ABSTRACT: Commercial off-bottom aquaculture of the eastern oyster Crassostrea virginica is challenged by repeated summer mortality events that appear to affect triploid oysters disproportionally. Many farmers believe common farming practices, especially when performed during hot summer months, may increase triploid mortality. The goal of this study was to investigate how diploid and triploid oysters react to common stressors imposed by farmers: tumbling during size grading and desiccation to prevent biofouling. Triploid and diploid oysters were deployed in floating cages at 3 farm sites along the US Gulf of Mexico coast. In May and July, oysters in 7 cages were subjected to 1 of 6 stress treatments: 1 of 3 levels of desiccation (18, 24, or 48 h) mixed with 1 of 2 levels of tumbling (tumbled or not tumbled), along with a never handled, submersed control. The mortality and growth rate of oysters were assessed in June, August, and September. Growth rates of both ploidies were affected by compounding stressors; that is, treatments with both tumbling and the longest desiccation period exhibited slower growth. Triploid oysters exhibited a greater increase in mortality in response to farm stress than diploid oysters, and mortality increased in all oysters subjected to extreme stress treatments when compared to the control. Based on this study, farmers should limit the desiccation time of oysters (particularly triploids) in the summer months to avoid any mortality or reduced growth resulting from compounding stressor effects.

中文翻译：

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耕作方式对三倍体和二倍体东部牡蛎Crassostrea virginica的生长和死亡率的影响

摘要：东部牡蛎Crassostrea virginica的商业化水底养殖反复出现的夏季死亡事件对三倍体牡蛎造成了巨大的挑战。许多农民认为，特别是在炎热的夏季进行的常规耕作方法可能会增加三倍体死亡率。这项研究的目的是研究二倍体和三倍体牡蛎对农民施加的常见压力如何反应：在分级过程中翻滚和脱水以防止生物结垢。三倍体和二倍体牡蛎被部署在美国墨西哥湾沿岸三个农场的浮笼中。在5月和7月，对7个网箱中的牡蛎进行了6种压力处理中的1种：3种干燥水平中的1种（18、24或48小时）与2种水平滚动中的1种（翻滚或不翻滚）混合，以及从未处理过的潜水控件。在六月，八月评估牡蛎的死亡率和增长率，和九月。两种倍性的生长速率都受到复合胁迫的影响；也就是说，翻滚和干燥时间最长的处理均显示出较慢的生长。与二倍体牡蛎相比，三倍体牡蛎在应对养殖场应激时表现出更大的死亡率增加，并且与对照相比，所有经过极端胁迫处理的牡蛎的死亡率均增加。根据这项研究，养殖者应在夏季限制牡蛎（特别是三倍体）的脱水时间，以避免因复合应激源造成的任何死亡率或生长减慢。与二倍体牡蛎相比，三倍体牡蛎在应对养殖场应激时表现出更大的死亡率增加，并且与对照相比，所有经过极端胁迫处理的牡蛎的死亡率均增加。根据这项研究，养殖者应在夏季限制牡蛎（特别是三倍体）的脱水时间，以避免因复合应激源而造成任何死亡率或生长减慢。与二倍体牡蛎相比，三倍体牡蛎在应对养殖场应激时表现出更大的死亡率增加，并且与对照相比，所有经过极端胁迫处理的牡蛎的死亡率均增加。根据这项研究，养殖者应在夏季限制牡蛎（特别是三倍体）的脱水时间，以避免因复合应激源造成的任何死亡率或生长减慢。