Location: Cool and Cold Water Aquaculture Research
2016 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 was to develop and improve technologies that enhance the sustainability and reduce the environmental impacts of the modern fish farming industry. Progress was made within both of the 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 support of this objective we investigated the potential for woodchip bioreactors to remove nitrate in row crop tile drainage and aquaculture effluent applications. A benchtop column experiment was completed that paired columns of woodchips for denitrification-based nitrogen removal with columns of either an acid mine drainage treatment residuals or steel slag for phosphorus removal. The experiment was designed to determine if it is better to remove nitrate first in the woodchips (i.e., denitrification treatment upstream of phosphorus sorption treatment) or phosphorus first in the P-filters (i.e., phosphorus removal upstream of the denitrification treatment). Findings suggest that acid mine drainage residual and steel slag were both effective at removing phosphorus, but the acid mine drainage residuals worked for longer and removed more overall phosphorous. Locating the P-filter upstream or downstream of the woodchip bioreactors did not impact nitrate removal, but downstream placement demonstrated higher P-removal rates. As an added benefit, acid mine drainage residuals are also renewable multiple times by removing the media from the system and flushing the captured phosphorus off with a sodium hydroxide wash. Our research also suggests that the high levels of suspended solids in aquaculture effluent could create plugging and hydraulic problems in woodchip bioreactors operated over extended periods or at short hydraulic retention times. To further extend this work, a follow-up study has begun to test whether an improved flow-distribution system can reduce plugging and extend the operating life of woodchip bioreactors without compromising nitrogen and solids removal efficiency.
Also in support of objective 1, we examined the efficiency of carbon dioxide stripping and aeration when using a low lift aeration unit operated within a sump at three hydraulic retention times (sub-objective 1.2). This experiment improved the effectiveness of stripping carbon dioxide from water before reuse in a fish culture tank by adjusting the hydraulic retention (i.e., flow rate) through a basin containing a floating aerator pump. Process optimization has improved energy efficiency compared to traditional technologies.
Optimizing water treatment process system designs will further increase the sustainability and improve the economics of closed production systems (sub-objective 1.3). In support of this objective we analyzed three different system design configurations by comparing capital costs and energy required for a model farm of 3000 tonnes per year of salmon. The outcome was an economies of scale analysis for designs that produce 500, 1000, and 5000 tonnes of salmon per year.
In support of Objective 2, progress within three separate studies supported improvements in salmonid performance, health and well-being in land-based systems.
Sustainable aquafeeds that contain no fishmeal show potential for replacing traditional fishmeal-based diets, but they can result in slower growth and their lower digestibility may compromise the performance of recirculating aquaculture systems (RAS). In fiscal year 2015, preparations began for a research study designed to compare the effects of a practical and relatively cost effective alternative protein diet (zero-fishmeal diet) compared to a traditional fishmeal diet on rainbow trout growth performance, welfare, processing/product quality, and RAS performance. Rainbow trout were obtained from the breeding program at Troutlodge (Sumner, Washington), the world’s largest rainbow trout egg producer, to determine whether genetic variation in the diet response can be exploited for selective breeding purposes. Economically important performance variables were measured throughout the growth period, from December 2015 through May 2016, and included survival, length, weight, feed conversion ratio, and fin condition. Although survival was similar between the two feeds, as a whole, rainbow trout fed the traditional fishmeal-based grew 30% larger than trout fed the zero-fishmeal diet, indicating that the later formulation requires optimization before it can replace traditional fishmeal diets as a viable commercial feed. However, some rainbow trout families grew better on the zero-fishmeal diet than the traditional diet, suggesting that these families may be particularly valuable for Troutlodge selective breeding programs. Data are currently being analyzed for additional indices of growth performance, including carcass and fillet yield, fillet quality attributes such proximate composition and off-flavor analysis, multi-tissue histopathology, and whole blood analyses (chemistry and gasses). Measurements of water quality and RAS performance were also monitored. The RAS were robust in compensating for water quality differences between diets and, regardless of diet, maintained water quality that was acceptable for optimal fish health and performance. In addition, the zero-fishmeal diet produced less phosphorous per kg feed in the system effluent compared to the fishmeal-based diet, which can reduce environmental impact or the cost of treating phosphorus in the discharge. Research progress collectively supports that alternative-protein diets require further modification to improve rainbow trout growth before these diets are suitable for use in commercial production systems.
