[Oyster_seed_group] August 18, 2011 Willapa Oyster Bulletin

From Alan Trimble

Hello All,
We have completed our duplicate blind counts from yesterday evening’s
pump samples. We can confirm that after a wait of several years we
finally have a cohort of Pacific Oyster larvae that are surviving and
growing to setting size in measurable numbers.

This group is notable for having survival rates on par with those of
good setting years in the past. Unfortunately, the initial size of the
group was small so the overall numbers are small.

We deployed shell strings to measure spatfall at 16 sites yesterday;
the largest larvae at many sites are within 2-3 days of setting.

Here are the counts (per 20 gallons):

Site         Low Count    High Count     Smallest     Largest
(microns)    (microns)
Lewis Slough    30           88            210          250
Long Isl Sl      0           30            200          240
Cougar Bend      0           24            220          290
Naselle Bridge   0           16            210          280
Mill Channel     5           28            210          220
Smokey Hollow   26           35            180          280
Peterson Stn    53          120            180          240
Bear River      10           51            120          250

We did see a handful of new Pacific Larvae but not enough to
warrant counting, yet. Native oyster larvae are nearly as
abundant as Pacifics at all sites and arrived in a spatfall
averaging 8 per shell over the past week in Mill Channel. The
cumulative native oyster spatfall this year is over 25 per shell
which exceeds counts for much of the past decade.

A new cohort of straight hinge clam larvae is present in all samples
and should grow in numbers as the sunny, warm weather continues.

Our next sampling will occur tomorrow morning on the dawn high tide.
We hope to have those samples processed in time for another report
in the evening.

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