Comparative life cycle assessment (LCA) of raising rainbow trout (Oncorhynchus mykiss) in different production systems

The production of rainbow trout (Oncorhynchus mykiss Walbaum 1792) is practiced in different production systems including extensive system (ES), intensive system (IS) and recirculating aquaculture systems (RAS). These production systems are different in their quantitative requirements of resource utilization and subsequent output and emissions that impact the environment. In this paper, consequential life cycle assessment (LCA) is used to analyze the environmental impact of rainbow trout production using these production systems in an attempt to determine the relative performances and identify options for future improvements. The life cycle impact assessment (LCIA) indicate that impact from four impact categories chosen, RAS showed the largest impact in global warming (GWP), acidification (AP) and land competition (LC), while its impact on eutrophication (EP) and water-use was the lowest relative to ES and IS. This signified that while RAS has the capability to reduce impacts in the EP category by avoiding water emissions, the increased use of energy for water filtration and reuse increases impact through global emissions. However, sensitivity analysis revealed that RAS has the potential to reduce the overall impact when using a marginal energy source based on wind power as compared to ES and IS. In conclusion, impacts which are specific to aquaculture need to be considered in LCA to draw comprehensive analysis of the impacts. In addition, identification of the underlying problems of the different impacts is important in finding solution leading to sustainability of aquaculture.     

Life cycle assessment of aquaculture systems: Does burden shifting occur with an increase in production intensity?

Life cycle assessment (LCA), a tool used to assess the environmental impacts of products and processes, has been used to evaluate a range of aquaculture systems. Eighteen LCA studies were reviewed which included assessments of recirculating aquaculture systems (RAS), flow-through systems, net cages, and pond systems. This review considered the potential to mitigate environmental burdens with a movement from extensive to intensive aquaculture systems. Due to the diversity in study results, specific processes (feed, energy, and infrastructure) and specific impact categories (land use, water use, and eutrophication potential) were analyzed in-depth. The comparative analysis indicated there was a possible shift from local to global impacts with a progression from extensive to intensive systems, if mitigation strategies were not performed. The shift was partially due to increased electricity requirements but also varied with electricity source. The impacts from infrastructure were less than 13 % of the environmental impact and considered negligible. For feed, the environmental impacts were typically more dependent on feed conversion ratio (FCR) than the type of system. Feed also contributed to over 50 % of the impacts on land use, second only to energy carriers. The analysis of water use indicated intensive recirculating systems efficiently reduce water use as compared to extensive systems; however, at present, studies have only considered direct water use and future work is required that incorporates indirect and consumptive water use. Alternative aquaculture systems that can improve the total nutrient uptake and production yield per material and energy based input, thereby reducing the overall emissions per unit of feed, should be further investigated to optimize the overall of aquaculture systems, considering both global and local environmental impacts. While LCA can be a valuable tool to evaluate trade-offs in system designs, the results are often location and species specific. Therefore, it is critical to consider both of these criteria in conjunction with LCA results when developing aquaculture systems.     

Expanding the concept of sustainable seafood using Life Cycle Assessment

Fisheries management and sustainability assessment of fisheries more generally have recently expanded their scope from single‐species stock assessment to ecosystem‐based approaches, aiming to incorporate economic, social and local environmental impacts, while still excluding global‐scale environmental impacts. In parallel, Life Cycle Assessment (LCA) has emerged as a widely used and recommended framework to assess environmental impacts of products, including global‐scale impacts. For over a decade, LCA has been applied to seafood supply chains, leading to new insights into the environmental impact of seafood products. We present insights from seafood LCA research with particular focus on evaluating fisheries management, which strongly influences the environmental impact of seafood products. Further, we suggest tangible ways in which LCA could be taken up in management. By identifying trade‐offs, LCA can be a useful decision support tool and avoids problem shifting from one concern (or activity) to another. The integrated, product‐based and quantitative perspective brought by LCA could complement existing tools. One example is to follow up fuel use of fishing, as the production and combustion of fuel used dominates overall results for various types of environmental impacts of seafood products, and is also often linked to biological impacts of fishing. Reducing the fuel use of fisheries is therefore effective to reduce overall impacts. Allocating fishing rights based on environmental performance could likewise facilitate the transition to low‐impact fisheries. Taking these steps in an open dialogue between fishers, managers, industry, NGOs and consumers would enable more targeted progress towards sustainable fisheries.     

