2007 Annual Report
Aerator placement strategy. Orientation of traditional paddlewheel aerators in large commercial catfish ponds can potentially impact water quality and fish production costs. USDA ARS CGRU collaborated with Dillard and Company Inc. to conduct a second study of unique aerator placement strategy on ten 11.5-23 acre commercial ponds. Net fish production, feed consumption, feed conversion, electricity usage for routine aeration, and the need for emergency aeration will all be measured. The initial study showed promise, and if similar results are obtained in this study farmers can easily adapt existing equipment to this new system, increasing fish production and reducing production costs. Action Plan Components 5b – Production Intensity, and 6e – Environmental Sustainability.
Mortality of catfish eggs and fry in commercial hatcheries is highly variable but usually ranges from 10 to 30% of the eggs brought into the hatchery. Previously (FY2005 and 2006) USDA ARS CGRU and Mississippi State University Extension Service studied oxygen management practices in 20 commercial hatcheries while measuring oxygen requirements of catfish eggs and fry. It was shown that the highest oxygen concentration (approximately air-saturation) is required by catfish eggs during the last day of incubation. A follow-up study was conducted this year that further confirmed the impact of dissolved oxygen concentration of embryo development, hatch rate and survival. Spawns incubated with a DO concentration of 5.9 mg/L (approximately 74% air saturation) hatched an average of 23.5 hours later than those incubated with 16 mg/L, and had a survival to hatch of only 37%, compared to 75%. Through collaborative work between CGRU and Mississippi State Extension Service (MAFES) a technology transfer program was instituted that has resulted in widespread adoption by the industry of their oxygen management recommendations. The changes already adopted by the industry are expected to result in a 10-20% increase in fry production by the catfish industry. Action Plan Component 3e – Early Life Stage Development and Survival.
Remote sensing in highly turbid Case 2 waters. Rapid assessment of ponds to detect harmful algal blooms is appealing as a management tool for producers. USDA ARS and University of Nebraska tuned plant biomass models for application in aquaculture production systems. The tuned model provided a model that was 80% accurate, and over 25% better predictor of biomass than previous models. Action Plan Components 5b-Production Intensity, and 6e – Environmental Sustainability.
A toxin produced by algae has been purified. Four years ago, evidence was found for production of toxins by a division of algae previously thought of as benign. Two species of the division Euglenophyta were found to produce toxins. USDA-ARS and NOAA isolated the toxin-this compound is a low molecular weight protein. Current efforts are underway to assess what induces toxin accumulation in this common algal species. Action Plan Components 5b-Production Intensity, and 6e – Environmental Sustainability.
Aquascanner SONAR. Research efforts have continued with University of Mississippi (UM), continues to collaborate with Dillard and Company Inc. and researchers at MSU-MAFES and MS Valley State Univ., on the field use of the AquaScanner side scan sonar system. The units were used to predict, in advance, estimated biomass in ponds including at least one that had an unexpectedly low yield. A provisional patent was filed in Spring 2007 and work continues to focus on the best route to use the technology in the field whether through UM construction with direct sales, licensing to a third party manufacturer or a spin off service company. Action Plan Components 5b – Production Intensity; 5e – Live Aquatic Animal Handling, Transport, and Inventory.
Individual fish sizer. Current acoustic modeling techniques allows for estimation of total biomass in ponds, but producing actual counts or size distribution of said fish is problematic. Preliminary work on the development of an individual fish sizer by UM/NCPA in conjunction with colleagues at the University of Arkansas Pine Bluff shows promise. It is anticipated that this acoustic fish sizer can determine the size distribution of a small sub-sample of fish as they are passed through a restrictive pipe and back to the pond. Preliminary field tests indicated that the correlation between the acoustic echo and fish weight in an in-situ dynamic test was comparable to previous static tests. Future work will focus on improving repeatability, ease of use and large scale field testing. Action Plan Components 5b – Production Intensity; 5e – Live Aquatic Animal Handling, Transport, and Inventory.