Location: Warmwater Aquaculture Research Unit2012 Annual Report
1a. Objectives (from AD-416):
The objective of this cooperative research project is to test and further develop a novel incubator for use in commercial channel catfish hatcheries.
1b. Approach (from AD-416):
Catfish incubators have been largely unimproved since first developed in 1929. Egg masses are held in baskets made with ¼” mesh hardware cloth. Paddles held on a rotating shaft turn through the water between baskets, moving water through the baskets, aerating the eggs. As the eggs hatch, the sac fry pass through the mesh of the basket and sink to the bottom of the trough, where they are siphoned up. Farmers often experience problems (fungus and/or bacteria on eggs, resulting in poor hatch rates) during the peak of the spawning season when hatchery space is limited and egg masses are often crowded in the baskets at higher than desired densities. Recent research conducted by ARS has demonstrated that the oxygen requirements of catfish egg masses are higher than previously thought. This research has led to a preliminary design for a new hatchery system.
3. Progress Report:
During the 2009 spawning season the first comparative trial of the See-Saw with conventional incubators was conducted. Survival to swim-up stage was significantly higher in the See-Saw than the traditional control troughs, averaging 53.6 ± 7.1% in the See-Saw, versus 23.3 ± 6.5% for the control troughs, a 2.3-fold difference. While survival in the See-Saw was lower than expected, that was attributed to the generally poor egg quality from eggs collected at the end of the season (June 17-20, 2009). Over-winter, an additional sixteen hatchery roughs were equipped with the See-Saw incubator, bringing the total to 32 troughs. During the 2010 spawning season a test of egg loading rates was conducted in the new incubators. Egg loading rates of 15, 30, 45, and 60 pounds of egg masses per trough were tested with six replicate troughs per treatment using hatchery water (at air saturation with respect to Disolve Oxygen (DO)) exchanged at a rate of approximately 2 gal/min. Hatch rates were similar among the three lower egg loading densities but decreased significantly at the highest (60 lb/trough) loading rate. During the 2011 spawning season the use of supplemental oxygen was examined. Troughs were loaded with 36 spawns per trough (45.7 lbs; 662,000 eggs) and supplied with water near air saturation with oxygen at an average flow rate of 2.1 gal/min with a mean temperature of 80.5°F. Troughs were maintained with either water exchange only (N=15 replicate troughs) or with water exchange and liquid oxygen added at an average rate of 0.12 L/min through individual diffusers in each trough. Mean DO concentrations averaged 6.59 vs. 9.83 ppm in the water exchange only vs. the oxygen-supplemented troughs. Hatch rated averaged 71.2% with 462,000 swim-up fry (10,323 fry per pound of eggs loaded) produced per trough. There were no significant differences between the two treatments with respect to any parameter except for mean DO concentration. While increasing loading rates above 45 lbs/trough may require oxygen supplementation to prevent a decrease in hatch rate, a loading rate of 45 lbs/trough only requires a water exchange of approximately 2 gal/min of air-saturated water. The See-Saw incubator operating at this capacity reduces the per-pound water requirement to incubate catfish eggs by 83%, a significant savings for a hatchery operation. During FY 2012 an additional 16 troughs were fabricated by the collaborator, bringing the total at the facility to 48 troughs with a single-batch capacity of 28 million eggs. Efforts of the ARS collaborator focused on technology transfer to other hatcheries.