Integrated Multi-trophic Aquaculture System Research Articles

Real-world waste dispersion modelling for benthic integrated multi-trophic aquaculture.

In real-world situations, marine fish farms accommodate multiple fish species and cohorts within the farm, leading to diverse farm layouts influenced by cage dimensions, configurations, and intricate arrangements. These cage management practices are essential to meet production demands, however, farm-level complexities can impact model predictions of waste deposition and benthic impact near fish cages. This is of particular importance when the cages are used for integrated multi-trophic aquaculture (IMTA) with benthic feeders, where this waste not only affects environmental conditions but also provides a potential food source. The Cage Aquaculture Particulate Output and Transport (CAPOT) model incorporated multiple species, cohorts, and cage arrangements to estimate waste distribution from a commercial fish farm in the Mediterranean between October 2018 and July 2019. This spreadsheet model estimated dispersion for individual fish cages using a grid resolution of 5 m x 5 m. The study categorized discrete production periods for each fish cage every month, aligning with intermittent changes in biomass and food inputs due to different cage management practices throughout production. This approach facilitated the use of detailed input data and enhanced model representativeness by considering variations in cage biomass, food types, settling velocities, and configurations. Model outputs, represented in contour plots, indicated higher deposition directly below fish cages that varied monthly throughout fish production cycles. Deposition footprints reflected changes in cage biomass, food inputs, and farm-level practices reflecting this real-world scenario where aquaculture does not follow a production continuum. Moreover, cohort dynamics and cage movements associated with the cage management practices of the fish farm influenced the quantity and fate of wastes distributed around fish cages, revealing variability in deposition footprints. Clearly, these findings have important implications for the design of benthic IMTA systems, with species such as sea cucumber and polychaetes. Variability in waste deposition creates challenges in identifying where the benthic organisms should be placed to allow optimal uptake of waste to meet their food requirements and increase survivability. Evidently, models have an important role to play and this study emphasizes the need for representative input data to describe actual food inputs, cage biomass changes, and management practices for more representative farm-scale modelling and essentially to improve particulate waste management. To effectively mitigate benthic impacts through IMTA, models must quantify and resolve particulate waste distribution and impact around fish farms to maintain a balanced system with net removal of wastes. Resolving farm-level complexities provides vital information about the variability of food availability and quality for extractive organisms that helps improve recycling of organic wastes in integrated systems, demanding a more representative modelling approach.

Optimising seafood nutritional value and environmental sustainability in aquaculture through a novel integrated modelling tool applicable to IMTA and monoculture

Aquaculture policies that decrease the reliance on wild-caught fish and promote integrated multi-trophic aquaculture (IMTA) both aim to lessen the environmental footprint but often overlook economic-environmental trade-offs and neglect social, health, and broad-scale sustainability considerations. Here we present a new bio-physical model (FYNE) that bridges some of these gaps, by linking farm operational choices, such as feed choices and farm siting, with the nutritional value of the farm-gate seafood products and the resulting environmental eutrophication footprint at the farm level. The FYNE model operates both in conditions of monoculture or of IMTA production, and estimates feed composition effects on growth and omega-3 fatty acid content of Atlantic salmon (Salmo salar) and blue mussel (Mytilus edulis), and nitrogen and carbon concentrations, the latter being a measure of the environmental eutrophication footprint of the farm. The model here developed integrates for the first time (i) an ecosystem model of an IMTA and (ii) a fatty acid dynamics model, with new models for salmon feed digestibility and mussel ingestion. The outputs span (i) production analysis for simulation of biomass; (ii) farm mass-balance analysis on deposition analysis and environmental eutrophication footprint; and (iii) product nutritional quality, in terms of fatty acid content. An application of the model to an IMTA farm in Scotland (UK) demonstrates how fatty acid and environmental changes can be modelled in tandem and could be used to support the industry to optimize the nutritional value of cultured species and manage aquatic environmental eutrophication footprint at farm level, informing feed and siting decisions. The model effectively predicts changes in omega-3 fatty acids, particularly DHA and EPA, in response to variations in feed composition. Notably, our results confirm that salmon waste has limited influence on mussel growth due to the spatial separation within the IMTA system, which emphasizes the need for strategic siting to enhance system productivity through effective waste recycling. Additionally, results show that while increasing fishmeal in diets enhances environmental outcomes, it reduces levels of critical fatty acids like DHA and EPA, underscoring the need for balanced feed formulations. The method developed in this study described a novel integrated model (FYNE) that extend previous modelling work by incorporating the influence of farmed species feed composition on fatty acid dynamics as well as the farming environmental factors.

