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A selective breeding program for Crassostrea virginica was established in 1997 as part of an initiative in Virginia to address declining oyster harvests caused by the two oyster pathogens Haplosporidium nelsoni (MSX) and Perkinsus marinus (Dermo). Housed in the Aquaculture Genetics and Breeding Technology Center (ABC), the objective of the program was to develop and disseminate disease-resistant lines that would enable an oyster culture industry. Today, culture of disease-resistant cultivars accounts formore than 90%of oyster production in the state, where 28.1 million half-shell oysters and 2 billion eyed larvae were sold in 2012. Results of our line development program as of 2006 are reported. Eight ABC lines from 3 genetic groups—East Coast (EC), Louisiana (LA), and hybrids between the 2 (HY)—and 1 wild control line, were produced and tested. These 9 groups were deployed in 4 replicates across 4 Virginia sites characterized by low (Kinsale (KIN)), medium (York River (YRK) and Lynnhaven (LYN)), and high (Wachapreague (WAC)) salinity regimes. Groups were sampled routinely for survival, growth, and disease diagnosis between November 2004 and December 2006. At KIN, where salinity was low and below the threshold for MSX and Dermo, survival was 41%–46%greater than survival at the other 3 sites by the end of the trial.Where the diseases were present (LYN,YRK, and WAC), ABC lines in general had greater survival than the control, but this varied by genetic group. The EC groups had 52%–82%greater survival, the HY groups had as much as 40% greater survival, and the LA groups performed worse than the control. Poor performance of the LA groups was a result of their susceptibility toMSX, and the majority of them died before the end of the study. The genetic effects varied with site, and the rank of the lines was inconsistent, such that the best line in one site was, in some cases, one of the worst in another. Genotype-y-environment interaction is clearly driven by disease and

A selective breeding program for Crassostrea virginica was established in 1997 as part of an initiative in Virginia to address declining oyster harvests caused by the two oyster pathogens Haplosporidium nelsoni (MSX) and Perkinsus marinus (Dermo). Housed in the Aquaculture Genetics and Breeding Technology Center (ABC), the objective of the program was to develop and disseminate disease-resistant lines that would enable an oyster culture industry. Today, culture of disease-resistant cultivars accounts formore than 90%of oyster production in the state, where 28.1 million half-shell oysters and 2 billion eyed larvae were sold in 2012. Results of our line development program as of 2006 are reported. Eight ABC lines from 3 genetic groups—East Coast (EC), Louisiana (LA), and hybrids between the 2 (HY)—and 1 wild control line, were produced and tested. These 9 groups were deployed in 4 replicates across 4 Virginia sites characterized by low (Kinsale (KIN)), medium (York River (YRK) and Lynnhaven (LYN)), and high (Wachapreague (WAC)) salinity regimes. Groups were sampled routinely for survival, growth, and disease diagnosis between November 2004 and December 2006. At KIN, where salinity was low and below the threshold for MSX and Dermo, survival was 41%–46%greater than survival at the other 3 sites by the end of the trial.Where the diseases were present (LYN,YRK, and WAC), ABC lines in general had greater survival than the control, but this varied by genetic group. The EC groups had 52%–82%greater survival, the HY groups had as much as 40% greater survival, and the LA groups performed worse than the control. Poor performance of the LA groups was a result of their susceptibility toMSX, and the majority of them died before the end of the study. The genetic effects varied with site, and the rank of the lines was inconsistent, such that the best line in one site was, in some cases, one of the worst in another. Genotype-y-environment interaction is clearly driven by disease and

A selective breeding program for Crassostrea virginica was established in 1997 as part of an initiative in Virginia to address declining oyster harvests caused by the two oyster pathogens Haplosporidium nelsoni (MSX) and Perkinsus marinus (Dermo). Housed in the Aquaculture Genetics and Breeding Technology Center (ABC), the objective of the program was to develop and disseminate disease-resistant lines that would enable an oyster culture industry. Today, culture of disease-resistant cultivars accounts formore than 90%of oyster production in the state, where 28.1 million half-shell oysters and 2 billion eyed larvae were sold in 2012. Results of our line development program as of 2006 are reported. Eight ABC lines from 3 genetic groups—East Coast (EC), Louisiana (LA), and hybrids between the 2 (HY)—and 1 wild control line, were produced and tested. These 9 groups were deployed in 4 replicates across 4 Virginia sites characterized by low (Kinsale (KIN)), medium (York River (YRK) and Lynnhaven (LYN)), and high (Wachapreague (WAC)) salinity regimes. Groups were sampled routinely for survival, growth, and disease diagnosis between November 2004 and December 2006. At KIN, where salinity was low and below the threshold for MSX and Dermo, survival was 41%–46%greater than survival at the other 3 sites by the end of the trial.Where the diseases were present (LYN,YRK, and WAC), ABC lines in general had greater survival than the control, but this varied by genetic group. The EC groups had 52%–82%greater survival, the HY groups had as much as 40% greater survival, and the LA groups performed worse than the control. Poor performance of the LA groups was a result of their susceptibility toMSX, and the majority of them died before the end of the study. The genetic effects varied with site, and the rank of the lines was inconsistent, such that the best line in one site was, in some cases, one of the worst in another. Genotype-y-environment interaction is clearly driven by disease and

