Fermented Fish for Sauce and Fertilizer

Add an umami kick to your kitchen and a soil-benefiting boost to your garden with homemade fish sauce.

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by AdobeStock/Pixel-Shot

Fish sauce is a concentrated mystery. From its smell to its stability, range of flavors, origin, and history, the simple concoction of fish and pure salt packs an alluring and unparalleled flavor. And while the thought of fish being enzymatically digested on your hot roof may not feel immediately arresting, upon closer examination, the liquid condiment that’s a staple in Asian cuisine is supremely easy to make, and surprisingly versatile in the home, no matter what flavor profiles dominate your kitchen. A look at the history of fish sauce, the science behind its characteristics, and the modernization of its production also provides a lens into the evolution of fermentation in the hands of people all over the world.

A Fishy History

The earliest evidence of fish sauces, or garums, dates back to the ancient Greeks in the 3rd century B.C. The Carthaginians were also early producers of the sauce, and some of the oldest evidence of production can be found in old garum factories carved from limestone in modern-day Tunisia.

Speculation exists regarding whether the practice traveled from the Mediterranean to the many other regions where garums are currently found, or if people across the world spontaneously developed a similar method of preserving fish without the help of trade. When the Roman Empire took over and sprawled across the Mediterranean, much of Europe, and the Middle East, culinary traditions spread with it. However, this doesn’t explain the origins of Scandinavian fish sauces, or garums found in Indonesia. One thing about the sauce’s ancient history is certain, though: Wherever fish were abundant, garums were the primary means of preserving and deriving maximum flavor and nutrition from fishery resources.

fish sauce on the table

pasta with fish sauce on a plate

Fish Sauce Science

Fish sauce is simply fish that’s been slowly hydrolyzed, or broken down with water, by proteolytic (protein-digesting) enzymes. These enzymes come from the fish viscera and muscle tissue, as well as enzymes from microorganisms that may have been living on the fish. All animals have endogenous (internally originating) enzymes that aid in the digestion of their flesh. These only come in handy when the animal dies and the process of autolysis, or an organism digesting itself, begins.

Regardless of its origin, the common ingredients of any fish sauce consist of whole fish, water, and salt. The fish and its internal organs and tissue provide the enzymes, and the salt offers stability by excluding harmful microorganisms that may spoil the product before autolysis can digest the fish. Thus, the production of fish sauces the world over includes a mosaic of approaches to these basic ingredients, each method seeking to balance enzymes with salt as their palates and climates allow. The ratio of these two ingredients within the context of temperature and time is what produces the lively variation in flavor, smell, stability, and overall character in garums everywhere.

Analyses of almost 50 different fish sauces from the Philippines, Southeast Asia, and Italy found salt contents ranging from 10 to 30 percent, overall protein content varying widely, and chemical and biological composition being similar, yet distinct from sauce to sauce. Given all the variations in garums around the world, it’s as glib to generalize fish sauces as it would be to broadly generalize fish. Think of it this way: There are many animals we call “fish,” but the species, shapes, colors, and other characteristics differ fantastically within their kingdom. Similarly, fish sauces, though similar at their basic level, vary in their chemical composition and flavor. What we can say is that at their core, all fish sauces are fishy-tasting, nitrogen-rich, and probiotic, to varying degrees and delights. (Analyses of different sauces found 39 microorganisms representing 11 species of bacteria, one yeast, and three filamentous fungi.)

Fish Sauce Around the World

Variations in the different fish sauces throughout the world are a result of the fish available in the area, the preference of the people making it, and the implications of the climate. Version of fish sauce can be found in numerous countries, identifiable by their distinct names.

  • Indonesia:kecap ikan
  • Thailand:nam pl?
  • Philippines: patis
  • Japan: shottsuru
  • Vietnam: Nuöc mâm
  • Malaysia: budu
  • Myanmar: ngapi
  • France: pissala
  • Greece: garos
  • Iran: mahyaveh
  • Pakistan: Colombo-cure
  • China: yeesu
  • Korea: aekjeot

Traditional Techniques

Techniques for making fish sauce vary somewhat, but a traditional approach typically goes something like this: Once the ingredients are mixed, the fish is left to ferment in concrete vats for nine months at temperatures between 86 and 98.6 degrees Fahrenheit. Then, the liquid, known as liquamen, is drained off and aged three months. Some cultures flavor the liquamen as it ages with spices favored in the region. The residue, or allec, from this initial extraction is often leached 2 to 3 times and mixed with brine to produce sauces of varying lower qualities, which are usually blended with various amounts of the primary extract. The final residue of bones and sludge is used as a fertilizer.

Most traditional accounts call for a ratio of 1.5 to 4 parts fish for every 1 part salt. Higher salt contents are likely attributed to regions with warmer temperatures, as heat encourages microbes that may out-compete proper enzymatic reactions. Jeremy Umanksy, chef co-owner of Larder Delicatessen and Bakery in Cleveland, Ohio, says that a salt content of at least 10 percent is a necessity for their fermentation program when a product is dominated by autolytic processes rather than bacterial processes. “Salt content in garums depends on how long the makers want to ferment, seasonal temperature flux, and time of year,” Umanksy says.

