Home > Projects > Science and Technical > Fisheries

FISHERIES

Fisheries Assessment Study

Background

As the suburban and rural upper Charles River watershed develops at one of the fastest rates in the state, so does the demand for water destined for streams. Rainfall patterns also impact the river, as there have been frequent droughts in recent years. In 1999 and 2002, the Charles River had its lowest flow levels since the United States Geological Survey (USGS) started monitoring flow in 1931.  The results of these natural and man-made influences are the destruction of aquatic habitats, decreasing the native fish diversity, and sometimes even the complete collapse of fisheries.

The flow regime of rivers and streams affects the distribution of macroinvertebrates and fish, and impacts aquatic organisms’ ability to gather food, meet respiratory requirements, avoid competition and predation, and colonize or vacate certain habitats.  Flows affect the amount of river channel that is under water and riverbank and substrate stability. Lower flows as a result of drought or less discharge of groundwater to the river may induce the downstream drift of benthic organisms: aquatic wildlife living on the river floor will move downriver to disperse and escape decreasing water levels. 

As flows diminish, the dangers to the ecosystem increase. Low flow can severely alter the riparian zone (the land bordering the river), create pond-like conditions, and reduce habitat and diversity of species.  Decreased flow levels also alter the biological integrity of rivers and streams causing changes in temperature and oxygen availability that can, in turn, lead to the demise of certain aquatic species.

Goals & Objectives

CRWA assisted the Massachusetts Department of Fisheries, Wildlife, and Environmental Law Enforcement (DFWELE) in assessing the current community of fish species found in the mainstem and selected tributaries of the Charles River.  In addition, we helped to define an expected river (target) fish community based on assessing historical records of fish in the Basin and identifying the appropriate community for a natural river in southern New England.  This project was funded by the Massachusetts Environmental Trust.

The project was an important study that established clear restoration goals. Determining the stream flow level necessary to support river fish populations will allow for development of recommendations for a watershed-based fishery management plan that protects and enhances these species and the diversity of the fish community.  By participating in this study and assisting DFWELE, CRWA has strengthened its own knowledge of flow and fishery habitat issues in the river.  This will inform our advocacy work on management and permitting decisions affecting the river.  It will also provide a vehicle for educating the watershed communities and the public about the importance of in-stream flow to ecosystem health.  

Project Work

Our research included the following tasks:

  • Coordination with DFWELE.  CRWA provided DFWELE with background information about current conditions and issues and assisted DFWELE in finding pertinent historical data on the Charles River, which helped establish trends in river health and determine sites that may require future monitoring.
  • Expand Site Selection for Fish Studies.  CRWA assisted DFWELE in developing a list of predominant habitats where fish sampling should be conducted.  This assessment was conducted through the use of GIS, previous field experience, our water quality data and consultation with local officials.  The objective was to identify 20 to 50 sites that represent the relative proportions of different fish habitats (riffle, pool, and run), and 28 sites were identified. 
  • Assist with Fish Sampling.  CRWA staff were trained by and then assisted DFWELE scientists in conducting fish sampling.  
  • Process Data.  CRWA provided data analysis of survey results to DFWELE.
  • Continue Habitat Assessments.  CRWA examined eight priority fish sampling sites for characteristics such as vegetation, land use, sediment/substrate, available cover, channel alteration, bank stability, and protection.
  • Promote Public Education.  CRWA promoted public awareness and education of the effects of low flow on the fisheries population of the Charles River by writing a newsletter article describing the project and hands-on public involvement.  
  • Promote Improved Environmental Conditions.  As part of this project, CRWA focused the attention of state regulators, developers, and municipalities on various legal and technical mechanisms that could be used to improve flow conditions in the river, thereby promoting a shift in the fish population to represent one found in a more natural riverine system.

Outcome

This study concluded with the publication of a final report entitled Assessment of Fish Communities and Habitat in the Charles River Watershed in December 2003. Current fish communities were characterized and compared to the historical data so that CRWA, DFWELE, the US Environmental Protection Agency and other experts will be able to establish a target fish community: one that would exist in a healthy Charles River environment.

As a result of this study, CRWA has recommended to the MA Department of Environmental Protection (DEP) to raise the current minimum streamflow limit.  This change would necessitate monitoring of water withdrawals and usage along the Charles to ensure that there is a minimum streamflow to properly support fish communities and habitat along the length of the river.  CRWA hopes to promote the cooperation of the DEP and DFWELE to achieve this goal.

More fish and fisheries projects