Spontaneous autopolyploidy is a condition of genome duplication (increased chromosome number) that occurs between p arents and progeny within a species in the absence of hybridization or induction using traditional methods of thermal, pressure, or chemical shocks to produce triploid fish . This condition is known to occur in nine sturgeon species worldwide, including w hite sturgeon (Acipenser transmontanus ) in the Columbia River Basin in the United States and Canada. Although this species is normally octoploid, having 8 copies of each chromosome (8N), spontaneous autopolyploid w hite st urgeon (12N) have been recently confirmed in conservation and commercial white sturgeon production facilities in California and the Pacific Northwestern US and British Columbia, Canada . Some of t hese 12N individuals are fertile and when spawned with 8N fish can produce 10N progeny, which may have reduced fitness, performance, and reproductive viability. This condition in white sturgeon results from retention of the second polar body during meiosis, the same mechanism intentionally used in hatchery programs to produce sterile triploid (3N) fish. Although s pontaneous autopolyploidy in white sturgeon was initially documented in hatchery programs that artificially spaw n adult broodstock , a small number of wild (naturally-produced) 12N fish have recently been confirmed.
W e briefly discuss the detection and causes of spontaneous autopolyploidy for white sturgeon in the conservation aquaculture setting and describe six general and 13 specific Hatchery Best Practices to reduce the incidence and risks of spontaneous autopolyplo idy in such programs . Recommended Best Practices involve a range of activities from rigorous screening of broodstock and progeny groups to collectively holding pre-spawning male and female broodstock and maintaining strict ranges of environmental conditions and handling protocols in the hatchery before , during , and after ovulation and spawning. While s pontaneous autopolyploidy in conventional conservation hatchery programs can pose risks to recipient populations , implementing Best H atchery Practices can significantly reduce the incidence and risks of 12N fish. Additional focused studies to better understand the relationships between specific hatchery practices and the incidence of spontaneous autopolyploidy will help sturgeon culturists and hatchery managers balance short-term production and population rebuilding goals with the need to meet long-term population restoration and viability targets.