Smooth Saturday screening
Today I screened and counted larvae using a 60 micron screen. I’m getting much faster at it! Shoutout to Kaitlyn for coming and helping me screen.
Figure 1. Kaitlyn screening larvae
While counting, I took this picture of a dead larvae and alive larvae side-by-side to use as a reference if I was ever unsure if something was dead. Using the compound scope and Sedgewick Rafter cell, it’s much easier to focus on the larvae see if a shell is completley empty.
Figure 2. Dead larvae (left) and alive larvae (right).
Totes 2, 6 and 8 all had their immersion heater alarms go off because they reached 27ºC. The immersion heater is generally about 2ºC warmer than the bucket, so this means the larvae were at 25ºC. That temperature is the maximum they should be kept at in the larval period. I took out the buckets in those totes and we screened them immediately. We waited for the temperature alarm to go off before putting the buckets back in, which was about 15 minutes. I think the alarm goes off when there’s only one bucket in the big gray totes. Because the water level drops when we take the buckets out and there’s less water for the heater to heat, the temperature may rise quickly. For future screening days, I think it’s a good rule of thumb to ensure there are at least two filled buckets in each gray tote at at time.
After Kaitlyn helped me screen, I had her count the number of algae cells in a mix of C.iso, 609 and Chagra in a 2:1:1 ratio. We then fed each bucket 250 mL C.iso, 150 mL 609 and 150 mL Chagra. I fed the larvae a more 609 and Chagra than I measured because I didn’t want to use a tripour to measure out 125 mL, and to give the larvae a little extra food to compensate for the stress of screening. I then filled all buckets to 4 gallons and drained the header tank.
- Feed Joth’s scallops
- Feed larvae
- Change 1 micron filter
- Flush heated line
- Drain and fill header
- Heat new water
- Prepare tripours and screening table
Here’s a copepod I found while counting larvae, just for fun: