State fisheries experts see promise in West Tisbury streams
Photo by Nelson Sigelman
Touring Island streams on a cool, sunny Monday morning in West Tisbury, Division of Marine Fisheries (DMF) scientist and herring expert Brad Chase found reasons to be optimistic that several species of fish would benefit from some human assistance to pass over dams that now block long-lost natural water passageways.
Just below the Mill Pond, Mr. Chase reached into the Mill Brook stream bed at the foot of the dam, and held up a handful of gravel. Two small, glassine eels, known as elvers, wriggled in his palm as drivers in trucks and cars passed by on the road above, unmindful of the elvers' long journey from their birthplace in the Sargasso Sea to this small corner of West Tisbury.
Not far away, on an inspection of the Tiasquam River just above Town Cove, Mr. Chase picked up a rock from the stream bed just below the dam used to create Farm Pond, on leased land owned by The Trustees of Reservations. To his delight, Mr. Chase discovered the eggs of white perch adhering to the stone.
Further up the Tiasquam, Mr. Chase spoke with Geraldine Brooks, owner with her husband, Tony Horwitz, of property through which the Tiasquam runs after it exits Look Pond over a dam now impassable by fish. Their conversation was about creating a fish passageway that would allow river herring to pass upstream.
"What we have here is an opportunity," Mr. Chase said, as he outlined for Ms. Brooks some of the complexities and costs associated with overcoming the dam's drop. "The question is how to do it."
Mill Pond passage
The answers were simpler at Mill Pond, where Mr. Chase, DMF program manager and fisheries scientist Greg Skomal, and DMF fishway expert Ed Clark described the relatively straighforward measures that could used to modify the dam so that fish can pass over it.
The DMF trio, on a visit to Island fishways, inspected the Mill Pond dam in the morning with Prudy Burt, West Tisbury conservation commissioner, West Tisbury herring warden Johnny Hoy, and civil engineer Kent Healy, a member of the Mill Pond committee and the man responsible for timing the opening to the sea of Tisbury Great Pond through which the herring, white perch, and eels swim.
Mr. Healy, the respected overseer of pond openings — a responsibility rooted in fisheries science, instinct, water levels, and the local politics of flooded basements — asked the scientists to provide recommendations on how best to manage pond openings for the health of the fisheries.
In the spring, herring arrive on their journey to spawn in their natal streams. In late summer or early fall, the juvenile herring seek to return to the sea.
Putting aside for the moment the debate in town about dredging Mill Pond or removing the dam entirely to allow Mill Brook to return it its natural course, all agreed that a project to install a temporary fish ladder could be accomplished relatively easily before the herring return next spring — without affecting the level of the pond.
Mr. Chase said that if the town agreed, DMF would proceed with the project. It would entail reducing the drop on one side of the sluiceway to concentrate the flow and provide more depth and traction for the fish, which key in on stream flow, and adding steps or baffles.
"It's a pretty simple process," Mr. Chase said of the required permitting and engineering.
Following his visit, Mr. Chase said, "I think we have a project. I think everyone agreed to go ahead and my crew would construct the fishway in the offseason and then we would go before the conservation commission. I think we could have it in place before next spring."
A tour of the Tiasquam began with the Look Pond dam, which, because of its height and age, presents certain challenges for what would ultimately be a private project to create a fish passage.
Ms. Brooks was enthusiastic about the notion of herring returning to the brook that cuts through her family's property on their journey to spawn. Mr. Chase recommended a habitat assessment, a two-year survey used to determine the viability of the water body to support herring, before any steps were taken to create a herring run.
"What we have here is an opportunity," Mr. Chase said.
Farther down the Tiasquam, Mr. Chase saw immediate promise. Just below the small dam used to create Farm Pond, Mr. Chase picked up a rock. "Those are all perch eggs," he said, pointing out the small dots.
"If you could take this dam out, you could reconfigure the channel to provide more spawning habitat for white perch," He said. "It's a small job."
Although there are no current plans to remove the dam, a decision that would require the permission of The Trustees, Mr. Chase said the project would benefit more than river herring. Asked to elaborate, he said that smelt were once present here.
"Smelt are basically gone from the Vineyard," he said. "So you could augment habitat that would serve smelt, white perch, eels, brook trout — it wouldn't just be river herring. So for me, it not just a single species project."
DMF regularly surveys herring runs across the state. The visit to the Vineyard Monday was one of several visits made over the years and included a stop at the Gay Head herring run managed by the Wampanoag Tribe and the run shared by Oak Bluffs and Tisbury.
By state statute, property owners are responsible for maintaining existing fish ways. "DMF will work with property owners to help them," Mr. Chase said, "but the legal responsibility is always going to rest with the property owner."