长江流域2种水产养殖模式的生命周期环境影响评价

本研究以长江流域内的池塘养殖和稻渔综合种养2种水产养殖模式为对象，应用生命周期评价方法，分析2种养殖模式对能源消耗(EU)、全球变暖潜势(GWP)、酸化潜势(AP)、富营养化潜势(EP)以及水资源消耗(WU) 5种环境指标的影响，并探究2种主要输入因子(饲料和电力供应)和养殖过程对各环境指标的影响，从而评价2种养殖模式对环境影响的差异。生命周期评价结果标准化处理和加权评估显示，稻渔综合种养模式的WU、EP、GWP、AP和EU值分别为11.650、0.770、0.141、0.096和0.003，总环境影响指数(TEII)为12.660；池塘养殖模式的WU、EP、GWP、AP和EU值分别为31.453、1.187、0.210、0.174和0.007,TEII为33.031。与稻渔综合种养模式相比，池塘养殖模式的各项环境指标均较高。对环境影响的贡献率分析表明，饲料供应对EU、GWP和AP的贡献率最高，EP主要受饲料供应和养殖过程的共同影响，而WU主要集中在养殖过程中，电力供应主要影响EU、GWP和AP。生命周期评价的结果表明，与池塘养殖模式相比，稻渔综合种养模式显示出更友好的环境效益，在我国...     

Evaluation of the structural strength and failure for floating collar of a single-point mooring fish cage based on finite element method

Deep-water fish cage floating collar also referred to as float, bears a load in the form of waves, fishing nets, and moorings, in which the longitudinal wave force is the main type of loading. The long-term continuous effects caused by wave force could cause reduction in strength, or vibration failure in the floating collar. In this study, the peak responses of a single-point mooring (SPM) cage floating collar, due to either static or vibration loadings, were calculated by the finite element method (FEM) based on an elastic model. In this model, the float exhibited macro-plastic deformation when the stress of 26.1 MPa, generated under 100 kN load, was greater than the yield limit (25 MPa). With the increase in order modes from 1 to 18 (1.2–7.9 Hz), the stress increased. Moreover, the harmonic stress corresponding to 8 and 0.1 Hz was clearly higher than that for 0 Hz under 100 kN loads, due to structural resonance. The range of stress values due to the random vibration was 16.0–63.7 MPa, when the angular velocities (k) were in the range of 0.01–16 rad s^―1. Moreover, the transient response (34.4 MPa) was maximum when the angular velocity was 10 rad s^―1 (range 1–100 rad s^―1). The reliability rate of the entire body was 53.1% and 97.0% after 10⁸ loading cycles for 100 kN and 10 kN loads, respectively. Furthermore, the fatigue modes of the key components were determined from the outer triangular tops and inner hexagonal intersections. In short, static analysis, vibration analysis, and fatigue analysis of FEM could be used as reliable ways to evaluate structural strength and failure for floating system. Finally, the floating parts could be strengthened with partially double pipes or optimized by increasing the stiffness, and appropriate damping could be widely used.     

Benthic cages versus floating cages in Octopus vulgaris: Biological performance and biochemical composition feeding on Boops boops discarded from fish farms

Some benthic cephalopods are considered potential candidates to diversify marine aquaculture, as they show fast growth and high market price. Most research on cephalopod culture is currently focusing on the development of specific enrichments and compound feeds, while little research has been conducted in order to test new rearing systems for cephalopods. The rigid characteristic of the floating cages commonly used for the ongrowing of Octopus vulgaris has restricted their use to calm water conditions (estuaries and harbors). Such sites are scarce and highly demanded, especially by the tourism industry; therefore the development of O. vulgaris grow out at these locations competes with touristic interests. The present study was set to compare the biological performance of O. vulgaris reared in a benthic cage (2 m²) as opposed to the traditional floating cage (2.5 m²), during two ongrowing trials. Initial rearing density was 10 kg m⁻³ and octopuses (892 ± 125 g) were fed on bogue Boops boops, discarded from fish farms, for 60–67 days. High growth (1.8–1.9% day⁻¹) and high survival (91–97%) were observed, regardless of the rearing system, and led to best biomass increment (178–212%) and food conversion rates (2.3–2.6) ever recorded for O. vulgaris under industrial rearing conditions. These results underline the adequacy of the benthic cage for the ongrowing of this species, and also the potential of aquaculture discarded fishes, particularly bogue, as a single diet for this species. High growth rates obtained and the high lipid content of bogue (44% dry weight) suggest efficient lipid utilization in this species. Proximate composition and fatty acid profile in octopus muscle was not affected by the rearing system. High dietary lipid content was not reflected in muscle proximate composition, which showed high protein (87% dw) and low lipid content (5% dw) by the end of the experimental period. Farmed octopus showed high levels of n-3 HUFA (42%), which should enhance its value for the consumers.     

