Thursday, November 18, 2010

Two Barges on the Coos River, Oct 25, 2010

Five scientific divers from the Oregon Coast Aquarium inspected two barges for invasive tunicates on the Coos River on October 25th, 2010.    Because the barges were suspected of hosting the invasives, the owners had towed them eight miles up the Coos River to soak in fresh water.   This inspection was to check on the results of the two-weeks of fresh water soaking.

The river current and the muddy water made it difficult to operate underneath the barges.  The first barge was inspected only on a three meter section of the lower starboard side.  The second barge was inspected more thoroughly as the divers used a thick line to "rappel" in the current under the barge from bow to stern in two passes.  Critical to the divers' success, the thicker line was easier to hold and did not flutter in the turbulence and threaten entanglement.

The barges did have abundant Molgula present, but all observed specimens appeared dead (dissolved to mush as they were plucked off the hull).The Mogula were evenly distributed on the hull bottom in approximately 100+ mature individuals in any two meter diameter circle.  The informal circles (an arm span) were established by the diver rapelling down-current a short distance and stopping to count with one hand holding the line and the other holding a light.

The nonnative species of Coos Bay have been ably documented by such researchers as Dr. James Carlton and institutions including the Smithsonian. One class of invasive species, the tunicates, includes Molgula manhattensis, most recently recorded by Dr. Gretchen Lambert during October's PICES effort. The bottom of boats can easily support such fauna--barges are particularly susceptible.

The contingent of scientific divers wish to thank all involved for their concern and precautions in controlling the spread of marine invasive species to Oregon estuaries.

No comments:

Post a Comment