Ploidy Verification of Postmortem Black and Grass Carp: How and Why

Habitat impacts from Asian carps can be substantial regardless of their ploidy status.  Reproduction, with subsequent negative ecological effects, is significantly reduced with triploids.  Individual states have the constitutional authority to decide which Asian carp produced by aquaculture (diploids, triploids, or none) are legal within their borders.  Produced triploids of grass carp Ctenopharyngodon idella and black carp Mylopharyngodon piceus are certified by the USFWS to provide state resource agencies a means by which live-haul shipments do not contain diploids.  Triploid and diploid grass- and black carp have been caught within the Mississippi River Basin, and grass carp outside the Basin.  Since 2004, eyeballs of postmortem carp from resource agency catches have been examined with flow cytometry to determine ploidy; these catches are increasingly diploid.  Out of 80 fish, 61 were diploid, 18 were triploid, and one was mosaic.  Triploid grass carp males can produce haploid gametes and normal spermatocytes have been found in triploid black carp males.  For accurate ecological risk determinations, whereby the probability of grass- and black carp establishment along with ramifications determine overall risk potential, studies are required on the reproductive consequences of diploids with triploids.  Continuing to document the geographic distribution of wild-caught grass- and black carp and their ploidy will continue to inform the science.