Sedimentation from mussel (Perna canaliculus) culture in the Firth of Thames, New Zealand: Impacts on sediment oxygen and nutrient fluxes

Shellfish aquaculture is growing worldwide and previous studies have shown a range of associated environmental impacts. In the Firth of Thames, New Zealand, there are more than 2000 ha of existing and approved farm area with applications pending for approximately another 6000 ha, however, no previous studies have examined the impacts of mussel culture in this region. To determine the impact of a mussel farm (45 ha) in the Firth of Thames we measured sedimentation rates by deploying sediment traps, sediment characteristics by collecting sediment cores and sediment oxygen and nutrient fluxes by deploying benthic chambers in four seasons. Sedimentation under the farm was increased by 106 g m^− 2 d^− 1 compared to the reference site. Similarly sediments under the farm had elevated organic carbon, nitrogen, chlorophyll a and phaeopigment concentrations indicative of the additional organic input due to bivalve biodeposition. Oxygen consumption was higher under the farm compared to a reference site (1.1-2.1×) but this increase was only significant (p < 0.001) in summer when rates reached 3083 μmol m^− 2 h^− 1 under the farm. Ammonia release rates ranged from 80 to 319 μmol m^− 2 h^− 1 and were higher under the farm compared to the reference site in spring (1.8×, non-significant p = 0.588) and autumn (3×, significant p = 0.006) but in summer release rates at the reference site (275 μmol m^− 2 h^− 1) were 1.4× higher than those under the farm. Nitrate fluxes (3.1 to 21.8 μmol m^− 2 h^− 1) were significantly (p = 0.001) higher at the farm site. Oxygen and nutrient fluxes generally demonstrated the typical response to increased organic input due to sedimentation from mussel culture. Unusually low nitrogen release rates in summer may indicate enhanced denitrification under the farm. Benthic regeneration at the reference site could supply 74% of nitrogen required by pelagic primary producers whereas under the farm it could account for 94%. This demonstrates the importance of benthic nutrient regeneration in this region and that mussel culture can lead to a redistribution of nutrients. The farm we studied is small and located in a high-energy environment and impacts from larger farms or in areas where biodeposit dispersal is limited are likely to be even more significant and we suggest that site-specific hydrodynamic and biogeochemical conditions have to be taken into account when planning new mussel farms to prevent excessive modifications of nutrient dynamics.     

Periphyton characteristics influence the growth and survival of Holothuria scabra early juveniles in an ocean nursery system

Floating hapas (fine mesh net enclosures) are a cost‐effective ocean nursery system to culture post‐metamorphic Holothuria scabra to release size. The growth of periphyton biofilm on hapas is a natural food source for early juveniles. This study investigated the effects of periphyton quality (i.e. chlorophyll‐a, phaeopigment, total biomass, autotrophic index or AI), water quality (nutrients, chlorophyll‐a) and environmental parameters (temperature, rainfall) on the temporal variation in the growth and survival of early juvenile (~3 mm) H. scabra reared in floating hapas. Five trials where the juveniles were reared for 60 days each in the eutrophic coastal waters of Bolinao, the Philippines were conducted during different months over 2 years. Significant differences in the growth and survival of juveniles among trials were found. Absolute growth rates (AGR) ranged widely (0.01–0.09 g/day). Trials with high AGR of juveniles (0.07–0.09 g/day) during the first 30 days of rearing had significantly higher chlorophyll‐a (chl‐a) in biofilm (15.9–27.5 mg/m²) and lower AI. Conversely, during the subsequent 30 days, trials with high AGR of juveniles (0.06–0.11 g/day) had significantly lower chl‐a and higher AI. Multivariate analyses showed that chl‐a in biofilm, AI and nutrients in the water column are good indicators of periphyton quality and juvenile growth rates in floating hapas. Further, this study validates the expansion of the feeding mode of juveniles from primarily grazing on microalgae, to feeding on detritus and heterotrophs as they grow. These results are important in optimizing ocean nursery systems.     

