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Researchers using acoustic telemetry to track PIT-tagged salmon in the Penobscot River. Photo courtesy of Joseph ZydlewskiWater quality monitoring by the Water Resources Program of the Penobscot Indian Nation. Photo: C DaigleAssessing riverbed characteristics through geomorphology. Photo: CHarlie BaederElectrofishing the Penobscot River to survey fish communities. Photo: Charlie Baeder

Penobscot River Restoration - River Science & Monitoring 

Baseline (pre-dam removal) assessment of Maine's Penobscot River began in 2009 when the National Oceanic and Atmospheric Administration (NOAA) invested $7.3 million through the American Recovery and Reinvestment Act (ARRA) to help rebuild the sea-run fisheries of the Penobscot. This award to the Penobscot River Restoration Trust funded removal of the Great Works dam (complete in 2012), and initiated a scientific baseline monitoring program to track physical, chemical and biological changes in the river following the removal of Great Works and Veazie dams (removed in 2013), and the decommissioning and bypass of the Howland Dam (slated for completion Fall 2015).

Research and Monitoring on the river continued during the transition phase of the project (2012-2013) while the dams were being removed. In 2015, after the removal of both Great Works and Veazie dams, data from the baseline and transitional phases was compiled and analyzed, and post-removal studies began. This research and monitoring shed light on the "before and after" dam removal condition of the river and highlights the enormous opportunity provided by the Penobscot Project for fisheries agencies, academia, and the general public to better understand some of the ecological responses to large scale dam removals. Science and Monitoring focuses on important physical and biological areas of the Penobscot's ecological landscape; descriptions of each of the monitoring studies are below.

Gathering data on riverbed characteristics pre-dam removal. Photo: Charlie Baeder


Researchers are photographing the river, conducting bathymetry and seismology studies, and characterizing channel sediment changes. Within the study area, the Penobscot River channel in both flowing and impounded reaches is dominated by coarse sediment with a predominately sand matrix. This is in striking contrast to fine-grained sediment storage noted in many impoundments. Click to learn more: Geological Survey work

Rock baskets used to determine insect diversity and abundance and water quality parameters. Photo courtesy Penobscot Indian Nation

Water Quality/Insect Diversity

The Penobscot Indian Nation Water Resources Program monitors aquatic benthic macroinvertebrates from seven specific locations and characterize water quality conditions via water samples and measurements from 10 sites. Water quality parameters collected include dissolved oxygen, temperature, conductivity, BOD, bacteria, turbidity, secchi transparency, total suspended solids, pH, chlorophyll, and total phosphorous.

Researchers collect data on nutrients moving through the river system. Photo: Charlie Baeder

Nutrient Transfer

Researchers collect samples throughout the system that are used for stable isotope analysis to provide information on nutrient cycling and feeding habits of the various species at different places and times throughout the system. Stable isotope studies are based on the idea that "you are what you eat" because isotope signatures of consumers reflect the isotope values of their prey, which in turn can be used to infer food chain level and habitat associations (in this case marine vs. freshwater). Pre-dam removal data collected in 2009-2011 shows strong isotopic distinctions between the freshwater and marine food webs. Click to learn more: Marine Nutrients

Hyrdoacoustic monitoring on the Penobscot River. Photo: C Daigle


SONAR systems are used to monitor fish presence, abundance and movements in rivers, estuaries, and oceans. Our goal is to measure and understand changes in fish populations before and after the Penobscot River Restoration Project. We have been developing a standardized approach for long-term SONAR monitoring, and collecting pre-restoration data that will be the baseline for comparison in subsequent years following restoration activities. When correlated with other data, it is hoped that hydroacoustics will provide accurate estimates not only of biomass, but also of fish species.   

invasive survey 2014

 Riparian Zone and Wetlands

Researchers are collecting data on the recolonization of the riparian zone of the river with specific attention on native and invasive plants, as well as wetland characterization. 

Atlantic salmon at the Veazie fish trap

PIT detection

Atlantic salmon adults and other species including river herring and American shad, are being tracked as they move past dams on their upstream migration. PIT (Passive Integrated Transponder) technology allows fish to be tracked via loops of wire (antennas) tagged fish must swim through located near the entrances and exits of fishways. This allows researchers to determine if a fish entered a fishway, and, if so, if it was successful in passing upstream.  

Inserting an acoustic tag into a salmon smolt that was then released and tracked on it's migration route. Photo courtesy Joseph Zydlewski

Smolt telemetry

Atlantic salmon smolt, both hatchery and wild, are being tagged and tracked as they descend the river, passing over and through dams, to the Atlantic. Several years of results indicate that in the Penobscot River, migrating salmon move more quickly through areas without dams than those with dams. Survival is markedly higher in river reaches without dams. Click to learn more about Atlantic Salmon: spotlight on salmon

Shortnose sturgeon caught, tagged, and released in the Penobscot River.

Shortnose Sturgeon

Researchers are assessing habitat and spawning of two species of sturgeon (shortnosesturgeon and Atlantic sturgeon) in the Penobscot River. The presence of reproductive females and suitable spawning habitat in the upper river has been documented. Reproductive females from the Penobscot River have been tracked moving to the Kennebec River, potentially indicating a complex reproductive migration pattern. Click to learn more: spotlight on sturgeon

Electrofishing the Penobscot River to study fish communities. Photo courtesy of Steve Coghlan

 Fish Community

Researchers are electrofishing to provide detailed information on species, total fish biomass, and abundance. Pre-removal many diadromous species were restricted to tidal waters below Veazie Dam, although Atlantic salmon, sea lamprey, and American eel were  observed upstream. These data indicate that the restoration of connectivity through dam removal will likely result in predictable shifts in fish assemblages. Click to learn more: Electrofishing

Meet the Scientist!: Steve Coghlan describes the impact of dam removal on sea-run fish and his work investigating fish communities pre-dam removal.


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