Interim Results from BLM Conducted Fish Tissue Study

December 28, 2012

The George River

On December 20, 2012 BLM issued an interim report entitled “Mercury, Arsenic, and Antimony in Aquatic Biota from the Middle Kuskokwim River Region, Alaska, 2010-2011”.

Since 2010, the BLM and ADF&G have collected fish tissue samples from the Kuksokwim River and 17 of its tributaries, covering 730 miles of stream from McGrath to Aniak.  Over 1200 fish from the area were sampled, 570 of which were tagged with radio transmitters. Their movements will continue to be tracked over the next 1-2 years.  The tracking data will show the amount of time fish spend in specifc areas and allow the identification of areas that may contribute to elevated metals in fish within the study area.  

The interim report summarizes results and interpretation of mercury, arsenic, and antimony concentrations in fish and aquatic insects collected.  

In the summary located in the interim report, the following items are noted:

Most sampled fish were those favored by subsistence users, and other fish and insects were sampled to be representative of different places on the food chain.  Salmon were not sampled, due to the fact that they spend a good portion of their lives in the ocean.

Small fish (slimy sculpin, juvenile Dolly Varden and juvenile Arctic grayling) and insects from Red Devil and Cinnabar Creeks had significantly higher mercury concentrations than the same fish from other tributaries.  These levels exceeded “harmful levels” when compared to known harmful levels for fish.

Northern pike, burbot, and Arctic grayling had variable mercury levels across the entire Kuskokwim River area.

Northern pike from the George River had significantly higher mercury concentrations compared to other pike (the upcoming tracking results should give more indication of the reason for this elevation).

Total arsenic and antimony concentrations were higher in fish and insects collected from Red Devil Creek as compared to all other Tributaries.  

Results to date indicate that there is “a measurable and biologically significant elevation of mercury” in fish and insects in Red Devil Creek, and it is noted that similar levels are found near other abandoned mines in the middle Kuskokwim River watershed (Cinnabar Creek, located in the upper Holitna Drainage, on the George River).  

The BLM plans to present results from this study in February at the Alaska Forum on the Environment.  For more information, contact Matt Varner, Fisheries Biologist, at 907-271-3348.  

The Interim report can be found at