Influence of fertilizing water pH on the hatching success of stripped channel catfish eggs on channel x blue hybrid catfish embryo production in hatcheries

Authors: Chatakondi, Nagaraj

Submitted to: American Fisheries Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2016
Publication Date: 3/9/2016
Citation: Chatakondi, N.G. 2016. Influence of fertilizing water pH on the hatching success of stripped channel catfish eggs on channel x blue hybrid catfish embryo production in hatcheries. American Fisheries Society Annual Meeting. P. 21.

Interpretive Summary:

Technical Abstract: Variable egg quality is one of the most important constrains to the development of aquaculture. The quality of eggs that are manually stripped from channel catfish are affected by variation in parental genetics, maturity, type and dose of hormone, age and pre-spawning stress of female fish. Further, sub-optimal hatching conditions affect egg quality and often result in varied and lower survival of embryos in hatcheries. Production variables that are part of the hatching process need to be identified and optimized to improve the efficiency of hatchery production. Recent studies established a significant correlation between pH of stripped channel catfish eggs and hatch rate of hybrid catfish eggs, suggesting pH of the strip channel catfish eggs prior to fertilization to be predictive of hatching success of hybrid catfish eggs and considered as a predictor of egg quality. The range of pH of stripped channel catfish eggs vary from 6.5 to 9.0, however the fertilized eggs are incubated in hatchery waters of high pH (pH 7.5 to 9.5). Even though, great care is taken to optimize temperature and calcium hardness of hatchery waters, pH of hatchery water is seldom measured nor acclimated for varying pH of stripped eggs, typically a difference of 1.0 to 3.0 pH units. It is suspected that this range of pH difference between stripped eggs and hatching waters may be responsible for inconsistent and lower hatch of hybrid catfish eggs. The objective of this study was to identify progressive periodic exposure of pH waters during the transition from fertilization to incubation of fertilized eggs in hatching waters to improve hatching success. Stripped eggs from 12 hormone-induced channel catfish females of varying egg quality (pH) in replicated mesh cups were randomly exposed to fertilizing waters of pH: 7.0, 7.5, 8.0 and 9.0 for 30 minutes and progressively moved to the next higher pH level, followed by incubating in hatchery waters of pH 9.3 until hatching. Incubating stripped eggs of lower pH (pH < 7.0) in progressive periodic exposure did not improve the hatching success of hybrid catfish eggs. However, incubating stripped eggs with higher pH (pH >7.5) in progressive periodic exposure resulted in higher hatching success. The results of the study suggest that stripped eggs of lower quality incubated in higher pH fertilizing waters with gradual acclimation did not improve the hatching success of fertilized eggs. Hence, future studies need to be focused on improving genetics, nutrition, and hormonal manipulations of broodfish to produce consistent and higher egg quality of stripped eggs to maximize the hatching success of hybrid catfish eggs.