This research seeks to answer several questions pertaining to development of indoor shrimp aquaculture in the United States. Aquaculture is a rapidly growing food production system that is a potential solution to overfishing and fisheries depletion worldwide. Two competing systems for indoor shrimp culture, recirculating aquaculture systems (RAS) and bio-floc systems (BFS), will be evaluated and compared using lab-scale systems. Techniques will include advanced molecular biology and stable isotope methods and will address the following questions: Will the promotion of a more diverse microbial community of nitrifiers create a more stable RAS? Can the waste produced on RAS biofilters be recycled back into the production tanks to improve feed utilization efficiency? Will the performance of BFS be improved by manipulating solids retention times? How susceptible are shrimp raised in the two systems to an opportunistic bacterial pathogen? Additionally, a comprehensive cost benefit analysis using life cycle assessment will be performed. The research outcomes are anticipated to enhance the competitiveness of American shrimp aquaculture. Under represented group students will be involved in the research.
Aquaculture is the fastest growing food production system in the world and shrimp is currently the most popular seafood in the United States. Like all food production systems, shrimp production needs to intensify to provide for an ever growing demand. However, intensive shrimp farming can have negative environmental and social impacts. There is potential for shrimp farming to expand in the United States through indoor operations. A production system that shows much promise for indoor shrimp farming is a recirculating aquaculture system (RAS). In this system, shrimp are grown in culture tanks and microorganisms grown in biofilters are used to remove shrimp waste products and maintain water quality. The overall goal of this project was to improve the environmental sustainability of shrimp RAS systems operated indoors. Shrimp RAS systems were operated in the laboratory to evaluate if increasing ammonium concentrations during shrimp growth could be removed by the nitrifying microbes in the biofilters. The systems performed well and removed ammonium to below detection levels and no accumulation of nitrite was observed during a shrimp growth cycle. Nitrate gradually accumulated as expected because the systems were not operated for nitrate removal, but did not impact shrimp growth. Using microbial analyses, the biofilters were demonstrated to contain a robust nitrifying community of microbes. Results further indicate that microbial biomass regularly removed from the RAS biofilters can be used as a supplemental feed source for shrimp, although replacing half of commercial feed protein content with microbial biomass protein resulted in a decreased shrimp growth rate compared to a control system for which only commercial feed was used. However, the longer shrimp grow out time can be balanced by cost savings associated with using less feed. Shrimp farmers using RAS can consider using biofilter backwash waste or other biomass sources containing microbial biomass as a supplemental feed source to reduce feeding costs. To assess the environmental sustainability of shrimp produced in RAS in the United States, a life cycle assessment (LCA) was conducted. The results indicated that existing RAS are environmentally preferable to conventional systems only in terms of a few environmental impacts, but are more energy and carbon intensive. However, future RAS can greatly be improved by lowering energy demand and improving feed utilization efficiency, and could become competitive with conventional aquaculture systems. Local food production has received much attention due to pollution concerns associated with long distance transportation. However, expanding shrimp production from warm to cold climate regions using indoor RAS systems in response to such concerns would increase the overall greenhouse gas emissions and cumulative energy demand due to heating requirements. We conclude that buying domestically farmed shrimp rather than imported shrimp could help reduce certain environmental impacts, but with current technology would increase cumulative energy demand. Future research needs to integrate these results with economic and social indicators to guide opportunities for expanding shrimp production in the United States to enhance environmental sustainability. This research project provided numerous opportunities for research and training of undergraduate and graduate students and postdoctoral researchers, including several students underrepresented in science and engineering disciplines. In addition, high school students were introduced to science and engineering research and educational opportunities. All students and postdoctoral researchers involved in this project are continuing in engineering and science careers and currently have positions in industry, consulting engineering, or academic institutions, or are in graduate school. The training of undergraduate students and outreach activities to high school students improved the mentoring and teaching skills of the post-doctoral scholars and graduate students. Interactions with aquaculture farmers at local and regional conferences and direct visits of farms have allowed us to share research findings with practitioners. Additionally, our recent work involving an evaluation of a household-scale shrimp RAS system at an urban farm has provided opportunities for technology transfer to communities not previously exposed to aquaculture.