Circularity Assessment in Aquaculture: The Case of Integrated Multi-Trophic Aquaculture (IMTA) Systems

Aquaculture is a strategic sector that aims to meet the increased demands for healthy food for current and future populations. However, this progression needs to be sustainable, which can potentially be achieved by the implementation of circular practices. Integrated multi-trophic aquaculture (IMTA) systems promote the incorporation of circular principles. Nevertheless, the lack of harmonized definitions and standards impedes the quantification of these circular attributes. This study aims to explore the potential principles embedded in IMTA and the existing alternatives to quantify circularity. Two basic pillars (nutrient management and resource use efficiency) were identified as the most relevant circularity attributes for IMTA systems and were quantified through aquaculture-specific indicators. Bioremediation indicators, together with the efficiency indicators in terms of feed, water, energy, and infrastructure materials used, were selected to evaluate the circularity performance of four IMTA trials in three aquaculture facilities in Ireland, Brazil, and South Africa. Salmon, white shrimp, tilapia, abalone, and sea urchins were studied and cultivated together in various combinations with several low-trophic species in these IMTA trials to evaluate the improvement in circularity compared with corresponding monoculture conditions. The results showed an increase in circularity of up to 90% in terms of water recirculation, as well as bioremediation, which was improved by 80%–90%, providing evidence for the potential role of IMTA in the circularity transition.

Growth and survival of milkfish (Chanos chanos), tiger prawns (Panaeus monodon), and oysters (Crassostrea sp.) in integrated multi-trophic aquaculture (IMTA) system with varying stocking densities

Integrated Multitrophic Aquaculture System (IMTA) is a sustainable approach to aquaculture, utilizing ecosystem dynamics by integrating various species. This study examined the growth and survival of milkfish (Chanos chanos), tiger shrimp (Penaeus monodon), and oysters (Crassostrea spp.) in IMTA systems with different stocking densities. A 30-day experiment using a nonfactorial-completely randomized design with four treatments and three replications was conducted. The results showed that the implementation of IMTA had no significant impact on the survival rate of milkfish, tiger prawns or oysters in all treatments. However, important variations in growth parameters were observed. Milkfish and tiger prawns showed the highest weight and length gain in treatment B, followed by treatments A, C, and D. Similarly, oysters showed optimal growth in treatment B, followed by A, C, and D, based on weight gain, length, width, and shell thickness. Throughout the study, the physicochemical parameters of the water remained within acceptable ranges, thus supporting ideal growth conditions for the cultured species. These findings underscore the potential of IMTA to increase aquaculture productivity while upholding the principles of environmental sustainability. By optimizing stocking density and encouraging species diversity, IMTA presents a promising avenue for advancing integrated aquaculture practices, in line with the FAO's blue economy concept and ecosystem approach to aquaculture. Future research should concentrate on refining the IMTA system and evaluating its long-term ecological and economic consequences.

Growth Performance and Environmental Quality Indices and Biomarkers in a Co-Culture of the European Sea Bass with Filter and Deposit Feeders: A Case Study of an IMTA System

