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

Stable isotope ratios, carbon (δ13C) and nitrogen (δ15N), and fatty acids validated the trophic connection between farmed fish in a commercial nearshore fish farm and sea cucumbers in the Mediterranean Sea. This dual tracer approach evaluated organic matter transfer in integrated multi-trophic aquaculture (IMTA) and the ability of sea cucumbers to incorporate fish farm waste (fish faeces and uneaten artificial fish feed) into their tissue. Between October 2018 and September 2019, Holothuria (Roweothuria) poli Delle Chiaje, 1824, co-cultured at IMTA sites directly below one of the commercial fish cage , at 10m and 25m from the selected fish cage, and at two reference sites over 800m from the fish farm. Sea cucumbers were sampled from each site in February, May and September, except at 0m due to mass mortalities recorded here in the first month of study. Isotopic mixing models revealed that fish farm organic waste was the dominant dietary source for H. poli in IMTA at 10m and 25m from the cage. The contribution of marine plant-derived organic matter, Posidonia oceanica leaves and rhizomes, was least important. The isotopic signatures of sea cucumber tissues at reference sites were not explained by the sampled food resources. Importantly, fatty acid profiling revealed a high abundance of individual terrestrial plant fatty acids, such as oleic (18:1n-9), linoleic (18:2n-6) and eicosenoic (20:1n-9) acids in sea cucumber tissue at 10m and 25m from the fish cage, presumably linked to the terrestrial plant oil content of the fish feeds. At the reference sites, sea cucumber tissues were characterised by higher relative abundance of arachidonic acid (20:4n-6) acid, and the natural marine-based eicosapentaenoic (20:5n-3) and docosahexaenoic (22:6n-3) acids. These analyses revealed important differences in the composition of H. poli between the IMTA and reference locations, driven by aquaculture-derived waste near fish cages. Moreover, this study revealed temporal variation in food availability and quality, and possible differences in the physiological responses of H. poli. Stable isotope analysis and fatty acid profiling provided complementary evidence for the important dietary preferences of H. poli and validated the potential of sea cucumbers to uptake aquaculture organic waste as part of inshore fish-sea cucumber IMTA. It reveals the important implications that an established trophic link has on the viability of using sea cucumbers for the development of IMTA and the sustainable expansion of aquaculture.

Culturing the sea cucumber Holothuria poli in open-water integrated multi-trophic aquaculture at a coastal Mediterranean fish farm

Fish farming in open water releases dissolved and particulate waste (inorganic and organic) into the surrounding marine environment. To reduce this environmental impact, commercial extractive species can be grown alongside to utilize and reduce this waste, a technique known as integrated multitrophic aquaculture (IMTA). Information is lacking on whether (i) IMTA is generally successful with respect to extractive species growth responses and (ii) at what spatial scale they can be cultivated from fish cage nutrient sources. Focussing on bivalves and macroalgae as extractive species, this study uses a meta‐analysis approach to summarize and conclude peer‐reviewed data on IMTA to address these information gaps. We show that there are clear benefits to integrating bivalves and macroalgae with fish farms. Bivalves grown within, and relatively near, fish cages (0 m and 1–60 m distance categories, respectively) showed significantly higher biomass production relative to controls compared to those grown at larger spatial scales (61+ m). However, biomass production of macroalgae was significantly higher than controls only within close proximity to fish cages (0 m). This information shows increased extractive species production is generally greatest at relatively small spatial scales. It also highlights the need for more site‐specific information (e.g. seawater parameters, hydrodynamics, food supply, farm capacity) in future studies. The allocation of control sites and locating these at suitable distances (>1–8 km) from fish farm effluent sources to avoid fish farm nutrient contamination are also recommended.

Integrated multi-trophic aquaculture of red drum (Sciaenops ocellatus) and sea cucumber (Holothuria scabra): Assessing bioremediation and life-cycle impacts

Integrated multitrophic aquaculture (IMTA) is an innovative mariculture methodology that reduces the environmental footprint and increases the profitability of the farm. It combines the cultivation of species belonging to different trophic levels, simulating a natural food web. In this study, five Mediterranean species were co-cultured in three operating fish farms in the Aegean (E. Mediterranean) Sea with different trophic conditions. The co-cultivated species were sea bream (Sparus aurata), European sea bass (Dicentrarchus labrax), Mediterranean mussel (Mytilus galloprovincialis), rayed pearl oyster (Pinctada imbricata radiata), and sea cucumber (Holothuria polii). Bream, bass, and mussels were cultivated according to the traditional on-growing methods (fish cages and longlines), whereas the pearl oysters and sea cucumbers were cultivated in baskets designed specifically for oyster farms. To estimate the growth of the co-cultivated species, growth indicators were calculated using length and weight measurements. Furthermore, the growth measurements from co-cultivated species were compared to the respective ones from natural populations. All the species showed high survival rates in the integrated multitrophic aquaculture (IMTA) conditions. Pearl oysters and Mediterranean mussels had positive growth in fish farms with high concentrations of nutrients. Mussel condition index (CI) was 42% in Aquaculture 1 (Aq1) and 33% in Aquaculture 2 (Aq2), compared to 35% in a typical Mediterranean mussel farm. Pearl oysters CI in Aq1 was 53%, in Aq2 56%, in Aquaculture 3 (Aq3) 19%, and in natural populations ranging from 30% to 45%. In contrast, holothurians did not gain weight under the fish cage regime despite the high survival rate. Their final total weight was 17.3 g in Ag1, 8.3 g in Aq2, and 18.3 g in Aq3, but in the natural population, the mean weight was 80 g.

