Stand at the gate and you are standing on a boundary. Downstream the Mill River is an arm of the sea: salt water on the flood tide, mud flats on the ebb, twice a day, every day. Upstream it is a fresh water stream. The change is abrupt because it is engineered.
Why the gate is here
A tidal river floods. Push a high tide up against heavy rain coming down and the water has nowhere to go but sideways, over whatever has been built on the old marsh — which, on the Mill River, is most of it.
New Haven had been told this. The 1910 city plan by Cass Gilbert and Frederick Law Olmsted recommended a tide gate, along with a protective buffer of open land along the river rather than the vertical walls the city would eventually build. A gate duly appeared around 1930.
It does the job it was built for. It also changed the river permanently.
The spring run
River herring — alewives and blueback herring — are anadromous: they live at sea and spawn in fresh water, returning each spring to the river where they hatched. Historically they ran the Mill River in enormous numbers, and they fed everything, from osprey and eagles to striped bass waiting at the mouth to the people who netted them off the banks.
A run needs a clear path. The Whitney dam closed the upper river in 1860. Structures downstream narrow what is left. Fish that can find no way past a barrier simply do not spawn that year.
Undoing some of it
Connecticut has spent the last few decades reopening rivers: fish ladders and bypass channels built around dams, tide gates replaced with self-regulating designs that let fish through while still holding back storm surge, and in a growing number of cases dams removed altogether. Each project adds back miles of spawning habitat, and the herring find it quickly.
What to look for
In April and May, look for movement in the shallows and for the birds that follow it — osprey overhead, cormorants and herons working the edges. The tall feathery reed along the banks is Phragmites, an aggressive invader that crowds out the native marsh grasses fish and crabs shelter in, and it spreads fastest on disturbed ground.
The sign at this spot
The full sign, in English and Spanish. Zoom in to read it.
This sign is still a draft. The hatched boxes are photographs that have not been sourced yet.
Sources and further reading
Where a link goes to a scanned original — a newspaper page, a map, an engineering journal — it is the actual document, not a summary of it.
- Report of the New Haven Civic Improvement Committee, 1910 — Gilbert and Olmsted
- River herring — NOAA Fisheries
- Mill River Watershed Based Plan — Save the Sound
- Mill River history — Mill River Trail
Research and credits
Historical research for the Mill River Trail signage was carried out by Colin M. Caplan of Magrisso Forte and John R. Logan, with contributions from Jason Bischoff-Wurstle of the New Haven Museum and walk notes by Steve Hamm. Images are credited individually. Locator maps are drawn from OpenStreetMap, © OpenStreetMap contributors, ODbL.