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Submitted to: Southeastern Association of Fish and Wildlife Agencies Conference
Publication Type: Abstract Only Publication Acceptance Date: 8/20/2013 Publication Date: 10/13/2013 Citation: Chatakondi, N.G. 2013. Effect of type and concentration of water hardness on the fertilization and hatching success of channel X blue F1 hybrid catfish eggs. Southeastern Association of Fish and Wildlife Agencies Conference. P.22. Interpretive Summary: Technical Abstract: Consistent and improved performance of channel x blue F1 hybrid catfish fingerlings in production ponds in the US farm raised catfish industry has prompted an increase in demand of hybrid catfish fingerlings even at higher prices compared to commonly raised channel catfish. Hybrid catfish fry are exclusively produced by hand stripping hormone-induced channel catfish females, fertilized with blue catfish sperm and hatch fertilized eggs. Even though hatchery production of hybrid catfish has been steadily increasing, hatching efficiency is generally lower compared to hatcheries propagating naturally pond spawned channel catfish eggs. Embryonic development is the most sensitive stage in the life cycle of a fish. As fertilized egg development takes outside the fish’s body, water hardness is one abiotic parameter, suggested to have a major effect on the egg’s development and embryo survival. Ca2+ and Mg2+ contribute to water hardness, and are important for ionic regulation of freshwater fish. These ions influence the permeability of egg membranes, preventing diffusive flow and high ionic loss to surrounding water. Ca2+ ions play an important role in the chain reaction of fertilization in fish eggs in terms of stimulation, reception of stimulation, fertilization and activation of enzymes. Mg2+ ions activate numerous enzymes and modify enzyme substrates for energy metabolism. The aquifer used for hybrid catfish hatcheries has less than 10 mg/L of calcium hardness and 1- 25 mg/L of magnesium hardness. Magnesium hardness contributes to 1 to 25% of the total hardness of the hatchery waters. The effect of water hardness on fertilization and hatching success of hybrid catfish eggs is not known. Results of the five hatching trials conducted to assess the effect of water hardness on the hatching success of hybrid catfish eggs. Four independent aquaria rack systems were used in each trial with multiple strip spawned channel catfish eggs. Calcium concentration in hatching waters was determined to be 60 ppm of calcium carbonate for optimal hatching of hybrid catfish eggs. Effects of varying levels of magnesium hardness along with either fixed or varying levels of calcium hardness on the hatching success of hybrid catfish eggs was evaluated. Hatching trials were conducted to evaluate hybrid catfish eggs reared in natural vs prepared hatching waters. The hatching performance of hybrid catfish eggs in various type and concentration of hardness will be discussed, recommendations to optimize hardness in hatching waters will be provided. |
