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ARS Home » Northeast Area » Leetown, West Virginia » Cool and Cold Water Aquaculture Research » Research » Research Project #428109

Research Project: Developing and Refining Technologies for Sustainable Fish Growth in Closed Containment Systems

Location: Cool and Cold Water Aquaculture Research

2018 Annual Report


Objectives
Objective 1. Develop technically advanced, environmentally compatible, and sustainable closed production systems and techniques Sub-objective 1.1 Optimize the cost and effectiveness of technologies to remove nitrogen and phosphorus from recirculating aquaculture systems and their effluent. a) Optimize system water quality and evaluate salmonid performance when using membrane biological reactors to digest biosolids, remove nitrate, and practically eliminate water flushing requirements in each water recirculating system module. b) Evaluate effectiveness of woodchip bioreactors for treating the effluent from water recirculating systems. Sub-objective 1.2 Increase the energy efficiency of CO2 degassing technologies. Sub-objective 1.3 Use refinements in water treatment process design and economies of scale to decrease the capital cost required per tonne of fish produced within water recirculating systems. Objective 2: Improve salmonid performance, health and well-being in land-based systems through research on nutrition, rearing environment, and control of pathogens and fin erosion. Sub-objective 2.1 Field-test rainbow trout germplasm resources when reared to 2kg harvest size within intensive water reuse systems and ID top performing individuals and families. Sub-objective 2.2 Compare the effects of alternate protein (zero fish meal) versus fishmeal-based diets on growth performance and welfare of select families of Troutlodge rainbow trout when reared to 2 kg. We will also measure water quality, water treatment process performance, and waste production rates in recirculating aquaculture systems operated at low flushing rates. Sub-objective 2.3 Identify strategies to minimize losses of Atlantic salmon smolt to Saprolegnia infections following vaccination in water recirculating systems.


Approach
The ability to provide U.S. consumers with high-quality, sustainably-produced seafood hinges upon research that supports increased domestic aquaculture production and the development of new and improved technologies. This proposed work encompasses several USDA ARS Action Plan components, primarily technology development for sustainable production systems (Component 4), alternative protein investigation (Component 2), and disease prevention (Component 3). The first objective, which is focused on recirculating aquaculture system (WRAS) technology development, will investigate two water qualityimprovement technologies: (1) low-cost woodchip bioreactors for nitrate removal from aquaculture effluents, and (2) membrane biological reactors that produce a clean filtrate for reuse in the WRAS, which eliminates makeup water flushing and the point-source discharge. Refinement of water treatment processes and use of economies of scale to reduce capital costs of WRAS will also be a key focus. This work will also investigate a new and potentially more energy efficient and cost-effective carbon dioxide stripping technology. Within the second overarching objective, we will evaluate the performance of commercially available rainbow trout strains (fingerling to 2 kg) cultured in WRAS, and will identify strategies to minimize Saprolegnia infections in Atlantic salmon smolt cultured in WRAS after vaccinations. In addition, pressing societal concerns about the sustainability of fish feed and the rising cost of fish meal provide the emphasis to compare the effects of alternate protein (zero fish meal) and fishmeal-based feed formulations on trout health and performance, waste production, and water quality. Through this work plan, we are eager to support the USDA in their forward-thinking efforts.


