As the names rightly suggest, oyster sauce is made from oysters and fish sauce is made from fish. Like the basic ingredients, the method of preparation too differ. Both the sauces are different in color, consistency, and flavor. However, they are substituted for each other in some recipes. It is always better to have a basic understanding about these sauces, if you plan to use them. Method of Preparation Oyster sauce is made from oysters, which are allowed to boil in water over low heat, till the juices reduce to form a thick sauce. Nowadays, most of the store-bought versions are made with sugar, salt and cornstarch. They contain a small amount of oyster sauce or oyster essence for flavor. You may also find vegan versions of oyster sauce prepared with shiitake or oyster mushrooms. Fish sauce is prepared by fermenting fish along with salt. While anchovies are mainly used for making this sauce, other types of fish are also used for this purpose. Fermentation for a short period yields a sauce with a pronounced fishy flavor. The sauce will have a rich, nutty flavor, in case of longer fermentation. The longer the period of fermentation, the lesser the fishy smell. Usually, the period of fermentation ranges between one year to 18 months. Color, Consistency Oyster sauce is brownish, whereas fish sauce is reddish brown or amber-colored. You may also find some types of fish sauce that contain additives, like spices, garlic and green chilies. Oyster sauce is thick in consistency, whereas fish sauce is watery and clear. Flavor, Odor As it is prepared by reducing oyster extracts, oyster sauce is sweet, with a salty undertone. However, fish sauce has a prominent salty and nuttier flavor. It has a fishy smell too. This smell can be overcome by mixing it with a small amount of lime juice. Or else, you can use it in small amounts. As compared to the fish sauce, oyster sauce has a milder aroma. You can sample oyster sauce straight out of the bottle. Origin, Use While oyster sauce is Chinese in origin, fish sauce has been used in various regions, through the centuries. Though fish sauce is said to have originated in Asia or Europe, the exact place of origin is still unknown. Oyster sauce is widely used in Chinese cuisine, especially in stir-fries. It is also used as a dressing for noodles. It is an indispensable ingredient in some Chinese dishes. Fish sauce is widely used in Cambodian, Thai, and Vietnamese cuisine. It is used for marinating fish and meat, and as an ingredient in soups and casseroles. When mixed with lime juice, sliced green chilies and garlic, fish sauce can be used as a condiment. Nutrition A tablespoon of oyster sauce contains 15 grams water, 2 grams carbohydrate, and 0.3 gram protein. It has a calorific value of 9 kcal. A tablespoon of fish sauce has 13 grams of water, 0.9 gram protein, 0.7 gram carbohydrate; and amounts to 6 calories. The sodium content in fish sauce is around 1400 mg, whereas oyster sauce has only 500 mg. Though both the sauces have a low level of vitamins and minerals, fish sauce has a slightly higher amount of calcium, potassium, magnesium, iron, folate, and some vitamins. You can buy both these sauces from Asian stores in your area. Once opened, refrigerate them. It is better to use oyster sauce within six months from the date of opening. It is said that, fish sauce stays good for almost a year, from the date of opening. However, make sure to store them in air-tight containers. Now that you know the basic differences between oyster sauce and fish sauce, you can use the right sauce for a given recipe, and derive the best flavors from it.