Altered serum sex steroids and vitellogenin induction in walleye (Stizostedion vitreum) collected near a metropolitan sewage treatment plant

Several recent in situ studies have reported that domestic and mixed domest ic/industrial sewage effluents contain one or more natural or anthropogenic estrogenic substances. Those studies examined caged or feral fish for the presence of the egg yolk precursor protein, vitellogenin (VTG), in the bloo d of male fish. We have previously reported that male, feral carp (Cyprinus carpio) obtained from the effluent channel of a major sewage treatment pla nt (STP) exhibited depressed serum testosterone (T) concentrations, as well as detectable levels of VTG. The present study examines male and female wa lleye (Stizostedion vitrereum), a native species with a different life hist ory and feeding habits, collected from the same Mississippi River locations below the St. Paul metropolitan STP. All male and female walleye collected horn the effluent channel contained measurable levels of VTG in their bloo d. Males from that location also exhibited depressed serum T concentrations and elevated serum estradiol-17 beta (E2) concentrations compared with mal es from the Snake River reference site. Males obtained from Mississippi Riv er Navigational Pool #2 (MRP-2), 3-20 miles downstream of the STP also exhi bited reduced serum T concentrations, but showed no alterations in E2 conce ntrations or the presence of VTG in the serum. Females collected at the STP site had greatly elevated serum E2 concentrations, but serum T concentrati ons were not different from females collected in the Snake River. Our resul ts demonstrate that the St. Paul metropolitan STP continues to release an e strogenic effluent, capable of inducing VTG production and altering normal serum sex steroid concentrations in a commercially valuable, native fish, t he walleye. Additional studies will be required to determine whether these observations portend long-term population level effects.