From what I have read in the past, mercury and other heavy metal concentration levels are determined using the whole fish in their part per million or billion measurements. Just like other creatures the "bad stuff" accumulates in the liver and other organs. Anyone had crappie liver lately? And then too, some warnings are to not eat more than 6 meals a week, etc. etc.
In a lake like ours (the Lake of the Ozarks) the possibility of a concentration build-up of heavy metals in fish is less likely as the lake is a river system that 'self-flushes- itself. Because of the flow here, the water is totally changed an equivalent of 4 times per year. The older a fish is the more that fish's heavy metal concentration is if heavy metals are present. Just don't eat any catfish over 40 pounds or crappie over 6 pounds! :rolleyes:
the trick to catch that finnicky speck....
gently set the hook just before the peck