Protecting Trout Streams

Starting in 2012, this project aimed to assess and protect the ecological health of small trout streams in Sudbury. These streams have some of the few remaining native brook trout populations in eastern Massachusetts – well worth protecting!

Aside from being one nature’s most beautiful fish, Eastern brook trout (Salvelinus fontinalis) is a keystone species in the northeastern US. They inhabit flowing, highly oxygenated, cold-water streams and once occupied most of the cold-water streams in the eastern US. While brook trout are still relatively common in western and central Massachusetts, eastern populations are greatly reduced. Today, geographically isolated populations remain in only about 10% of the subwatersheds in eastern Massachusetts(see EBTJV report ). The survival of these remaining populations is threatened by the pressures of human development including: streamflow and temperature changes due to increased area of pavement, dams and undersized road culverts fragmenting the streams, non-point source pollution, climate change, and by competition and predation by non-native fish species (including rainbow and brown trout).

This project built on the joint efforts of Mass Fish and Wildlife, Greater Boston Chapter of Trout Unlimited, Sudbury Valley Trustees, and the Sudbury Conservation Commission to identify native trout-bearing streams in Sudbury.

OARS, Greater Boston Chapter of Trout Unlimited (GBTU), Sudbury Valley Trustees (SVT), the USGS Conte Fish Research Lab, and UMass Amherst collaborated to assess and protect brook trout habitat in the two Sudbury River tributary streams known to have wild brook trout populations. The project goals were to: review current regulatory protections for cold water streams, assess current conditions, identify remediable threats (undersized culverts, bank and streambed erosion, illicit discharges), create a restoration plan, and contribute to longer-term understanding of the effects of climate change on brook trout. Climate change effects were monitored with longer-term stream temperature logging. OARS reviewed the regulatory protections afforded to designated CFRs in Massachusetts. A project advisory committee assisted in project planning, assessment, and creation of a prioritized management plan based on findings.

Full report available (bottom of this page).

The stream quality in both Trout and Cranberry Brooks was good to excellent within the protected areas of Memorial Forest, the Desert Natural Area, and adjoining protected areas. The main difference between the “good” and “excellent” ratings in these protected areas were whether the stream was shaded or running through an open marshy area, where stream temperatures were generally warmer and cover less abundant.

The upstream areas of both Trout and Cranberry Brooks, are in developed areas in Marlborough and Hudson. Sections of the upstream areas of both brooks were dry during the course of the surveys in October 2013, so ratings are based on physical habitat and not on water quality measurements. Most upstream sections were rated “fair” to “poor” habitat for trout, limited mainly by the number of culverts, the proximity of development, or the presence of an active beaver dam.

Nineteen stream crossing surveys were conducted by OARS staff and volunteers. The stream continuity methodology developed by the River Continuity Partnership was used to assess culverts and bridge crossings as barriers to fish passage. Assessment data was entered into the River and Stream Continuity Database to rate each crossing as a barrier to fish and animal passage. These crossings are included in the Critical Linkages Analysis being conducted by UMass and The Nature Conservancy.

Of the crossings surveyed, ratings were: one “insignificant barrier”; seven “minor barriers”; nine “moderate barriers”; one “significant barrier”; and one “severe barrier.”

Many of the road crossings in the upper sections of Trout Brook, are part of a development done in the 1980’s. Some of the development in this section was in violation of the Mass Rivers Protection Act and Wetlands Protection Act. Four notable, problematic crossings in this section include:

  • a 300-ft long culvert at the corner of Harper and Woodcock Lane (fish, likely trout, were observed in the scour hole at the outlet of this culvert)
  • a buried section of stream (1200+ feet) under Minehan Lane; the inlet is a vertical concrete box overflow from a small pond
  • a 400-ft long culvert under Prendiville Way on a tributary branch of Trout Brook
  • an old dam forms a 36” drop at the inlet of the culvert under Hemenway Street

The upper section of Cranberry Brook is affected by a large, active beaver impoundment upstream of White Pond Road and is a section that appears to have been used as cranberry bogs. The culvert at White Pond Road, Hudson, has a large scour pool downstream. The section between Parmenter Road and Goodale Street was dry in October and was not surveyed. At the headwater of the stream, between Goodale Street and Vega Road, there is a 350-ft long culvert with a small pond at the inlet.

An unnamed tributary to Cranberry Brook runs from near the small parking lot at the junction of Mosher Lane and Concord Road into the Marlborough-Sudbury State Forest and the Desert Parcel (City of Marlborough). About half way down its course, the brook passes through a small culvert under Old Concord Road, which is now a walking trail. The culvert is rated a “moderate barrier” to passage, but is a severe flow constriction and forces the stream to take a 90-degree bend at each end of the culvert. About 18 feet upstream of the culvert is a small (20-inches tall) stone block dam. The stream joins Cranberry Brook downstream of White Pond Road and upstream Cranberry Brook’s crossing with Old Concord Road Trail. OARS collected water temperature data in the stream over the summer of 2014 that suggest that the stream is an good cold water fishery stream. The figure below shows water temperature data from the unnamed tributary compared with data from Cranberry Brook taken just downstream of the confluence of the tributary and Cranberry Brook.

Stream temperatures in Trout Brook and Cranberry Brook were, generally, within the acceptable range for brook trout habitat, with cooler temperatures found in the well-shaded areas. Temperatures in the two small (unnamed) tributary streams tested were in the ideal range for brook trout, staying below 18 degrees C for most of the summer. Temperatures in Hop Brook within the Memorial Forest were sub-optimal for trout; it is likely that trout use Hop Brook only during cooler parts of the year.

Genetic analysis of two sub-populations of brook trout (in an unnamed tributary and in Cranberry Brook) was conducted by Dr. Whiteley of UMass/Amherst. His findings: There are two major takeaway points from this analysis: 1) both sites had a surprisingly high amount of within-population genetic diversity; 2) there appears to be genetic connectivity among sites. Isolated populations lose genetic diversity each generation. However, gene flow serves to maintain genetic diversity within sites and minimize genetic divergence between sites. These results suggest that movement between Hop Seep and Cranberry Brook occurs, possibly seasonally when downstream conditions are favorable.

As a result of this work, OARS is seeking opportunities to restore several culverts in the section. Temperature data will continue to be collected, and shared, as long as the temperature logger's batteries hold up.

Project partners:

More about Eastern Brook Trout:
OARS' fish descriptions
Eastern Brook Trout Joint Venture
Mass Wildlife's Trout Information
Sea Run Brook Trout Coalition's restoring sea-run brook trout on the Northeastern seaboard
USGS trout population modeling and climate change

Project support
This project is supported by a grant from the Massachusetts Environmental Trust

Report(final)-OARS-Trout-Streams-Project.pdf2.52 MB
Report(final)-OARS-Trout-Streams-Project(Appendices).pdf2.15 MB