Rearing equipment on the quality aspects and growth performance of Crassostrea gigas (Thunberg, 1793): Implications for marketability

Shell characteristics and consequent marketability of the oyster Crassostrea gigas are influenced by several factors, and most important of which are the rearing methods and gears. In this study, we investigated the effects of two different gears on the quality aspect (shell shape, weight meat percentage, backward shell shape, epibionts and blisters) and growth rate (weight and length) of C. gigas by adopting the innovative Ortac Oyster Farming System, during the field grow‐out phase of production. Aspect and growth of oysters farmed in Ortac and floating bags were compared. After 14 weeks, the aspect of the animals was influenced by the gear, resulting in a lower quality in the Ortac (i.e. worse shell shape, lower weight meat percentage, higher percentage of backwards and blisters) than in the floating bag, while the incidence of epibionts was less in the Ortac. Regarding the growth performance, total wet weight gained in the Ortac was lower (~28.3 g) than in the floating bag (~32.4 g; p < .05). These results highlight the efficiency of the floating bag as oyster rearing system in the Mediterranean basin and suggest the need to alter the Ortac gear to these environmental conditions.     

饲料中不同磷水平对黄鳝生长、体成分及部分生理生化指标的影响

为探讨饲料中不同磷水平对黄鳝幼鱼生长、体成分、骨骼矿化及血液生化指标的影响,以商业配方为基础,磷酸二氢钙为磷源[Ca(H2PO4)2],配制磷含量分别为0.67%、0.91%、1.05%、1.29%和1.53%的5种等氮等能饲料。每种饲料投喂3个网箱(1.5 m×2.0 m×1.5 m),每个网箱放养实验鱼[初始体质量(34.4±0.3)g]100尾,进行70 d的养殖实验。结果显示:(1)随着饲料中磷含量从0.67%增加到1.05%,黄鳝幼鱼各组增重率(WGR)、蛋白质效率(PER)和饲料效率(FE)显著升高(P0.05),当磷含量高于1.05%后各指标进入平台期。折线模型分析[Y=104.67-46.07(1.10-X),R2=0.944]显示,当饲料中磷含量为1.10%时可满足黄鳝生长需要;(2)随着饲料中磷含量的增加,实验鱼体的粗蛋白含量和肥满度显著升高(P0.05),而粗脂肪含量和肝体比显著下降(P0.05);(3)饲料磷含量增加,可显著提高实验组全鱼灰分和全鱼磷含量(P0.05)。折线模型分析[Y=0.988-0.635 4(1.05-X),R2=0.928]显示,当饲料中磷含量为1.05%时可满足黄鳝全鱼磷累积需要;饲料磷含量增加也显著提高了脊椎骨钙和磷含量(P0.05),但脊椎骨钙磷比无显著差异。折线模型分析[Y=7.696-0.985 5(1.10-X),R2=0.956]显示,当饲料中磷含量为1.10%时可满足黄鳝脊椎磷累积需要;(4)饲料磷水平对血清中的磷和钙含量以及碱性磷酸酶活性有显著影响(P0.05)。研究表明,在本实验条件下,饲料中磷含量为1.10%,可以满足黄鳝对磷最大的组织储存需要以及最佳的生长效果。     

Impacts of climate change on the complex life cycles of fish

To anticipate the response of fish populations to climate change, we developed a framework that integrates requirements in all life stages to assess impacts across the entire life cycle. The framework was applied on plaice (Pleuronectes platessa) and Atlantic herring (Clupea harengus) in the North Sea, Atlantic cod (Gadus morhua) in the Norwegian/Barents Seas and European anchovy (Engraulis encrasicolus) in the Bay of Biscay. In each case study, we reviewed habitats required by each life stage, habitat availability, and connectivity between habitats. We then explored how these could be altered by climate change. We documented environmental processes impacting habitat availability and connectivity, providing an integrated view at the population level and in a spatial context of potential climate impacts. A key result was that climate‐driven changes in larval dispersion seem to be the major unknown. Our summary suggested that species with specific habitat requirements for spawning (herring) or nursery grounds (plaice) display bottlenecks in their life cycle. Among the species examined, anchovy could cope best with environmental variability. Plaice was considered to be least resilient to climate‐driven changes due to its strict connectivity between spawning and nursery grounds. For plaice in the North Sea, habitat availability was expected to reduce with climate change. For North Sea herring, Norwegian cod and Biscay anchovy, climate‐driven changes were expected to have contrasting impacts depending on the life stage. Our review highlights the need to integrate physiological and behavioural processes across the life cycle to project the response of specific populations to climate change.     

