AWRI Environmental Chemistry
PCBs in Saginaw Bay Walleye
Annis Water Resources Institute
Project Sponsor: University of Michigan Research and Development Grant
Jude, D.J., Rediske, R.R. O'Keefe, J.P., Hensler, S., Giesy, J.P. 2010. PCB Concentrations in Walleyes and Their Prey from the Saginaw River, Lake Huron: A Comparison between 1990 and 2007. Journal of Great Lakes Research 36(2); 267-276.
Concentrations of polychlorinated biphenyls (PCBs) were measured in composited samples of walleyes Sander vitreus and their prey during 2005–2007 from Saginaw Bay, Lake Huron. There was a linear relationship between fish length and PCB concentrations in walleyes between 356 and 608 mm, but fish 680 mm had lesser concentrations than 608-mm fish. When fish 222–550 mm from 1990 were compared with those from 2007, there was a decrease of 1315 ng PCBs/g wet wt (ww). Concentrations of PCBs in gizzard shad Dorosoma cepedianum (190 ng PCBs/g ww) were three-fold less than fish collected in 1990 (516 ng PCBs/g ww). Round gobies Neogobius melanostomus collected from the Saginaw River had the greatest concentrations of PCBs (range: 200–350 ng PCBs/g ww) compared with other prey fishes (45–190 ng PCBs/g ww). Concentrations of PCBs in Saginaw River round gobies were three-fold greater than those from Saginaw Bay. Zooplankton from 1990 and 2008 contained 8.0 and 32 ng PCBs/g ww, respectively, while zebra mussels Dreissena polymorpha from 2008 contained 351 ng PCBs/g ww. Principal components analysis showed that PCB congeners differed between the largest walleyes and other fish. There are several possible explanations for lesser concentrations of PCBs observed in 2007. These include effects of dredging, changes in the food web related to round gobies, loss of alewife Alosa pseudoharengus, which was a major walleye prey item in 1990, and replacement by yellow perch Perca flavescens, or decreases in release of PCBs from sediments due to weathering, burial, or diffusion.
Madenjian, C P., Jude,, D.J. Rediske, R.R. O'Keefe, J.P, Noguchi, G.E.. 2009. Gender difference in walleye PCB concentrations persists following remedial dredging. Journal of Great Lakes Research 35(3): 347-352.
Eleven male walleyes (Sander vitreus) and 10 female walleyes from the Saginaw Bay (Lake Huron) population were caught during the spawning run at Dow Dam (Midland, Michigan) in the Tittabawassee River during April 1996, and individual whole-fish polychlorinated biphenyl (PCB) determinations were made. Total PCB concentrations averaged 7.95 and 3.17 mg/kg for males and females, respectively. As part of the Natural Resource Damage Assessment remediation process, contaminated sediments from the Saginaw River, the main tributary to Saginaw Bay, were removed during 2000 and 2001. Total PCB concentrations of 10 male and 10 female walleyes caught at Dow Dam during April 2007 averaged 1.58 and 0.55 mg/kg, respectively. Thus, dredging of the Saginaw River appeared to be effective in reducing PCB concentrations of Saginaw Bay adult walleyes, as both males and females decreased in PCB concentration by more than 80% between 1996 and 2007. However, the ratio of male PCB concentration to female PCB concentration did not decline between 1996 and 2007. This persistent gender difference in PCB concentrations was apparently due to a gender difference in habitat utilization coupled with a persistent spatial gradient in prey fish PCB concentrations from the Saginaw River to Lake Huron.
Saginaw Bay and the Saginaw River, are designated as an designated Area of Concern by the International Joint Commission due to contamination of sediments with persistent inorganic and organic pollutants. This part of the Lake Huron watershed also is one of the more productive areas in the Great Lakes. Being the largest watershed in Michigan, the river and bay receive urban and agricultural runoff, as well as domestic sewage and industrial effluent. Sediments are contaminated with metals and anthropogenic compounds, such as PCBs, which has led to fish consumption advisories for this river for species such as channel catfish Ictalurus punctatus and common carp Cyprinus carpio and toxic effects in birds that feed on contaminated fish. Most toxicity has been attributed to several PCBs congeners. Similar contamination issues exist at other Great Lakes sites, with most restrictions on fish consumption due to relatively great levels of PCBs, even though concentrations of most contaminants have been declining and some advisories have been relaxed. Saginaw Bay hosts a world-class walleye Sander vitreus fishery and commercial fishers harvest large quantities of other important species. In efforts to rehabilitate this area, the Saginaw River mouth was dredged during 2000-2001 to remove accumulated toxic substances from the river mouth area. A subsequent Michigan Department of Environmental Quality sediment survey showed that concentrations of PCBs were less than the target level of 1 PCBs/kg. Concentrations of contaminants in forage fish and walleyes in this area were measured in 1990 as well as loadings to the river. These studies provide background data necessary to evaluate whether the dredging activity or other environmental processes, such as sedimentation, have caused a decline in concentrations of contaminants in top predators walleye Sander vitreus and their forage fishes.
It was hypothesized that substantial contaminant loads are transferred from the sediments and zooplankton to gizzard shad (planktivores) and then to walleyes, which enter the river in fall-spring and spawn in spring. Furthermore, it was predicted that dredging and sedimentation of PCBs over time, if most of the PCBs are not coming from the tributaries, would reduce the amount of PCBs bioaccumulated in this food web. The objective of this study was to determine if dredging and environmental processes reduced concentrations of PCBs in walleyes and forage fish by comparing concentrations measured during this study with those in fish collected in 1990.
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