cleaning juvenile heath stack screens

  • Per Matt’s direction, we cleaned the juvenile heath stack screens to prevent algae build up, especially since we know they are getting overfed. This was pretty nerve racking as Matt has never done this on geoduck this young before. But we tried to be gentle, using Matt’s sprayer on the lowest setting possible

  • The screens from H2 (right side heath stack with precious juveniles) had some algae build-up:

  • I sprayed H2-T2 first

video of spraying here

  • I returned the H2-T2 tray back to the stack and refilled it. It looked much cleaner

  • I took a total of 3 x 5 mL grabs from different areas in the tray with the turkey baster to check the animals after cleaning. I only saw one animal in the third grab, but it was pretty lively all things considered.
    • here’s a video of the juvi in action
    • I thought this might have been another juvenile, but it might just be sand. It wasn’t moving at all.
    • there were lots of swimming plankton in the water, copapods, something that looked like zoea

  • after seeing signs of life, Kaitlyn and I continued to spray the rest of the screens and trays.

  • we re-ordered the trays in the stacks when we put them back.

Sam’s experiment: low pH vs ambient

water chem

  • we took water chem samples around 2:30pm before we started cleaning.

  • kaitlyn poisoned them and ran the rest of the samples from the previous weeks that we were backlogged on.

  • T7 had no flow at all; we found out by taking pieces apart one by one that there was a clog in the main header tank line.
    • we blew it out with the hose to clear it and got flow back

cleaning screens

  • Low pH screens seemed more fouled than ambient screens:
    H1T1 before cleaning H1T1 after cleaning H1T3 before cleaning H1T3 after cleaning
    • T5 and T7 were not as fouled indicating maybe more food is going to the top trays.
    • We did not reorder these trays.
    • lots of juveniles were visible in all trays
      • After spraying and lifting the H1T1 screen from the holding tray, we notice about 100 animals in the holding tray. And we saw the same for H1T3, but not for any other screens. I suspect there may be a gap somewhere between the mesh and the screen frame.

Optimizing algae feed

  • Algal food has frequently been unevenly distributed with the setup with a T connecter to split the algae into the two header tanks set up on 04/29/2019.
  • I wasn’t able to add an additional head onto the pump because we didn’t have long enough screws
    • would need two 10” long 4mm or 1/8” screws, rods/wingnuts, or screw extenders
  • I made 2 6” pieces of the skinnier masterflex tubing and ran them both in the same pump head
    • This worked for even delievery over the few hours we monitored it. Matt will keep an eye on it.
    • Because this isn’t the best solution, I’m exchanging the pump head I previously ordered for a two channel pumphead that can accomodate two tubes and even smaller tubing. They are sending free samples of even skinnier tubing: 06402-13 and 14 that will be able to limit the flow rate even further so we aren’t overfeeding the juveniles.
  • Kaitlyn and I ran 2 lines of ~50 feet of 1/4” tubing out to the algae tank and into the pump.
  • We re-fixed the tubing above the header tanks