Checked on the spawning setup today and made some minor modifications.
The drippers I installed yesterday are 26 L/Hr (ordered from Dripworks.com – Woodpecker drip emitters, 6 GPH, #DNPC6). I tested flow rates today ad discovered some significant differences between lines (between 6-14 L/Hr).
To see how even flow rates are on just 8 lines I closed the valve leading to the bottom shelf. Here are measurements in seconds that each line filled 100 mL:
Average flow rate was 13 L/Hr. This led me to believe that there isn’t enough back pressure to supply all lines with 16 L/Hr. And in reality, 26 L/Hr (6 GPH) is over-kill. I had ordered 8 L/Hr drippers for the larval rearing, so I swapped these drippers in and tested flow rates on all valves with all valves wide open.
Here are the measurements in seconds for each line to fill 50 mL with the 8 L/Hr drippers:
Top shelf average flow rate = 5.25 L/Hr = 87.5 mL/min Bottom shelf average flow rate = 6.7 L/Hr 112 mL/min
With this low flow rate I noticed that the bottom shelf didn’t have any air bubbles, while the top shelf did. The buckets currently hold about 4 gallons, so this translates to full turn-over in 2.25 hrs and 2.85 on the bottom and top shelves, respectively.
According to the FAO’s manual, the “Hatchery culture of bivalves”, their target flow rate for heavily stocked tanks should exceed 25 mL/min. My animals are stocked at low densities (15 animals/bucket, ave. wet weight/animal = 7g), and flow rates are 3-6x greater then the minimum. I’m satisfied! I also considered that, with too high flow, I might risk flushing spermatids out of the buckets before females can “get” to them. Another added benefit of this lower flow rate is that temperature in buckets warmed up to ~17.5! The hatchery’s main heated line is set to 16degC. PSRF spawns their oysters at 18degC, and since Santos et al. (1993) showed that higher temperature corresponded to faster spawning in O. lurida I’d like temperatures to be as close to 18degC as possible.
Before leaving I decreased the algae dosing rate to 50 pulses/min, sprayed all mini-banjos/buckets clean with fresh water, and cleaned all the spawning buckets with vortex.
I also placed probes, making note of the location on manifold to assess differences in T & pH:
|Probe Name||Oly Group||Manifold Location|
|Temp 1||SN-10 Amb pH-A||North #1|
|Temp 2||NF-10 Amb pH-B||North #8|
|Temp 3||n/a||Header Tank|
|Temp 4||SN-10- low pH-A||North #5|
|Durafet 1||NF-6 Amb pH-B||South #6|
|Durafet 2||SN-10 low pH-A||North #5|
|Durafet 3||K-10 Amb pH||Top #8|
|HOBO “Tank 1”||NF-10 low pH-B||North #4|
Also, here’s a sippet from the FAO manual that I cited for flow rate: