treated with the consortium was always lower (4.8 ± 0.068 μML−1) than that of the control tanks without any bacteria (7.29 ± 0.292 μML−1). Increased residual concentration of nitrite and nitrate in the treatment tanks (6.9 ± 0.59 and 4.16 ± 0.58 μML−1 respectively) compared to the control tanks (0.28 ± 0.201 and 0.394 ± 0.964 μML−1 respectively) confirmed the efficiency of the consortium to convert ammonia to nitrite and further to the less toxic nitrate. Moreover, their values were never reached to the toxic level in the treatment tanks with a survival rate of 97.2 ± 0.58%, whereas in the control tanks death of fishes due to ammonia toxicity was observed (55 ± 0.25%). The study proved that the microbial consortium of Bacillus cereus, Bacillus amyloliquefaciens, and Pseudomonas stutzeri was efficient in reducing ammonia, nitrite, and nitrate in aquaculture wastewater and hence can be employed as a bioaugmentation agent to above-mentioned parameters in the aquaculture wastewater before discharging into the open system to reduce the environmental problems as well as to reuse the water.

Marine pollution from aquaculture wastewater is a widespread and increasing ecological problem. Algae, with their ability to remove surplus nutrients from wastewater, are a good tool for achieving more sustainable aquaculture. In this study, the capability of different biomasses of Chaetomorpha linum and Cladophora prolifera for the bioremediation of nutrient-rich (ammonium, nitrate and phosphate) seawater was compared. The results suggest that 10 g L−1C. linum is an excellent candidate for aquaculture wastewater bioremediation. However, the bioremediation efficiency of C. linum was significantly affected by seasonality, with the greatest performance in nutrient removal exhibited by algae harvested in summer. C. linum harvested in winter and acclimated to lab conditions for two months, significantly improved the removal efficiency of both ammonium and nitrate, while worsening that of phosphate. Irrespective of season and acclimation, the simultaneous presence of ammonium and nitrate in seawater strongly inhibited nitrate removal. Thus, we propose the use of a two-step system, tested at the laboratory scale, in which nutrient-enriched seawater can pass through two different algal ponds. C. linum was able to achieve almost complete removal of ammonium in 24 h in the first step, while the second step improved both nitrate and phosphate removal efficiency. The two-step system is an effective innovation for the use of algae in bioremediation of aquaculture wastewaters.

Removal of total ammonium nitrogen (TAN) is essential during transportation of live seafood due to its high toxicity to aquatic cultures. Recirculating TAN removal system has been proposed and installed for the transportation of live seafood, while TAN removal performance often deteriorates at low temperature range (10–20 °C) due to the decrease of nitrifying activity. The authors have previously developed down-hanging sponge (DHS) reactors as a recirculating TAN removal system, which is a trickling filter system that uses polyurethane-sponge media to retain nitrifying biomass. The present study aimed to examine TAN removal performance of DHS reactor operated at 10 and 20 °C, and the following 4 DHS reactors were operated for the purpose; the DHS reactor operated 1) at 20 °C, 2) at 20 °C with addition of powdered activated carbon (AC) as an additional biomass carrier, 3) at 10 °C, and 4) at 10 °C with AC (designated as 20 °C-DHS, 20 °C-DHS-AC, 10 °C-DHS, and 10 °C-DHS-AC reactors, respectively). The DHS reactors were operated for 472 d with feeding of artificial seawater media, and TAN loading rates increased stepwisely up to 200 mg-N L-sponge media−1 d−1. TAN removal performance was examined by determining the concentrations of TAN, nitrite and nitrate in influent and effluent. Additionally, amplicon sequencing of prokaryotic 16S rRNA gene sequence was performed at Day 34, 212 and 374 to identify the nitrifying bacteria involved in the TAN removal. Both the 20 °C-DHS and 20 °C-DHS-AC reactors showed 200 mg-N L-sponge media−1 d−1 of TAN removal rate, whereas the 10 °C-DHS reactor showed only 15 mg-N L-sponge media−1 d−1. Notably, the addition of AC enhanced TAN removal performance of the DHS reactor operated at 10 °C. The 10 °C-DHS-AC reactor showed 60 mg-N L-sponge media−1 d−1 of TAN removal rate, which was 4-folds higher than those found in the 10 °C-DHS reactor. The amplicon sequencing analysis revealed that ammonia-oxidizing (i.e., Nitrosomonas) and nitrite-oxidizing (Nitrospira and Nitrospina) bacteria (AOB and NOB, respectively) proliferated in the operated DHS reactors, and the relative abundance of those AOB and NOB were greater in the DHS reactors with AC addition (i.e., the 20 °C-DHS-AC and 10 °C-DHS-AC reactors). Intriguingly, temperature difference (20 °C and 10 °C) resulted in occurrence of different NOB communities, and Nitrospira and Nitrospina were prominent in the DHS reactors operated at 20 °C and 10 °C, respectively. DHS reactor is capable of removing TAN even at 10 °C, which is applicable as a recirculating TAN removal system for transportation of live seafood.