Progress Report
The overall goal of this project is to develop and improve technologies that enhance sustainability and reduce the environmental impacts of the modern U.S. fish farming industry. Progress was made within both specific research objectives that support this overall goal. Objective 1 aims to develop technically advanced, environmentally compatible, and sustainable closed production systems and techniques. In response to increasing eutrophication from high nitrogen (N) and phosphorus (P) inputs, nutrient reduction goals have been established in areas including the Mississippi River basin and Chesapeake Bay watershed. Both point source aquaculture effluents and diffuse agronomy nutrient sources are suitable for innovative nutrient removal technologies. This project began in FY2017, and we have continued in FY2018 to evaluate relatively low-tech and inexpensive trenches filled with woodchips that fuel heterotrophic bacteria that in turn remove nitrate nitrogen, phosphorus, and suspended solids from aquaculture effluent. We have previously observed that relatively high levels of suspended solids in certain aquaculture effluents can create plugging and hydraulic problems in woodchip bioreactors operated over extended periods or at short hydraulic retention times, and therefore the present study (FY2017-2018) is evaluating an improved flow distribution system to determine treatment efficiency and deviation in hydraulic grade line due to plugging after long-term operation. We also finished assessing the ability of membrane biological reactors to produce a clean filtrate for reuse in the fish production system (sub-objective 1.1a). By digesting biosolids produced by the fish and removing nitrate, this technology eliminated makeup water flushing requirements and the point-source discharge, allowing more flexibility in locating and permitting fish farms. Also, in support of Objective 1, cost and engineering assessments were further refined to characterize the economics of specific technologies for recirculating aquaculture systems. We continued our engineering assessment of water recirculating aquaculture system design and scale to identify critical factors impacting the economics of land-based closed-containment systems for salmon production (sub-objective 1.3). This engineering assessment included the biological planning, concept design, and cost assessment at several production levels, i.e., 1,200, 2,400, 3,000, and 4,800 tonnes of annual production. We also worked with engineers from a large commercial supplier to contrast the differences in capital costs between two different technology platforms at increasing scale. The modular nature of RAS (recirculating aquaculture system) facility designs suggests that there are only limited economies of scale beyond 3,000 tonnes. These findings address several of the largest technology challenges facing domestic producers by providing new technology to reduce capital costs, improve energy efficiency, reduce water requirements, and increase nutrient removal at these farms. The aim of Objective 2 is to identify culture practices to improve the performance of Atlantic salmon and rainbow trout produced in water recirculating systems. The intensity of water recirculation in these production systems produces a nutrient-rich environment with a diverse microbiome and potential to negatively impact the performance or welfare of the fish being cultured. To combat the harmful effects of nitrate accumulation and to dispose of concentrated waste biosolids many RAS are operated with makeup water as high as 0.3-3% of the total recirculating flow. However, complete closure of the RAS may be possible with membrane biological reactors. Using a series of membranes, a bioreactor operates with an activated sludge of suspended bacteria that is cycled between anoxic and aerobic stages so that complete nitrification and denitrification can occur. The ultra-filtration membranes exclude particulates, even bacteria, from escaping into the permeate that is withdrawn from the bioreactor as more system backwash water enters. We completed a study in six RAS, three with membrane biological reactors that digested biosolids produced by the fish, removed nitrate-nitrogen, and allowed backwash water that is normally wasted to be reclaimed. Membrane biological reactors almost eliminated water flushing requirements and bicarbonate addition requirements, as the mean hydraulic retention time of water in the system exceeded 100 days. Carbon provided by residual fish biosolids, however, was insufficient to sustain heterotrophic bacteria removal of all nitrate nitrogen. Thus, a carbon source (sucrose) was added at about 1% of the fish feed supplied over the same period, which was sufficient to reduce nitrate levels. As a result, only 1% of the total system volume had to be replaced, which is a nearly 10-fold reduction in water flushing requirement in many RAS. This technology ultimately decreases water resource use, decreases effluent volume and treatment requirements, increases the flexibility for siting near major seafood markets, and potentially eliminates point-source discharge. This research also determined that RAS containing membrane biological reactors were able to provide comparable rainbow trout growth, welfare, and product quality as systems operated more flushing. The technology was transferred at least one commercial U.S. RAS producer. Male Atlantic salmon tend to mature early – at a mean size of approximately 2 kg – when cultured in warm 13-15°C freshwater systems. To avoid early maturing males, we conducted two studies that examined the performance of all-female Atlantic salmon when cultured to market-size (> 4 kg) in relatively warm freshwater systems. Salmon sampled for gonadal size in the first study (2009-2010) found no female maturation when two strains of Atlantic salmon were cultured at approximately 13°C in a freshwater reuse system to market size (4 kg). The second study (2017-2018), however, found high levels of female maturation in an all-female germplasm, for unknown reasons. There is currently one commercial Atlantic salmon producer using land-based systems in the U.S. – and several other farms globally – that culture all-female germplasm to avoid the potential economic losses created with early maturing male salmon. In support of Objective 2.3 and as a follow-up to our research assessing post-vaccination saprolegniasis prevention using daily pulse applications of low-dose peracetic acid (PAA), we conducted a study assessing daily semi-continuous, low-dose PAA administration as a strategy to replace ozone in water recirculating systems, through a comparison of water quality, fish health, performance, and welfare, and fillet off-flavor content. Rainbow trout growth performance was not affected by semi-continuous PAA addition at any of the doses evaluated. Preliminary analyses indicate that oxidative reduction potential (ORP) and true color were affected at certain PAA doses. ORP was generally greater in RAS where PAA was added and true color was slightly lower. Nitrification was not negatively impacted. In addition, concentrations of the off-flavor compounds geosmin and 2-methylisoborneol in water, biofilm, and trout fillets were not affected by PAA at the tested doses. Overall, PAA dosing within the selected concentration range was compatible with rainbow trout production and RAS operation; however, PAA dosing did not create dramatic improvements in true color and did not improve total suspended solids, biochemical oxygen demand, dissolved metals, or ultraviolet transmittance levels, as has been reported in previous experiments when applying a relatively low, non-disinfecting ozone dose. The effect of PAA on ORP is an important finding and indicates potential for continuously monitored ORP to be integrated as an on/off control for PAA dosing in RAS. We also studied a novel bacterial agent, Flectobacillus roseus, that demonstrated ability to colonize RAS to levels that where detrimental to fish health. F. roseus has only been identified recently in Asian aquaculture and has been responsible for the disease condition known as flectobacillosis. We cultured F. roseus from replicated RAS and worked with ARS scientists to demonstrate that rainbow trout maintain high F. roseus-specific circulating antibodies following exposure to high waterborne bacterial counts. Under controlled pathogen challenge conditions, however, we were unable to replicate morbidity or mortality following injection of naïve juvenile rainbow trout with varying doses of F. roseus, leading us to conclude that this is not a direct pathogen of rainbow trout and therefore might only be associated with rainbow trout mortality as a consequence of the highly elevated total suspended solids observed during bacterial blooms in RAS. This collaboration is ongoing and further investigations as to the source of F. roseus (e.g., spring water, feed, etc.) will be carried out. At present, the results of this study are remarkable in that this is the first time we have documented that a single bacterial species can dominate a RAS culture tank microbiome, despite published theories to the contrary, i.e. that microbially-matured RAS water is resistant to rapid proliferation of opportunistic agents. These studies are providing new technologies, tools, and information contributing to improved precision culture systems to meet current and future fish production needs of domestic fish farmers and diverse consumers, while minimizing the environmental footprint of production and enhancing fish welfare.


