| dc.description.abstract | The objective of the this research was to determine the heritabilities and response to selection for fecundity, percent hatch and fry per kilogram body weight for channel catfish females induced to ovulate with luteinizing hormone releasing hormone analogue (LHRHa) for the production of hybrid catfish embryos.
Age and/or environmental effects influences the reproductive traits measured over two spawning seasons. When the fish were three years old the relative fecundity was 10,246 and 10,126 for the select and control lines, respectfully. The percent hatch and fry per kilogram female for select line was 34.7 and 2,817 and for the control was 35.5 and 3,465, respectfully. Realized heritabilities were 0.10, -0.03, and 0.06 for fecundity, percent hatch and fry per kilogram female, respectively.
When the fish were four years old, the relative fecundity was 9,429 and 8,968 for the select and control lines, respectfully. The percent hatch and fry per kilogram female for the select progeny was 9.79 and 1,088 and the control progeny was 13.28 and 675, respectfully. Realized heritabilities were 0.42, -0.13, and -0.06 for fecundity, percent hatch and fry per kilogram female, respectively.
A response to selection for fecundity was observed for both years with realized heritability ranging from 0.10-0.42. This trait appears to have additive genetic variation and can be improved via selection. Based on the results from both years the heritability for percent hatch is zero. No additive genetic variation was found for percent hatch. A potential economically significant improvement in fry output of the three year old females was observed, although heritability was extremely low. There was no improvement in fry output when the fish were four years old. This subtle difference could be a result of a genotype X environment interaction, with the severe cold conditions masking any genetic differences. Alternatively, genotype X age effect may explain the change in results.
Additive genetic variation for channel catfish reproductive traits may be higher than indicated by the results of this study. Fry per kilogram female and percent hatch for the progeny control was five to six times higher than that of the parental generation control, thus the performance of the control was dramatically improved. This increase could be due to improvements in husbandry, an inadvertent selection response or both. | en_US |
