2011 Annual Report
1a.Objectives (from AD-416)
To investigate and solve problems pertaining to aquaculture operations in the Mississippi hill area, including issues related to: water quality, production efficiency, and operational procedures (i.e., improving growth and reducing stress and disease). Further, to provide species diversification options for greater long-term economic stability.
1b.Approach (from AD-416)
The project will be designed to resolve issues of importance to the Eastern Mississippi aquaculture industry in the areas of water quality, production efficiency, environmental and disease-related stress and reproduction by conducting experiments in the laboratory and in research ponds at the Thad Cochran National Warmwater Aquaculture Center (NWAC) Eastern Research Unit, on commercial farms, and in collaboration with the NWAC Delta Research Unit in Stoneville, Mississippi. Because aquaculture ponds in Eastern Mississippi rely primarily on surface water and are deeper than conventional pond-designs used in the Mississippi Delta, an understanding of the unique water quality influences to this region are important. Further, improvement of aquaculture practices based on an understanding of operational and environmental stressors will be developed. Research on catfish reproduction and the use of hybrid catfish (female channel catfish x male blue catfish) will be conducted to reduce loss of fish during the grow-out process, and research on the culture of alternative species will be conducted to improve market stability.
Aquaculture: The first objective was to determine the physiological consequences of trematode infections. To accomplish this objective, data analysis on a preliminary study was completed. In this study, treatment levels did not result in mortality, and fish were resilient to the exposure levels both in terms of survival and internal ion regulation. Therefore, a follow-up study is planned when sufficient numbers of infected snails are available. The second objective was to determine the effects of long-term exposure to high seasonal temperatures to understand how physiological tolerances, health, and ultimately survival were impacted, and to make recommendations for when preventative procedures need to be implemented. This objective was accomplished through an experiment that utilized temperature treatments based on measured pond conditions taken in the Mississippi Delta. Interestingly, the best growth was found from a daily cycling temperature of 27-31C as compared to 23-27C or 31-35C. Activity did not change significantly between treatments, although food consumption did. This experiment is being followed-up with two more experiments on metabolic rates and forced swimming ability. The third objective was to develop methods for rearing species that can utilize existing pond systems. A study was initiated in 2011 on Gulf killifish Fundulus grandis. This study is currently underway. A fourth objective was to identify causes of mortality associated with anemia using metabolomic techniques. Samples are currently being analyzed.
Water quality: Water quality plays an important role in the sustainability of commercial aquaculture. The first research objective investigated how water depth influenced dissolved oxygen (DO), temperature and pH. Automated buoys have been upgraded (RDO sensors), made wireless, and had data setup with an ftp transfer. These units have been calibrated and tested since June 2010. The units will be tracked by pond in spring of 2011 and a second treatment of culture species will be added to understand changes in in situ water quality parameters as a function of depth and culture species. The split pond system (SPS) where water circulated from a fish holding compartment to a non-fish, lagoon compartment is showing promise in terms of biomass production, feeding rates as well as reductions of nitrogen toxicity. In situ water quality parameters showed that dissolved oxygen concentrations in the surface and water sediment interface provided conducive conditions for nitrogen removal. There were significantly better (low DO, low ORP) conditions in the SPS waste side than both SPS fish side and earthen pond combined. Low DO (<0.2 mg L-1) at the sediment water interface provided conducive conditions for denitrification, high DO concentrations (>20 mg L-1) at the surface was a result of highly productive phytoplankton remaining in suspension through water circulation (allowing for nitrification). Nitrogen pathway data highlight greater percentages of denitrification (based on proxy ORP data) in the SPS waste side vs. SPS fish and earthen ponds.