So track record for daily posts aren’t great, but I’m working on it. This was a pretty eventful week in the hatchery- setting up a system for settlement, some unfortunate mortality, and getting locked out of the molecular lab (now I know to keep a stash of ethanol/RNALater/tips in the hatchery!).
Since I cleaned out the 100L larval tanks on Sunday, on Mon-Wed-Fri I’m now only flushing the line with bleach, cleaning all the drippers, cleaning all the banjo filters, collecting any spawned larvae, and cleaning the broodstock/larvae catch buckets. On Tues-Thurs-Sat/Sun I’ll filter out the larvae from the 100L tanks and clean those, as well as the daily banjo filter and dripper cleaning. I’ll also check for newly spawned larvae on those days and filter those out to count and add to a 100L tank.
Checking for new larvae:
- Some: NF1(?), HC3
- Lots: SSS1, HC5, SS2, SS3, HC4, SS4, HC2
- Got about 222,000 larvae from the SS buckets to add to SS_Tank2 and 230,000 from the HC buckets to add to HC_Tank2
- None from NF
Had time to filter out what was spawned in the SS group bucket during cleaning but not the HC bucket, although there was no noticeable larvae in that one.
There’s been an issue with the algae cultures since Friday 6/26, where there hasn’t been any diatoms to feed the animals. The recommended diet is 50% diatoms and 50% flagellates, so the larvae might have a deficiency of necessary amino acids.
Checking for larvae:
- Some/Maybe: HC3, NF1(?), NF2(?), SS1(?), NF5(?)
- Lots: HC4
- none in SS1 or NF families, just poop
Today I decided to try out doing “weight counts” as well as my usual counts for the 100 L larval tanks. With this method, you filter out a 100 L tank over a few different sized mesh screens. The larvae of each size class is put in a small (approx. 15cm diameter, 10 cm height) pvc silo with a 100 micron mesh screen at the bottom, where the weight of each silo when empty is known. You weigh the silo+larvae, subtract the weight of the silo, and use a conversion sheet to get the estimated number of larvae based on their size. I’ll add a picture of the conversion sheet later, but you can see my data from the counts on the 4th sheet of my Google doc.
I screened each of my 5 tanks over 200, 160, and 100 screens. Since I’m not weighing every size class possible, I calculated a range for # of larvae- assuming that my 160 sample had larvae sized between 160 and 180 and my 100 sample had larvae between 100 and 150.
After counting, I threw out larvae from SS_Tank1 that was left on the 100 micron screen as these are mostly dead or sick.
When doing drop counts, I accidentally knocked over a tray with SS_Tank2 160, 100 and NF_Tank1 100 on it. I had already put the larvae back in their tanks, so except for weight counts I don’t have data for those.
Comparing the weight counts to drop counts, the weight counts usually overestimate compared to drop counts- particularly if there are less than 10,000 larvae.
Some Chagra (a diatom) is now available.
Steven Roberts came in to help today. I did all of the filtering of larval catch buckets, and he did all of the counts, helped with bucket cleaning, and helped me set up a growth rate experiment.
Checking for larvae:
- Some: NF3, NF5, SS3, HC1,HC5
- Lots: SS1,NF2,SS4
- Filtered out all buckets
- These were counted almost immediately after filtering out, but still saw a higher proportion of dead larvae in buckets than usual.
Growth rate experiment
As multiple families in each group spawned today, I started an experiment to look at differences in growth rate. Silos with 100 micron screens are put in beakers filled with seawater and algae. I have 3 replicate silo/beakers for each population, with ~900 larvae added inside of the silo.
This is referred to as a “static system”, as water is not flowing through it. Every day I have to rinse off the silo and transfer it to a clean beaker filled with seawater/algae. I’m taking samples of the water that goes into the beakers and samples after the larvae have been in there for a day to get an idea of feeding rate. To calculate the algal cell density in these samples, I put 10 mL into a 15 mL centrifuge tube and spin them down. I then take out the seawater and add some back so that they are all at a volume of .5mL. With this concentrated sample, I can use a hemocytometer to count algal cells and scale up to estimate the density in my original samples.
Notes: algae is 50% Tiso, 50% Chagra
On Wednesday night I bought a 24″ x 40″ sheet of PVC to make into 4″ x4″ tiles for oysters to settle on, as they were close to holding on a 224 micron screen on Tuesday (meaning they were almost large enough to be at the metamorphosis stage). However, when I got to the hatchery on Thursday there was no one around to show me how to cut it up. I noticed some larvae were piled up on the bottom of the SS_Tank1 and HC_Tank1. I thought this might be due to them being ready to settle. With the tiles not ready, I rigged a settlement system using large silos and cultch (ground up bits of shell around 450 microns in size). This system is static, like the growth rate experiment, so I have to change the water every other day and add in algae every day. I added 6,000 SS_Tank1 larvae to each of two silos.
I filtered out all of the 100L larval tanks over 224, 160, and 100 screens except for NF_Tank1 where I just did 160 and 100 (ran out of time). Based on the age of the HC_Tank1 and SS_Tank1 tanks, there shouldn’t be any screening below 160, but a significant number were in both cases. The larvae at all sizes did not move very much, even without ethanol added to the well. I took 20,000 of the SS_Tank1 larvae that were filtered on the 224 screen and added them to my settlement system. Not knowing what to do with the rest, I added them back into the SS_Tank1 tank. I threw out the 100 micron sized SS_Tank1 and HC_Tank1 larvae though.
- salinity: 29 ppt
- temp: 20C
- Food: Tiso, 609