2013 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.
During the 2009 spawning season, sixteen standard hatchery troughs were equipped with the See-Saw incubation system. Most of this first season was used to design the system, purchase motors and material for fabrication of the supports, racks, and hatching baskets, and preliminary stress-testing of the system without live eggs. Near the end of the 2009 spawning season the first comparative trial was conducted. Survival to swim-up stage averaged 53.6 ± 7.1% in the See-Saw, versus 23.3 ± 6.5% for the control troughs, a 2.3-fold difference.
Over-winter, an additional sixteen hatchery troughs were equipped with the See-Saw incubator, bringing the total to 32 troughs. In Year 2 of the project (2010 spawning season) ARS Scientist at Stoneville, MS, measured the effect of egg loading density in See-Saw incubators on survival to hatch and swim-up. Further comparisons with the paddle-type incubators were not conducted. We loaded See-Saws (n= 5 troughs for each treatment) with 15.0 ± 0.1 pound (lb) (220,300 eggs), 30.1 ± 0.1 lb (447,000 eggs), 45.1 ± 0.1 lb (669,600 eggs), and 60.1 ± 0.0 lb (893,100 eggs) of spawns. Water flow into the troughs averaged 2.1 gal/min, roughly half of the rate recommended for commercial hatcheries. The 15, 30, and 45 lb troughs produced an average of 132,700, 263,800, and 429,400 swim-up fry (survival from egg of 60 ± 9%, 59 ± 6%, and 64 ± 4%, respectively, similar to values reported in commercial hatcheries). However, the 60 lb treatment produced only 417,200 swim-up fry (survival of 46 ± 8%). The results of this year’s study indicate that both hatchery space and water use would be maximized with See-Saw incubators loaded at the 45 lb rate.
Year 3 of the project (2011 spawning season) aimed at further improvements in operational efficiencies. We examined the effect of oxygen supplementation on troughs loaded with 45 lbs of eggs. Fifteen troughs were incubated using no oxygen supplementation and had a mean oxygen saturation of 82.4%; 17 troughs were incubated using additional oxygen added through ceramic diffusers at an average rate of 0.12 liters/min resulting in an average oxygen saturation of 124.1%. Mean swim-up fry production overall was 462,363 fry/trough (10,327 fry/lb eggs), for a survival from egg to swim-up of 71.2%. There were no significant differences between treatments, confirming that 45 lbs of eggs can be incubated per See-Saw trough without additional oxygen if the hatchery water supply is near air saturation.
The results indicate that the See-Saw incubator can be loaded with at least 45 lb of eggs per trough without supplemental oxygen without impacting hatch rate or survival to swim-up. If sac fry are removed frequently we believe that up to 60 lb of eggs can be incubated per trough. The use of this incubator across the commercial industry would result in considerable savings in water alone, particularly for those hatcheries that need to heat their well water. During the last (current) year of this agreement the cooperator added a third row of See-Saw incubators (an additional 16 troughs), bringing the total number of troughs at this hatchery to 48.
This incubator may have even greater application in the numerous state and federal hatcheries which are tasked with hatching a growing number of fish species. The See-Saw can reduce both the space and water flow needed to meet their channel catfish production quota, making those resources available for other priority species.
This project produced a great deal of technology transfer, including three refereed journal articles, abstracts and presentations at Catfish Farmers of America Catfish Research Workshops in 2009 and 2012; Aquaculture America Conferences in 2010, 2011 and 2012; Southeastern Association of Fish and Wildlife Agencies conference in 2011; and the Mid-Continent Fish Culture Research Workshop in 2013.