Revue des pratiques d'elevage de poissons en cages dans les eaux continentalesA review of fish cage culture as practised in inland waters

The rearing of fish in cages could greatly contribute to increasing fish production in existing inland waters. Although it presents numerous advantages, its limitations and possible inconveniences must be borne in mind. Well-developed technology is available mainly from the Democratic Republic of Germany, The Netherlands, Japan, the U.S.A., the U.S.S.R. and the Lower Mekong region. Research is currently pursued in numerous other countries, where the use of floating cages in fish culture is becoming increasingly diversified.The most popular fish species used in intensive cultural systems are Cyprinus carpio, Ictalurus punctatus and Salmo gairdneri. In the semi-intensive Asian systems, Barbus spp., Pangasius spp. and murrels are among the favourite cage-reared fishes. Tilapia aurea and Tilapia nilotica have also proved to be well adapted to cage culture. Polyculture is only rarely practised.Floating cages seem to be the best suited for fish culture in most cases. Net cages are the simplest in design and the cheapest to build. The escape of fish, however, always remains an eventuality which might lead to choosing more expensive designs. Maintenance of cages must be regular. For flexibility of exploitation, cages should not be too large. Their location within the water body can play an important role in keeping production high.At high stocking rates, artificial feeding of a well-adapted diet is a necessity. Optimum conversion rates require a well-adjusted daily ration, possibly fractioned. Mechanized feed distribution is to be encouraged as a labour-saving practice. Less intensive systems rely more on locally available wastes, such as trash fish, but the feeding rate then depends mostly on feed prices.Best growth is generally achieved by C. carpio and I. punctatus. Attainable maximum production is as high as 35 kg/m³/month under intensive management. However, generally, production averages from 5 to 30 kg/m³/month for these two species. S. gairdneri is less productive. T. aurea and T. nilotica have both a very good potential. Production in less intensive systems varies greatly according to management practices.     

The effects of long-term 20 mg/L carbon dioxide exposure on the health and performance of Atlantic salmon Salmo salar post-smolts in water recirculation aquaculture systems

Previous research and experience has linked elevated dissolved carbon dioxide (CO₂) to reduced growth performance, poor feed conversion, and a variety of health issues in farm-raised fish, including Atlantic salmon Salmo salar. Supplemental control measures in water recirculation aquaculture systems (RAS) to reduce CO₂ accumulation, however, such as increased water pumping to decrease tank hydraulic retention time, can represent significant costs for operators. We exposed post-smolt S₀ Atlantic salmon (197 ± 2 g, 423 days post-hatch) to either high (20 ± 1 mg/L) or low (8 ± <1 mg/L) dissolved CO₂ in six replicated freshwater RAS for 384 days to investigate differences in performance and health as the salmon were grown to harvest size. All RAS were operated at moderate water exchange rates (1.0% of the total recirculating flow), a 24-h photoperiod was provided, fish were fed to satiation, and densities were maintained between 40 and 80 kg/m³. Over the study period, dissolved oxygen was kept at saturation, mean water temperature was 14.1 ± 0.1 °C, and alkalinity averaged 237 mg/L as CaCO₃. At study’s end, no significant differences in fish weight (high CO₂ mean weight = 2879 ± 35 g; low CO₂ mean weight = 2896 ± 12 g), feed conversion ratio (1.14 ± 0.12 vs. 1.22 ± 0.13, respectively), or thermal growth coefficient (1.45 ± 0.01 vs. 1.46 ± 0.01, respectively), were observed. No significant differences in survival (high CO₂ mean survival = 99.1 ± 0.4%; low CO₂ mean survival = 98.9 ± 0.3%) or culls due to saprolegniasis (3.5 ± 1% vs. 3.0 ± 1%, respectively) were determined, and no nephrocalcinosis was observed through histopathological evaluation. Blood gas and chemistry evaluation revealed higher pCO₂, bicarbonate, and total CO₂, and lower chloride and glucose, in the high CO₂ cohort. Molecular analyses of gill enzyme regulation showed significantly higher expression of Na⁺/K⁺ ATPase α1a in high CO₂ fish at 3-weeks post-challenge, indicating physiological adaptation to the higher CO₂ environment without any noticeable long-term impacts on health or performance. Overall, the results of this study suggest that, at 237 mg/L as CaCO₃ mean alkalinity, post-smolt Atlantic salmon can be raised in freshwater RAS to harvest size with up to 20 mg/L CO₂ without significantly impacting fish health and performance.     