The accumulation of waterborne hormones has been identified as a possible cause for early maturation of Atlantic salmon cultured in recirculation aquaculture systems (RAS). To extend objective 2, we determined the potential for ozone to reduce waterborne hormones that may accumulate in RAS. Water from RAS containing sexually mature Atlantic salmon was analyzed as follows: i) testosterone, 11-ketotestosterone (11-KT), and estradiol concentrations were assessed using enzyme immunoassays (EIA), and ii) a broad range of hormones and hormonally active compounds were assessed using liquid chromatography / mass spectrometry (LC/MS). Samples were collected from the makeup or incoming water supply, the biofilter inlet and outlet, and tank inlet and outlet. Analysis using EIA demonstrated that ozone reduced concentrations of all three measured waterborne hormones at various locations. Most notably, i) estradiol was reduced at all sampling locations (excepting makeup water) in ozonated systems, and ii) biofiltration significantly reduced concentrations of 11-KT in both ozone and non-ozone RAS. We therefore concluded that a low level, non-disinfecting dose of ozone is an efficient method to significantly reduce concentrations of estradiol, testosterone, and 11-KT in low exchange RAS. The LC/MS analysis, however, was not able to detect any hormones or hormonally active compounds above the test’s threshold of detection. Overall, the findings of this study demonstrate the potential for water ozonation to reduce key steroid hormones that could influence the most significant problem in RAS Atlantic salmon growout, namely decreased growth and product quality related to early male maturation.
In support of objective 2, a third study was completed to evaluate peracetic acid (PAA) as a strategy to minimize losses of Atlantic salmon smolts to vaccination-induced Saprolegnia infections and affect the biofiltration capacity of recirculating aquaculture systems (RAS). In the spring of 2016, Atlantic salmon parr were vaccinated via intracoelomic injection to induce onset of post-vaccination Saprolegniasis, a major source of mortality in the salmon industry. Daily administration of PAA (at three dosages) was applied to assess (i) if and at what dose PAA can prevent Saprolegniasis, and (ii) whether biofiltration was compromised as a result of PAA (sub-objective 2.3). Results indicate that PAA is an effective approach for prevention of vaccination-induced Saprolegniasis, as almost 100% of the disease cases were observed in untreated control RAS only. Furthermore, PAA did not compromise biofiltration capacity, indicating this treatment does not negatively affect RAS performance. However, benefits of PAA treatment were offset by negative effects on fish growth. Future analysis will include Saprolegnia spp. sequencing to determine whether certain species of Saprolegnia, among those cultured from water samples, are associated with external infection in salmon. Future histopathological assessments of gill, spleen, and anterior kidney tissues will provide additional information on how disease etiology is affected by treatment and vaccination. This study was completed in our mini-RAS systems and plans are to complete a follow-up study in fiscal year 2016 examining PAA administration in our larger-scale replicated RAS, which will focus on water quality, fish health, performance, and welfare, and RAS microbiomes (with a focus on off-flavor producing bacteria).
Accomplishments
1. Atlantic salmon can be raised to market weight in land-based systems using sustainable diets. The use of alternative protein sources in fish feed continues to increase as concerns persist surrounding the sustainability and cost of using ocean-harvested fish as protein and oil for fish feed. Furthermore, commercial farms are beginning to use land-based systems that recirculate water and allow production of market-size Atlantic salmon adjacent to markets, with less disease, and without perceived negative impacts on the marine ecosystem. The research of a scientist at the Conservation fund in Arlington, Virginia showed that a novel fishmeal-free diet fed to Atlantic salmon in recirculation aquaculture systems resulted in greater waste production but provided equal salmon growth, feed conversion, and survival compared to a traditional fishmeal-based diet. The “wild fish in to farmed fish out” ratio is often used as an index of sustainability as it represents the amount of capture fisheries ingredients required to produce one pound of farmed fish. The fishmeal-free diet did not use any capture fisheries ingredients that were directly purposed for production of aquafeeds, thus resulting in a “zero to one” wild fish in to farmed fish out ratio and indicating the fishmeal-free diet was highly sustainable. These findings were adapted to larger-scale salmon production, for which we provided the first evidence that Atlantic salmon can be effectively raised to market-size while consuming a sustainable diet in a commercially relevant land-based system. This research provides infrastructure requirements and rearing strategies that increase Atlantic salmon production efficiency yet alleviate environmental impacts and reliance upon capture fisheries.
