TU project opens blocked trout habitat in NH

By Colin Lawson

A recently completed Trout Unlimited project in Pittsburg, N.H., reconnected over 4 miles of high quality coldwater habitat for native brook trout populations in the Upper Connecticut River. 

Trout Unlimited reconnected Tabor Brook to the main stem of Indian Stream, which will now allow brook trout to access headwater habitat for both fall spawning and summertime thermal refugia.  

The culvert outlet was perched, effectively blocking fish from accessing upstream habitat.

More than 140 small brookies were collected using electrofishing gear from a 10-foot square scour hole, just below the perched culvert, prior to dewatering the stream channel and beginning construction. The fish, which were trapped with nowhere to go, were moved downstream and are likely already moving back upstream into the newly connected habitat. 

The primary focus of this project was to remove an impassable and deteriorating culvert blocking upstream fish passage and replace it with a new pre-cast bottomless bridge structure. This new structure was designed to pass the 100-year stream flows and was installed in just over two days. 

The new bridge will not only allow for fish passage but will be more resilient to flooding risks.

In addition to the bridge, four rock vanes were installed to stabilize stream bed elevations and eroded banks were repaired. Additional large wood habitat features are planned for 2020 once the stream has a chance to adjust and a new, more permanent low-flow channel, called a thalweg, develops both upstream and downstream.  

The new structure will not only benefit trout and other stream inhabitants, it is now expected to last at least 75 years and will be completely resilient to severe weather events. TU will revisit the site annually over the next three years to monitor how well the new structure functioned post each winter’s freshet. 

By Trout Unlimited Staff.