Survival, growth, food selection and fecal production of the sea cucumber Holothuria leucospilota bottom-cultured at different sites in a subtropical bay.

Testing the digestibility of seabream wastes in three candidates for integrated multi-trophic aquaculture: Grey mullet, sea urchin and sea cucumber

Commercial salmonid farming is typically performed in open-water net cages where interactions between the environment and production unit might be widespread and not easily predicted or controlled. Integrated multi-trophic aquaculture (IMTA) has been suggested to mitigate some of the environmental impacts. Based on empirical data, the assimilation of particulate waste from a commercial fish farm was modeled by two approaches to salmon/blue mussel IMTA: a system with mussels at the surface next to the fish farm and an alternative setup with mussels submerged under the farm. According to the model, 15% of the feed was defecated and assumed available to the mussels and the submerged mussel farm could assimilate 14.6% of the feces. Sensitivity analysis showed that the current speed, the mussel filtration rate, and the proportion of the material that settles slowly had an impact on this assimilation estimate, which could be significantly higher. However, the model did not include assimilation limitations due to particle size, which may contribute significantly to the submerged farm. The mussel farm at the surface mainly received small slow settling particles, and according to the model, only 0.4% of the fish farm waste was assimilated. The maximum obtainable assimilation was 5.5%. The fraction of slowly settling waste had the most pronounced influence on waste assimilation in the mussel farm at the surface. This is also among the most uncertain parameters, since the relative portion of different settling velocities of fish feces is highly variable, and more information on the size distribution of waste is needed.

Is Holothuria tubulosa the golden goose of ecological aquaculture in the Mediterranean Sea?

Abstract: World aquaculture has been growing sharply in recent decades and Brazilian production of fish in cages has grown considerably since the end of the 1990s. This increase is related to the development of federal government regulations and the large number of medium and large hydroelectric reservoirs. The main areas of fish production in cages in Brazil are currently located in the Northeast and Southeast regions and along the Southeast/South border. Tilapia production in cages in Brazil, as well as other species produced in cages in other regions of the world, has economic advantages for the producer. On the other hand, limnologically, tilapia production in cages causes enormous damage, as it promotes the process of artificial eutrophication and, possibly, introduces this exotic species. One way of reducing artificial eutrophication is the use of Integrated Multi-trophic Aquaculture (IMTA); however, its use in fish cages installed in Brazilian reservoirs is not possible yet. Therefore, our view is that government agencies restrict the production of fish in cages to the utmost.

Technical feasibility of integrating Amazon river prawn culture during the first phase of tambaqui grow-out in stagnant ponds, using nutrient-rich water

The present study investigated the applicability of integrated polychaete-fish culture for fish waste removal to offset negative impact induced by organic benthic enrichment. A field study demonstrated that deposition rate was significantly higher underneath the fish farm than that in control area. The material settling under the farm was characterized by a high amount of fish feces (45%) and uneaten feed (27%). Both feeding rate (FR) and apparent digestibility rate (ADR) increased with decreasing body weight, as was indicated by significantly a higher rate observed for the groups containing smaller individuals in a lab study. The nutrient in fresh deposited material (De) was higher than that in sediments collected under the farm (Se), resulting in lower feces production but higher apparent digestibility rate for the De group as feeding rate was similar. Consequently, higher nutrient removal efficiency was observed in the De group. A mass balance approach indicated that approximately 400–500 individuals m−2 is required for removing all waste materials deposited underneath the fish farm, whereas abundance can be lower (about 300–350 individuals m−2) when only the fish waste needs to be removed. The results showed that a significant amount of waste had been accumulated in the fish cages in Sanggou Bay. The integration of fish with P. aibuhitensis seems promising for preventing organic pollution in the sediment and therefore is an effective strategy for mitigating negative effect of fish farms. Thus such integration can become a new IMTA (integrated multi-trophic aquaculture) model in Sanggou Bay.

This paper presents the results of growth rate and condition index analysis of Mytilus galloprovincialis in integrated system and monoculture. The aim of this study was to show if there are differences in growth and condition index of mussels between integrated multi-trophic aquaculture (IMTA) and monoculture farming. The growth rate and condition index were monitored during a 13-month study at three different sites: 1) close to fish cages (NBL), 2) 100 m removed from fish cages (NUD), 3) at a monoculture mussel farm (SVN) around 8 km far away from cages. The most intense growth of mussels was recorded in spring, and the least intense in summer. After 13 months, monitored individuals at all three locations achieved commercial size. The growth rate was very similar at all sites. The condition index showed spatial and temporal differences. Condition index values on site NUD were mostly higher compared to SVN and NBL, which were very similar, exept for the period from October to December when CI was similar on NBL and NUD site and higher in comparation with SVN. CI values on NBL an NUD site during cold period indicate on fact that mussels probably feed on the nutrients from fish farm origins.The highest mortality rate was recorded at the NBL site, probably due to the effects of fouling organisms.

Integrated open-water mussel ( Mytilus planulatus) and Atlantic salmon ( Salmo salar) culture in Tasmania, Australia

Role of deposit feeders in integrated multi-trophic aquaculture — A model analysis