I doubt mercury is or any other pollutant is cleaned by pressure cooking, frying etc. I'm just saying this fish, the common carp is non native, bottom feeding, destructive fish to our environment and in MOST waters is not fit to eat. JMHO.
I simply ask you to contact your local DNR and ask about consumption of fish in your area especially bottom feeding fish. It's usually listed in fishing regs but most people don't even read it. Putting it in your garden is really questionable in my humble opinion.
I'm not saying that we shouldn't bow fish them as they are NON NATIVE fish that destroy the habitiat for native and game fish! They need controlling and I'm in for that! Bowfishing is my favorite way of helping my local enviourment.