Disease outbreaks are a major concern in aquaculture. This is particularly true in intensive recirculating aquaculture systems (RASs), due to the high rearing densities in a system where high concentrations of organic matter are produced with minimal water exchange. This study assessed the survivability of the common fish pathogen Streptococcus iniae in a solid-removal unit of a RAS, the upflow anaerobic sludge blanket (UASB). A PCR detection method, along with an improved protocol for the extraction of high-quality DNA from sludge samples, were utilized for this purpose. This method enabled detection of S. iniae at a minimum concentration of 7.6 × 10 5 CFU mL − 1 raw sludge. We examined the survivability of S. iniae in batch digesters, which consisted of sealed serum bottles filled with sludge from the UASB reactor, and in laboratory-scale flow-through UASB reactors that were continuously fed with fish waste sludge. Results demonstrated a gradual decrease in the intensity of the PCR-amplified product to the point of no detection in either batch or UASB digesters, suggesting that the conditions present in the UASB reactor are not favorable for S. iniae . The PCR-based detection method was successfully applied to sludge from a commercial RAS enabling detection of potentially pathogenic bacteria. Statement of relevance The manuscript addresses the control of bacterial disease-causing agent in a near-zero discharge aquaculture system which contains a novel solid removal unit. The bacteria studied is S. iniae , a significant disease-causing agent in aquaculture. The potential threat of disease outbreaks increases with the intensification of the culture system, such as the one described and analyzed in this study. This intensification is of high relevance to the industry, as it reduces environmental contamination due to fish production as well as enables fish culture in places distant from a natural water source.

This paper examines how value chain coordination affects the ability of aquaculture producers to engage in eco-certification. Through a comparison of global salmon and shrimp value chains, it is argued that production risks and producer capacity are key determinants in the type of chain coordination adopted by lead firms. The results challenge global value chain governance theory by indicating that it is hierarchical (or vertically integrated) forms of coordination that are associated with high capabilities and low risk rather than market forms of coordination. It is also shown that eco-certification is more likely to be adopted in value chains with more engaged forms of coordination. This in turn means that eco-certification is a far less ‘hands off’ form of regulation than widely thought. The paper concludes that for certification to engage producers operating under market forms of chain coordination new arrangements are needed that can respond to challenges of improving producer capability and production risk. Statement of relevance By understanding the role of risk and producer capability this paper contributes to improving the application and impact of eco-certification in global aquaculture production.

The literature on late-stage larval and puerulus settlement of tropical spiny lobsters suggests that a broad range of visually-assessed variables may play a role in the selection of settlement substrates. These variables include light level, luminosity, degree of exposure, and the availability of edges, crevices and clefts. A fishery has developed in Indonesia, that captures pueruli for grow-out purposes, along the entire southern coastline from Java to Sumbawa. The present study builds on knowledge gained on the behaviour and substrate preferences of settling pueruli by examining aspects of collector design and substrate surface characteristics in regard to catch rates. A series of tank-based experiments were used to examine preferences for various attributes of collector materials, and preferred material characteristics were then tested in a field experiment to verify the laboratory results. In the tank experiment the most preferred substrate was cement bag paper, followed by insect mesh, weed netting, PVC rubber and cement bag plastic. Crevice angles of 10° and 20° were significantly preferred over 30°. The substrate level and other substrates had less influence on settlement. However, both the lunar phase and type of materials tested in the field had a significant effect on settlement. Significantly greater numbers of pueruli were caught at the time of the new moon than at other moon phases. Cement bag paper was the most preferred material in the field, followed by cement bag plastic, insect mesh, weed fabric, and PVC rubber.

India is the world's second largest producer of farmed fish, and the state of Andhra Pradesh (AP) is by far the most important producer of farmed fish in India. Freshwater aquaculture has boomed in AP since the late 1970s, first with carps, then pangasius catfish. Over this period fish pond area and farmed fish production grew from nothing to reach 142,000 ha and 1.5 million tons, respectively. Despite its scale and dramatic consequences, the boom has received little attention in the international literature. The present paper addresses this gap by analyzing changes in the structure and conduct of each segment of AP's freshwater aquaculture value chain during four distinct phases of development (incubation, take-off, maturation and modernization). This analysis reveals that aquaculture development in AP shares many characteristics with agricultural commodity booms elsewhere in Asia. The paper contributes to the literature on crop booms by: 1) characterizing Southern domestic demand for agricultural products as an important but overlooked driver of agrarian development, and; 2) identifying interlinked processes of innovation and transformation in off-farm segments of the supply chain as a central feature of crop booms.

Feeding is a major factor that determines the production costs and water quality of aquaculture. Analysis of fish feeding behavior forms an important part of the feeding optimization. Fish feeding has generally been performed with automatic feeding machines which can lead to excessive or insufficient feeding. Recognition of fish feeding behavior can provide valuable input for optimizing feeding quantity. Due to the complexity of the environment and the uncertainty of fish behavior, the correlation and accuracy of behavior recognition are generally low. The accurate identification of fish feeding behavior till faces substantial challenges. This paper reviews the technical methods that have been used to identify fish feeding behavior in aquaculture over the past 30 years. The advantages and disadvantages of each method under different experimental conditions and applications are analyzed. Many methods are effective at evaluating and quantifying fish feeding intensity, but the recognition accuracy still needs further improvement. It is proposed by this paper that technologies such as data fusion and deep learning has great potential for improving the recognition of fish feeding behavior.

