Not just one type but almost all kinds of fish, to include some of the most popular gaming fish like bass and walley, are changing.
What – wait. Changing? Yes, and at least one local news team has been documenting these changes since 2002, when concerns were first emerging. A decade later, “scientists are beginning to call it a significant threat,” the Northlands Newscenter reported in February.
“Walleye cakes, walleye bites, walleye sandwich…it’s a popular delicacy in restaurants around the northland,” the Newscenter said. “It’s also a multi-million dollar industry, attracting hundreds of thousands of anglers to the Northland’s beautiful lakes year round.”
Feminization of male fish
While many area residents and not a few visitors to the area take the industry for granted in believing that the waters can be fished forever, scientists have discovered a major threat to the abilities of many kinds of fish to reproduce.
“Changes in, for example, the external characteristics of males where they start to resemble females,” Dr. Gary Ankley of the U.S. EPA Lab in Duluth, Minn., told the Newscenter.
Dr. Pat Schoff added, of the Natural Resources Research Institute at the University of Minnesota-Duluth: “The small mouth bass and large mouth are sensitive to fish feminization. We’re seeing lots of symptoms in these species.”
How can fish actually change genders? Scientists aren’t sure but they do know that it is a frightening phenomenon that is happening all over the world. Studies show thus far that a feminized male fish can suffer a reproductive disability of at least 76 percent and more; the more researchers look into this, the more they are finding fish that cannot reproduce at all.
The phenomenon has “actually caused some fish populations to go extinct,” said Ankley.
Some of the leading scientific research examining the problem is taking place in Duluth, at UMD’s NRRI, and also at an Environmental Protection Agency lab there. Scientists believe chemicals are behind the fish gender transformation.
“There’s only a few labs in the world that can do this very effectively when we deal with these very potent chemicals,” Ankley said. “There’s a number of chemicals that can act as what we call estrogens.”
Scientists and environmentalists note that there are literally thousands of chemicals that make it into the nation’s streams, rivers and other waterways every day. They include medications, agricultural run-off and other substances that carry very powerful estrogens scientists believe may be altering fish genders.
“We can see everything from testicular tissue that is growing like an ovary. Or some fish have one teste and one ovary,” said Schoff.
“The male testes actually has eggs in it,” Ankley added.
5,000-8,000 different medications could be altering environment
Researchers know when they expose fish in the lab to such powerful estrogen compounds they will see nearly complete transformations from one gender to another, and that such transformation is dramatically harming fish populations.
“There’s lower rates of reproduction or even no reproduction,” Dr. Schoff said.
Scientists say they aren’t sure what other substances and chemicals, besides estrogen, might be contributing to the gender transformations in nature.
“It turns out there are chemicals that can mimic natural estrogens and when you expose males to these chemicals they can start to achieve these female characteristics,” Ankley said. “There’s probably 5,000 to 8,000 different medications that are used and could enter the environment.”
They say even substances as common as Ibuprofen might be contributing to the problem as well.
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