This study aimed to evaluate the efficiency of an integrated multi-trophic aquaculture (IMTA) system comprising co-cultured fed fish and organic extractive species representing three distinct trophic levels as well as the impact and potential utilization of two commercially available fish feeds made up of 35% fish meal (FM) and 20% fish meal (LFM) ingredients, using a multi-indicator assessment approach. Significant alterations were observed in growth performance indicators (GPIs), water and sediment quality indices, toxicity tests and biomarkers within the IMTA system. The fish survival, weight gain (WG), and specific growth rate (SGR) were higher in the IMTA system with significantly lower feed conversion ratios (FCRs) and higher feed efficiency (FE) in comparison to the fed fish monoculture system. Yet, organic filter feeders displayed 100% survival, and increased shell growth, while deposit feeders exhibited successful survival and significant weight gain. In the comparison between FM-IMTA and LFM-IMTA, fed fish in FM-IMTA showed higher WG, SGR, and FE with lower FCR. Environmental parameters like temperature, oxygen, and nutrient concentrations fluctuated but generally improved in the IMTA system, indicating lower mesotrophic conditions. Sediment fatty acid profiles differed between systems and toxicity assessments, which suggested a lower impact in IMTA and FM-IMTA systems. The sediment microbial community displayed high similarity within IMTA systems and between FM-IMTA and LFM-IMTA. These findings underscore the potential of IMTA systems for sustainable aquaculture, emphasizing improved growth performance and reduced environmental impact, particularly when using fish meal feeds.

Yield, nutrients uptake and lipid profile of the halophyte Salicornia ramosissima cultivated in two different integrated multi-trophic aquaculture systems (IMTA)

The nutrient removal, biomass production and nutritional value of the halophyte Salicornia ramosissima were evaluated in the context of an Integrated Multi-Trophic Aquaculture (IMTA) system. The experiment consisted of an indoor fish RAS whose effluent was used to feed two different halophyte hydroponic systems: a Nutrient Film Technique (NFT) system or a Deep Water Culture (DWC) system. The highest yield of S. ramosissima was observed in the DWC (320 g m−2 day−1), this system showed significantly higher yields compared to the NFT. Both hydroponic systems were effective in removing nutrients from the fish RAS wastewater, contributing to the wastes valorization process. Maximal nutrient uptake efficiencies were: 82.8% and 68.6% NO3− in the DWC and the NFT, respectively; 72.6% PO43− in the DWC and 82.9% in the NFT; 63.6% NO2− in the DWC vs 56.4% in the NFT; and 89.2% NH4+ in the DWC vs 94.1% in the NFT. The lipid profile of the halophytes in the DWC was analysed. The total lipid content ranged from 2.99% to 3.83%. The fatty acids (FA) profile in the leaves was dominated by polyunsaturated fatty acids (about 66%), which were represented by α-linolenic acid (41%) and linoleic acid (24%), followed by saturated fatty acids (28%) with palmitic acid (22%) as the major component. A small component of monounsaturated fatty acids accounts for about 12% of total FA. Regarding lipid classes, pigments were the most abundant compounds followed by glycolipids, phospholipids, flavonoids and sterols. The study supports the potential of S. ramosissima to valorise aquaculture wastes and its high nutritional interest. The experimental systems minimized waste and maximized resources utilization. Such integrated approaches can contribute to the sustainability and resilience of aquaculture systems while providing additional economic opportunities through the production of high value halophyte products.

Maximum entropy modelling to identify optimal locations for an IMTA system comprising Sparus aurata, Mytilus galloprovincialis and Ulva rigida on Europe’s Atlantic coastline

Meeting the resource demand for an increasing human population has led to the emergence of the aquaculture industry as the fastest growing sector for food production worldwide. Modern finfish aquaculture has raised environmental concerns and, to address this, Integrated Multi-Trophic Aquaculture (IMTA) has gained popularity as a means to minimise environmental impacts. This is done by culturing extractive species alongside fed species to utilise excess nutrients and enhance their own growth. The current study, based within the Atlantic Area of Europe, identified suitable habitats for the three species Sparus aurata, Mytilus galloprovincialis and Ulva rigida, for use in a new IMTA system. Models were created using MaxEnt software and input into GIS software (ArcMap 10.8.1) for analysis. For all species, the AUC results in the model were >0.9, with values of 0.931 (S. aurata), 0.928 (M. galloprovincialis) and 0.939 (U. rigida), demonstrating significant predictive power. Jackknife testing of the model for each species identified the mean sea surface temperature (°C) and Chlorophyll A (mg m–3) concentration as the two most important variables. The model showed that areas of >50% suitability could be found throughout the study area, although the most suitable sites were in coastal areas in more southern latitudes. To identify the feasibility of establishing an IMTA system in different areas, the shipping density, MPA status and the locations of harbours were added to the maps for further consideration. Using this study, and the species-specific information identified by the model, the aquaculture industry will be better equipped to identify potential IMTA sites and integrate these systems into the EU market for sustainable production.

