Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2007
Publication Date: 10/15/2007
Citation: Davis Jr, K.B., Goudie, C.A., Simco, B.A. 2007. Sex Genotype and Sex Phenotype Contribute to Growth Differences Between Male and Female Channel Catfish. North American Journal of Aquaculture 69:324-329. Interpretive Summary: Male channel catfish grow faster than males and may be 10-12 per cent larger by the time they have reached market size. This study was done to test if the difference in gender growth was predominately due to the genotype or the phenotype of the fish. The growth and body composition of channel catfish with normal male (XY) genotypes and sibling males sex reversed to females with hormone treatment (XY females) were compared in outdoor ponds over an 18 month growing period. Phenotypic males regardless of genotype generally had higher body weight, standard length and condition factor while phenotypic females had higher liposomatic index and dress-out percentage. Males had about a 10% growth advantage while the dress-out advantage for females was only about 1.5%. Presently equal numbers of male and females are grown in a pond. Consequently, a growth advantage of about 5% would be realized from the monoculture of male channel catfish.
Technical Abstract: Channel catfish have an XX:XY genotypic system of sex determination, and until the present study, the influence of sex genotype on growth could not be distinguished from sex phenotype. Genotypic male fish (XY) were produced by mating normal (XX) female fish with YY male fish. A subsample from each family was hormonally feminized and the growth rate and body composition of sibling phenotypic males and females were compared. Phenotypic males generally had higher body weight, standard length, and condition factor, while phenotypic females had higher liposomatic index and dress-out percentage. Statistical differences between the phenotypic sexes were not as consistent as observed in previous studies with normal males and females; however, males had about a 10% growth advantage. Equal numbers of male and female catfish are typically cultured; consequently, a 5% growth advantage would be realized from the monosex culture of male channel catfish.