[Oyster_seed_group] July 12, 2011 Willapa Bay Oyster Bulletin

From Alan Trimble

Hello everyone,
We finally have a small group of Pacific Oyster larvae in the water. A small spawning on July 6-7 produced viable swimmers that we detected on Friday July 8th at 80-85 microns. The maximum counts have been hovering between 20 and 35 larvae per 20 gallons pumped. They have
been growing, but haven’t been detected in some samples, while they are present in others from the same locations. The maximum size of any individual yesterday was 130+ microns – most were closer to 110 microns.

We are monitoring this cohort daily, as early larvae have historically been more robust than later ones.

The pdf file attached to this message contains a composite plot of summer water temperatures in Nahcotta for 2005, 2010 and 2011 as compared to the average daily temperatures for 1990-2005. This should help everyone understand how the Bay is doing this year… finally catching up to average after a cool spring – and warmer than last year.

The year 2005 was the last year of robust oyster spatfall. It is very easy to see how much warmer that year was than either of the past two years. In fact, a simpler metric of Bay warmth is “degree days.” If we set 16 degrees C as the baseline then the number of degree days accumulated at or above that temperature, through July 10 for our three years plotted in the chart are:

2011 = 34.8 degree days
2010 = 29.1 degree days
2005 = 85.5 degree days

2005 was much warmer than either of the past two years, having a full FIFTY more warm water days by July 10 than this year.

We are hoping our rising water trend will continue for the next month (in spite of today’s rains) and the upcoming neaps produce a larger spawning. Unfortunately, none of the adult oysters we have sampled so far this year are close to spawning condition… If only we could find those that have already spawned – they must be better adapted to local conditions.

A final note for this bulletin is that we have begun collecting (about 1,000 so far) wild spawned adults from the past 2-3 years of sets. We now have broodstock from several areas of the Bay that accumulated during these “bad years” and may contain heritable robustness/adaptations.
We would like to get more adults into this pool, so we ask that you please collect and bring adults (in bushel baskets) from areas that you know have set recently.

The areas we already have adults from are: above the Naselle Bridge near Mill Ranch Road (>+1 MSL) deep dredged near the Wilson cabin on the Naselle River deep dredged near Lewis Slough

We would like adults from:
Peterson Station
Anywhere in the Nemah
South of Long Island
Smokey Hollow
Anywhere north of Nahcotta

Thank you.