Nitrogen excretion by the lobsters Panulirus ornatus and Thenus australiensis and uptake by the brown algae Sargassum siliquosum: Implications for integrated recirculated aquaculture systems

Farming extractive species such as macroalgae that take up nitrogen (N), with fed species (e.g., lobsters, finfish, prawns) is termed integrated multi-trophic aquaculture (IMTA). In recirculating aquaculture systems (RAS), high concentrations of nitrogenous waste can become toxic to the fed species and macroalgae offers a method of mitigating N waste. To utilise macroalgae as a biofilter for N waste, an understanding of their N ecophysiology of both the fed and extractive species is needed. In this study we first determine the ammonium and urea excretion rates for emerging aquaculture candidates the tropical rock lobsters, Panulirus ornatus (TRL) and slipper lobster, Thenus australiensis (SL). Using multiple flask uptake experiments, we then determined the N ecophysiology of the tropical brown macroalga, Sargassum siliquosum, to assess its potential use as a biofilter in a lobster RAS. Routine (basal) N excretion was predominantly ammonium with only a minor contribution of urea (8 and 13% for TRL and SL respectively). For both lobster species, ammonium and urea excretion substantially increased post-prandial, peaking at levels 3.6 times greater than basal amounts for TRL and 3.2 times greater for SL, and remained elevated for between 32 and 38 h. Uptake of both ammonium and nitrate by S. siliquosum showed saturating kinetics, where the kinetic parameter Vmax is the maximum rate of uptake, Ks is the half-saturation constant and the Vmax:Ks-ratio is a proxy for the algae's affinity of uptake for that respective nutrient: for ammonium Vmax = 110.9 μmoles g−1 dry weight (DW) h−1 and Ks = 37.9 μM and for nitrate Vmax = 152.7 μmoles g−1 DW h−1 and Ks = 58.52 μM. Urea uptake was highly variable with both positive and negative (i.e. urea release from tissue) rates recorded; when positive values were considered, Vmax = 55.5 μmoles g−1 DW h−1 and Ks = 17.65 μM. We used uptake and excretion rates from our study to derive a unit mass stocking ratio of algae to lobster (algae: animal) to offset N pollution in RAS. The ratios of TRL to algae to offset NH4+ and urea post-prandial were 5.15E-04 and 3.09E-04 respectively and for SL, 4.46E-04 and 6.31E-04 respectively. The findings serve as a reference for future studies on integrating Sargassum species into RAS and IMTA systems.

Temporal force governs the microbial assembly associated with Ulva fasciata (Chlorophyta) from an integrated multi-trophic aquaculture system.

Ulva spp., one of the most important providers of marine ecosystem services, has gained substantial attention lately in both ecological and applicational aspects. It is known that macroalgae and their associated microbial community form an inseparable unit whose intimate relationship can affect the wellbeing of both. Different cultivation systems, such as integrated multi-trophic aquaculture (IMTA), are assumed to impact Ulva bacterial community significantly in terms of compositional guilds. However, in such a highly dynamic environment, it is crucial to determine how the community dynamics change over time. In the current study, we characterized the microbiota associated with Ulva fasciata grown as a biofilter in an IMTA system in the Gulf of Aqaba (Eilat, Israel) over a developmental period of 5 weeks. The Ulva-associated microbial community was identified using the 16S rRNA gene amplicon sequencing technique, and ecological indices were further analyzed. The Ulva-associated microbiome revealed a swift change in composition along the temporal succession, with clusters of distinct communities for each timepoint. Proteobacteria, Bacteroidetes, Planctomycetes, and Deinococcus-Thermus, the most abundant phyla that accounted for up to 95% of all the amplicon sequence variants (ASVs) found, appeared in all weeks. Further analyses highlighted microbial biomarkers representing each timepoint and their characteristics. Finally, the presence of highly abundant species in Ulva microbiota yet underestimated in previous research (such as phyla Deinococcus-Thermus, families Saprospiraceae, Thiohalorhabdaceae, and Pirellulaceae) suggests that more attention should be paid to the temporal succession of the assembly of microbes inhabiting macroalgae in aquaculture, in general, and IMTA, in particular. Characterizing bacterial communities associated with Ulva fasciata from an IMTA system provided a better understanding of their associated microbial dynamics and revealed this macroalgae's adaptation to such a habitat.

