Throughout the history of the Herring River Restoration Project, shellfishermen have been concerned about the possible adverse effects of the project on their livelihood – apprehension that restored tidal flow would cause silt to smother shellfish beds in Wellfleet Harbor.

Two studies have addressed aspects of this issue:

• "Hydrodynamic and Salinity, Modeling for Estuarine Habitat Restoration at Herring River, Wellfleet, Massachusetts" by Malcolm L. Spaulding and Annette Grilli (2001)
• "Sedimentation Concerns with Proposed Restoration of Herring River Marsh" by Amy J. Dougherty (2003)

Spaulding and Grilli sampled sediment and analyzed distributions at various locations and depths in the Herring River. They found that finer particles – silt and clay – tended to be concentrated along the central channel axis and typically in deeper water. They did not sample sediment in Wellfleet Harbor, where commercial shellfish beds are located.

Dougherty cited S&G's water velocity data, which showed ebb flows in the Herring River of around 10 cm/sec, which is half the threshold of 20 cm/sec required to keep sand suspended. But she did not acknowledge that finer sediment, such as silt and clay, would remain suspended on ebb tides at much lower velocities. Without evidence, she speculated that "smaller silt-and clay-sized grains will widely disperse and deposit in the fringing marshes of The Gut or offshore."

Contradicting her speculation that silt and clay suspended on ebb tides would widely disperse, Dougherty concluded from historical events that the deposition of fine sediment, "as the velocities slowed near the dike," were responsible for suffocating "the shellfish that had recently colonized."

• "With respect to the shellfish grants on Egg Island, they are simply too far away to be affected by any alteration of flow through the dike. Realworld evidence to support this fact was provided in 1968 with the rusting out of a sluice gate allowing tidal exchange for the next six years. There is no evidence that areas of high shellfish production such as Egg Island experienced increased sedimentation during this time. On the contrary, the consensus was that shellfish actually colonized in the area around the dike and subsequently died after the dike was repaired. An explanation of the brief colonization is that increased flood currents caused by the deterioration of the tide gates moved the fine sediment coming from Cape Cod Bay past the dike and up into the marsh. Salinity behind the dike also increased, favoring estuarine bivalves. In contrast, rebuilding the dike structure once again restricted flow. As the velocities slowed near the dike, fine sediment that would have otherwise been carried into the far reaches of Herring River, were once again deposited directly above and below the dike, thus covering the shellfish that had recently colonized."

So, Dougherty, a geoscientist commissioned by the Cape Cod National Seashore and the town of Wellfleet, opined from historical evidence that the deposition of silt originating from the Herring River caused the death of shellfish in Wellfleet Harbor many years ago.

In 2020, I engaged in a robust email correspondence with John Portnoy to seek direct (as opposed to inferential) scientific evidence that restoration of tides in the Herring River estuary will not cause sedimentation in Wellfleet Harbor to threaten shellfish. In the email thread, I cited evidence from other venues that this could be a problem. But we never came to a mutually satisfactory conclusion on this matter.

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RG note: When I sought a gender-neutral alternative for the word "shellfishermen" in the first paragraph above, two opinions resonated. "For some women, being referred to as a 'fisherman' is a point of pride as it signifies they're able to do the same work as men" and "Some women may prefer to have a gender-neutral term applied to their work, but we are yet to meet any who object to being called a fisherman."

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