Location: Warmwater Aquaculture Research Unit
Title: Producing Monosex Male Populations for Catfish Culture Author
Submitted to: Aquaculture America Conference
Publication Type: Abstract Only
Publication Acceptance Date: July 30, 2010
Publication Date: N/A
Technical Abstract: There are a number of uses for the preferential production of male catfish in aquaculture operations. Several studies have demonstrated that male channel catfish grow faster than female fish and would be expected to reach market size faster. Also, in the production of hybrid catfish male blue catfish are needed as sperm donors and since the male fish must be killed, there is a need for a large supply of males each year. At birth most species of fish have a gonad that has not completed gonadal commitment to develop into a testis or ovary. Many fish species can be hormonally sex reversed by administering the appropriate hormone during the phenocritical period for gonadal differentiation; estrogen treatment feminizes and androgen treatment masculinizes the population. However, in channel catfish, hormone treatment with either type of hormone feminizes the population. Hormonal treatment for channel catfish can be achieved by feeding the hormone for the first 21 days of feeding. Blue catfish can be feminized with dihydrotestosterone, a non-aromatizeable androgen, during the sac fry stage. Selective back crosses have shown that channel catfish have an XY sex genotype model, however the sex chromosomes are not morphology distinct, and until recently the only method of determining sex genotype was by progeny testing. Crossing a sex-reversed (XY female) with a normal (XY) male results ia phenotypic ratio of 3:1 males to females and this represents a genotypic ratio of YY:2XY:XX. Further, this population can be hormonally feminized which allows the production of YY females. This allows continual production of YY fish by mating YY males with YY females. Females for the continuation of the YY strain must be produced by hormonal feminization. Male fish with a YY sex genotype will produce all male offspring. Alternately, female XY channel catfish when reproduced by gynogenesis produce 1:1 populations and the male fish would be expected to all have a YY sex genotype. However, one effort with meiotic gynogens did not produce males that were all YY, and mitotic gynogens of XY females have not yet been produced. The use in aquaculture would come from using YY male channel catfish as broodstock for the production of all male progeny for food fish production. Much less work has been done with sex reversal of blue catfish, however if the genetic model in blue catfish is similar to that of channel catfish, it should be possible to produce YY male blue catfish. The YY blue catfish would then be used as broodstock to produce all male blue catfish that could then be used as sperm donors for the production of hybrid catfish. This would avoid raising female blue catfish which are of no use in producing hybrids. The two major disadvantages are in the time required for producing mature fish for successive generations and having to determine the sex genotype by progeny testing. The first disadvantage is particularly important in blue catfish since they require 4 to 5 years to become sexually mature. We have decreased the time to maturity in channel catfish by shortening the annual warm and cold periods. We have recently developed a method to determine the sex genotype in channel catfish by the use of microsatellite DNA markers. This will allow us to determine the sex genotype early and allow us to raise only fish with the desired genotype.