Temperature is at 23 ºC!

On Monday, Grace went out to Manchester and increased the setpoint on the left heater to 27 ºC. Olivia vacuumed the oysters and did not find any mortalities. Dana fed the oysters the remaining 350 mL of Reed’s paste. On Tuesday, Ryan noticed that the algae dosing pump lost it’s prime sometime overnight. He fixed it so it was working when I got to the hatchery. Temperature’s been peaking at 23 ºC every day, but it still drops to about 22 ºC due to diurnal fluctuations. When I checked the heater setpoints this morning, I saw they were heating the water a few degrees hotter than my goal.

Figures 1-2. Heater setpoints upon arrival.

I increased the setpoint on the left heater by one degree just to smooth out fluctuations and have temperature hover at 23ºC during the day.

Figure 3. Heater setpoint after increasing it.

Because the oysters haven’t had much food over the past few days, I wanted to feed them really well. I filled the algae header tank with 800 mL of Reed’s for one day and set the dosing rate at 60%. I vacuumed the oysters and found 5 dead :0 Two were from Tank 6A, and three were from Full Ambient A.

Table 1. Revised 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
Full Amb	4	8	12
Spare	2	3	5
Total	52	63	117

My original plan today was to shuck some oysters, look at gonad development and sex them. Since the oysters that died had died recently, I figured I might as well examine their gonads! Out of the five that died, four were still mostly intact. All four had nice opaque white gonads, one of which was quite milky! I think with increased feeding and temperature they’ll become even milkier. I wanted to sex the oysters, but the microscope at PSRF didn’t let me zoom in enough. Plus it was difficult to pull a bit of the gonad from the degrading oysters. I was able to pull gonad from one oyster, and I think it was a male.

Figures 4-7. Gonadal development for oyster mortalities.

Figure 8. Gonad under the microscope for first oyster pictured above. I couldn’t zoom in enough, but I believe this is a male gonad.

The next time I go out to Manchester, I’ll bring better tools to pull gonad and see if I can get help from Dana to look at the gonad.