Deterring coastal birds from roosting on oyster culture gear in eastern New Brunswick,Canada

An ornithological survey was conducted along the eastern coastline of New Brunswick, Canada, where oysters are cultivated in suspension using PVC bags and wire-mesh cages. Thirteen bird species and a variety of unidentified shorebirds were observed roosting on the floating oyster gear. The double-crested cormorant (Phalacrocorax auritus) was the most common species observed (47.6% of all counts), closely followed by herring gulls (Larus argentatus) and common terns (Sterna hirundo) at 18.7% and 13.0%, respectively. Birds were densely aggregated where few cages or bags had been deployed. A gear-type effect was also detected: birds were more abundant on floating cages (mean = 47.9/100 m² of exposed area, S.E. = 5.8) than on floating bags (mean = 32.8/100 m², S.E. = 1.9). The survey was followed by two experiments designed to test the effects of gear modifications on bird abundance and diversity. For bags, results indicated that shallow immersion (～6 cm below surface) and floater instability were effective deterrents to P. auritus, reducing its abundance by a 37-fold factor. For wire-mesh cages, a dented triangular structure mounted on top of floaters was a harassing physical barrier to roosting behaviour, consequently reducing bird abundances to null (or near null) values.     

Bioremediation and reuse of shrimp aquaculture effluents to farm whiteleg shrimp,Litopenaeus vannamei : a first approach

Shrimp aquaculture effluents were bioremediated in a two‐phase system (System A) using the black clam Chione fluctifraga and the benthic microalgae Navicula sp., and then reused to farm whiteleg shrimp Litopenaeus vannamei. In the experimental design, Systems B and C had an identical structure as System A, but no clams or microalgae were added. System B received the same shrimp effluents while System C received only estuarine water. Shrimp raw effluents had a poor water quality. System A improved the water quality by decreasing the concentrations of total nitrogen, total ammonia nitrogen (TAN), nitrites, nitrates, phosphates, total suspended solids (TSS) and organic suspended solids (OSS). System B also decreased the concentration of TAN, TSS and OSS via sedimentation, but the effect was less pronounced than that observed in System A. Shrimp reared in the bioremediated effluents (System A) had better production (3166 kg ha^?1) and higher survival (89.2%) than those reared in effluents from Systems B (2610 kg ha^?1, 75.1%) and C (2874 kg ha^?1, 82.1%). It is concluded that the bioremediation system was moderately efficient and the bioremediated effluents were suitable to farm L. vannamei.     

The effect of dosing with sodium hydroxide (NaOH−) on water pH and growth of Haliotis midae in an abalone serial-use raceway

Abalone culture systems are characterised by high water exchange rates as abalone are sensitive to changes in water quality. To reduce the costs of pumping, serial reuse systems have been tested. As water pH can decline in these systems, this study determined the effect of raising pH through the addition of sodium hydroxide (NaOH^?) on weight gain, length gain and feed conversion ratio of H. midae in a serial-use raceway. Dosing with NaOH^? increased pH by 0.3, 0.27 and 0.21 units at positions 1, 2 and 3 of a serial-pass system, respectively. Weight gain (Wg) and length gain (Lg) were correlated with pH (Wg: F _{1, 16} = 16.35, P = 0.0009, r ² = 0.51; Lg: F _{1, 16} = 16.16, P = 0.0009, r ² = 0.50), and using pH, dissolved oxygen and free ammonia nitrogen as independent variables suggested that water pH was the best predictor for abalone growth.     

Potential environmental effects of probiotics used in aquaculture

Probiotics are a live microbial feed supplement that beneficially affects the host animal. As aquaculture is one of the main areas where probiotics can be applied, the environmental suitability of using probiotics in hatching and nursing facilities for turbot farming was evaluated through the life cycle assessment (LCA) methodology. This LCA study showed that the potential environmental impacts associated with probiotic production are generally offset by the impact reductions linked to lower consumption levels and reduced waste and emission generation rates within the hatching and nursing subsystem. Thus, the use of probiotics is recommended in order to enhance the performance of turbot aquaculture systems provided that operational and economic advantages are attained.     

