By Alan Trimble
Oyster Bulletin No. 4 – 9 August 2011
Monday’s oyster larvae counts are diminished from 4 days previously, and the larvae are still at very early stages. Average size is about 100 microns, compared to 90 microns last Friday. Standard growth is 10 microns
per day, so the observed sizes are small, with two possible explanations:
1) Poor growth of a single cohort, or
2) Ongoing small spawns that add new small larvae.
We are collecting environmental data that will provide some insight into conditions for growth – specifically chlorophyll levels indicating food supply and aragonite saturation state that could influence larval shell deposition – but these environmental parameters are not instantaneously available, since they require some laboratory processing. The small amount of upwelling wind makes it unlikely that high-CO2 water is being advected into Willapa Bay from the ocean with tides, but the Naselle River is a regular CO2 source and is expected to reduce aragonite saturation on the east side of the bay.
Water temperatures have remained stable and are likely to do so for the next week, given the extended forecast of atmospheric troughs and thick marine layer on the coast: we expect little sunshine and little wind, with air temperatures slightly below normal for the next few days and slightly above normal over the weekend.
Oyster larval counts from Monday 8 August (morning high tide):
EAST SIDE (Monday temperatures 65.3-66.7 degrees F):
Station 3: Last Tuesday 42, Friday 168, Monday 29
Long Island Slough: Last Tuesday 54, Friday 262, Monday 128
Cougar Bend: Last Tuesday 38, Friday 321, Monday 25
Naselle Bridge: Last Tuesday 22, Friday 6, Monday 29
WEST SIDE (Monday temperatures 65.3-65.8 degrees F):
Mill Channel: Last Tuesday 14, Friday 510, Monday 132
Peterson Station: Last Tuesday 157, Friday 570, Monday 286
Smokey Hollow: Last Tuesday 70, Friday 255, Monday <30
Bear River: Last Tuesday 65, Friday 82, Monday 52
These larval counts are not expected to produce a detectable set of oysters. Clam larvae are also low currently. Barnacle larvae have apparently just been released by adults and dominate the zooplankton, especially on the east side. Sampling is planned for this Wednesday and Friday in conjunction with Alan Sarich at WDFW to sample 8 sites/day.
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