The implementation of gamete cryobanking in aquaculture may improve hatchery practices such as assisted reproduction and genetic selection of desired strains. This paper preliminarily investigated the technical feasibility of cryobanking semen of the common pandora Pagellus erythrinus, an important fishery resource in the Mediterranean area and a promising species for the diversification of productions. Post-thawing motility was evaluated in common pandora semen samples cryopreserved according to eight previously selected protocols and stored in liquid nitrogen for eight years. In order to mimic the practical use of long-term cryostored semen samples, the proportion of living sperm in which motility could be activated was evaluated, by computer-assisted analysis, on thawing and after 3 h of post-thawing incubation at 18 °C as biomarker of sperm viability. The assessed parameters were percentage of motile spermatozoa (TM), curvilinear velocity (VCL), lateral head displacement (ALH), beat-cross frequency (BCF) and dance (DNC). The cryostored sperm of the common pandora proved to have promising features. In fact, percentages of motile sperm higher than 40% were always obtained on thawing; moreover, the semen retained its activation ability in the times after thawing, showing no or slight alterations in the motility profile also when activated after 3 h of post-thawing incubation. The best post-thawing performances were recorded with the EG5%-based extender under the F1 curve (equilibration at 2 °C; freezing from +2 °C to −70 °C at 3.8 °C/min), that showed the highest percentages of motile cells (80 ± 3) and no significant alterations in any of the evaluated motility parameters, followed by the EG10% based extender under the F2 curve (equilibration/cooling from 20 °C to 2 °C at 1 °C/min; freezing from +2 °C to −150 °C at 23.3 °C/min). Such a post-thawing resistance of long-term cryostored samples, encourages further studies for the inclusion of the semen of the common pandora in cryobanks aimed at use in reproductive biotechnologies for aquaculture applications and as a model in laboratory research. Therefore, the present paper contributes to the implementation of semen cryobanking as a technological tool in support to aquaculture, using as a model a species of potential aquaculture interest. In addition, the creation of germplasm cryobanks for aquatic species comply with the EU ARRIVE (Animal Research: Reporting of in Vivo Experiments) guidelines that promotes a coordinate use and sharing of biological samples from animal models in laboratory research.

High incidence of cancer and other diseases have boosted the interest in herbal products to be used as alternatives to synthetic drugs worldwide. Plants that present biological activity are frequently processed, and their extracts are marketed as over-the-counter natural medicines. Such a trend is also observed in the aquaculture sector. The number of studies investigating the potential activity of plant-based products to substitute synthetic fish anesthetics has increased substantially over recent years. This paper summarizes the current data available and knowledge about the use of essential oils and active substances for fish sedation and anesthesia. Clove oil is the most commonly used plant-based anesthetic in aquaculture and several other studies have been conducted on the use of essential oils of basil, thyme, mint, rosemary, lavender, citronella, verbena and camphor for the different fish species. In recent years, active substances such as eugenol, menthol, myrcene, 1,8-cineole, linalool, limonene, citronellal, thymol, carvacrol, spathulenol, α- and β-pinene, 4-allylphenyl acetate and globulol, found as constituents of essential oils have also been investigated for sedation and anesthesia purposes in fish. This paper describes some of the sedative and anesthetic effects of essential oils and their active substances on the modulation of fish behavior, physiology and biochemistry. Such structured information could be useful for the aquaculture industry as natural anesthetics could be potentially more environmentally friendly, cost-effective and safer products than synthetic drugs for the management and welfare of aquatic organisms.

White spot syndrome virus (WSSV) is one of the most devastating pathogens, which inflicted huge losses to the shrimp farming sector in India and the world. The current study maps the WSSV research output during 1998–2017 using Web of Science (WoS) database. A total of 1786 tags were subjected to the present analysis which covers various parameters viz., growth, rank and global publications share, research collaborations and other bibliometric indicators like total citation counts, average citations per paper, and h-Index. India accounted for 17.24% of the global WSSV publications, and stood second among the 15 most productive countries in terms of number of publications in this period. The Indian researchers had networked with 23 collaborating partners across the world, of which USA, the lead collaborating country accounted for 18.51% of the total papers with international collaboration. The study showed a positive correlation between the grants awarded to the research laboratories and their research productivity. The paper provides quantitative analysis on the leading institutions and individual researchers, significantly contributing to the WSSV research in India. The journal Aquaculture carried the maximum number of research papers on WSSV from India (53 papers), followed by Fish and Shellfish Immunology (32 papers) and Diseases of Aquatic Organisms (25 papers). The analytical results of the present study provide insights into the trends of WSSV research in India and calls for concerted efforts to enhance focussed research on this significant threat to the 4.8 billion USD worth shrimp farming sector, which has the potential to reverse the fortunes of the farmers.

Rainbow trout is one of the promising cultivable fish species in coldwater and has enormous scope for its expansion in the Himalayan region. Being a low volume high value commodity, the trout has good potential for domestic consumptions as well as foreign export. In spite of having excellent positive traits and prosperity, the development and expansion of trout farming in Himalayas has yet to be intensified for large-scale productions. There are enormous aquatic resources in the form of river, reservoirs and lakes in the Himalayan region yet agricultural production of trout is very limited. This paper presents the available trout production system, available infrastructure and production trend highlighting the need of improved feed, infrastructure, improved strain, application of triploid trout production for stocking in cages and pens and also the possibilities of organic trout farming so as to clinch the production intensification, environmental management and trout promotion objectives. Based on 15 years experience of trout culture in India, potential success in trout production could be acquired through technological modernization, better governance and significant improvement in the management practices. The knowledge needed to form a comprehensive trout-farming ecosystem beyond farm activities has been suggested in this paper which will be useful not only to the country but also to the transboundary Himalayan region where trout farming is still rudimentary.

The Nan'ao Golden Scallop discussed in this paper is a new breed of noble scallop, Chlamys nobilis, produced by four generations of genetic breeding selections and two generations of culture demonstrations. Performed for the first time at Shantou University, the genetic breeding program was motivated by the need to reduce vulnerability and improve the adaptive capacity of noble scallops to the dynamic environment. This paper reviews the scientific evidences on aquaculture advantages of Nan'ao Golden Scallop, and identifies gaps in knowledge that require further research. From the analysis of published data, it is obvious that Nan'ao Golden Scallop is more nutritious and less susceptible to stress than common brown scallops. The high TCC of Nan'ao Golden Scallop up-regulate the expression of various immune related genes under stressful conditions. Since molluscs do not possess specific immunity, the information in this paper is very useful for improving the aquaculture performance of molluscs by selective breeding techniques.

The environmental effects of fish culture operations are important issues in Michigan as well as many other parts of the world. The State of Michigan Department of Natural Resources operates the Platte River State Fish Hatchery (PRSFH) located near Honor, Michigan (USA). This facility has a restrictive discharge permit that limits the input of phosphorus into the Platte River that subsequently drains into a downstream oligotrophic lake (Platte Lake). The permit has been violated on occasion in recent years. Hatchery managers and operators need to understand the cause of these violations and prevent them in the future; and at the same time meet production goals to satisfy fishery management objectives. This paper describes the development and application of models designed to quantitatively analyze these issues. First, a bioenergetic growth and consumption model is developed for juvenile coho ( Oncorhynchus kisutch ) and Chinook ( Oncorhynchus tshawytscha ) salmon to quantify the relationship between fish production and by-product phosphorus loads. Next, phosphorus mass balance equations are used to calculate the phosphorus discharge from the facility as a function of the by-product phosphorus load and the efficiency of various phosphorus removal equipment and processes. The accuracy and consistency of the energy and mass balance equations are verified using extensive measurements. The ability of the model to successfully match various aspects of system performance supports the contention that the bioenergetic modeling approach developed here can provide reliable estimates of salmonid growth and feed requirements for a variety of food compositions, rations, and temperatures. This capability, along with knowledge of the effectiveness of phosphorus removal equipment, forms the basis of a practical operational and management tool. An example of model utility is presented that analyzes the PRSFH phosphorus discharge and provides insights into why permit violations occurred in 2009 but not in 2010. The model demonstrates how to avoid food waste caused by over feeding, lower the food conversion ratio, and evaluate the effectiveness of phosphorus removal treatment processes. A steady-state version of the model can be used by managers to establish production goals that avoid future violations of the phosphorus discharge limits. Statement of relevance The environmental effects of fish culture operations are important issues in many parts of the world. This paper describes the development and application of models designed to quantitatively analyze the relationships among fish production, by-product phosphorus loads, and the phosphorus concentration of the discharge following treatment. The ability of the model to successfully match various aspects of system performance supports the contention that the bioenergetic modeling approach developed here can provide reliable estimates of salmonid growth and feed requirements for a variety of food compositions, rations, and temperatures. This capability, along with knowledge of the effectiveness of phosphorus removal equipment, forms the basis of a practical operational and management tool. The model demonstrates how to avoid food waste caused by over feeding, lower the food conversion ratio, and evaluate the effectiveness of phosphorus removal treatment processes. A steady-state version of the model can be used by managers to establish production goals that avoid future violations of the phosphorus discharge limits.

This paper reports on successful hatchery production of the winged pearl oyster, Pteria penguin, without the use of live micro-algae. Larval nutrition was provided by commercially available micro-algae concentrates, Instant Algae® (“Isochrysis 1800®” and “Pavlova 1800®”, Reed Mariculture Inc., San Jose, CA, USA). Larvae were first transferred to settlement tanks on day 17 when their mean antero-posterior measurement (APM) was 240.2 ± 8.6 μm. Approximately 6.4% of larvae survived to day 17 and more than 700,000 eyed pediveligers were transferred to settlement tanks between day 17 and day 25. Approximately 33,000 spat were harvested from spat collectors on day 105, representing a survival rate of 4.7% from the eyed pediveliger stage. Growth and development of larvae in this study were superior to those reported in a prior study that used a ternary live micro-algae diet to feed P. penguin larvae. Our results indicate that the products used in this study proved nutritious for P. penguin larvae and supported normal growth and development through settlement. The use of commercially available micro-algae concentrates as a replacement for live micro-algae in pearl oyster hatcheries supports development of simplified larval rearing protocols, without live micro-algae culture, that are more appropriate to Pacific island nations. Statement of relevance This paper reports for the first time on successful hatchery production of pearl oysters without the use of live micro-algae. Successful replacement of live micro-algae with commercially available micro-algae concentrates as a larval food source supports development of simpler, cheaper hatchery facilities, and larval rearing protocols that are more appropriate to Pacific island nations.

The archeospore is an asexual reproduction strategy for some red algae, including Pyropia. Since cultivation of Pyropia yields important economic returns, whether or not it forms archeospores that can reseed nets becomes a key feature for this commercial seaweed. In this paper, desiccation, diurnal temperature changes and irradiance were tested for their effects on archeospore production by Pyropia yezoensis Ueda. Our results first showed that 2–3 h of daily, rhythmic desiccation and diurnal temperature changes strongly induced archeospore production, especially for the group with an increased temperature during the light period and a decreased temperature during the dark. The results also confirmed that a short photoperiod and a relatively higher light intensity benefitted the production of archeospores.

Aquaculture farms' efficiency may be different across regions due to spatial variation in their production environment. Thus, if efficiency is measured and compared without accounting for regional differences in the production environment, it may lead to a biased evaluation of efficiency and correspondingly erroneous policy suggestions. This paper uses the meta-frontier approach to compare efficiency among a sample of 625 farms producing pangas and tilapia located in different regions of Bangladesh and exposed to different production environments. Furthermore, Spearman correlation is employed to identify factors, such as sources of water supply, water and soil quality that influence efficiency. The results suggest that efficiency varies significantly across regions due to variation in the production environment, the individual producers' ability to manage inputs and selection of species depending on local environmental conditions. This study implies that policymakers should take into account variation of the production environment between regions and the performance of specific species within these environments when making plans for future expansion of aquaculture production to use the resources most efficiently.

