|Yant, R -|
|Kritanto, A -|
|Umali-Maceina, G -|
|Dunham, R -|
Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 14, 2011
Publication Date: December 1, 2011
Citation: Chatakondi, N.G., Yant, R.D., Kritanto, A., Umali-Maceina, G.M., Dunham, R.A. 2011. The effect of luteinizing hormone releasing hormone analog regime and stage of oocyte maturity for induced ovulation of channel catfish, Ictalurus punctatus. Journal of the World Aquaculture Society. 42(6):845-853. Interpretive Summary: Hormonal Intervention is the most effective method for inducing maturation and spawning in channel catfish to produce channel x blue hybrid catfish. The extent of the ovarian development in individual fish varies considerably and the ovarian maturation needs to be determined prior to hormone induced ovulation. A threshold degree of maturity must be reached before brood fish can be induced to spawn, but selection of such fish can be very subjective. The objective of this study was to determine the effective dose of luteinizing hormone releasing hormone analog (LHRHa) dose on varying levels of gonadal maturity of channel catfish to optimize hybrid catfish production. Non-invasive method to assess gonadal maturity was validated by determining the germinal vesicle position in the biopsied oocytes. Gonadal maturity contributed to the majority of the variation in hormone induced ovulation of channel catfish. Higher ovulation correlated significantly with higher quality of eggs, resulting in higher fry production. This study addresses the importance of maturity and effective hormone dose to synchronize ovulation to produce large quantities of hybrid embryos that would be cost effective and efficient to the U. S. catfish industry.
Technical Abstract: The effective LHRHa (luteinizing hormone releasing hormone analog) dose based on the gonadal maturity of channel catfish, Ictalurus punctatus to optimize channel x blue hybrid catfish production was evaluated in 4 trials (twice in early part of the season and twice in the peak spawning season) in a commercial catfish breeding facility in Mississippi. In each trial, gonadal maturity of one-hundred randomly selected mature female channel catfish were scored by external and internal evaluation. Individual fish were graded (Excellent, Good and Average) according to external observations: softness of belly, fullness and coloration and size of the genital openining. Twenty to 30 oocytes were cannulated to ascertain the germinal vesicle position in oocyte to classify the internal maturity as: GVC (germinal vesicle in central) or GVS (germinal vesicle is sub-peripheral) or GVM(germinal vesicle fully migrated). Twenty fish were randomly assigned to one the three LHRHa doses (µg/kg body weight, 82% active ingredient): initial/resolving at 15 h intervals; LHRHaH 20/80; LHRHaM 20/60; LHRHaL 20/40 and the fourth and the fifth treatment (CPEC and CPEO) were CPE (common carp pituitary extract), the standard ovulating agent, injected at 2mg/kg of body weight as an initial dose and 15 hours later with 8mg/kg body weight. Females of the CPEC treatment were catheterized prior to injection to determine the stage of egg development and the CPEO were not catheterized. External evaluation methods to identify broodfish maturity correlated (r=0.63, p< 0.05) with the internal methods. CPE and LHRHa treatments did not differ (P>0.05) in effectiveness for ovulating channel catfish females. LHRHaH was more effective (P<0.05) than the other doses of LHRHa for ovulation. LHRHaM resulted in higher hatch compared to other LHRHa treatments, but did not differ (p=0.629) from CPE treatment. Higher percent ovulation was obtained in fish exhibiting excellent > good > average level of maturity in channel catfish. A positive and significant correlation (r=0.629, p=0.003) was established between the percent ovulation of channel catfish females and the egg quality (visual classification) of the stripped females, emphasizing the importance of gonadal maturity of channel catfish in hormone induced spawning in the channel x blue hybrid catfish production.