Different types of mercury have different effects on the body because they are metabolized differently (http://www.atsdr.cdc.gov/toxprofiles/tp46.html). Both metallic mercury and methylmercury cause damage to the brain and kidneys.
Cooked shrimp can be refrigerated for up to 3 days. Flour: Can be stored for up to 6 months at room temperature because higher temperatures create a hospitable environment to bugs and mold. (Itâs not a bad idea to store it inside a plastic bag just to be safe in case you forget to throw it out in time.).
Fresh shrimp are extremely perishable. You should try your absolute best to cook them within 24 hours of purchasing them. If the only fresh shrimp available at the market were farmed in a far-flung location (like Thailand), they were probably previously frozen anyway.