Individual contributions to pooled-milt fertilizations of silver catfish Rhamdia quelen

Abstract

Supplementary stocking of fish in natural environments is a way to mitigate or compensate for the changes imposed on wild populations by river damming. Since little is known about the genetic composition of the supplementary stocks obtained by pooled-milt fertilization, the aim of this study was to determine the individual contributions of male jundiá Rhamdia quelen to offspring. Sperm from four males were mixed using equal volume of sperm from each of the males to fertilize eggs from only one female, kept in three blend with six males and three females. The proportions of larvae sired by the different males were quantified using five polymorphic DNA microsatellite loci. Analysis of these loci allowed paternal determination of 84% of the progeny, at a 0.972 combined exclusion probability. Broodstock milt had good fertilizing capacity when used alone, but when pooled the fertilizing capacities, its fertilizing possibility varied from 4 to 65%. Results show that milt pools favor gametes of some males over others, thus reducing the progeny's genetic variability. © 2009 Sociedade Brasileira de Ictiologia.