Yaamini’s Notebook: Revised Spawning Plan

Featuring reduced crosses and pools

After showing Steven and Brent my preliminary spawning plan, I used their feedback and Joth’s comments from the July hatchery update meeting to make a revised plan. I was also able to think through the actual steps of spawning and materials needed for this plan because I shadowed a C. gigas spawn at Taylor Shellfish on Monday.

Crosses and pools

Here are the current oyster counts in my conditioning tanks.

Table 1. Oyster counts in each tank.

Tag Label A B Total
1 7 9 16
2 8 8 16
3 6 6 12
4 6 7 13
5 9 8 17
6 5 8 13
Heat Shock 5 6 11

Assuming there is a 50/50 sex ratio, I calculated the number of males and females I’d have from each tank. I assumed I would have more males than females, just for the numbers.

Table 2. Sex ratios for each tank.

Tag Label M F Total
1 8 8 16
2 8 8 16
3 6 6 12
4 7 6 13
5 9 8 17
6 7 6 13
Subtotal 45 43 88
Heat Shock 6 5 11
Total 51 48 99

To make my crosses, I will pool all of the eggs from my six tanks and from the heat shock treatment. Keeping males separate, I will cross all of the males from Tanks 1-6 with the females from Tanks 1-6. Separately, I will cross the heat shock oysters with eachother. Therefore, I will have (45 males)(6 egg pools) + (6 males)(1 egg pool) = 276 crosses.

After measuring hatch rate for each cross, 24 hours post-fertilization, I will pool hatched D-hinge larvae from each cross according to Table 3.

Table 3. Treatment pools for crosses.

Pool Parent 1 Parent 2 Parent 1 Tank Parent 2 Tank
1 Low pH Female Ambient pH Male Tanks 1-3 Tanks 4-6
2 Ambient pH Female Low pH Male Tanks 4-6 Tanks 1-3
3 Low pH Female Low pH Male Tanks 1-3 Tanks 1-3
4 Ambient pH Female Ambient pH Male Tanks 4-6 Tanks 4-6
5 Heat Shock Female Heat Shock Male Heat Shock Tank Heat Shock Tank

Once pooled, I will count the number of live and dead larvae in each pool. Based on these counts, I will calculate how many larvae I need to add to each bucket to get a density of 1/2 larvae per mL. I will then redistribute larvae into the static system.

Static system description

For the static system, I want to keep larvae in five gallon buckets. Each pool listed in Table 3 will have five replicates, meaning I need 25 buckets total. Buckets will be placed in larger totes with water and immersion heaters to keep water temperature at 25 ºC for the larval period. I think five buckets will fit nicely into a tote, but I need to check. I’m planning on keeping the totes on the middle table where Laura had her buckets.

Materials needed

  • Shucking knives: 4
  • Oyster separators: Enough to hold 200 oysters
  • Glass capilary tubes: 150
  • Tripours: ~300
  • Scoring knives: 4
  • Spatulas: 4
  • Microscope: 1
  • 80 micron screens: 2
  • 20 micron screens: 2
  • 5 gallon buckets: 50
  • Totes: 8
  • Immersion heaters: 6

Questions

  • Should I try and separate crosses between conditioning tanks (Tank A and Tank B)? I’ve had more mortalities in Tank A.
  • Should I include Ambient x Heat shock crosses?
  • Are we rearing larvae in a static system for the full duration, or are we going to switch to a flow-through at 100 microns?

Ask Molly and/or Rhonda

  • How to calculate the amount of sperm and egg to use when fertilizing
  • An easy way to calculate hatch rate

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