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Title: The influence of ovarian fluid ph of stripped unfertilized channel catfish Ictalurus punctatus eggs on the hatching success of channel catfish x blue catfish I. furcatus hybrid catfish eggs

Author
item Chatakondi, Nagaraj
item Torrans, Eugene

Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2012
Publication Date: 8/2/2012
Citation: Chatakondi, N.G., Torrans, E.L. 2012. The influence of ovarian fluid ph of stripped unfertilized channel catfish Ictalurus punctatus eggs on the hatching success of channel catfish x blue catfish I. furcatus hybrid catfish eggs. Journal of the World Aquaculture Society. 43(4):585-593.

Interpretive Summary: Hormone-induced fish often ovulate eggs of varying quality largely due to variation in brood fish maturity, husbandry, nutrition, genetics and mechanical damage during the stripping process. Poor quality eggs often succumb to fungus and spread to healthy eggs. Presently, there are no known methods to identify egg quality prior to hatching, hence all the stripped eggs are fertilized and incubated in catfish hatcheries that incur cost of labor and facilities. Our findings suggest that pH of the ovarian fluid of stripped eggs prior to fertilization was predictive of hatching success in hybrid catfish embryos. It appears that pH > 7.0 of the stripped eggs need to be fertilized and incubated in hatcheries to improve the efficiency and hatchery resources. Higher calcium hardness in hatching waters does not seem to improve the hatching success of low quality eggs. The practical tool can be easily adopted to identify poor quality eggs in catfish hatcheries to reduce the spread of disease to healthy eggs and to better utilize labor, time and hatchery resources to improve the efficiency of hybrid catfish fry production.

Technical Abstract: This study was designed to determine the effect of ovarian fluid pH of stripped unfertilized channel catfish (Ictalurus punctatus) eggs on fertilization and hatch rate of channel catfish ' x blue catfish (I. furcatus) ' hybrid catfish eggs. A significant correlation was established between ovarian fluid pH of stripped channel catfish eggs and hybrid embryo hatch rate (R2 =0.63, P < 0.01) suggesting ovarian fluid pH of stripped catfish eggs prior to fertilization can be predictive of the hatching success of hybrid catfish embryos. These data were used to categorize egg quality based on the pH of stripped eggs: pH <7.0 as “low”, pH 7.0 to 7.4 as “medium” or pH >7.4 as “high” quality eggs with hatch rates of < 15%, 15 – 30%, and > 30%, respectively. Higher calcium concentrations in hatching waters do not appear to improve hatching success of lower quality stripped channel catfish eggs. The predictive egg quality model derived from this study is a practical tool for management and incubation of hybrid catfish eggs in catfish hatcheries to effectively utilize hatchery resources.