The type of fish varies too. While most fish sauces are made from small fish, such as anchovies or sardines, larger sea fish are also used. The recipe below uses mackerel, not an uncommon fish for garum. Most fish sauces are made with saltwater species; however, there are accounts of ancient people using freshwater species from the Nile. Umanksy uses freshwater fish exclusively for his signature Great Lakes Fish Sauce, and only uses saltwater specimens when he gets access to Alaskan wild catch once or twice a year.

Modern Garums

Like many ferments in modern kitchens, garums are experiencing a revival. Fish sauces the world over are being liberated through modern adaptations of traditional techniques. Far from falling into a strictly Asian culinary category, the sauces are being recognized for their usefulness across the flavor spectrum. Umansky says he and his partners use fish sauces in mushroom soups and vegetable pickles, and they’ve even whipped it into sour cream. Because the flavor profile from their in-house sauce differs so much from a more familiar garum, such as one from Vietnam, eaters at Larder recognize the umami kick their sauce provides, but otherwise can’t identify it as fish sauce.

In the excitement of expanding the usage of garums, there’s been an urge to hasten and modify the production process. One way of recasting how fish sauce is made has been the popularization of using the mold koji (Aspergillus oryzae) as the enzymatic catalyst for autolyzation, which reduces the need for fish viscera in the recipe and speeds production. Makers pair koji with fish trimmings, absent of innards, using just the fins, bones, heads, and meat, and still achieve proteolysis, because koji possesses the enzymes to do the job, and do it quickly. With the power of koji comes the ability to further play with temperature and salt. Paired with the technology of incubators and other control devices, the evolution and variation of fish sauces advances and telescopes with an ever-quickening pulse. As you craft your own fish sauce, you’ll jot your record in the ancient tablet of garum stories; a messy, smelly, mysterious, and wild effort oddly organized by a common quest for concentrated deliciousness.

Home Fish Sauce Recipe

For this sauce, I purchased 2 whole mackerel and then filleted them. My family and I ate the filets smeared with miso and pan-fried, but the rest of the fish­ — bones, heads, eyes, guts, and fins — went into this sauce. Yield: 2 quarts.

Directions: Cut the mackerel into 1-inch pieces and place in a bowl. Crumble koji and place in a separate bowl.

Sterilize 2 quart jars. Place each jar on a scale, and divide the ingredients evenly between them. Once the jars are filled, mix the contents thoroughly with a wooden spoon.

Work a piece of plastic wrap down into each jar until it sits snugly on top of the sauce. Trim the edges, and ensure the sauce is completely covered by the plastic. Place lids on the jars. (If the lid seals are removable, take them off, as you’ll want gases to escape as the sauce develops.)

Label the jars with the type of fish used, the percent of salt (20 percent, in this case), and the type of koji. Place the jars into an incubator set to 98 to 100 degrees Fahrenheit.

Allow the sauce to ferment for at least 10 weeks, and then taste the liquamen. If you want to age it further, return the jars to the incubator. If you’re happy with the taste, decant the solids and then bottle the liquamen; consider aging it for 2 to 3 months in a cool, dark cabinet or cellar. You may choose to add chiles, spices, or aromatics during this aging phase. Be sure to use your residues, or allec, as well. If you don’t make fish paste, use them in your compost pile or on your garden. Hydrolyzed fish protein is excellent food for beneficial soil fungi.

The fish sauce should have stable water activity because of its salt content. As such, it doesn’t need to be refrigerated; however, you may choose to refrigerate it to cut down on the smell in your kitchen. Add it by the drop to enhance soups, dressings, vegetables, and more.


  • 1 pound mackerel parts
  • 4.25 ounces pearl barley koji, store-bought or homegrown
  • 14 ounces nonchlorinated water
  • 3.5 ounces kosher or noniodized sea salt

Nutrition and Status

In the oldest historical accounts of fish sauce, varying quality garums were associated with status. Liquamen, made from the blood and guts, was called haimation and considered most valuable, whereas pastes made from the allec (residue from the liquamen) were relegated to lower classes. Fish sauce was so valuable in the Roman Empire that amounts as little as 1 gallon were traded for nearly 1 ton of wheat. This is likely because fish sauce is so full of umami, but also because of its important nutritional qualities. Research on the nutrient density of fish sauces has shown they can contain significant levels of nitrogen, mostly in the form of essential amino acids, making them a valuable source of protein.

Over the past 17 years, Meredith Leigh has worked as a farmer, butcher, chef, teacher, nonprofit executive director, and writer, all in pursuit of good food. Meredith works part time for Living Web Farms, for which she travels extensively teaching charcuterie and food production and processing. For more information, visit here.