Location: Warmwater Aquaculture Research Unit
2012 Annual Report
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: 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.