Location: Warmwater Aquaculture Research UnitTitle: Effects of calcium and magnesium hardness on the fertilization and hatching success of channel X blue hybrid catfish eggs) Author
Submitted to: American Fisheries Society Annual Meeting
Publication Type: Abstract only
Publication Acceptance Date: 2/6/2013
Publication Date: 2/20/2013
Citation: Chatakondi, N.G., Jeffers, C.D. 2013. Effects of calcium and magnesium hardness on the fertilization and hatching success of channel X blue hybrid catfish eggs. American Fisheries Society Annual Meeting. P. 16. Interpretive Summary:
Technical Abstract: The aquifer used for hybrid catfish hatcheries is less than 10 mg/L of calcium hardness and 1- 25 mg/L of magnesium hardness. Embryonic development is deemed to be the most sensitive stage in the life cycle of a teleost. As egg development takes outside the fish’s body, water hardness is one abiotic parameter, suggested to have a major effect on egg 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. Hence, this study was conducted to ascertain whether varying levels of magnesium hardness (0, 6, 15 or 30 mg/L) with either fixed (60 mg/L of calcium hardness) or varying levels of calcium (60, 54, 45 or 30 mg/L of calcium hardness) in hatching waters affect fertilization and hatching success of hybrid catfish eggs. In the first study, strip spawned eggs from 6 females were fertilized with blue catfish sperm. Hybrid catfish eggs from each female were randomly assigned to two aquaria per (hardness level) rack systems. In the second study, strip spawned eggs from 4 females were fertilized with blue catfish sperm and randomly assigned to four aquaria per (hardness levels) rack system. In both the studies, percent fertilization, neuralation and percent hatch of hybrid catfish eggs incubated in various combinations of hardness waters did not differ (P > 0.05). The results of the study suggest that magnesium hardness (up to 50% of the total hardness) with calcium hardness in hatching waters synergistically facilitates fertilization and hatching success of hybrid catfish eggs.