Submitted to: Hatchery International Magazine
Publication Type: Popular Publication
Publication Acceptance Date: December 1, 2006
Publication Date: January 1, 2007
Citation: Small, B.C., Bates, T.D., Torrans, E.L. 2007. Optimal Conditions Pay Healthy Dividends For Catfish Hatcheries. Hatchery International Magazine. 8(1):19-20. Interpretive Summary: Nationally, average hatch rates are reported to be around 79% with some hatcheries getting less than 60% egg survival. Several factors, including disease, environment, and overall management practices, can affect the number of viable fry produced from a single egg mass. Several experiments were conducted to put numbers to the effects of temperature, transport, calcium-hardness, dissolved oxygen, and chemotherapeutics on hatching success. These studies define the optimal conditions for rearing catfish eggs to obtain maximal hatch rates. The combined results of each of these studies identify management practices for improving below-average hatch rates by 30% or more for an industry that produces over 21 million eggs annually.
Technical Abstract: Several experiments were conducted at the Thad Cochran National Warmwater Aquaculture Center over the past seven years to put numbers to the effects of temperature, transport, calcium-hardness, dissolved oxygen, and chemotherapeutics on hatching success. The results of theses studies indicate hatch rates to be highest between 26 and 28 degrees Celsius. Extended delays (> 30 min) in transporting eggs to the hatchery were shown to significantly lower hatching success by 10-30%. Low water hardness (< 10 ppm as CaCO3) was found to have a significant negative effect on hatch rates, and eggs without any supplemental calcium during the first 24 hours post-fertilization had 72% lower hatch rates. Mean limiting oxygen concentration determined on eggs 1 day prior to hatch was 87.1% air saturation, with the highest value determined for an individual sample reaching 95.8% air saturation. When eggs were within 1 day of hatching, it was observed that allowing the dissolved oxygen concentration to fall below the limiting oxygen concentration resulted in premature hatching and reduced survival, suggesting that dissolved oxygen concentrations in the trough should be maintained near air-saturation (8.1 mg/L at 26º C) as eggs approach hatching. Chemotherapeutic research conducted at 26 degrees Celsius showed that hydrogen peroxide was effective for reducing egg disease and improving hatch rates, with 30% improved hatch rates resulting from a once daily 15-minute bath in a 250 ppm hydrogen peroxide solution. In another study, temperature was found to affect hydrogen peroxide efficacy. At 28 degrees Celsius, a 100 ppm solution of hydrogen peroxide yielded the highest hatch rates, but at 24 degrees Celsius, 500 ppm yielded the highest hatch rates. The combined results of each of the presented studies identify management practices for improving below-average hatch rates by 30% or more.