Location: Cool and Cold Water Aquaculture Research2011 Annual Report
1a. Objectives (from AD-416)
Recirculating aquaculture systems (RAS) provide control of water quality and temperature to optimize fish production and health, provide barriers that prevent escape of fish and entry of pathogens, contain and remediate waste flows to curtail environmental impact, and minimize water use. RAS can allow a commercial fish farm to locate where power, feed, or oxygen is relatively inexpensive, where environmental impact can be minimized, and/or adjacent to their primary markets. However, RAS are dependent on relatively larger energy inputs than traditional flow-through or net-pen systems. Thus, strategies are required for reducing energy consumption and improving waste disposal, which both are major factors in a fish farm’s overall life cycle assessment. In addition, production techniques must be developed to improve biosecurity and reduce stress and disease outbreaks in fish cultured in closed containment systems. This work will integrate research and technology advancements, and resolve current and emerging constraints to the expanded use of land-based, closed containment systems for the production of safe and nutritious salmon and other cool- and cold-water species. Objective 1: Identify criteria to optimize the performance, health, welfare and consumer value of Atlantic salmon and other salmonids grown to food-size in intensive, land-based, closed-containment systems. Objective 2: Improve the effectiveness, energy efficiency, and economics of water reuse and waste treatment technologies and practices. This will include developing technologies to minimize waste and reclaim water, protein, and/or energy to improve the economic and environmental sustainability of closed-containment systems. Objective 3: Conduct production trials of fish and feeds developed through ARS collaborations.
1b. Approach (from AD-416)
Research at The Conservation Fund’s Freshwater Institute focuses on developing and improving technologies to enhance the sustainability and reduce the environmental impact of the modern fish farming industry. To this end, the proposed projects listed in this plan will continue our work in pioneering land-based, closed containment water recirculation systems that are biosecure, have an easily controlled rearing environment, produce healthy and optimally performing fish, and produce manageable effluent for significant reduction in waste discharge. Specifically, our proposed research will investigate, among other things, the biological and economic feasibility of raising Atlantic salmon to market size in freshwater recirculation systems (as opposed to coastal net-pens); the potential for raising rainbow trout in semi-closed or closed water recirculation systems to further reduce the amount of influent water and point source discharge required for these systems; the health and welfare of salmon and trout in relation to dissolved oxygen and carbon dioxide levels, swimming speed in circular tanks, soy-based feeds, and water ozonation in low-exchange systems; and the potential for greater energy efficiency in water recirculation systems through improved low-lift pumping and gas transfer processes. In addition, our experimental systems will continue to serve as field testing sites for alternative-protein feeds and for salmon and trout strains selected through genetic improvement programs at other USDA facilities. The investigations proposed in this plan will build on the findings of previous years of USDA-funded research to develop a sustainable, environmentally responsible, and economically viable aquaculture industry in the United States.
3. Progress Report
The goal of this project is to develop and improve technologies enhancing the sustainability of the modern aquaculture industry. Progress was made in several areas. A low-head and high-flow aerator pump mounted directly against the side of the culture tank was found to provide efficient O2 transfer and CO2 removal, which effectively increases carrying capacity of the culture volume. The fixed and variable costs for two types of partial water reuse systems were estimated and compared for trout culture. The partial reuse system using sidewall box airlift pumps at each culture tank reduces fixed costs by approximately 37% and electric and oxygen costs by as much as 54% compared to more conventional partial water reuse technology. The sidewall box airlift pump can therefore be integrated into the design of larger recirculation aquaculture systems (RAS) to improve gas control, provide culture tank rotation, and reduce total power requirements. To investigate improving the fish rearing environment through use of water ozonation, we compiled the results from three studies conducted in our six replicated RAS that were either operated with or without ozone at various water exchange rates. Ozonation of recirculating water in systems operated at the same low water flushing rate was found to improve fish growth while significantly reducing suspended solids, biochemical oxygen demand, copper, iron, and color concentrations in the culture tank water. In addition, water quality and fish growth were similar within ozonated systems operated with low water exchange as compared to the same systems operated without ozonation but with 10-times more flushing. Thus, ozonation improves water quality and fish growth and survival in production systems that must operate in environments where water use is restricted due to water availability, temperature control, or pollution abatement requirements. The effects of elevated nitrate nitrogen (NO3-N) on rainbow trout performance, health, and welfare are being examined in a controlled and replicated study. Fish are being raised from 15g-150g and exposed to either elevated (~100mg/L) or normal (<30mg/L) NO3-N concentrations. Outcomes being examined include survival, deformities, side-swimming, swimming speed, and fin condition, and their association with elevated NO3-N is being investigated. The study is currently nearing completion; findings will be important in establishing boundary water quality criteria in tightly closed RAS. The ADODR is in frequent contact with the cooperator through phone calls, email, and site visits in addition to receipt of written reports.