BUFFALO, NY – The U.S. Army Corps of Engineers Research and Development Center recently completed an innovative 2-year, multiphase study tracking the residency of the common carp and determining if tagged carp could help assess where polychlorinated biphenyls (PCBs) exposure areas are within the area of concern (AOC) in the Manistique River and Harbor, near Manistique, Michigan. This study was conducted because despite sediment remediation from 1995-2000 and navigational dredging in 2010, PCB concentrations in fish remain elevated.
“The idea was to release common carp, not to be confused with the invasive Asian Carp, into the AOC with various tracking devices and inflatable tags to figure out where they were being exposed to PCBs,” said Gabriel Schmidbauer, a project manager for the Army Corps of Engineers, Buffalo District. “Once we can determine where the PCBs are we’ll be able to remediate the sediment.”
Common carp was used for the study because it’s a heartier fish, heavily adaptable and relatively easy to raise. The carp are a scavenger bottom feeder fish who typically feed within the bottom sediment of water bodies like the Manistique River and the PCB levels are elevated in the bottom feeder type fish, said Schmidbauer.
During the first year of the study, 25 Common Carp were collected from the Manistique River, tagged and released back into the Manistique River AOC.
This phase of the study found that common carp are mostly a transient species in the Manistique River AOC, with all but four fish spending less than 50 percent of the study period, which was June 8 to Oct. 26, 2015, within the harbor. Radio telemetry was used to determine the location of fish after they departed the AOC.
“We learned a lot about the common carp behavior and their migratory patterns,” said Schmidbauer.
While in the system, tagged carp associated with preferred areas, suggesting those areas drive site-related contaminant exposures.
During the second year of the study, 25 hatchery raised common carp were tagged with a newly developed inflatable Fish Recovery Device (FRD) then released into the Manistique River AOC.
Three hatchery raised fish actively moved within the AOC for the duration of the monitoring period, July 10 to Aug. 9, 2018. Six fish moved out of the study area and did not return. The remaining fish either lost their tracker or died during the study.
One of the Carp that was implanted with the FRD was caught after inflation and sent for PCB testing. This fish had undetectable levels of PCBs.
“The carp that was retrieved with the new tracking device spent most of its detection period in an area that has not been known to have elevated PCB levels in the sediment,” said Schmidbauer. “Even though only one fish was caught, 20 of the 25 tags were still retrieved.”
The study was able to determine the residency and exposure areas of common carp in the Manistique Harbor AOC. They also discovered that carp were generally non-resident or transient visitors to the AOC.
Additionally, carp are likely not reliable indicators of site-related contaminant concentrations or remedial effectiveness in the AOC.
”We’re going to take our lessons learned and apply them to future studies,” said Schmidbauer. “Now that we know the migratory patterns of the carp we’ll be able to put more controls in place to not only keep the inflatable tracking devices in place, but hopefully find a new more effective way to test for PCBs within the Areas of concern.“