Accomplishments
1. Growth and fillet quality in commercially available rainbow trout. Determining if commercially available rainbow trout exhibit variable growth performance and fillet quality in recirculating aquaculture systems (RAS) is critical to identifying genetic lines that maximize profitability. ARS extramural researchers in Shepherdstown, West Virginia, determined that there was considerable variation in growth performance between genetic lines of rainbow trout; the fastest growing line reached 3 kg while the slowest line lagged 30% behind. These findings indicate that farmers interested in maximizing product yield on either a fractional (percent yield) or absolute basis (total biomass) should familiarize themselves with the growth potential of available stocks before purchasing eggs or fish for their system. In contrast, indices of fillet quality such as the nutrient profile, texture, and color did not differ among commercial genetic lines. Therefore, a farmer or processor who values optimal fillet quality above growth-related traits can be more flexible in their genetic stock selection. Researchers also defined changes in processing yields and indices of fillet quality at different harvest weights throughout the production cycle, providing valuable data that RAS producers can use to predict growth trajectories and fillet characteristics.

2. Use of woodchip bioreactors for the removal of nutrients and suspended solids from fish farm effluents. As with all intensive agricultural systems, fish farms produce waste that has the potential to impact the surrounding environment. Certain aquatic environments, such as Chesapeake Bay and the Mississippi River basin, have become significantly impacted by the agricultural release of nutrients and other effluent components into their ecosystems. Woodchip bioreactors are trenches containing woodchips which in turn fuel heterotrophic bacteria that remove nitrogen (N) and total suspended solids (TSS) from passing effluent. ARS extramural researchers in Shepherdstown, West Virginia, established that woodchip bioreactors can capture the percent of NO3-N and percent of TSS from aquaculture effluent streams to minimize nutrient discharge into surrounding waterways. A cost and engineering assessment shows that the woodchip bioreactor is a relatively low cost, low maintenance technology to treat aquaculture effluent and reduce environmental impacts and wastewater treatment costs.


