From Alan Trimble
Hello Everyone,
I am happy to say that the spatfall we were hoping for did actually happen. It was small, but occured throughout the southern reaches of the Bay. We placed three stacks of 11 Pacific Oyster shells at each of 16 sites on August 17 and retrieved them yesterday, August 27, and today. The shells were drilled to allow a 3/8″ dowel to pass through the middle and the shells were stacked smooth face down, with the dowel placed vertically in the sediment at approximately +1 ft above MLLW.
We counted spat on the smooth faces of all 528 shells and here are the results (# of spat per 11 shells):
Site Stack 1 Stack 2 Stack 3 Avg Spat/Shell
South Katzer 4 2 2 0.2
Long Isl Sl A 16 20 20 1.7
Long Isl Sl B 9 15 8 0.9
Chetlo Bank 3 0 0 0.1
Wilson Shack 19 13 8 1.2
Cougar Bend 20 29 25 2.2
Mill Ranch Rd 15 22 16 1.6
Mill Channel N 6 12 8 0.8
Mill Channel S 9 6 8 0.7
Peterson Channel 4 5 4 0.4
Peterson Hummock 11 14 3 0.8
Smokey Entrance 8 4 10 0.6
Smokey Inside 4 5 1 0.3
Ivan’s Island 7 2 4 0.4
Bear River 13 5 14 1.0
Lewis Slough 15 26 23 1.9
Simple observations reveal that setting was slightly higher on the east side of Long Island than the west side. Also, Long Island Slough finally had a spatfall after many years without anything measurable. Also of interest is the difference in setting across opposite sides of the Naselle Channel (Lewis vs. South Katzer) and (Chetlo vs. Wilson.) Patterns like this are easy to observe but very difficult to explain.
We are continuing to track the younger larvae still swimming. As of Friday, here are the numbers for 1/2 of the samples. (we didn’t have time to count the other half and the shells at the same time…) Counts are per 20 gallons for the larger size classes (Early Umbo and Small Umbo, 80-180 microns).
There were also new straight hinge Paciic Larvae but those counts aren’t yet completed.
Site Count Max Size
Lewis Slough 81 120
Long Isl Slough 30 150
Cougar Bend 72 160
Naselle Bridge 18 160
Mill Channel 110 120
Peterson Stn 108 120
Smokey Hollow 120 140
Bear River 111 140
My general impression is that the larvae closer to the ocean (mostly on the west side) are slowing down in growth rate and that the overall survival isn’t quite as good as the last cohort. The water temperatures are holding very close to “the same” for the past 2 weeks.
We will sample again tomorrow and hope for continued good news.
Regards,
Alan
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