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Actively participating in the conservation of fish, wildlife and the wise use of the natural resources of Marin County, our state and the nation since 1926. |
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Oyster Habitat Restoration
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Indigenous Oyster Habitat Projectby: Bud Abbott and Rena Obernolte Our native Olympia oysters “Olys” have come back strong since the devastating rainfall events of March and April 2006. You may recall those wet, miserable days as inconvenient and dreary but for our native oysters and eelgrass projects, it was a total unmitigated disaster. For weeks at a time the Bay waters in front of the MRGC were close to being fresh water not brackish. Olympia oysters do best when the salinity is about 20 parts per thousand (PPT). The ocean beyond the Golden Gate is around 30 PPT and drinking water is 0 PPT. The water in front of the MRGC was down to 0-10 PPT for weeks at a time.
We lost over 90% of our native oysters during that rainy period. The water was also a rich brown, from all the suspended sediment washed down from the hillsides and the Sacramento-San Joaquin Rivers. The sediment blocked out the light and the eelgrass starved to death for lack of solar energy. There may have been other factors but the evidence seems to points to too much rain in 2006. |
The spring of 2007 was not very wet at all
and our new crop of oysters and eelgrass spawned in the summer of 2006
are doing just fine, thank you. We have numerous eelgrass sprouts
coming up but a new nemesis lurks in the shallows.... bat rays! Yes, bat rays. It appears that there has been an unusual influx of bat rays this year. Anglers complain of catching 20 in a few hours. Bat rays use their wings to waft up the sediment to find clams and marine worms, and end up digging basket ball diameter depressions all over the mud flats. We hope they do not settle on our new eelgrass bed before they have a chance to become established.
And yes, the three new reefs you helped construct last July are holding up very well. The herring just loved our reefs. They loved them so much that they spawned millions of eggs on them last winter. But most importantly, on each reef there are thousands of juvenile oysters. Dr. Jim Moore from CDFG came down and looked at them on May the 6th and determined that they were not in spawning condition yet. |
Probably another month before the mothers start releasing the baby (veligers) into the water to start the next generation. Olympia oysters are free swimming for several weeks and they are called veligers at this stage.
Note the hair like cilia around the margin. These little hairs propel the larvae through the water. Speaking of reefs, we need to build again. We will need lots of volunteers Saturday, June 9th to help build the next set of reefs. We also need three boats. We need people that can load bags into the boats and people in the boats to unload the bags from boats and people in the water to build the reefs, strong men to bend the iron hooks, people to register volunteers and collect data throughout the day. It should be great fun.
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