Coliform closes pond to shellfishing
In a meeting Monday, Massachusetts Division of Marine Fisheries (DMF) biologists told Edgartown and Oak Bluffs shellfish constables that Sengekontacket Pond would need to be closed to shellfishing during the summer months as a result of sustained high levels of fecal coliform bacteria.
The state has reclassified the salt pond that is connected to Nantucket Sound by two channels spanned by bridges as a "conditionally approved area." Shellfishing is now only allowed from October 1 to May 31 until further notice.
The pond remains open to boating and swimming.
The announcement of a seasonal closure was not unexpected. The pond was closed to shellfishing at the beginning of June, then reopened and closed again at the beginning of July when water sampling once again revealed levels of bacteria above the safe level for shellfish consumption.
On Monday, DMF senior marine fisheries biologists Dave Whittaker and Mike Syslo met with Oak Bluffs shellfish constable David Grunden and Edgartown shellfish constable Paul Bagnall to talk about the state closure.
Sengekontacket is closed to shellfishing. Photo by Ralph Stewart
In a telephone interview Tuesday, Mr. Whittaker said he reviewed all of the data with the constables to explain why it was necessary to reclassify the pond from approved status to "conditionally approved, seasonal."
Mr. Whittaker said one obvious cause is waterfowl. Less obvious is circulation.
Nitrogen loading, while not directly responsible for bacteria, clouds the water, which makes it much warmer and allows bacteria to grow more quickly.
DMF will continue to monitor the pond on a regular basis. Based on a two-year review period, the pond could be reclassified if coliform levels drop.
The pond is regularly sampled for water quality. On June 5 fecal coliform levels were well above the safe level at eight of nine testing points on the pond.
The pond was retested on June 19 and met the criteria to reopen. But when the pond was retested on July 2 all nine samples were well above the safe level.
Those results raised a red flag, according to Mr. Whittaker, and prompted an extensive review by Mr. Syslo of past testing data relative to rain, seasonality, and other factors. The result was a change in classification.
Mr. Whittaker said it is important to note that the closure is based on natural occurrences and is not a reflection on the local shellfish constables. "Both do an excellent job," he said.
Mr. Bagnall and Mr. Grunden point to a lack of sufficient water circulation and an abundance of waterfowl, primarily geese and cormorants, as the main causes of elevated levels of coliform bacteria.
Planned dredging in the future is expected to help provide better flow through the channels that flow under what are locally known as big bridge and little bridge. But regular dredging is costly both in terms of the time needed to secure permits and the cost of permitting, as well as the actual work.
The results of a Mass Estuaries Project study are expected to shed some light on the dynamics of pond water quality and point to some possible remedies.
The problem of expanding bird populations is more problematic. In recent years, a lack of hunting pressure and the easy availability of food in many Massachusetts communities, including Martha's Vineyard, has led many geese to break from their natural migratory cycle.
Instead of moving with the seasons, the geese stay in one area throughout the year, fouling fields, golf courses, water bodies, and causing significant agricultural damage.
Massachusetts created an early goose season in September designed to address the growing problem of nonmigratory resident geese during which hunters are allowed to shoot five geese. But many Island hunters shy away from populated areas like Sengekontacket.
The state also targets nonmigratory geese in a late winter goose season from mid-January to mid-February.
However, southern coastal communities including the Vineyard are not included in the hunt because state and federal wildlife officials want to protect true migratory populations of Canada geese that may be passing through or wintering in these areas.
Mr. Grunden said he participated in a tagging study coordinated by the Wampanoag Tribe in an effort to convince wildlife authorities that the Vineyard should have a late winter goose season but to little effect.
Increasing populations of double-crested cormorants, a protected species under the Migratory Bird Treaty Act, are creating conflicts as well across the country. Most often, those calling for controls are fishermen and fish farmers.
An adult bird eats an average of one pound of fish per day. The waste produced can be harmful to vegetation.
According to the U.S. Fish and Wildlife Service, cormorants do kill trees, shrubs, and other vegetation, due to accumulation of their guano, which is highly acidic, and removal of foliage for nesting material.
The Wildlife Service will issue depredation permits to control cormorants depending on the circumstances. However non-lethal methods for which no permit is needed are preferred. That could include scaring birds from sites or changes to preferred nesting areas.
For example, the Wampanoag Tribe employs a sound cannon to scare cormorants from the tribal herring run at the head of Menemsha Pond.
Bill Wilcox, Martha's Vineyard Commission water resource planner, said that in his view waterfowl and not humans are the primary cause of high coliform levels in the pond. "There are just a whole load of birds in that pond system," he said. "And my suspicion is that it is not human wastewater that we are dealing with."
Improved water circulation created as a result of dredging may do little to offset a constant source of bird waste. Mr. Wilcox said that fecal coliform can survive in warm and sheltered areas of the wrack line during the day waiting for the next tide. As it now stands, he said the pond flushes fairly well. He estimates there may be as much as a 95 percent exchange with Nantucket Sound every three days.
Mr. Wilcox said that the Mass Estuaries Project would provide valuable information. Any management plan he said would need to take the large number of cormorants into account.
Rick Karney, director of the Martha's Vineyard Shellfish Group, agrees that waterfowl, not humans, are the major contributor to the problem. He said dredging would likely improve water quality. For now though, an important recreational and commercial resource is out of bounds. "It's really sad because it is such an important pond for recreational shellfishing," he said.