Performance Evaluation of Aquaponics-Waste-Based Biochar as a Cathode Catalyst in Sediment Microbial Fuel Cells for Integrated Multitrophic Aquaculture Systems

The sustainable development of aquaculture faces a significant challenge due to the need for the frequent treatment of aquacultural waste. This research presents a pioneering solution by concurrently utilizing aquacultural waste to produce biochar and enhancing a sediment microbial fuel cell (SMFC)’s treatment efficacy for waste generated from the integrated multitrophic aquaculture (IMTA) system. The water quality parameters of the aquacultural pond water were analyzed, and synthetic wastewater was prepared to validate the system’s efficiency. Over a period of more than 50 days, the SMFC was operated and monitored, yielding an average chemical oxygen demand (COD) removal efficiency of 86.31 ± 2.18%. The maximum operating voltage of the SMFC reached 0.422 V on the 21st day of operation when connected to an external resistance of 975 Ω. A novel-activated aquacultural biochar catalyst was synthesized from aquaponics waste and used as a cathode catalyst, substantially improving the SMFC’s performance. Characterization studies demonstrated that the aquacultural biochar catalyst was an active electrocatalyst, accelerating the oxygen reduction reaction rate and leading to increased power output and overall efficiency of the SMFC. The SMFC utilizing the aquacultural-waste-based biochar cathode catalyst showcased the highest maximum power density, with a range of 101.63 mW/m2 (1693.83 mW/m3), and the lowest internal resistance, indicating superior performance. These results validate the reliability of implementing SMFCs in actual aquaculture systems. A novel modular design for SMFC reactor-assisted small-scale integrated poultry–fish culture systems is proposed for further practical application in real-life aquaculture settings. This research contributes to finding sustainable and effective methods for waste treatment for aquaculture, promoting the development of environmentally friendly practices in the industry.

Habitat suitability modelling for an integrated multi-trophic aquaculture (IMTA) system along Europe's Atlantic coast

As the human population grows, so too does the demand for resources. This demand has led to aquaculture becoming the fastest growing food production sector in the world. Due to environmental concerns associated with finfish aquaculture, Integrated Multi-Trophic Aquaculture (IMTA) has been proposed to minimise any negative impacts, by co-culturing extractive aquaculture species from different trophic levels to remove excess organic and inorganic nutrients, using them for their own growth. This study, in the Atlantic area of Europe, aimed to identify the most suitable locations to establish a new IMTA system for the 3 species Salmo salar (Linnaeus, 1758), Mytilus edulis (Linnaeus, 1758), and Laminaria digitata ((Hudson) JV Lamouroux, 1813). Habitat suitability models were created using spatial jackknifing testing within MaxEnt software and analysed using ArcGIS (ArcMap 10.8.1). All Maxent models were better than random when predicting species distribution, with AUC values of 0.889 (S. salar), 0.876 (M. edulis) and 0.901 (L. digitata), indicating a high level of predictive power. Jackknife testing identified Chlorophyll A (mg m−3) and Salinity (PSS) as the 2 most important variables in the model for each species. Coastal areas of the United Kingdom, Ireland and Northern France were identified as highly suitable, with suitability decreasing in more southern environments. These areas were then assessed based on local vessel density, whether they were within a Marine Protected Area (MPA), and the site accessibility from nearby ports, according to the expected needs of a large-scale aquaculture system. As MaxEnt used wild population data to produce the models, environmental conditions at suitable areas were compared against known Salmo salar aquaculture sites in Scotland to further validate the suitability for IMTA purposes. The results of this study, and the identification of optimal conditions for each species, will provide aquaculture businesses with the information required for preliminary site selection, with the goal of further incorporating IMTA systems into the EU market in a sustainable way.

