Is This the Canary in the Coal Mine? 
A recent editorial from the Harrisburg, PA Patriot News 

 Something is killing fish across the country, including in our own Susquehanna and Juniata rivers, and scientists have yet to figure out what precisely is causing it. Whatever it is, it could well have implications for other aquatic species and ultimately the human species. 
Last July, the Fish and Boat Commission found thousands of fish dead from Sunbury to south of Harrisburg on the Susquehanna and parts of the Juniata. Their deaths were attributed to Columnaris, a common fish bacterial infection, but the cause of the outbreak has yet to be determined. 

There have been similar outbreaks in the Shenandoah and Potomac rivers. In Chesapeake Bay, as many as 70 percent of bay rockfish have "fish tuberculosis," or myco bacteriosis, an infection that has increased from just 11 percent of the rockfish showing signs of the disease in 
1997. The Public Education Center has tracked similar outbreaks from New York to California. 

Low water flows, high temperatures and low oxygen levels are contributors. But they don't by themselves explain the growing incidence of fish diseases and kills. Scientists are looking to other factors, including various chemical pollutants. 

It probably should not surprise us that fish are dying in our rivers. To some degree, it is amazing that anything can live there if you consider everything that makes its way to our streams in the form of runoff from farmers' fields, streets and parking lots, and the effluent from waste-water treatment plants and various industries, as well as airborne sources. 

While there are many chemicals known to cause cancer and other diseases, the risks posed by many others have been barely researched. The chemicals humans take into their bodies in the form of prescription drugs also leave the body in wastes that eventually make their way into our waterways, where they can accumulate in the tissue of fish and other aquatic life, even in humans, who in many cases drink municipal water taken from rivers, such as the Susquehanna. 

There are growing indications that excreted synthetic hormones taken by humans may be affecting fish life. Staff writer Brett Lieberman reports that diseased fish taken from the Shenandoah and Potomac rivers displayed microscopic evidence of exposure to endocrine-disrupting chemicals. This can cause male fish to grow eggs. 

Humans have been mindlessly tampering for centuries with the underlying natural processes that make all life possible, but the pace has quickened. The Millennium Ecosystem Assessment, prepared by 1,300 researchers from 95 nations over four years and released earlier this year, found that humans had changed most of the world's ecosystems beyond recognition, and had done it in a remarkably short time. 

Some of the destruction is obvious, but much of it is not -- the pathogens killing fish, for example. 

Addressing these issues is far from simple or easy. Modern society is built on exploitation of nature's assets to the greatest possible degree at the least cost and maximum possible profit. There are, to be sure, certain standards that pertain to biological and chemical releases. But far from all potential hazards are removed under the prevailing treatment technologies. 

A greater effort to identify the substances and practices that are making our waterways unhealthy for fish is urgently needed. It's fish today but it could be people tomorrow.