Wet cat, dear, why does fish sauce taste like wet cat? It's important to phrase the question correctly. And part of the answer is that a couple hundred million people in Southeast Asia use it almost daily as a condiment or cooking ingredient.Fish sauce is made by salting and fermenting anchovies and other small fish in vats or barrels for months (yes, months) and drawing off the clear liquid that rises to the top of the barrels. It surely is no longer a wonder to you why it smells and has such a pungent taste! But its importance in Southeast Asia cannot be underestimated. Fish sauce has been a vital source of protein and vitamins in cultures that for thousands of years were fed largely on rice.
With a hint of understatement in her Encyclopedia of Asian Food (Canada, UK), Charmaine Solomon says, "For those not brought up with this ingredient, the smell may take a little getting used to but if you have eaten and enjoyed the food of Thailand and Vietnam it is certain that you have survived a close encounter with this pungent seasoning. There are a few dashes of fish sauce in most dishes"But not all fish sauce (or fish gravy, as it is known further north in China and further east in the Philippines) is created equal. It may be that you got a fish sauce that swings closer to wet cat, or it may be that in following the recipe exactly, you used more fish sauce than you should. James Peterson, author of Fish and Shellfish ( Canada , UK ), says he thinks of fish sauce as a substitute for salt, and - of course he tastes as he goes along - when the saltiness of the dish is right, he has added the right amount of fish sauce. Just as with olive oil, there are different grades and qualities of fish sauce. Thai fish sauce ( nam pla ) is milder than Vietnamese ( nuoc nam ). The first yield drawn from the barrel (think extra virgin) is most often used as a condiment, while subsequent batches (which are less expensive) are more likely to be used for cooking.
Finally, the reason fish sauce is used in many dishes is that, in reasonable doses, it adds a complexity or richness that the dish would otherwise be missing - a little bit of its soul, in the words of Mr. Peterson.
Related Article: What is Fish Sauce, Nam Pla, Nuoc Nam, Patis?