Application of the IMTA (Integrated Multi-Trophic Aquaculture) System in Freshwater, Brackish and Marine Aquaculture

Application of the IMTA (Integrated Multi-Trophic Aquaculture) System in Freshwater, Brackish and Marine Aquaculture

Bivalves Improved Water Quality by Changing Bacterial Composition in Sediment and Water in an IMTA System

Integrated multitrophic aquaculture (IMTA) maximises the nitrogen cycle between system components, including bacteria. In order to maximise the bacterial role in nitrogen elimination in an IMTA system, we investigated the effect of bivalve culture on water quality and bacterial community structure in overlying water and sediment in the “shrimp-crab-bivalve-fish” IMTA system. The bacterial composition in overlying water and sediment was measured by Illumina -MiSeq high-throughput sequencing technology. The results show that dissolved oxygen was higher in the bivalve culture area. Ammonia and nitrite in the bivalve culture area were lower than those in the nonbivalve culture area; however, the nitrate and phosphate in the bivalve culture area were higher than those in the nonbivalve culture area. The Chao1, Shannon, and Ace indexes were higher in the bivalve area. More bacteria with nitrification and denitrification functions were detected in bivalve culture areas, such as Ruegeria (1.05%–4.79%), Thalassobius (0.11%–0.69%), Limibaculum (0.07%–0.69%), HIMB11 (0.13%–0.21%), and Rubellimicrobium (0.01%–0.16%). More Cyanobacteria were detected in bivalve culture areas with higher phosphate concentrations. To sum up, bivalves can release phosphorus through bioturbation, increasing the abundance of Cyanobacteria, which release dissolved oxygen into overlying water through photosynthesis, enhance nitrification (mainly ammonia oxidation), and improve the ammonia nitrogen removal capacity of the system. Meanwhile, bivalves can increase bacterial diversity and abundance by regulating dissolved oxygen. This study provided insight into bivalve interaction with bacterial activity in the IMTA system.

The green seaweed, Enteromorpha intestinalis: An efficient inorganic extractive species for environmental remediation and improved performances of fed species in brackishwater integrated multi-trophic aquaculture (BIMTA) system

Seaweed has vast utilization benefits, in terms of food, cosmetics, fertilizers, and extraction of industrial gums and chemicals. Moreover, in integrated multi-trophic aquaculture (IMTA), seaweed can be utilized as an inorganic extractive species, but a very few studies were conducted so far involving the green seaweed, Enteromorpha sp. An experimental trial of 60 days was executed to ascertain the effect of varied stocking densities of Enteromorpha intestinalis on growth parameters, survival and physiological status of milkfish, Chanos chanos and the Pacific white-leg shrimp, Penaeus vannamei, and bioremediation effect in brackishwater IMTA (BIMTA) systems. There were three BIMTA systems with different biomass densities of seaweed, 0.5 (T1), 1.0 (T2), and 1.5 (T3) kg m−3 placed in 1000 L FRP tanks stocked with C. chanos (3.50 ± 0.01 g) at 25 number m−3 and P. vannamei (4.25 ± 0.04 g) at 50 number m−3 as fed species. The control (polyculture) had same number of milkfish and shrimp with no seaweed. Three treatments and control were maintained in triplicate. The fed species were provided with a polyculture feed containing 30% crude protein at 5% of the biomass daily. The results displayed that nitrogenous and phosphorus compounds were significantly lower (P < 0.05) in all three BIMTA treatments compared to the control. A better growth (P < 0.05) of C. chanos (12.52 ± 0.24 g) and P. vannamei (14.77 ± 0.35 g) was obtained in T3 and T2 BIMTA systems, respectively when compared with the control (milkfish: 11.01 ± 0.08 g, shrimp: 11.79 ± 0.58 g). Survival in shrimp was the highest in T3 treatment, but in milkfish, survival did not vary between different systems (P > 0.05). The blood (red blood cells, white blood cells and haemoglobin) and haemolymph (haemocyanin and total haemocyte count) parameters were better in fish and shrimp, respectively under BIMTA at harvest. Presence of seaweed provided a significant positive effect on the welfare parameter (glucose), whereas stress parameters (catalase, superoxide dismutase and cortisol) were comparatively low in fed species of BIMTA treatments than that of polyculture system. This trial suggested that T2 and T3 performed better among all and E. intestinalis can be an efficient inorganic extractive species for BIMTA at the optimum stocking density of 1.0–1.5 kg m−3.

