2013 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.
A number of aquaculture research projects were conducted this past year, with emphases on addressing important issues in commercial catfish production, and in the development of alternative species for regional aquaculturalists. In terms of catfish, studies built upon research on temperature effects on growth, survival and physiology completed over the past few years. Elevated temperatures and extreme weather events are predicted to increase in magnitude and frequency, yet little is known as to how they may impact the catfish aquaculture industry. Therefore, two different geographic strains of channel catfish were evaluated to determine if there are geographic differences in resilience to extreme temperature conditions. In addition, hybrid catfish, derived from a cross with an industry standard blue catfish strain with each of the geographic strains of channel catfish were also compared. Results appear promising for hybrid catfish.
Studies on alternative species included salt treatments for freshwater prawns, oxygen requirements of paddlefish, and low salinity rearing techniques of Gulf killifish. Freshwater prawns were reared in ponds and then placed into post-harvest salt treatments to improve consumer acceptance. A number of low cost salt treatments were derived. Results showed that survival was highest in marine salts, but that several other salt mixes also had relatively high survival. Consumers preferred prawns that had been subjected to post-mortem brining, which is also the most inexpensive and least difficult solution for growers and processors. Paddlefish tolerance to hypoxia was moderate, meaning that paddlefish require higher oxygen levels than catfish. The effects of hypoxia on paddlefish swimming ability were also assessed to understand how this unique species may react to low oxygen culture conditions. Paddlefish are unique in that they continuously swim, and were found to have a reduced swimming capacity in hypoxic conditions. Gulf killifish, which offer the potential of an alternative species and market for catfish growers or former catfish growers, were able to reproduce in freshwater. Egg fertilization was decreased in freshwater, and hatching rate was also decreased in freshwater compare to optimal salinity conditions. However, the significance of the findings is that this species can be cultured in freshwater, and refinement of egg incubation techniques will likely lead to higher survival rates.
Water quality: Water quality plays an important role in the sustainability of commercial aquaculture. Research objectives have mostly been met with the completion of catfish nitrogen and dissolved oxygen (DO) dynamics being completed in later 2011 and early 2012. Automated buoys have been upgraded (RDO sensors), made wireless, and had data setup with an ftp transfer. However, unfortunately there are still issues within these units. Wireless communications as well as calibration issues with the sensors have jeopardized the data collection efforts of these units. The work that was completed with low-input production shrimp culture is showing some interesting results. The cultures were evaluated based on feeding treatments for changes in in-pond water quality and then the effluent was monitoring 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. Throughout 2011 and 2012, the role of best management practices for the mitigation of aquaculture effluent has been the focus. The first set of pond discharges were performed in fall of 2011 and the practices are being evaluated for effectiveness. In 2012 nine ponds were discharged through a vegetated drainage ditch with weirs to determine their effectiveness in reducing nutrient and sediment loads moving through the system as a result of aquaculture effluent discharge. The results are very promising showing across the board reductions in nitrogen and phosphorus species, as well as total suspending solid and volatile suspended solids.