Researchers are reeling in male fish with female characteristics, causing concerns about water quality. Let’s dive in:

Intersex smallmouth bass: Found, in Pennsylvania river basins! (Great Lakes Environmental Research Lab, NOAA)
A study in Pennsylvania river basins has turned up evidence of intersex fish—males carrying immature eggs. The result has raised concern about the widespread level of hormones in our waterways.
“We use fish as an indicator that there is something we should be concerned about,” explains research biologist Vicki Blazer with the U.S. Geological Survey. “This is something that is having effects on fish, and probably other organisms as well.”
While more research is needed to pinpoint the precise source of these estrogenic chemicals, agricultural runoff seems to play a role, since manure often contains hormones. Estrogen from the use of human birth control pills may also end up in wastewater.
Get schooled:
- Check out Bay Times coverage of the study, “Intersex smallmouth bass found in all 16 PA sample sites,” to learn more about the problem with intersex fish
- Learn more about how “Changes in fish signal problems with waters” via the Virginian-Pilot
- Dig into study itself, as published in Environmental Monitoring and Assessment
The fine print:
- This segment was produced in partnership with Cornell’s Atkinson Center for a Sustainable Future






