David Taylor – Georges River Shellfish Committee
Joanie Mcdonald – Georges River Shellfish Committee
short project summary (PDF)
The Georges River Shellfish Committee (GRSC) manages harvesting in the towns of St. George, South Thomaston, Thomaston, Warren, and Cushing. Many of the flats within the five-town region are closed due to pollution. The committee is working to identify the source of pollution through DNA testing, and hoping the restricted flats can be reclassified with data provided from a drifter bucket study.
In particular, GRSC is focused on an area near the mouth of the St. George River known as “the Bay,” which has experienced heavy depuration digging. The Bay may affect shellfish populations downriver, and if reopened, will once again fall under GRSC conservation measures, and ideally function as a nursery for the rest of the river.
GRSC received a grant for DNA testing to track the source of E. coli bacteria that is keeping the flats closed. In the first year, David Taylor collected twenty-seven water samples and sent them for testing to the University of New Hampshire. A few of the sites tested for human waste, and all of the samples tested positive for mammal pollution, indicating a significant amount of dog waste. The Shellfish Committee is conducting public outreach around proper removal of dog waste and cattle manure.
With over 5,000 acres under state management, the GRSC has more DNA testing to do. The UNH lab is able to provide specificity on the type of pollution—mammal or human, but legwork is still required to ground truth the pollution sources. The DNA testing has allowed Broad Cove to reopen for clamming, and GRSC hopes the DNA work can support the reopening of the Bay in the future.
To get a better picture of estuary dynamics, and how the wind and current move clam seed through the bay, University of Maine PhD student Gabby Hillyer brought bucket drifters to Thomaston.
The drifters are equipped with GPS and released into the river. Tracking their movement provides a picture of tidal circulation patterns. An Acoustic Doppler Current Profiler (ADCP) was also used to measure how fast the current moves across a water column. With the data gathered by the drifter buckets and ADCP, Gabby and UMaine professor Lauren Ross created models of the St. George River estuary.
The models are helpful in understanding tidal circulation in the river, and therefore the movement and settlement of clam seed. The Georges River Shellfish Committee can use the model to ask questions and hone in on areas of interest, which may help inform management decisions.
The Georges River Shellfish Committee manages a large area, and estimates that several more years of DNA testing will be needed to reopen pollution sites. The Shellfish Committee has struggled with coordination among the five towns, and finding volunteers. However, the DNA testing has successfully reopened broad cove, and the drifter models are an exciting new way for the committee and harvesters to engage with the estuary. The St. George river is in flux; the mussels beds have disappeared, affecting clam habitat, but anecdotal evidence suggests that species such as otters and sturgeon are finding their way back into the river. The GRSC will continue their work to ensure that there are clams in the flats for future generations.
GRSC receives funding for DNA testing
Water samples collected and sent to the University of New Hampshire
Broad Cove reopened for clamming
DNA testing continues
Drifter bucket deployments
Drifter bucket study continues