Pacu (Piaractus mesopotamicus) is one of the most important Neotropical freshwater fish species produced by aquaculture in South America. This study is the first attempt to inquire about aquaculture stocks in Argentina regarding genetic diversity and structure. Neither genetic characterization nor pedigree records are available for pacu stocks in farms in Argentina. The presence of hybrids in both natural environment (Lower Paraná River) and farms has not been evaluated yet at the southern region of pacu distribution. Genetic characterization of pacu broodstocks, corresponding to 8 farms, and wild individuals from four areas at Lower Paraná River was performed. Pacu hybrids were not detected neither in wild nor in farm stocks analyzed. In general, similar levels of genetic diversity were observed between cultured and wild fish populations. Global genetic differentiation (F_st = 0.055) indicated a low level of structure and AMOVA showed that genetic variation was mostly within populations. Reduced contemporary effective population size (Ne) was observed, and probably reflects the bottleneck by founder effect in farmed fish populations. Moreover, kinship analysis showed that in fish farms, on average, 43.00% of the individuals were genetically related, whereas in wild population it was 36.40%. We recommend that broodstock management practices, such as using large Ne, single pair mating, precise records, and tagging of brood fish, should be implemented to avoid unintentional mismanagement.

Pacu（Piaractus mesopotamicus）是南美水产养殖生产的最重要的新热带淡水鱼类之一。这项研究是首次询问有关遗传多样性和结构的阿根廷水产养殖种群。阿根廷农场中的pacu种群都没有遗传特征或家谱记录。在帕库分布的南部地区，尚未评估自然环境（下巴拉那河）和农场中杂种的存在。对帕库（Pacu）亲鱼的遗传特性进行了表征，这些亲鱼对应于下巴拉那河（LowerParanáRiver）四个地区的8个农场和野生个体。在野生和分析的种群中均未检测到Pacu杂种。通常，在养殖和野生鱼类种群之间观察到相似的遗传多样性水平。全球遗传分化（F _st  = 0.055）表明结构水平低，AMOVA表明遗传变异主要在种群内。观察到当代有效种群数量（Ne）减少，这可能反映了养殖鱼类种群受创始人影响的瓶颈。此外，亲缘关系分析显示，在养鱼场中，平均有43.00％的个体与遗传相关，而在野生种群中则有36.40％。我们建议应采取亲鱼管理措施，例如使用大Ne，单对交配，精确记录和对亲鱼进行标记，以避免意外管理不善。