Larvae collection, counting, and sampling
I’m being really paranoid at this point as I want to try and “catch ’em all”. I’ve modified my larvae collecting a little bit by stacking a 400 micron screen on top of the 100 micron screen to catch the poop/gunk.
- SS3, SS5, SS4, HC4, and HC5 had low or suspect number of larvae
- SS1, SS4, SS2, HC2 had a definitely noticeable or large number of larvae
- HC4 and HC5 did not have any larvae when checked with the dissecting scope
- Data sheet with larval counts
After I counted the larvae samples, I dumped them into into the appropriate HC or SS 100 L tanks, after they had been cleaned and filled up with water. In the afternoon, Ryan (the hatchery manager) told me that there had been a malfunction with the heated seawater line sometime between Friday afternoon and Saturday when he came in. All of the tanks were at ~15C, and they observed severe mortality in their larvae tanks. The larvae I had collected from the larval catch buckets were mostly healthy. There were a few empty shells (from now on I’ll count those too), but they were definitely less than 5%. The problem might be if there was a severe mortality event in my 100 L tanks. Those dead larvae would have been filtered out with the healthy ones while I was cleaning and put back in, this could make the rest of the larvae sick from swimming around with dead ones. Unfortunately I had already put my newly collected larvae in those same tanks.
There were 29,000 larvae in the HC tank and 87,850 in the SS tank over the weekend. There are now 83,600 larvae in the HC tank and 363,437 in the SS tank. On Wednesday when I clean these out, I will filter them over a 160 micron screen stacked on a 100 micron screen. I’ll do counts of both sizes, and in particular look at the proportion of dead larvae in the smaller size. Any larvae that didn’t die or get sick on Saturday would have grown since, while those that did would still be passing through a wider screen.