Effects of Steroid and Prostaglandin Injections on Hybridization Success Between Female Channel Catfish and Male Blue Catfish
Type of Degreethesis
Fisheries and Allied Aquacultures
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Hybrid catfish produced from female channel catfish, Ictalurus punctatus, and male blue catfish, I. furcatus, exhibit superior traits for commercial aquaculture when compared to those of the channel catfish. However, one of the primary obstacles in the production of these hybrids is the shortage of fingerlings available to producers which is due to low hybridization success of the parent species. Increasing hybridization success using traditional spawning methods such as pen spawning could result in a greater production of hybrid fingerlings. In the following experiments, hormonal pheromones were evaluated as a means of increasing the male blue’s interest in the female channel during spawning so that the blue male might more readily mate with the female leading to increased spawning success. In the first experiment, female channel catfish were injected with one of the following three hormonal pheromones: 17α, 20β-dihydroxy-4-pregnene-3-one (17,20β-P), (17,20β-P-20-glucosiduronate), and prostaglandin F-2α (PGF-2α). Females were then placed into traps in ponds containing either male channel or blue catfish. The male’s responses to the pheromone treatments were recorded at various intervals over a ninety-six hour period. Males of both species were more likely to respond to a female injected with PGF-2α than a female injected with any of the other pheromones. Blue males were equally attracted to PGF-2α and 17,20β-P-20-glucosiduronate. Males were more susceptible to being attracted to females 48 to 96 hours after female injections. In the second experiment, female channel catfish received PGF-2α injections during priming injections of LH-RHa used for induced spawning. Females receiving PGF-2α were paired with blue males in concrete tanks and spawning success was compared to channel females not receiving PGF-2α and paired with either blue or channel males. PGF-2α did not increase spawning success up to the level of channel catfish nor above spawning rates for hybrids where females did not receive PGF-2α injections. However, ovulation did appear to be positively influenced by additional PGF-2α injections. These experiments prompt further investigation of the role of prostaglandins in attracting male blue and channel catfish to con-specific females during spawning which may be a reproductive isolating mechanism. Future research should also be directed towards the use of prostaglandins like PGF-2α as ovulation inducing agents for channel catfish.