Productivity and economic viability of snakehead Channa striata culture using an aquaponics approach

This study was carried out to investigate the viability of utilizing aquaponic technology in culturing local fish: snakehead Channa striata and water spinach Ipomoea aquatica. Snakehead was raised for 150 days in a floating plastic pond with an area of 3 × 4 × 1.2 m having a capacity volume of ∼14.4 m³. Fish were randomly arranged into two experimental systems at density of ∼0.3 kg fingerlings/m³ e.g. SAQ – snakehead in aquaponics; SC – snakehead in normal system where control ponds were continuously aerated with ∼20% daily exchange of water. Fish were fed commercial feed twice a day. Initial results showed that in aquaponics compared with normal systems the SAQ efficiency exhibited 70% water exchange; five times lower in NH₃ level: (0.01–0.03 mg/L vs. 0.05–0.16 mg/L); three times lower in NO₂ level: (0.28–0.58 mg/L vs. 0.56–2.59 mg/L). Snakehead production was significantly higher in aquaponics with higher survival ratio of fish: 99.76% vs. 71.40%; ∼3 times higher in fish yield: 366 kg vs. 130 kg. The production of water spinach was also elevated in aquaponics versus normal systems 406.4 kg vs. 188 kg. The total income from snakehead and water spinach in SAQ were 4 times higher than in normal farming systems: 1219.42 $US and 307.04 $US. Based on the results of the current study, it is expected that applying aquaponics utilizing local available materials and species will enhance the sustainability of the overall system and keep the aquaponics lasting and expanding to social life especially on sustainable culturing snakehead Channa striata.     

Effects of feeding rate and frequency on growth performance,digestion and nutrients balances of Atlantic salmon (Salmo salar) in recirculating aquaculture systems (RAS)

A 10‐week study was conducted to investigate the effects of feeding rate and frequency on growth performance, digestion and nutrients balances of Atlantic salmon (Salmo salar) in replicated recirculating aquaculture systems (RAS). Replicated groups of juvenile salmon weighing 90 ± 2.5 g (mean ± SD) were fed a commercial feed (21.63 MJ kg^?1 gross energy) to designed feeding rate (1.4%, 1.6% and 1.8% body weight day^?1, BW day^?1) and feeding frequency (2 and 4 meals day^?1) combinations. Specific growth ratio varied between 1.15 ± 0.02 and 1.37 ± 0.16% day^?1, and feed conversion ratio ranged from 0.96 ± 0.03 to 1.16 ± 0.02. The nitrogen and phosphorus retention rates were from 36.50 ± 1.94 to 47.08 ± 5.23% and from 20.42 ± 1.05 to 38.59 ± 2.80%. Apparent digestibility coefficients (ADC) in dry matter, protein, lipid and energy showed no significant differences for all groups. However, fish fed at 1.6% BW day^?1 and 4 meal day^?1 groups had relatively better growth and nutrient retention efficiency compared to other groups. In addition, concentrations of nitrogenous and phosphorous compounds were also detected in this study. These results suggested that salmon of 100–200 g in RAS could in practice be fed at 1.6% BW day^?1 and 4 meals day^?1, taking environmental impacts into account.     

Suitability and optimization of FAO’s small-scale aquaponics systems for joint production of lettuce (Lactuca sativa) and fish (Carassius auratus)

Aquaponics is a developing technique that combines the simultaneous production of plants (hydroponics) and fish (aquaculture). With it, the use of resources (i.e., water, nutrients, land) is reduced whilst at the same time minimising residues’ discharge to the environment. Among its benefits, it allows the production of healthy vegetables and fish in reduced spaces by means of small-scale systems. In this work, three of them based on FAO models with different hydroponic subsystems (nutrient film technique -NFT-, floating raft, and vertical felt) are tested to produce lettuce (Lactuca sativa) and goldfish (Carassius auratus). Water parameters as well as the growth of plants and fishes were monitored in two different production cycles. The hydroponic subsystem that outperformed the best was the NFT, both in terms of crop production and water consumption. All systems showed similar results in fish production. Further research is needed to corroborate the outputs obtained when using other combinations of plants and fishes. Small-scale aquaponic systems are particularly interesting for self-production and even more so in urban environments with reduced available space.