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Anchorage Field Office
Release Date: 12/20/12
Contacts: Teresa McPherson, 907-267-1420,    

BLM Releases Kuskokwim River Fish Tissue Study Results

Anchorage — The Bureau of Land Management (BLM) is releasing an interim research report, “Mercury, Arsenic and Antimony in Aquatic Biota from the Middle Kuskokwim River Region, Alaska, 2010-2011.” The report evaluates mercury, arsenic and antimony concentrations in fish tissue samples collected during 2010 and 2011 in the Kuskokwim River and 17 tributaries. 


The purpose of this study is for a better understanding of the concentrations of metals in fish that live in the Kuskokwim watershed year round.  Study results indicate that many natural mercury deposits and historic mine sites are contributing to mercury and arsenic levels in the Kuskokwim watershed. 


The study encompasses the Kuskokwim River from McGrath to Aniak and numerous tributaries.  It reflects the efforts of multiple agencies.  The BLM and the Alaska Department of Fish and Game collected water, sediment and fish tissue data, assisted by Kuskokwim residents who provided local knowledge on where and when to collect pike and burbot samples for this study.  The U.S. Fish and Wildlife Service analyzed the contaminants data and prepared the interim report for the BLM.


The natural geology of the region includes numerous mineralized areas that contain over two-thirds of all known mercury deposits in Alaska.  Those same mineral deposits also contain other metals, including arsenic and antimony.


The study found the highest concentrations of mercury were in adult pike from the George and Holitna rivers, two major tributaries of the Kuskokwim River.  Smaller fish sampled from Cinnabar Creek on the Holitna and Red Devil Creek on the Kuskokwim had elevated concentrations of mercury and arsenic compared to small fish from tributaries where no mining occurred.


The data from this study will inform the ongoing efforts by the BLM, which is in the process of completing a remedial investigation of the Red Devil Mine site. The data will be available to the State of Alaska, U.S. Environmental Protection Agency, and Agency for Toxic Substances and Disease Registry for consideration regarding future guidance on fish consumption in the Kuskokwim River watershed.


On Feb. 5, the BLM will present results from this study at the 2013 Alaska Forum on the Environment.


For more information on the fish tissue study, visit the project website at

The BLM manages more than 245 million acres of public land, the most of any Federal agency. This land, known as the National System of Public Lands, is primarily located in 12 Western states, including Alaska. The BLM also administers 700 million acres of sub-surface mineral estate throughout the nation. The BLM's mission is to sustain the health, diversity, and productivity of America’s public lands for the use and enjoyment of present and future generations. In Fiscal Year 2015, the BLM generated $4.1 billion in receipts from activities occurring on public lands.

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Last updated: 07-22-2016