Certification and third party accreditation schemes are examples of private-social partnerships that make up a form of hybrid governance. We argue that hybrid governance is changing the way traditional governance is being utilised. In this paper we examine the rise of third party certification and the challenges these governance arrangements bring to traditional governance. We examine this through analysis of the Aquaculture Stewardship Council (ASC) and the application of the ASC standard in salmonid aquaculture in Tasmania, Australia. This example emphasises that market and consumer engagement is challenging government policies and posing key questions over the role of traditional state practice in the evaluation of sustainable aquaculture. A key factor, however, underpinning such engagement is trust. Thus ASC certification is likely to be a necessary, but not a sufficient, condition supporting the granting of social licence to operate.

Control of reproduction is one of the key issues to extend tilapia aquaculture. In most fish species, reproduction is a rhythmic process which ensures that reproduction timing matches the most favorable environmental conditions to maximize the survival of offspring. Although the existence of daily spawning rhythms has been reported for a number of fish species, the daily rhythms in neuroendocrine factors along the BPG (brain-pituitary-gonadal) axis remains mostly unknown. The objective of this paper was to investigate the existence of daily rhythms in BPG gene expression and plasma sex steroids in tilapia (Oreochromis niloticus). To this end, 36 males and 36 females were kept in separate tanks at 29 ± 0.5 °C and in a 12 h:12 h light/dark cycle. After 4 weeks of acclimation, male and female tilapia were mixed into six groups at a female:male ratio of 6:6. Two weeks later, fish were anesthetized and sampled every 4 h during a 24-hour cycle, and blood, brain, pituitary, gonad and eggs were collected for later analyses. The expression levels of the genes from the brain (gnrh1, gnrh2, gnrh3, kiss2, gnih), pituitary (fshβ and lhβ), gonad (star, cyp11a, cyp17, cyp19a1a and amh) and eggs (zp3b and fyna) were analyzed by qPCR. ELISA was used to analyze testosterone and estradiol in male and female plasma, respectively, and maturation-inducing hormone (MIH) in plasma in both sexes. The results revealed timely-coordinated daily rhythms along the BPG axis of tilapia. The expression of the brain genes showed that their acrophase was distributed throughout the LD cycle. However, a coordinated and harmonious pattern of daily rhythms appeared on the following levels of the BPG axis. The peaks in expression of the pituitary genes were reached at night, while the gonadal genes and plasma sex steroids peaked in the light phase. These findings can be useful for improving breeding protocols for tilapia aquaculture and for defining optimum timing for reproduction in captivity.

Monitoring an aquatic environment in aquaculture is usually carried out by controlling its physicochemical and biological parameters. The global state of the process is evaluated though the individual conditions shown in each parameter. However, the correlation structure in the data, caused by interdependence between these parameters, provides relevant information which must be controlled. Thus, the complex structure of the data requires a multivariate control method to explore both the individual and interactive effects of the environmental parameters. To achieve this goal, this paper presents a statistical method based on a Multivariate Exponentially Moving Average (MEWMA) chart to monitor the multivariate structure of an aquatic environment in aquaculture, especially in a crop of tilapia in Mozambique. The results show that the adjusted MEWMA chart is more consistent when controlling the conformity and stability of environmental parameters. Therefore, it can be considered an efficient statistical method to monitor an aquatic environment in aquaculture.

Recently, Vibrio harveyi has emerged as an important pathogenic disease with a high mortality rate (50%–70%) in Chinese tongue sole. The aim of this study was to estimate genetic parameters for resistance to V. harveyi in Chinese tongue sole and to evaluate the genetic correlation between resistance and growth traits (i.e. body weight and total length) (involving 50 full-sib families and 8547 individuals). Longitudinal linear models and cross-sectional threshold models were fitted by using different trait definitions (binary and categorical). After a 14-day test, the overall challenge test survival was 57.86% (ranging from 9.30% to 94.30% in families). The heritabilities of survival were ranging from 0.11 to 0.28, estimates obtained by linear models were higher than threshold models. The genetic correlations between resistance (binary and categorical traits) and two growth traits were moderately positive (0.27–0.51). Very high Pearson and Spearman correlations (0.99 to 1) of full-sib family EBVs between different models were all close to unity which might reveal the similar predictive ability of the four models. The favourable heritabilities and moderate positive genetic correlations indicate that joint genetic improvement of vibriosis resistance and growth performance would be feasible. Statement of relevance This paper offers guidelines to disease-resistance selective breeding strategies in Chinese tongue sole.

Feed is the most main expenditure in outdoor intensive culture system. The improvement of feeding efficiency has great significance for increasing production and reducing costs. Presently, with the development of precision agriculture, automatic adjustments of the feeding amount according to the demands of the fish has become a developing trend. The objective of this paper was to develop an automatic feeding decision-making system based on the water quality parameters to solve the problem of inefficiency in artificial feeding control. In this study, we proposed an effective control method using adaptive neural fuzzy inference system (ANFIS) to achieve this purpose. First, two input variables (dissolved oxygen saturation [DO]; temperature [T]) and one output variable (feeding percent [FP]) were selected and defined. Second, the model of the linguistic variables and the optimal fuzzy rule base were obtained by the training and learning by utilization of hybrid learning methods. Finally, an ANFIS controller for on-demand feeding was developed and the performance was compared with Fuzzy logic control (FLC) and artificial control (AC) by the Nash-Sutcliffe efficiency coefficient (NS), the root mean squared error (RMSE), and fish growth parameters. The results indicated that the NS and RMSE of the ANFIS model were 0.8539 and 0.0541, respectively, and were better for forecasting feeding decisions compared with the FLC and AC methods. Compared with the AC, there was no significant differences in promoting fish growth (P > 0.05), whereas the feed conversion rate (FCR) was reduced by14.35%. In addition, the mean of ammonia nitrogen concentration decreased by 22.59%, and the mean of turbidity increased 5.5 cm to 28.9 cm, reducing eutrophication and pollution of water in pond. Therefore, applying those approaches based on ANFIS control to the feeding decision system in outdoor intensive culturing is flexible and effective, and has potential for the design of fine feeding equipment and to guide this practice for other species.