This study reports mortality under laboratory conditions in unselected controls and two lines of juvenile Pacific oysters Crassostrea gigas, previously selected for their high or low survival in the field during the summer period. Oysters were also deployed in field conditions and mortality between both conditions was then compared. In the laboratory, mortality was observed in all experiments and it always lasted for a week indicating that mortality under laboratory conditions was a short-term event. It was also shown that mortality could be repeated for a batch in several experiments using oysters which never experienced any abnormal mortality. This approach could facilitate further studies to investigate the causes of mortality by allowing repeated trials during a summer. Differences in mortality between the resistant and the susceptible selected lines confirmed the positive response to selection under laboratory conditions. Batches that performed well in the laboratory also showed high survival in the field, and the results of those exhibiting low survival in the laboratory trials were also mirrored in the field. Finally, challenging oysters with heat stress is proposed as a useful method for estimating the survival capacity of hatchery-produced and wild-caught spat used by the oyster industry.

This study reports mortality under laboratory conditions in unselected controls and two lines of juvenile Pacific oysters Crassostrea gigas, previously selected for their high or low survival in the field during the summer period. Oysters were also deployed in field conditions and mortality between both conditions was then compared. In the laboratory, mortality was observed in all experiments and it always lasted for a week indicating that mortality under laboratory conditions was a short-term event. It was also shown that mortality could be repeated for a batch in several experiments using oysters which never experienced any abnormal mortality. This approach could facilitate further studies to investigate the causes of mortality by allowing repeated trials during a summer. Differences in mortality between the resistant and the susceptible selected lines confirmed the positive response to selection under laboratory conditions. Batches that performed well in the laboratory also showed high survival in the field, and the results of those exhibiting low survival in the laboratory trials were also mirrored in the field. Finally, challenging oysters with heat stress is proposed as a useful method for estimating the survival capacity of hatchery-produced and wild-caught spat used by the oyster industry.

This study reports mortality under laboratory conditions in unselected controls and two lines of juvenile Pacific oysters Crassostrea gigas, previously selected for their high or low survival in the field during the summer period. Oysters were also deployed in field conditions and mortality between both conditions was then compared. In the laboratory, mortality was observed in all experiments and it always lasted for a week indicating that mortality under laboratory conditions was a short-term event. It was also shown that mortality could be repeated for a batch in several experiments using oysters which never experienced any abnormal mortality. This approach could facilitate further studies to investigate the causes of mortality by allowing repeated trials during a summer. Differences in mortality between the resistant and the susceptible selected lines confirmed the positive response to selection under laboratory conditions. Batches that performed well in the laboratory also showed high survival in the field, and the results of those exhibiting low survival in the laboratory trials were also mirrored in the field. Finally, challenging oysters with heat stress is proposed as a useful method for estimating the survival capacity of hatchery-produced and wild-caught spat used by the oyster industry.

This study reports mortality under laboratory conditions in unselected controls and two lines of juvenile Pacific oysters Crassostrea gigas, previously selected for their high or low survival in the field during the summer period. Oysters were also deployed in field conditions and mortality between both conditions was then compared. In the laboratory, mortality was observed in all experiments and it always lasted for a week indicating that mortality under laboratory conditions was a short-term event. It was also shown that mortality could be repeated for a batch in several experiments using oysters which never experienced any abnormal mortality. This approach could facilitate further studies to investigate the causes of mortality by allowing repeated trials during a summer. Differences in mortality between the resistant and the susceptible selected lines confirmed the positive response to selection under laboratory conditions. Batches that performed well in the laboratory also showed high survival in the field, and the results of those exhibiting low survival in the laboratory trials were also mirrored in the field. Finally, challenging oysters with heat stress is proposed as a useful method for estimating the survival capacity of hatchery-produced and wild-caught spat used by the oyster industry.