Egg quality in fish: pH of stripped eggs can predict catfish hatching success

Authors: Chatakondi, Nagaraj

Submitted to: Global Aquaculture Advocate
Publication Type: Trade Journal
Publication Acceptance Date: 10/25/2012
Publication Date: 11/1/2012
Citation: Chatakondi, N.G. 2012. Egg quality in fish: pH of stripped eggs can predict catfish hatching success. Global Aquaculture Advocate. P. 30-31.

Interpretive Summary: Variation in egg quality of cultured fish is an important limiting factor of fry production and a major obstacle for large-scale aquaculture production. Stripped eggs from hormone-induced channel catfish females often result in lower and varying degrees of egg quality which is due to a consequence of the hormone (type, dosage or administration protocol), varying stages of maturation, mechanical damage from the stripping process, and earlier handling than pond-spawned channel catfish eggs. No effective predictive marker exists in strip-spawned channel catfish eggs, even though non-viable stripped eggs can be occasionally identified by their whitish color and less glossy appearance. A positive relationship was established between pH of stripped unfertilized channel catfish eggs and hatching success of hybrid catfish eggs, suggesting pH of stripped unfertilized eggs can be predictive of egg quality. Hybrid catfish fry production is an expensive and labor-intensive process. Egg quality can be assessed by simple pH measure of stripped eggs to removal of low-quality eggs to reduce the use of hatchery resources and spread of fungal diseases to healthy eggs to improve hatchery efficiency. Egg quality can also be used objectively by researchers to develop broodfish management practices.

Technical Abstract: This study was conducted to determine the feasibility of measuring the pH of stripped unfertilized channel catfish eggs to predict the hatching success of channel x blue hybrid catfish eggs. A significant correlation was established between the ovarian fluid pH of stripped eggs and subsequent hatch of hybrid catfish eggs (R2=0.75, P < 0.01). The data from 71 hormone-induced channel catfish females used to categorize pH of stripped eggs: pH < 7.0 as ‘low pH’ eggs, pH 7.0 to 7.4 as ‘medium pH’ eggs or pH > 7.4 as ‘high pH’ eggs. The range in percent hatch rate for these pH categories was < 15%, 15 to 30% and > 30% respectively.