Sustainable food products have become significantly more important over the last decades. One example is the constant growth in the market for organic food. However, market shares for sustainable aquaculture products remain small. Parallel to emerging markets for sustainable foods, consumers' interest in the geographical origin, in particular domestic and local food production evolved. The aim of this paper was to elicit target groups for fish from sustainable aquaculture and their preferences for different countries of origin. Choice experiments and structured interviews were conducted with 447 German consumers of fish to analyze heterogeneous consumer groups. The results of latent class modelling yielded five target groups. One consumer segment (19%) was predominantly considering sustainability labels and claims on production criteria, i.e. ‘production in natural ponds’ and ‘sustainably produced’. The largest consumer segment (39%) placed highest importance on the COO while sustainability labels and claims had a positive but much weaker impact. Yet, another consumer segment (20%) gave the country of origin priority over all other attributes. Two more classes based their choice primarily on price, with one class preferring premium prices and the other class low prices. Marketers of sustainable aquaculture products are advised to source products from countries of origin that consumers prefer, and prominently declare the country of origin. For reaching new target groups, certified sustainable producers should not only rely on their label. It is recommended to focus on production criteria of consumer interest, for example the production in natural ponds, and state these on the product package.

9 pages, 8 figures, Marine aquaculture takes advantage of marine ecosystem services to produce goods that can be relevant from a food security point of view. However, this activity is subject to multiple stressors as the ones exerted by global climate change. Local stressed conditions due to environmental drivers may be exacerbated by the COVID19 pandemic crisis. In this paper we analyze the pre-COVID-19 situation in two Spanish regions with the highest aquaculture production, Galicia and the Valencian Community. The incidence of storms, heat waves and mussel farming closure were analyzed, and surveys were used to define the perception of producers in terms of economic problems derived from COVID-19 and synergistic environmental concerns. Also the temporal trend of mussel production was analyzed. Spanish marine aquaculture has been intensively subjected to climatic stressors that made it more vulnerable to COVID-19, showing some weakness in terms of production as can be seen in mussel production and fresh consumption. Anyway, extensive aquaculture and aquaculture developed by Integrated Multi-Trophic Aquaculture (IMTA) was reported as somewhat more resilient to the impact of COVID-19. In order to ensure the environmental and economic sustainability of marine aquaculture - under a future uncertain pandemic scenario – our outcomes underline the need for more resilient adaptation programs and recovery plans taking into account the climate change effects, M.C.M.’s research activity was supported by the European Union’s Horizon 2020 Research and Innovation pro- gramme under the Marie Skłodowska-Curie Action (Grant agreement no. 835589, MIRROR Project)

The supply chain for salmon is, in many respects, the world's most efficient seafood supply chain. Adopting new technologies and expanding the scale of production have improved competitiveness leading to increased production and industry growth. The transfer of knowledge and processes from other food producing industries has facilitated growth in salmon aquaculture in particular, and in aquaculture in general. As such, the maturity of the salmon industry relative to other food producing industries can provide indications of further growth potential. We argue that the salmon industry still has much to learn from similar processes in other food-growing industries. Notably, the production and processing of poultry has experienced significant increases since the 1940s, becoming the fastest growing and most rapidly changing highly-intensive livestock farming segment, with often fully-automated processing environments. Although farmed salmon has a production history closely following that of poultry, it remains semi-automated with less control over production processes and a more limited product specter than poultry. While this gives important avenues of growth for salmon, it holds even more potential for other aquaculture species with even less control over the production processes and supply chain. Statement of relevance Innovations leading to productivity growth and improved competitiveness throughout the supply chain have been key to the development of successful aquaculture industries. To a large extent, innovations have built on knowledge from the agrosciences. In this paper we compare the development of salmon aquaculture, one of the most sophisticated aquaculture industries with chicken, one of the most sophisticated terrestrial animal production industries. This sheds new light on the development of salmon aquaculture and it show that there is s large knowledge potential still to be tapped form chicken production, giving substantial promise of further development.

Although aquaculture is the fastest growing food producing sector in the world and generates significant employment opportunities at multiple scales, men and women are not necessarily able to participate in aquaculture value chains in the same way, and benefits may not be evenly distributed between them. This paper aims to elucidate current knowledge of gendered engagement in and returns from aquaculture value chains. It does so by presenting a review of existing evidence on gender issues in aquaculture value chains along five key dimensions: gender division of labor, distribution of benefits, access and control over assets and resources, gender and social norms, power relations and governance. Subsequently, the potential results for value chain performance and potential upgrading pathways are presented. The review shows that there is limited high quality sex-disaggregated data regarding aquaculture value chains, in particular related to the distribution of benefits in the chain. It also shows that evidence is limited regarding other aspects of the quality of women's participation in and returns from these chains. Existing evidence, however, indicates gendered imbalances in all five dimensions assessed, with formal and informal barriers, including gender norms, limiting women's equal engagement and returns. The specifics were found to vary by context and to be shaped in relation to factors such as class, needs, and social and religious norms. The impact of gender inequity on value chain performance was also found to be an area of literature for which evidence is still limited. While the upgrading pathways as described in the literature may result in economic upgrading, they may have limited effect on improving inequity or social conditions in the chain, if they do not take underlying inequities in institutions into account. Together the evidence indicates the need for research to elucidate practical ways to increase women's engagement in and returns from aquaculture value chains through addressing formal and informal barriers to women's control over assets, including shifting underlying gender norms and relations towards gender equality.