Life history traits for Ophryotrocha craigsmithi (Wiklund, Glover &amp; Dahlgren, 2009), a candidate species in integrated multitrophic aquaculture

Ophryotrocha craigsmithi (Wiklund, Glover &amp;amp; Dahlgren, 2009) has repeatedly been observed in high densities at salmonid fish farms in Norway and has been shown to feed on the organic waste released during fish production. This species has therefore been pointed out as a candidate for the benthic component of integrated multitrophic aquaculture (IMTA). Little is known about the life history traits of Ophryotrocha species found at greater depths in temperate waters. Insight into life traits is of key importance in evaluating the bio-mitigation and harvest potential of (benthic) species within IMTA systems. In this study, we aimed to describe key life history traits for O. craigsmithi, such as growth, reproductive pattern, and offset of reproduction. The main findings are as follows: (I) O. craigsmithi exhibits early sexual maturation and rapid growth, going from 5 to 16 mm in length in 8 weeks; (II) their estimated lifetime is approximately 15 weeks with a generation time of 4 weeks; (III) there are strong indications that they are gonochoric semicontinuous spawners; (IV) the majority of mature eggs ranged from 120 to 150 µm; and (V) the larvae developed into a free-swimming stage after approximately 1 week. To this end, we present a framework for assessing the suitability of deposit-feeding polychaetes as candidate species in IMTA, considering environmental adaptiveness, production potential, as well as carbon and nitrogen mitigation capacity. On the basis of this, O. craigsmithi shows a high suitability as an extractive farmed species in benthic IMTA.

Perspectives for Exploitation of Sabella spallanzanii’s Biomass as a New Integrated Multi-Trophic Aquaculture (IMTA) By-Product: Feeding Trial on Amphiprion ocellaris Using Sabella Meal

This paper is part of a series of studies aimed at understanding the potential exploitation of the biomass of the polychaete worm Sabella spallanzanii (Gmelin, 1791), which is obtained as a by-product of an innovative Integrated Multi-Trophic Aquaculture (IMTA) system. IMTA systems are designed according to an ecosystem approach with the aim to reduce marine monoculture impact while further increasing production via exploitation of valuable by-products. S. spallanzanii can remove large amounts of suspended matter by filtering large volumes of water per hour and performs well as an extractive organism under IMTA; however, it currently lacks any economic value, thus hindering its sustainable large-scale implementation. However, S. spallazanii has the potential to become competitive as a newcomer in fish bait, as an ornamental organism, and in fish feed markets. Notably, sabella meal has already been successfully tested as an attractant in an innovative fish feed. Here, we refer to the use of sabella meal as the main component (60%) in the formulation of a novel aquarium fish feed. Following the biochemical analysis of farmed sabella meal, the experimental feed was formulated by adding spirulina (25%) and dry garlic (15%) in such proportion as to be isoproteic and isoenergetic to the commercial control feed. After preliminary observations of the palatability of sabella meal for several tropical fish species, the novel experimental feed was tested on ocellaris clownfish, Amphiprion ocellaris (Cuvier, 1830), by evaluating their growth response in a 70-day feeding trial. The fish seemed to enjoy the experimental feed at least as much as the control, and both the control and treatment groups showed no significant differences in weight gain (p = 0.46), specific growth rate (p = 0.76), and feed conversion ratio (p = 0.48), reinforcing the suitability of S. spallanzanii as a viable source of animal proteins to be employed in the fish feed industry in a circular economy perspective.

Can IMTA provide added ecosystem value services in the fish farms of Greece?

