Author
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Torrans, Eugene |
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Ott, Brian |
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Submitted to: Aquaculture America Conference
Publication Type: Abstract Only Publication Acceptance Date: 11/16/2010 Publication Date: 3/1/2011 Citation: Torrans, E.L., Ott, B.D. 2011. Improving Catfish Fry Survival. Aquaculture America Conference. P.117. Interpretive Summary: NONE Technical Abstract: Catfish hatchery management practices have improved considerably in recent years. Use of well water (rather than a pond reservoir) results in better temperature control and minimizes introduction of disease organisms. Several prophylactics which minimize pre-hatch losses are available. Increasing DO to air saturation or above increases survival in all stages of development from egg to fry. Two new incubators are in development that may greatly improve hatchery efficiency with both channel catfish and blue X channel catfish hybrids. Exchanging water in a transport tank is an established practice used to minimize temperature shock when stocking swim-up fry, and the effect of pH shock on stocked fry has recently been discovered. While most commercial catfish hatcheries are now relatively sophisticated operations, the weak link is fry pond management. Catfish produce large eggs and fry compared to many cultured species. While we typically see higher survival of catfish fry to fingerling stage than those of species with smaller eggs, catfish fry survival in ponds is still highly variable. Catfish fry readily accept artificial feed as soon as they absorb their yolk sacs, but due to limited space during the peak of the spawning season most hatcheries feed fry for only a few days before stocking them in ponds. In three weeks fry will begin to take small floating pellets from the surface, but their survival to that point is largely dependent on zooplankton that are poorly controlled by most farmers. The composition and density of the zooplankton bloom is critical for fry survival in ponds, and new fertilization practices that promote the desired zooplankton blooms and result in high and more uniform fry survival have been determined. A fertilization program can be implemented and ponds can be sampled daily for zooplankton, with swim-up fry being stocked in ponds with the best blooms. Zooplankton management, coupled with an insect control program, can produce more consistent fry survival in ponds but is not universally practiced. An alternative to the somewhat complicated fry pond zooplankton management techniques is to rear fry to a larger size before stocking them in ponds. In 2-3 weeks, fry maintained in confined culture systems can reach 1.5” in length, by which time they are immunocompetent, large enough to consume floating pellets, and have outgrown most insect predators. With higher and more consistent survival of these larger fish, pond stocking rates are more relevant and pond space can be utilized more efficiently. Raceway systems for advanced fry production have been successfully operated in Alabama for over 15 years. The use of large (0.15-acre) temporary net enclosures for production of advanced fry in ponds is being studied in Mississippi as an alternative where gravity-flow water is not available. As catfish hatcheries gradually shift to blue X channel catfish hybrids, with increased fry production cost, implementing an integrated management program for increased fry survival will be increasingly important. |