Review Publications
Waldrop, T., Summerfelt, S.T., Mazik, P., Good, C. 2018. The effects of swimming exercise and dissolved oxygen on growth performance, fin condition and precocious maturation of early-rearing Atlantic salmon Salmo salar. Aquaculture Research. 49(2):801-808. https://doi.org/10.1111/are.13511.
Good, C., Davidson, J., Earley, R.L., Styga, J., Summerfelt, S.T. 2017. The effects of ozonation on select waterborne steroid hormones in recirculation aquaculture systems containing sexually mature Atlantic salmon Salmo salar. Aquacultural Engineering. 79:9-16. https://doi.org/10.1016/j.aquaeng.2017.08.004.
Crouse, C., Davidson, J., Good, C., May, T., Summerfelt, S., Kenney, P., Leeds, T.D., Cleveland, B.M. 2018. Growth and fillet quality attributes of five genetic strains of rainbow trout (Oncorhynchus mykiss) reared in a partial water reuse system and harvested at different sizes. Aquaculture Research. 49:1672-1681. https://doi.org/10.1111/are.13623.
Chun, C., Vinci, B., Timmons, M. 2018. Computational fluid dynamics characterization of a novel mixed cell raceway design. Aquacultural Engineering. 81:19-32. https://doi.org/10.1016/j.aquaeng.2018.02.002.
Good, C., Davidson, J., Terjesen, B., Takle, H., Kolarevic, J., Baeverford, G., Summerfelt, S. 2018. 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. Aquacultural Engineering. 81:1-9. https://doi.org/10.1016/j.aquaeng.2018.01.003.
Gorle, J.M., Terjesen, B.F., Mota, V.C., Summerfelt, S.T. 2018. Water velocity in commercial RAS culture tanks for Atlantic salmon smolt production. Aquacultural Engineering. 81:89-100. https://doi.org/10.1016/j.aquaeng.2018.03.001.
Christianson, L.E., Feyereisen, G.W., Lepine, C., Summerfelt, S.T. 2018. Plastic carrier polishing chamber reduces pollution swapping from denitrifying woodchip bioreactors. Aquacultural Engineering. 81:33-37. https://doi.org/10.1016/j.aquaeng.2018.01.001.
Gorle, J.M., Terjesen, B.F., Summerfelt, S.T. 2018. Hydrodynamics of octagonal culture tanks with Cornell-type dual-drain system. Computers and Electronics in Agriculture. 151:354-364. https://doi.org/10.1016/j.compag.2018.06.012.
Davidson, J., Good, C., Williams, C., Summerfelt, S. 2017. Evaluating the chronic effects of nitrate on the health and performance of post-smolt Atlantic salmon Salmo salar in freshwater recirculation aquaculture systems. Aquacultural Engineering. 79:1-8. https://doi.org/10.1016/j.aquaeng.2017.08.003.
Davidson, J., Kenney, P., Barrows, F., Good, C., Summerfelt, S. 2017. Fillet quality and processing attributes of postsmolt Atlantic salmon, Salmo salar, fed a fishmeal-free diet and a fishmeal-based diet in recirculation aquaculture systems. Journal of the World Aquaculture Society. 49(1):183-196. https://doi.org/10.1111/jwas.12452.
Good, C., Iwanowicz, L., Meyer, M., Davidson, J., Dietze, J., Kolpin, D., Marancik, D., Birkett, J.E., Russell, C., Summerfelt, S. 2016. Investigating the influence of nitrate nitrogen on post-smolt Atlantic salmon Salmo salar reproductive physiology in freshwater recirculation aquaculture systems. Aquacultural Engineering. 78:2-8. https://doi.org/10.1016/j.aquaeng.2016.09.003.
Redman, N., Good, C., Vinci, B. 2017. Assessing the utility of ultraviolet irradiation to reduce bacterial biofilms in fish hatchery well water supplies. Journal of Aquaculture Research and Development. 8(7):1000501. https://doi.org/10.4172/2155-9546.1000501.
Summerfelt, S.T., Mathisen, F., Holan, A., Terjesen, B. 2016. Survey of large circular and octagonal tanks operated at Norwegian commercial smolt and post-smolt sites. Aquacultural Engineering. 74:105-110.
Vinci, B., Davidson, J., Naveh, E., Engler, O. 2016. Low head oxygenator performance characterization for marine recirculating aquaculture systems. Aquacultural Engineering. 22:22-28.