2012 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.
The first objective was to determine the physiological consequences of trematode infections. To accomplish this objective, a follow-up study to a previous pilot study is planned when sufficient numbers of infected snails are available. Snails were not available in 2011 but may become available, likely in the late summer or early fall of 2012.
The second objective was to determine the effects of long-term exposure to high seasonal temperatures on bioenergetic responses. This objective was accomplished through an experiment that quantified resting and active metabolic rates and swimming endurance at three different temperatures (27, 31 and 35°C) characteristic of high seasonal temperatures in ponds in Mississippi and the southeast. Resting and active metabolism generally increased with temperature, but active metabolism decreased at the highest temperature indicating a reduced metabolic scope. Therefore, 35°C diminishes physiological performance. Similarly, swimming endurance, such as would occur in sustained swimming behind pond aerators decreased with temperature. This experiment is being followed-up with experiments on growth and gene expression at high temperatures in different strains of channel catfish and hybrid catfish in cooperation with the USDA Catfish Genetics Research Unit in Stoneville, Mississippi.
The third objective was to develop methods for rearing species that can utilize existing pond systems. Studies evaluating rearing and growth of Gulf killifish Fundulus grandis in low salinities are currently underway. Fish were obtained, transported to the Mississippi State University South Farm Aquaculture Facility and held in ponds. Preliminary results indicate that they can survive for at least a year in fresh water and survive cold winter conditions. Also, a study on paddlefish low oxygen tolerance and optimal conditions for pond growth is also underway. Paddlefish have been obtained both from Kentucky State University, and from local broodstock in Mississippi.
Samples to investigate a fourth objective, to identify causes of mortality associated with anemia using metabolomic techniques, are being further evaluated. Samples have been collected, and are being processed and analyzed.
Water quality plays an important role in the sustainability of commercial aquaculture. Research objective investigated in 2010 and continuing in 2011 is how water depth influences dissolved oxygen (DO), temperature and pH. Automated buoys have been upgraded (RDO sensors), made wireless, and had data setup with an file transfer protocol (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. With In Situ Inc the buoys have been evaluated for performance and it was decided that the pH data was unreliable. The pH calibration curves drifted within days of deployment which rendered unusable data.
In 2011, a second year of experiments occurred with low-input production shrimp culture. The cultures were evaluated based on feeding treatments for changes in in-pond water quality and then the effluent was monitored and evaluated with discharge. Discharge best management practices of vegetated drainage ditches and low-grade weirs are being evaluated for the effect on reducing nutrient concentrations and loads to downstream ecosystems. The first set of pond discharges were performed in fall of 2011 and the practices are being evaluated for effectiveness. In 2012, the next set of discharge experiments will take place to further substantiate the role of best management practices (BMP's) for reducing impacts of aquaculture effluent to downstream aquatic ecosystems.