Study Finds Causes for Mutant Bass in Susquehanna River
Pittsburgh Post-Gazette - 15 December 2015
By Don Hopey
The Susquehanna River’s decade-long mutant bass mystery moved a
cast closer to a solution with the release of study findings that
for the first time identified herbicides and
endocrine-disrupting compounds from agricultural sources as likely
causes.
The multi-year study released Monday by the state Department of
Environmental Protection and the Pennsylvania Fish and Boat
Commission also found that pathogens and parasites are probable
contributors to the mutations and population decline afflicting
what was once one of the best bass fisheries in the eastern U.S.
“This study does not identify a single smoking gun. But it does
point the way toward likely causes, which we will continue to
pursue,” said DEP Secretary John Quigley, who said the complexity
of the lengthy river system has challenged researchers.
The Susquehanna River flows from upstate New York, south through
Pennsylvania’s agricultural middle, and Maryland, and is the
largest source of fresh water entering the Chesapeake Bay. It’s
also a major source of agricultural runoff containing phosphorous,
nitrogen and sediment pollutants, and natural animal hormones in
manure, which could disrupt bass reproduction.
“The study is important because it admits that the river is sick
and that the bass are sick,” said Fish and Boat Commission
executive director John Arway, who has worked on the issue since
2001, when fingerling bass populations in the river declined
precipitously.
The small bass population crashed again in 2005, and the DEP and
the commission began to identify older bass with tumors, round
sores and lesions.
“We could have said in 2005 that parasites and pathogens were
likely causes,” Mr. Arway said, “but now to say that herbiicides
and endocrine disrupting compounds are also scientifically likely
causes is the new thing and a big step.”
The next step is to identify the sources of those endocrine
disruptors and herbicides, and follow up with a long-term,
mandatory plan to reduce them in the river, Mr. Arway said.
“We know where the herbicides are being applied most heavily and
we know that exposure to them is depressing the immune systems of
the bass,” Mr. Arway said. “We’re inching closer, but the DEP
is still not willing to say its the [farm] nutrients reaching the
river.”
Researchers also must determine how the herbicides from farms,
roadside weed spraying and lawn application interact with
naturally occurring, normally benign bacteria and pathogens, said
Neil Shader, a DEP spokesman. He said the DEP is seeking to widen
streamside buffers next to farm fields to reduce runoff of
herbicides.
“Somehow those parasites and pathogens have been turbocharged,”
Mr. Shader said, “and are proving to be lethal to those bass.”
Don Hopey: dhopey@post-gazette.com, 412-263-1983 or on Twitter
@donhopey