Manchester Conditioning Update 10

It’s getting ugly

I had 16 oysters die today from various treatments. Based on Steven’s suggestion on Monday, I moved the oyster bags to individual 5 gallon buckets on Laura’s larval heated line, around 18 ºC. When I opened oysters that were dead, they all looked really ripe, and there were no signs of any disease. My guess is there’s something in the combination of the kiddie pool and high temperature that’s getting to them.

Table 1. Revised oyster counts in each tank, as of July 25.

Tag Label A B Total
1 3 7 10
2 5 8 13
3 2 6 8
4 2 7 9
5 6 8 14
6 4 8 12
Heat Shock 3 4 7
Full Amb 0 6 6
Spare 1 3 4
Total 26 57 83

I cut open the ones that were dead and with the exception of two, preserved them for future testing. Three oysters were stored in falcon tubes with ethanol, three in the freezer and a jar with about six oysters was put in the fridge. Not entirely sure what to do with them yet, but at least I have them. The ones that were died were quite ripe and did not look unhealthy.





Figures 1-4. Examples of oysters that died.

Oysters in Figures 1-4 were also sexed. All were male.





Figures 5-8. Microscope images of male gametes.

Other things I did today:

  • Turned off immersion heaters
  • Cleaned algae header and filled with 1.6 L Reed’s paste
  • Removed lines from oyster tanks and bleached algal line
  • Counted about 30 2 gallon buckets that can be used for fertilization
  • Set up buckets for each bag of oysters with 26 L/hr drippers and airstones


Figure 9. New set-up.

  • Cleaned gigas and counted mortalities
  • Tried measuring pH of kiddie pool water. Both durafets read different pH values for Pool B (farthest from wall).


Figure 10. Durafet monitor readings for Pool B.

  • Put the Heat Shock B oyster we thought had died back into a different bucket since it’s shell was completely closed as we were about to leave.
  • Pumped T.iso in for oysters to feed instead of paste, dosing pump at 50%

Main changes:

  • Each oyster bag has it’s own 5 gallon bucket, increasing flow and reducing density
  • Temperature is now around 18ºC instead of 23ºC. I talked to Rhonda and she’s a bit concerned that the oysters may start to reabsorb their gametes. She once had to drop broodstock to 15ºC two days before a spawn and it was fine. Maybe this will also be okay? Can they really reabsorb that quickly?
  • Oysters are being fed live algae

I will be back Thursday to check on oysters and continue preparing for spawn. I’m really hoping that no more die — I think we’ve eliminated all possible stresses! All I need is for them to be alive until I spawn them.

Written on July 25, 2017