Mercury levels in fish are not as high as previously estimated.  The water quality standard for mercury is based on methyl mercury (CH3Hg+), which is the bioavailable fraction of total mercury.  The current standard for methyl mercury is 0.3 mg/Kg and was developed for safe human consumption of fish.  (Excess mercury is a health concern for the nervous system.)  The Ohio River Sanitation Commission (ORSANCO) used improved analytical methods to test fish tissue for both total mercury and methyl mercury.  Analytical results using fish tissue collected from 2009 to 2013 show that the western stretch of the Ohio River in Kentucky is meeting the water quality standard for mercury.  The previous method used to conduct analytical testing accounted for total mercury but did not include a breakdown of methyl mercury.

On June 2, 2015, the Division of Water released a proposal to remove 370 miles of the Ohio River from the 303(d) List of Impaired Waters.  This request for removal from the 303(d) list is open for public comment and subject to EPA approval.  Public comment on the request for removal from the Impaired Waters List is open until July 13, 2015 and can be found at http://water.ky.gov/Pages/PublicNotices.aspx.

Source:  https://kydep.wordpress.com/2015/06/02/division-of-water-plans-removal-of-western-ohio-river-from-impaired-waters-list/

So fear not anglers – the next time you pull out that big ‘ole catfish from the mighty Ohio River, consider celebrating your catch by throwing it on the grill instead of tossing it back into the water!