Technical support in aquaculture engineering, fish health and biosecurity has been provided to rainbow trout producers across the Appalachian region and Native Americans across the United States. This work supports economic development in a region where many counties are rated as economically distressed and unemployment rates are greater than 10%. We provided support to Native Americans in North Carolina (Eastern Band of Cherokee Indians) and Washington State (Yakama Indian Nation).
Review Publications
Christianson, L., Lepine, C., Tsukuda, S., Saito, K., Summerfelt, S. 2015. Nitrate removal effectiveness of fluidized sulfur-based autotrophic denitrification biofilters for recirculating aquaculture systems. Journal of Aquaculture Engineering. 68:10-18.
Sharrer, K.L., Christianson, L.E., Lepine, C., Summerfelt, S.T. 2016. Modeling and mitigation of denitrification 'woodchip' bioreactor phosphorus releases during treatment of aquaculture wastewater. Aquacultural Engineering. 93:135-143. doi:10.1016/j.ecoleng.2016.05.019.
Davidon, J., May, T., Good, C., Waldrop, T., Kenney, P., Terjesen, B., Summerfelt, S.T. 2016. Production of market-size North American strain Atlantic salmon Salmo salar in a land-based recirculation aquaculture system using freshwater. Aquacultural Engineering. 74:1-16. doi: 10.1016/j.aquaeng.2016.04.007.
Davidson, J., Barrows, F., Kenney, P., Good, C., Schroyer, K., Summerfelt, S.T. 2016. Effects of feeding a fishmeal-free versus a fishmeal-based diet on post-smolt Atlantic salmon salmo salar performance, water quality, and waste production in recirculation aquaculture systems. Aquacultural Engineering. 74:38-51. doi: 10.1016/j.aquaeng.2016.05.004.
Good, C., Davidson, J., Wiens, G.D., Welch, T.J., Summerfelt, S. 2014. Flavobacterium branchiophilum and F. succinicans associated with bacterial gill disease in rainbow trout Oncorhynchus mykiss (Walbaum) in water recirculation aquaculture systems. Journal of Fish Diseases. DOI: 10.1111/jfd.12249.
Lepine, C., Christianson, L.E., Sharrer, K.L., Summerfelt, S.T. 2016. Optimizing hydraulic retention times in denitrifying woodchip bioreactors treating recirculating aquaculture system wastewater. Journal of Environmental Quality. 45:813-821. doi: 10.2134/jeq2015.05.0242.
Liu, Y., Rosten, T.W., Henriksen, K., Hognes, E., Summerfelt, S., Vinci, B. 2016. Comparative economic performance and carbon footprint of two farming models for producing atlantic salmon (salmo salar): Land-based closed containment system in freshwater and open pen in seawater. Journal of Aquaculture Engineering. 71:1-12. doi: 10.1016/j.aquaeng.2016.01.001.
Schmidt, V., Amaral-Zettler, L., Davidson, J., Summerfelt, S., Good, C. 2016. The influence of fishmeal-free diets on microbial communities in Atlantic salmon Salmo salar recirculation aquaculture systems. Applied and Environmental Microbiology. doi: 10.1128/AEM.00902-16.
Stockton, K.A., Moffitt, C.M., Watten, B.J., Vinci, B.J. 2016. Comparison of hydraulics and particle removal efficiencies in a mixed cell raceway and burrows pond rearing system. Aquacultural Engineering. 74:52-61. doi: 10.1016/j.aquaeng.2016.04.005.
Weber, G.M., Davidson, J.W., Kenney, P.B., Good, C.M., Manor, M.L., Welsh, C., Aussanasuwannakul, A., Summerfelt, S.T. 2015. Changes in sex steroids, growth hormone, and insulin-like growth factor-I during ovarian development in Rainbow Trout cultured within a recirculating system with 24-hour Light. North American Journal of Aquaculture. 77:186-194. DOI: 10.1080/15222055.2014.987933.
Good, C., May, T., Crouse, C., Summerfelt, S., Welch, T.J. 2016. Assessing the impact of swimming exercise and the relative susceptibility of rainbow trout oncorhynchus mykiss (walbaum) and atlantic salmon salmo salar L. following injection challenge with weissella ceti. Journal of Fish Diseases. 39(11): 1387-1391.
