Volitional Tank Spawning of Female Striped Bass with Male White Bass Produces Hybrid Offspring

Abstract

We report the first volitional tank spawning of female striped bass Morone saxatilis with male white bass M. chrysops. The female striped bass were reared for 6 or 8 years from larvae to mature adults in captivity. The wild-caught male white bass were acclimated to captivity 1 year before spawning trials. The fish were induced to mature with implanted pellets containing synthetic analogue of mammalian gonadotropinreleasing hormone, [D-Ala6-Pro9-NEt]-LHRH, at 10 μg/ kg body weight in a cholesterol and cellulose matrix. Males later received an additional injection of human chorionic gonadotropin at 500 IU/kg body weight to maintain spenniation. At hormone implantation, females were in an advanced state of maturity with oocyte diameters ranging from 650 to 1,000 μm and males were producing milt. Eight females were placed in tanks with three or six males for spawning. Three females did not release eggs within 14 d. The remaining five females spawned, but only two produced fertilized eggs and hybrid offspring. All spawnings had large numbers of overripe eggs, which suggests that striped bass females had a behavioral aversion to spawning with white bass males.