In addition to food supply, there is a growing recognition of the wider ecosystem benefits of Integrated Multitrophic Aquaculture (IMTA) systems in coastal waters, including regulating services such as carbon sequestration and nutrient remediation. The water trophic status and the co-cultured species combinations affect IMTA productivity. In this study, we examined the ability of different combinations of IMTA organisms to remediate nutrients and the economic/environmental gain for reducing the environmental footprint in potential IMTA systems of the eastern Mediterranean. The results showed that the co-cultivation of organisms can reduce the negative effects on the marine environment of a fish farm both on the water column and the sediment. Meso- and eutrophic water states do not show a high variation in terms of foot print mitigation, with all three of the co-cultivated organisms to perform well. In oligotrophic waters, the obligatory absence of mussels reduces the effectiveness of the IMTA system. As expected, larger-sized IMTA systems have higher production rates and as a result higher percentage of nutrient removal. Finally, bivalve harvesting helps to remove the carbon that is trapped in their shells, contributing to the mitigation of processes related to climate change, such as the acidification of the oceans.

Sponges as Emerging By-Product of Integrated Multitrophic Aquaculture (IMTA)

The use of marine sponges dates back thousands of years, and interest in these animals is increasing as new applications are discovered. Their potential is extensive, both in their ancient and still popular use as bath sponges for cosmetics and regarding the more recent discovery of bioactive secondary metabolites mainly of interest for the pharmaceutical industry and the less developed aquariology. Despite their proven biofiltration and ecosystem restoration ability and the biomass supply problem for the interested industries, few integrated multi-trophic aquaculture (IMTA) systems incorporate these invertebrates in their facilities. Therefore, in this brief review, the benefits that marine sponges could bring to rapidly growing IMTA systems are summarized, highlighting their suitability for a circular blue economy.

Potential of innovative marine aquaculture techniques to close nutrient cycles

AbstractAquaculture is an established technique for producing marine species. However, it creates large amounts of nutrient‐rich waste. Therefore, it is worth examining the methods available to use these nutrients and close the nutrient cycle. This review covers research activities of different saline water methods for food production. These are Integrated Multi‐Trophic Aquaculture (IMTA), Biofloc Technology (BFT) and marine aquaponics. IMTA combines on‐ and offshore aquaculture with macroalgae and filter feeder production. Commercial implementations have been achieved but are not widely used. Especially shrimp are suitable for cultivation in saline BFT systems. Few commercial deployments exist. There is a well‐established market for the products of IMTA and BFT systems. Marine aquaponics is increasingly being tested as part of an expansion of Recirculating Aquaculture Systems (RAS) and BFT systems, but commercial implementations are not known. Moreover, there is no established market for the resulting salt‐tolerant plants (halophytes). Market prices and popularity were evaluated to assess the economic potential of the different plant and aquaculture species farmed with IMTA, BFT and marine aquaponics. There are established markets for well‐known products, but therefore the competition is greater. Niche products are offered occasionally, but often achieve top prices. Closing nutrient cycles and increasing saline water usage for food production as well as high product diversity are necessary to mitigate the increasing pressure on freshwater resources and to be able to feed the growing world population. Therefore, IMTA, BFT and marine aquaponics are promising techniques for reducing pressure on freshwater resources and improving food supply.

A Comparative Approach to Detect Macrobenthic Response to the Conversion of an Inshore Mariculture Plant into an IMTA System in the Mar Grande of Taranto (Mediterranean Sea, Italy)

The expected bioremediation effect, driven by the conversion of an inshore mariculture plant into an Integrated Multi-Trophic Aquaculture (IMTA) system, which could mitigate the fish farm impact, related to the accumulation of organic matter on the seabed, has been studied. The ecological quality status was studied following a Before-After-Control-Impact (BACI) design and variation measured through M-AMBI and compared with the results of univariate and multivariate analyses of variance, to evaluate the sensitivity of the two methodologies. Results from M-AMBI indicated a sharp change in the ecological quality status, just after one year of the conversion of the plant. By contrast, although changes were detected also utilizing univariate and multivariate statistical analysis, the natural temporal variability characterizing the area partially masked evidence of environmental amelioration.