Fish Tissue Contaminant Monitoring Project

The Water Monitoring Group routinely collaborates with the DEEP Fisheries Division and the CT DPH Environmental Health Division to assess fish tissue contamination in Connecticut.  This collaboration maximizes the benefit of limited available resources and provides for the collection and analysis of data that is mutually beneficial to both programs.  DEEP utilizes the data to assess water quality concerns, while CT DPH utilizes the data to support public health advisories related to fish consumption. 

Program History

Monitoring of toxic contaminants in tissues of fish and invertebrates has been conducted by DEEP in partnership with the CT Department of Public Health (DPH) since the late 1970s.  Efforts have historically included analysis of levels of mercury and polychlorinated biphenyls (PCBs).  More recent work has sought to study new contaminants of emerging concern, such as per- and polyfluorinated alkyl substances (PFAS).

Additional data collection has occurred in Connecticut in response to site specific releases and as part of larger regional US EPA-led studies.

Mercury in Lake Fish Tissue Studies

Mercury is a naturally occurring heavy metal that can accumulate in living tissue.  Mercury is introduced into the environment though both natural and human facilitated activities. Unfortunately, exposure to mercury causes a variety of health issues. Pre-natal exposure is of particular concern as it can cause issues with neuro-development.

Given these concerns, DEEP partnered with the Connecticut Institute of Water Resources in the mid-1990s to conduct a study to evaluate ambient mercury concentrations in Connecticut lakes and ponds. Between 1996 and 1997, fish were collected from 56 different waterbodies throughout the state. The study confirmed that mercury levels in fish tissue were elevated and that non-point sources such as atmospheric deposition play a key role in mercury concentrations within Connecticut waterbodies.  In order to protect the public, a statewide fish advisory consumption was put in place .

The statewide lakes study was repeated again in 2005-2006 by the University of Connecticut with funding from DEEP. Results from this study were encouraging, demonstrating that mercury levels in Connecticut fish tissues are declining on a statewide basis. However, contamination levels still commonly exceeded threshold levels used to establish the statewide consumption advisory.

A third round of study is presently underway.  DEEP has provided funding to the University of Connecticut to collect tissue samples from all lakes included in the original study.  Ongoing repetition of this study, at approximately ten-year intervals, is planned (funding permitting) to continue to evaluate trends in mercury contamination across the state.

Related Reports

Related Pages

For More Information Contact:

Meghan Lally
Fish Tissue Contaminant Project Lead
DEEP Water Monitoring Group
79 Elm Street, Hartford, CT 06106
(860) 424-3061

Content last updated March 23, 2020.