The Mill Pond decision, a complex, expensive calculus
To the Editor:
Nelson Sigelman's choice of title for his September 13 fishing column [Mill Pond is one of the dots in a bigger picture] couldn't have provided a better image for preservation of the Mill Pond and its upstream cousins: Mill, Priester, Crocker, Fisher (Woods), plus two or more smaller ponds, each with dams. They are eco-gems strung together by a silver chain, the Mill Brook. While the four major ponds and several smaller ponds, including Mill Pond, may be called manmade, they are also indeed nature-made, as only nature can do, filled with and rimmed with a plethora of natural diversity that, in the older ponds, has evolved over hundreds of years. The Mill Brook wetlands system is immensely enriched, expressly because these diverse pond habitats exist.
Prudy Burt's dream of restoring Mill Brook as habitat for salter brook trout, by removing the dams on each of the ponds, would cause the loss of the ponds themselves, resulting in shrub swamp habitats or swamp maple/beetlebung woodlands, with Mill Brook running through them. Shrub swamps are excellent wildlife habitat, but fail to provide that open water quality so attractive to many water-loving vertebrates, including humans. Gone would be the small, intensely wary flocks of teal, ring-necked ducks, and other waterfowl that use these largely secluded ponds in spring and fall passage. Not to mention the loss of osprey and kingfisher, that regularly fish the ponds. And the beloved otter would likely be reduced in numbers also. As well as the photographer, the bird watcher, the leaf peeper, and the hunter. So too, we who are destined to endure the annual Christmas Bird Count, for these ponds, when not fully iced, provide rare winter sightings of teal, wood duck, hooded merganser, kingfisher, and other open water foragers.
Yes, the Mill Pond has "remained a cherished scenic vista," not only for the people of West Tisbury but for the Derby fishers Nelson spoke of, heading past the Mill Pond en route to their favorite up-Island haunts, not to mention the thousands of other passersby each year. It reminds us of West Tisbury's agricultural past — Takemmy, "the place where corn is ground" — the object of the town's seal, depicting a water mill, dated 1669. (From every perspective: historical, social, scenic, legal, wildlife diversity, it is inconceivable to me that Prudy's vision of swapping the Mill Pond for a stream would ever become a reality.) As Nelson's article points out, many New England dams have been removed, to the betterment of the environment for trout, salmon, shad, alewives, eels, and other fishes. But, because it is advisable in one location doesn't mean it should be done on every dammed stream in New England. The West Tisbury Mill Pond is an asset for the Island as a whole.
The Mill Pond Committee (MPC) was formed by the selectmen in 2008, to make recommendations to the town for management of the pond. Two studies done for the town in the past six years have recommended removing accumulated organic matter, silt, and sand by dredging, as the only practical, long-range means for preserving the pond from eventually becoming a shrub swamp.
I have stated publicly that the pond is in no immediate danger of disappearing. I may have spoken too soon. In May, Craig Saunders, hydrogeologist and member of the MPC, and I placed three silt traps in the pond to attempt to measure just how fast the muck is accumulating in the pond. When we pulled the traps a couple of weeks ago we were stunned to see that two of the three traps were filled with more than two inches of organic muck. This is not to say that in the space of four months the pond accumulated two inches of sediment, but it clearly indicates that sediment is moving, and accumulating, in the pond, at a rate far greater than we had imagined.
Even more eye-opening is the fact that it is becoming more difficult to move a dinghy or canoe in the pond. Although the studies found the pond's average depth to be 1.7 feet, we are now barely able to move the boats through the upper reaches of the pond, which now averages about six inches in depth. Taking full advantage of this warm, shallow, organic-rich environment, emergent vegetation rimming the north end of the pond is expanding rapidly, creating islands of plants well out into the pond, a hint that rapid expansion may be imminent.
The Mill Pond Committee's recommendation to the selectmen is that the pond be dredged to an average depth of four feet. This would more than double the volume of water in the Pond, improving habitat for fishes such as perch, bluegill, minnows, as well as ducks, geese, swans, muskrat, otter, turtles, frogs, and snakes as well. And scores of invertebrates, upon which the higher animals depend.
No, the brook trout will not benefit from the dredging. They are doing just fine in the upper reaches of Mill Brook, where the spring-fed waters are cooler, and have suitable sand/gravel areas for spawning. They will live out their lives without any access to Tisbury Great Pond, just as millions of brook trout do all over New England and beyond — with no access to the sea or coastal estuaries. Sea-run "salter" brook trout are a marvelous adaptation to coastal estuaries, and restoring streams for them to access the estuary, where appropriate, is a desirable conservation goal. The key words are "where appropriate."
Dredging Mill Pond will guarantee that a lot of kids will have the opportunity to catch a yellow perch, a bluegill, or a frog for many years to come, and that seems like a pretty good investment for the future.
Ultimately, the people of West Tisbury and the owners of the several impounded ponds will decide what is appropriate for the Island's Emerald Necklace, including the Mill Pond. And the brook trout will continue to flourish. Dredging won't be cheap. Neither would be removal of the dam. The Mill Pond Committee estimates dredging can be done for $400,000. Prudy has a dam removal estimate of $558,000.
West Tisbury Mill Pond Committee
Bob Woodruff, a wildlife biologist, lives in West Tisbury. He has done research and managed brook trout and other salmonid fishes in Maine.