1. ASSESSMENT OF MAJOR FACTORS AFFECTING TRIPLOID INDUCTION USING HYDROSTATIC PRESSURE IN THE EASTERN OYSTER (Crassostrea virginica)
Name: Ian Sewell (MSc candidate)
Supervisor: Dr. Sarah Stewart - Clark
Date: January 25, 2018

2. Research Problem/Project Goals
MSX outbreak within the Bras D’or Lake occurred in 2002 [1]
95% decimation rate within the Bras D’or Lake [1]
MSX still prevalent to this day
To increase the resilience of the CB oyster industry through studying and implementing triploidy technology
Fig 1: Haplosporidim nelsonii
Fig 2: Spread of MSX within the Bras D’or Lake

3. Potential Solution
MSX initial outbreak in the US dated back to the 1950s [2]
The effects of MSX completely eradicated through polyploidy and breeding [2]
Transfer of resistant/triploid/tetraploid oysters– Not a possibility
Oysters in Canada are uniquely adapted to Canadian environmental and disease pressures
Research Approach: Learn from them and implement these practises

4. Method & Results Deliverables Triploidy experiment
3x3 Multifactorial approach - 9 treatment combinations
To determine the effect of:
Pressure intensity (3 levels): 6000, 7000, 7500 PSI
Pressure duration (3 levels): 3, 5, 10 mins
3. FIXED treatment initiation stage: 60% 1st Polar body [3]
Larval ploidy level checked using flow cytometry (ABC hatcheries, VIMS) [4]
Deliverables
Triploid induction success in all treatments
Up to 44% triploid induction rate
No significant differences among treatments (P=0.229)
Unintentional tetraploid success through late PB timing (70% 1st Polar body)
Successful triploid groups deployed in the Bras D’or Lake for 2N/ 3N growth analysis

5. Acknowledgements & References
I’d like to thank the AANS, DAL Aquaculture staff , VIMS – ABC Hatchery staff, my supervisor – Dr. Sarah Stewart-Clark, Scott Jeffrey, my academic committee, and all the involved farms for their assistance and participation throughout the project.
References
[1] Ford, S.E. and Haskin, H.H History and Epizootiology of Haplosporidium nelsoni (MSX), an oyster pathogen in Delaware Bay, 1957 – J. Invertebr. Pathol. 40: 118 – 141
[2] Aquaculture Genetics and Breeding Technology Center Virginia Institute of Marine Science, School of Marine Science, College of William and Mary. pp 28.
[3] Allen Jr, S.K., Downing, S.L., Chew, K.K Hatchery manual for producing triploid oysters. University of Washington Press, Seattle, WA, USA.
[4] Allen Jr, S.K Flow cytometry: assaying experimental polyploid fish and shellfish. Aquaculture. 33: 317 – 328

6. End of Presentation