Differences Observed in Qualitative and Quantitative Traits of Five Red Sea Bream Strains Propagated under the Same Rearing Conditions

Abstract

Qualitative and quantitative traits of 5 red sea bream strains developed for fish farming were evaluated using offsprings which were propagated under the same rearing conditions. The fertilized eggs collected from five different hatcheries on the same day were used to remove the effects of age and environmental differences on the traits. The genetic variability observed in the parameters, average number of alleles per locus (q<0.99) and proportion of polymorphic loci were reduced in selection strains (S2, S3). These reductions of genetic variability seemed to be caused mainly by extinction of minor alleles, possibly caused by the bottle-neck effect. Growth performances of selection strains (S2, S3, S4, S5) were significantly different from the non-selection strain (S1). Significant differences among the 5 strains were also found in the morphological traits such as body depth and orbito diameter. Slight genetic change and genetic improvement were observed in qualitative and performance traits respectively, but there were no symptoms of inbreeding such as homozygous excess in the genetic traits. © 1995, The Japanese Society of Fisheries Science. All rights reserved.