Yaamini’s Notebook: Gigas Larvae Day 7

Anoxia is no bueno

My main goal today was to flush out any anoxic water from the heated line. When I got to the hatchery, I started draining the header tank and opened the heated line to flush any water out. I let this run while I prepared tripours for tomorrow’s screening and fed Joth’s scallops. After 30 minutes, I shut the heated line off and replaced the 1 micron filter. I noticed that the filter casing didn’t have the black rubber ring around it anymore, but water wasn’t leaking from it. I rinsed the casing and put a new filter in, then turned the heated line back on. I let the line run for 2 minutes while I took a freshwater hose and cleaned the inside of the header tank. After a few more minutes of letting the tank drain, I closed the bottom valve and started filling it.

While the tank was filling, I fed my larvae. I noticed that the buckes were relatively clear, and most of the algae had settled to the bottom.


Figure 1. Tank color upon arrival.

I figured I would increase the algal density to about 65,000 cells per mL and check the color of the buckets tomorrow morning before screening. I don’t want the larvae to go without food dispersed throughout the water for more than an hour, so maybe increasing the amount of food will help maintain the algae level I want. It’s also possible they’ve started to eat more as they’re growing.

After feeding my larvae, the header tank was about halfway filled. I plugged all three heaters back in, kept the heated line open so the tank could finish filling, and rushed out the door to catch the 11 a.m. ferry back. In my haste, there were a few small screening preparation tasks I forgot to do, so they’re at the top of my list tomorrow!

For tomorrow:

  • Record which buckets are in which totes (I need this before I rerandomize my buckets!!)
  • Turn off cold water input
  • Label tubes for larval samples
  • Measure out amount to feed ahead of screening, so larvae can be fed while being restocked
  • Screen larvae on 80 and 60 micron screens
  • Count larvae and drop stocking density to approximately 2 larvae/mL
    • Based on my current count data, Buckets 3, 9, 10 and 11 are the four that are above this stocking density
  • Drain heating header and unplug heaters
  • Clean and/or replace filters
  • Return Rick’s silver heater

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Yaamini’s Notebook: Gigas Larvae Day 6

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.

For tomorrow:

  • 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:


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Yaamini’s Notebook: Gigas Larvae Day 5

Lots of maintenance today

Aside from daily feeding, I don’t have much urgent work on days I don’t screen and count. I used my off day to get my system fully set up and catch up on counting larvae from my first screening.

What I did today:

  • Recorded which tote each tank was in
  • Wireless monitoring
    • I have four AVTECHs available for my larvae: Temp 1, Temp 4, WISH 9 Ext 1 and WISH 9 Ext 2. Temp 3 is for my heating header tank
    • Changed names on OA Monitor Dashboard on GoToMyDevices and placed in totes
      • Temp 1 = Gigas-Larvae-1 = Tote 5
      • Temp 2 = Gigas-Larvae-2 = Tote 1
      • WISH 9 Ext 1 = Gigas-Larvae-3 = Tote 7
      • WISH 9 Ext 2 = Gigas-Larvae-4 = Tote 9
      • Temp 3 = Gigas-Larvae-Header
    • Labelled AVTECHs with tape so I knew which one was which
    • Set up alerts if temperature gets above 27ºC or below 22ºC
  • Decided against relabelling HOBOs because I didn’t want the Sharpie to leech into the water. This is something I need to think of an alternative for
  • Set high (27ºC) and low (24ºC) temperature alarms on immersion heaters
  • Flushed header and heated line
    • Turned off all heaters
    • Removed and cleaned Rick’s heater
    • Added a third heater to replace Rick’s
    • Drained header tank and flushed heated line
    • Refilled header tank
    • Heated water
  • Fed Joth’s scallops
  • Cleaned tripours for Saturday screening
  • Replaced PSRF’s blue screens with green screens
  • Counted Plate 2 and 3
    • While I was counting Bucket 10 (Plate 2, Wells C1-C3) I found there dark blobs that were bigger than the larvae. I sent images to Rhonda and she didn’t know what it was. I couldn’t zoom in and make the image clear enough to take a photo, but here are the blurry images I took. I found 30 in Well C1, 38 in C2 and 18 in C3.


Figures 1-3. Big blobs found in Bucket 10

  • Because of this weird contamination and the fact that I incorrectly counted Plate 1, I these data may end up being an outlier.
  • Fed larvae a mix of Chagra, C.iso and 609. Again, the algae was really dense!
    • I fed 15 and 16 extra 100 mL of 609 and 100 mL Chagra by accident

For tomorrow:

  • Feed Joth’s csallops
  • Screen and count on 60 micron screen
  • Feed larvae
  • Drain header tank

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