Mutant Bass Are Changing Sex in America’s Rivers

[dropcap size=small]S[/dropcap]cientists from the U.S. Geological Survey have unearthed an astonishing trend in America’s rivers—male bass are carrying eggs.

The discovery was reveled three weeks ago in a Washington Post report that highlights bass populations in the Chesapeake Bay watershed. That watershed encompasses some of the nation’s most well-known rivers in the Delaware, Ohio and Potomac Rivers. Both smallmouth and largemouth bass in those rivers are, according to the USGS, becoming “intersex” organisms.

That means the fish have two genders. And it’s an alarming sign of industry’s affect on fisheries.

Dissections of intersex bass in the Susquehanna river near Hershey, Pennsylvania uncovered a 100 percent margin of smallmouth bass carrying eggs. Following the research in Pennsylvania—scientists from the U.S. Fish and Wildelife Service found female germination cells in 82 percent of the smallmouth and 23 percent of the largemouth bass near the Blue Plains water treatment facility in Washington, D.C.

The source? Hormones.

In both cases, fish that were dissected came downstream from locations releasing hormones into the water. At Hershey, that source proved to be agricultural runoff from farm operations—estrogen from manure used to fertilize fields. In urban areas, the report says, the estrogen comes from city drain pipes.  But aside from the mutant sex of these fish, the Post reports that catch rates for adult smallmouth bass near Hershey fell 80 percent during the four year span of a 2001-2005 study.


It seems then, that there may be less fish to catch due to hormone introduction. Reports say the ones that are being caught have been found with sores and lesions presumably created by parasites that feed on chemicals.

This isn’t the first time the Chesapeake Bay watershed has come under fire. For decades, industrial pollution discolored the Potomac, turning the river into a national punchline and a conservation rallying cry. And though efforts are underway to restore its waters—along with much of the other rivers in the region—the mutant bass infestation may not be limited to New England.

Researchers say intersex bass are starting to show up elsewhere in America, in some of the nation’s largest rivers like the Mississippi, Colorado and Columbia. Those rivers already carry much of the nation’s industrial runoff, which in the case of the Mississippi has resulted in a well-known marine life dead zone surrounding its outfall in to the Gulf of Mexico. It’s a safe bet that if problems are showing up in these rivers, where incredible volumes of water flow each day, they aren’t far behind in the tributaries.

Government agencies differ on the severity of the hormone crisis. The USGS and USFWS findings combat reports by the Environmental Protection Agency, which claim water quality is drastically improving in the Chesapeake Bay watershed. However, this particular marine problem could go all the way to the roots of America’s food chain. After all, humans need agriculture to survive. From food to fuel and household products, America depends on farms for a supply of daily necessities.

But the root of this problem, the reason bass are suddenly changing sex—hormones—are regulated for human consumption by the Federal Drug Administration. Obviously, the FDA does not regulate hormone consumption by fish.

That does raise an interesting question though: if hormones are creating mutant bass, what are they doing to people?