Submitted to: Catfish Farmers of America Research Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 12/11/2008
Publication Date: 3/6/2009
Citation: Torrans, E.L., Ott, B.D., Jones, R., Jones, B., Baxter, J., Mccollum, B., Wargo, Iii, A., Donley, J. 2009. The "See-saw" – A High-intensity Catfish Egg Incubator Designed to Save Space and Conserve Water [Abstract]. In: Research and Review; A Compilation of Abstracts of Research on Channel Catfish. Catfish Farmers of America Catfish Research Symposium, March 5-7, 2009, Natchez, Mississippi. p. 23.
Technical Abstract: Catfish spawns (egg masses) have been incubated and hatched in much the same way for nearly a century. Spawns are placed in ¼”-mesh hardware cloth baskets suspended in metal troughs and water is circulated with paddles placed between the baskets. While this practical system has apparently worked well, recent research has cast doubt on the overall efficiency. It has been determined that DO in the center of a spawn may be 5 mg/L less than in the surrounding water, and that this oxygen stress can cause premature hatching and reduced survival. Oxygen stress would be particularly severe during the peak of the spawning season when troughs are more heavily loaded with spawns. A new incubator was designed and tested on two commercial hatcheries during the 2007 and 2008 spawning seasons. Rather than moving water, as is done with paddles, the new incubator moves the spawns through the water, much like a tea bag being dipped in and out of a cup of hot water. A rack made from 1.5-in angle aluminum is placed inside a standard hatchery trough. Three baskets made from 1/4”-mesh PVC-coated hardware cloth (18” X 26” X 3” deep, with internal dividers and hinged lids) are placed in each aluminum rack and filled with spawns. The rack is connected with chain at both ends to overhead bars which oscillate up and down, operating a pair of troughs with alternating up/down cycles, resembling a playground “See-Saw”. As the rack is lifted, water is forced down through the spawns. The rack continues to rise completely out of the water, allowing the spawns to drain and to absorb oxygen directly from the atmosphere. The rack then moves down, forcing water back up through the spawns. Several pair of troughs can be linked together using one motor and overhead drive rod. Six cycles per minute appear to provide adequate movement without damaging the spawns. With no trough space needed for paddles, there is room in the trough for more spawns. With superior agitation, spawns can be “stacked up” without apparent harm. Eighteen pounds of spawns per trough (n=5) were incubated in the traditional system (paddles and forced air aeration) using 2.5 GPM water flow per trough. The new system incubated from 18-47 pounds per trough (n=5), with 2.9 GPM water flow and no additional aeration. Survival through swim-up stage was similar in both systems, averaging 85.9%. Final fry/water flow ratio in the old and new systems was 82,132 vs 120,015 fry per GPM water flow. At the end of the season an additional trough produced 600,000 sac fry using only 2 GPM water flow (with supplemental oxygen), for a ratio of 300,000 fry per GPM water flow.