Aquaculture in Zambia is growing and likely to play an important role for food and nutrition security in the country. While outputs in capture fisheries and small-scale aquaculture are stagnating, commercial aquaculture holds promising potential to help increase the availability and accessibility of fish in the country, especially for the poor. While fish supply per capita has increased over the last decade, little is known on the food consumption patterns and the role of farmed fish in the diets of resource-poor households. The aim of this paper is to (1) generate information on the fish consumption patterns of poor households in urban Zambia and (2) explore the role of Zambian aquaculture as a source of fish among poor urban households. Multi-stage stratified cluster sampling was used to sample poor households in Lusaka. Data on fish consumption were collected through a cross-sectional study that analyzed a quantitative household survey (N = 714). Using Principal Component Analysis (PCA), the sample of poor households was further disaggregated into four socio-economic strata (asset-based) to compare household fish consumption in respect to poverty levels. The results of the study show that the poorest households almost exclusively rely on small, dried fish products from capture fisheries while the slightly better off households among the poor strata tend to consume larger, fresh fish, such as tilapia, which are partly supplied by aquaculture producers. These results imply that the poorest of the poor households – unlike the better off households – are less likely to supplement their diets with fish products from aquaculture. This could have negative consequences for the food and nutrition security of disadvantaged consumers, given the stagnation of fish supply from Zambian capture fisheries and an increasing population that demands fish. For aquaculture to contribute more effectively to fish supply among poor consumers, we conclude that the sector would need to further expand its economies of scale (to decrease unit production costs), explore producing smaller-sized fish (to increase accessibility), promote the development of small and medium-sized fish farming, and diversify production with respect to species and products that better respond to the needs of poor consumers.

Highlights • Despite the most important role of Penaeus vannamei in shrimp aquaculture, population genetics information for broodstock from either domesticated or wild population is limited; in this paper we report on genetic (microsatellite) variation for this important culture species captured in 36 Chinese breeding lines from 22 hatcheries which is the most comprehensive sampling design to our knowledge. • Microsatellite data analysis successfully resolved different origins of P. vannamei culture stocks used in China that resulted in the detection of four lineages with genetically diverse origins. • Results of the analysis here has provided the foundation and guidelines to develop a base line for genetic improvement program with optimal levels of genetic variation and a relatively low inbreeding coefficient. • We believe that the data presented here clearly demonstrate the utility of accessing genetic resources from a variety of sources (particularly when natural populations are not available) and show this as a viable and necessary first step for developing a base population for pursuing subsequent genetic improvement in alien aquaculture species. Abstract Knowledge about the origins and relative levels of genetic variation available in domesticated strains can be used to develop robust synthetic populations for use in stock improvement programs, in particular, where wild stocks are unavailable or the target species is alien. Here, we undertook a case study of Pacific white shrimp (Penaeus vannamei) where we utilised neutral molecular genetic variation data, population structure, and genetic relatedness as an initial step towards producing a base line for a long-term family-selection breeding program in China. The objective was to capture and maximise genetic variation in the base population while at the same-time to control inbreeding levels. Genetic diversity in 1162 individuals from 36 breeding lines sourced from 22 hatcheries with domesticated broodstock available in China was assessed using seven microsatellite loci. Genetic diversity levels in the sampled lines were considered to be healthy, with a mean number of alleles (A) 5.85, ranging from 4.00 in B4 to 12.43 in T1, and mean allelic richness (Ar) 4.46, ranging from 3.35 in B4 to 6.69 in T1 breeds. Mean inbreeding coefficient (Fis) was 0.07 among the 36 lines indicating acceptable levels of inbreeding. Genetic differentiation between lines from different hatcheries was moderate, with a mean FST estimate of 0.09 among all pairs of hatchery lines. Bayesian assignment and phylogenetic analyses indicated that hatchery lines in China could be broadly divided into four groups: i) a line from North America (NA1), originally sourced from Mexico (north Sinaloa) and Ecuador, ii) two representatives of the Kona line developed in Hawaii (Oceanic Institute) (NA2,3), iii) a line developed in Thailand (Southeast Asia 1 (SA1)), and iv) a mixed group containing stocks that originated in Latin America (predominantly from Panama and Colombia) (LA; SA2; CN1,2; NA4,5). From these data, we argue that a complete 4 × 4 diallel cross (16 crosses) of the four subpopulations should be trialled in China to develop a base line for a family selection breeding program with optimal levels of genetic variation and a relatively low inbreeding coefficient.

Despite Japanese flounder ( Paralichthys olivaceus ) is of importance in aquaculture of Northeast Asia, selective breeding programs for growth performance traits remain limited. The aim of this study was to estimate parameters of growth performance traits in this species. The heritabilities, genetic and phenotypic correlations, and breeding values were estimated for body weight (BW), total length (TL), condition factor (K), and average daily gain (ADG). The genetic analyses were performed on a total number of 186 full-sib families (108 sires and 146dams, 16,807 individuals with integrated pedigree information) from 4 year-classes based on three mixed animal models with tank and year-class as fixed effects, mean family trait values at tagging as a covariate, and additive genetic effect as a random effect using the restricted maximum likelihood method. For all growth traits the maternal and sir-dam interaction effects in proportion to phenotypic variance were very low (0.00–0.05). The heritability estimates for growth traits ranged from 0.12 to 0.39, which is in a low to moderate level. These results indicated that there is a considerable additive genetic variation in growth traits, and the ongoing selective breeding project will produce considerable genetic improvement in growth traits of Japanese flounder. The genetic and phenotypic correlations among BW, TL and ADG were high and positive (0.87–0.94, P Statement of relevance This paper offers guidelines to select breeding strategy in Japanese flounder.

