Believe it or not, seafood is not actually supposed to smell "fishy." It should have a fresh ocean aroma. If shrimp does smell like ammonia, it's usually a sign of protein degradation, but not always. If the shrimp hasn't reached the expiration date, the smell may be coming from purge—harmless, liquefied amino acids that seafood releases in the package, similar to the pink liquid in a steak package.
Checking for Freshness
Check for sliminess on the shrimp, a telltale sign of protein degradation that usually appears in tandem with the fishy odor. If this is the case, toss them. Fresh shrimp is usually still good for two days past their sell-by date.
Prepping the Shrimp
A.J. Andrews' work has appeared in Food and Wine, Fricote and "BBC Good Food." He lives in Europe where he bakes with wild yeast, milks goats for cheese and prepares for the Court of Master Sommeliers level II exam. Andrews received formal training at Le Cordon Bleu.