Wednesday, July 14, 2010

Invasives Survey at Oregon Oyster Farms - July 10, 2010

A team of Oregon Coast Aquarium scientific divers received a lesson in aquaculture then went in the water at Oregon Oyster Farms, 6878 Yaquina Bay Road, to survey the docks' fouling community.

The operation grows both Pacific and Kumamoto oysters, utilizing old oyster shell as substrate. After allowing oyster spat to recruit on the shells, they are suspended by strings or in bags from floats, or they are broadcast onto the sandy bottom of the river channel. Bottom cultured oysters are later harvested by dredge.

View Oregon Oyster Farms in a larger map
While salinity remains high this far upriver in the summer, divers did not find many of the fouling community members they have been accustomed to seeing in the bay. Styrofoam flotation was wrapped in polyethylene, perhaps posing a more difficult substrate to which to attach, though mussels still grew thickly. Barnacles made up only a minor component, mostly on older mussels and pilings. No nudibranchs were seen and only the occasional young fish. While divers saw small specimens of the yellow invasive sponge, Botrylloides violaceus was conspicuously absent despite its prevalence in the bay. Invasive tunicate Molgula manhattensis tolerates brackish conditions, and we found it in Yaquina Bay for the first time May 30. Divers found no sign of it here, increasing the likelihood that the infestation on the bottom of the spud barge is a unique occurrence.

Divers surveyed some three hundred feet of the underside of floats,the occasional piling, and the perimeter of the oyster dredge on the port side for a total bottom time of 300 minutes and a maximum depth of twelve feet. Divers Bruce Hansen, Jim and Chris Pendergrass, John Estabrook, Scott Martin, and Lorne Curran participated with Fritz Batson tending.

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