When conducting digestibility experiments with fish many researchers encounter problems that result in erroneous digestibility coefficients. Erroneous digestibility coefficients result from variability in the raw data which is amplified by the formulae used to calculate them. Variation can stem from natural differences in the digestibility of the same diet between individuals or groups of fish. It can also creep insidiously into studies due to poor preparation and mixing of ingredients or problems with the collection of faecal material or the veracity of analytical results. Therefore, it is fairly common to expect variability in data collected from digestibility trials with fish. But what can be done about it? In this paper, we present an experiment with yellowtail kingfish (Seriola lalandi) that was done to determine whether the digestibility of extruded wheat (EW) was affected by its inclusion rate (10, 20, 30 or 40% diet− 1). The experiment, based on the indicator–ratio method, was conducted without incident, but the raw data on the nutrient and marker concentration of faecal samples was variable. We dealt with this problem by using linear regression to estimate more reliable analytical values for faecal samples. These values were used to recalculate logical digestibility coefficients for EW. Using this approach, we show that dry matter (≈ 57%–40%), carbohydrate (≈ 48%–27%) and gross energy (57–42%) digestibility of EW decline as its inclusion rate rises, whereas the digestibility of protein (≈ 84%) and the digestibility of fat (≈ 94%), remain reasonably constant. We validated the regression approach applied to yellowtail kingfish by examining published data from a similar digestibility experiment on Australian snapper Pagrus auratus. A regression approach was useful in reducing the variability in our raw data because the design of our experiment approximated a dose-response relationship. Designing digestibility experiments using a dose-response approach may prove useful in overcoming the inherent variability often encountered in these types of experiments.

This paper reports a case of natural co-infection of Tilapia Lake Virus (TiLV) and Aeromonas veronii in a Malaysian red hybrid tilapia (Oreochromis niloticus × O. mossambicus) farm. In May 2017, a tilapia farm operator reported a mass mortality among cultured red hybrid tilapia juveniles, approximately 45 days after introduction into earthen ponds. Affected fish showed lethargy, loss of appetite, swim near the pond edge, pale and isolated from schooling group. There were skin redness and haemorrhages, particularly at the operculum area and at the base of dorsal, caudal and anal fins. Histopathological examinations revealed swollen hepatocytes, haemorrhagic spleens and perivascular cuffing consisted of mononuclear cells in the brains. PCR and sequence analyses confirmed the presence of TiLV and A. veronii in the diseased fish. Phylogenetic tree revealed that Malaysian's TiLV strain was more closely related with the virus isolated in Israel than in Egypt or Thailand, while Malaysian's A. veronii strain 5L was closely related with strains from China. TiLV infection is a significant threat to global tilapia industry. However, synergistic co-infection of TiLV and other bacterial might aggravate the problem.

Crystalline amino acids and nucleotides, previously identified as potential feed-intake modulators in krill hydrolysate (KH), were mixed into low fish meal diets for Atlantic salmon in five combinations: A1) Arg, A2) Arg + Ala + Pro, A3) Arg + Ala + Pro + Leu + Phe, A4) Arg + Ala + Pro + Leu + Phe + nucleotides (AMP, GMP, CMP, IMP), and A5) Arg + Ala + Pro + Leu + Phe + nucleotides + rest free amino acids as in KH. Each compound mix was added to one of five otherwise identical 3% fishmeal diets. A 15% fishmeal (MFM) diet and a 3% fishmeal diet (LFM) served as positive and negative controls, respectively. The experimental diets were fed to seven triplicate populations of 60 salmon smolts for a period of 83 days. The initial mean body weight of the fish was 130 g while the final weights for the different treatments ranged between 500 and 560 g, with feed efficiency ratio (FCR) values of 0.8 or lower. The compound mixes were efficient in modulating feed intake rates, A1 negatively and A3, A4 and A5 positively, and resulted in a complex matrix of differential physiological responses related to growth, apparent nutrient digestibility, plasma and liver lipids and appetite-regulating neuropeptide relative gene expression, which are analysed in this paper.

Attempts were made to study the effect of stocking density and water saving approach on water and sediment quality, growth and production performance of shrimp (Litopenaeus vannamei). The experiment was carried out with three stocking density of post-larvae i.e. 400,000 per ha (T1), 500,000 per ha (T2) and 600,000 per ha (T3). Water exchange was carried out depending on water quality parameters. Water quality suitability index (WQSI) was lower at higher stocking density as was evident in T3 followed by T2 and T1. A very good WQSI (7.5–9.0) was recorded up to 13th, 12th and 9th week of culture in T1, T2 and T3, respectively; which was ascribed to stocking density, smaller shrimp size and less initial feed input. In L. vannamei culture, optimum stocking density of 50 post-larvae per m2 (T2) led to total water use of 3.42 × 104 m3 and water exchange of 0.80 × 104 m3. It was perceived as a way to improve shrimp productivity (10.31 t ha− 1 120 d− 1), consumptive water use index (1.93 m3 kg− 1 biomass), total water footprint (1426 m3 t− 1 biomass), net consumptive water productivity (USD 1.13 m− 3) and ratio of output value to the cost of cultivation (1.99). Further, farming systems with low to moderate water exchange as in T2, helped maintain water quality suitable for the shrimp growth, improved water use efficiency (518 g biomass m− 3 water), minimized quantity of sediment load (41.7 m3 t− 1 biomass) and effluent outputs (0.8 × 104 m3). The knowledge derived from this study could provide the basis to optimize pond rearing efforts in shrimp culture and the water management strategies can be tailored to minimize production costs. Statement of relevance This paper presents findings and analysis, from a methodologically rigorous investigation and provides insight regarding density-dependent optimum water use, its effect on pond water quality, sedimentation rate, growth performance, water productivity and water footprint. The knowledge derived from this study may be a basis to optimize pond rearing efforts in shrimp culture and the water management strategies can be tailored to prevent wasteful use of water and enhance water use efficiency and water productivity.