07
May
Tests Confirm Rare Cancer in Susquehanna River Smallmouth Bass
(Beyond Pesticides, May 7, 2015) The Pennsylvania Fish and Boat Commission (PFBC) has confirmed that a rare malignant tumor was found on a smallmouth bass caught in the Susquehanna River by an angler late last summer. The finding was confirmed by two independent laboratory tests, including the U.S. Fish and Wildlife Service (FWS) and the Aquatic Animal Health Laboratory at Michigan State University. Although it only represents one individual fish from the overall population, it provides additional evidence —which includes the prevalence of intersex fish discovered last summer”” that the health of the fish community residing in the river is being compromised, according to PFBC executive director John Arway.
Though the findings do not point to a specific cause for the cancer found on the smallmouth bass (SMB), agricultural pesticides, particularly endocrine disrupting chemicals, that have been found in the watershed, likely play a part in the rampant disease issues in SMB in the Susquehanna River.
“As we continue to study the river, we find young-of-year and now adult bass with sores, lesions and more recently a cancerous tumor, all of which continue to negatively impact population levels and recreational fishing,” Mr. Arway said. “The weight-of-evidence continues to build a case that we need to take some action on behalf of the fish.” Cancerous growths and tumors on fish are extremely rare throughout the U.S., but they do occur.
Since 2005, PFBC biologists have observed more than 22,000 adult SMB as part of routine surveys in the Susquehanna River basin and have not documented any fish with obvious signs of tumors. However, PFBC biologists continue to find sores and lesions on young-of-year bass during late spring and early summer surveys at alarming rates.
The PFBC first documented disease-related mortality of young-of-year SMB in the Susquehanna River in 2005. The continued mortality has contributed to the decline in abundance of SMB. Since 2012, the PFBC has unsuccessfully petitioned the state Department of Environmental Protection (DEP) to add the river to the state’s bi-annual list of impaired waterways.
“The impairment designation is critical because it starts a timeline for developing a restoration plan,” said Mr. Arway. “We’ve known the river has been sick since 2005, when we first started seeing lesions on the smallmouth. Now we have more evidence to further the case for impairment.”
Last summer, research by the U.S. Geological Survey (USGS) showed a strong correlation between the occurrence of intersex characteristics on fish and areas of high agricultural use in Pennsylvania. Three species of fish were examined in three separate watersheds in the state to assess whether characteristics caused by hormones and hormone-mimicking compounds, such as immature eggs in male fish, were present. In aquatic environments, the presence of these intersex characteristics is widely used as a biomarker for assessing exposure to estrogenic chemicals, as well as anti-androgenic chemicals which inhibit development of male characteristics. Male smallmouth bass from all sites sampled had immature eggs in their testes; however, SMB in the Susquehanna drainage had a significantly higher prevalence and severity of these effects than sites in the Ohio drainage. When compared against the percentage of agricultural land use, which is higher in the Susquehanna, a link was established.
Fish and other aquatic organisms face numerous risks from pesticide exposures, even at low levels. In fact, USGS scientists identified pesticides as one of the contaminants in the Potomac River linked to intersex-fish observed there. Atrazine, one of the most commonly used herbicides in the world, has been shown to affect reproduction of fish at concentrations below U.S. Environmental Protection Agency’s (EPA) water-quality guidelines. Concentrations of atrazine commonly found in agricultural streams and rivers have been associated with a reduction in reproduction and spawning, as well as tissue abnormalities.
In fish and humans, endocrine disrupting effects include direct effects on traditional endocrine glands, their hormones and receptors, such as estrogens, anti-androgens, and thyroid hormones, as well as signaling cascades that affect many of the body’s systems, including reproductive function and fetal development, the nervous system and behavior, the immune and metabolic systems, the liver, bones and many other organs, glands and tissues. Hundreds of scientific articles have been published across the globe demonstrating how a broad selection of chemicals can interfere with the normal development at all ranges of exposure. Scientists discovered effects for some widely used chemicals at concentrations thousands of times less than federal “safe” levels of exposure derived through traditional toxicological tests. Whatever the exposure level, neither fish nor human are protected from most endocrine-disrupting chemicals present in our waterways.
“If we do not act to address the water quality issues in the Susquehanna River, Pennsylvania risks losing what is left of what was once considered a world-class smallmouth bass fishery,” Mr. Arway said. “DEP is expected to release its 2016 list of impaired waters in late fall. We are urging them once again to follow the science and add the Susquehanna River to the list.”
PFBC biologists conduct annual young-of-year and adult SMB surveys on this stretch of the river from late June through the end of October when sampling conditions are appropriate. In addition, PFBC has enlisted the assistance of certain anglers and guides to provide fish with obvious masses or lesions if they encounter any when fishing the river.
PFBC staff are continuing to work with DEP, FWS, USGS, the U.S. Environmental Protection Agency and other partners to focus efforts on better understanding what factors are impacting the SMB inhabiting the middle Susquehanna and lower Juniata rivers. In the meantime, catch-and-release regulations for SMB are already in place on 98 miles of the middle portion of the Susquehanna River where the symptomatic fish was captured and on the lower 31.7 miles of the Juniata River from Port Royal to the mouth.
Beyond Pesticides continues to fight to prevent water pollution and harmful agricultural practices. Visit our Threatened Waters page and learn how organic land management practices contribute to healthy waters in the article, “Organic Land Management and the Protection of Water Quality.”
Source: Pennsylvania Fish & Boat Commission Press Release
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Image: Smallmouth bass with confirmed malignant tumor. Caught by angler in Susquehanna River near Duncannon, Dauphin County, on Nov. 3, 2014. Photo credit: John Arway
