I may not be the right person to ask this question since I don't recommend eating fish in any form, whether it has bee contaminated with metals and chemicals or not. Unless you eat fish alive and raw, it will putrefy within a matter of minutes and hours after death. If heated, the already damaged cell protein will coagulate and therefore not be used by the body. Any proteins not eliminated by the liver and colon will clog up the basal membranes of the blood vessel walls and cause circulatory problems, the most common cause of chronic illness (see more information in Timeless Secrets of Health & Rejuvenation, http://www.ener-chi.com.
Canned foods should be avoided, as the can's metals are solvable and enter the food and fluids. Besides, the food they contain is dead (without any life force left) and the body doesn't digest or utilize dead food.