Fish meal is made by cooking raw fish to break down the protein, pressing out the liquids, then drying and grinding the remaining solids into a powder. The process applies whether you’re looking at a commercial factory producing thousands of tons or a small operation sun-drying fish on wooden tables. The end product is a nutrient-dense feed ingredient, typically 60 to 70% protein, used in aquaculture, poultry, and livestock diets.
Raw Materials: What Goes In
Most fish meal comes from small, oily forage fish: anchovies, sardines, herring, and menhaden. These species are abundant, reproduce quickly, and have high protein and oil content that translates into a rich final product. Beyond whole fish, a significant portion of global fish meal now comes from processing byproducts, the heads, frames, trimmings, and offal left over when fish like tuna, cod, or pollock are filleted for human consumption. Using these byproducts turns what would be waste into a high-value feed ingredient.
Freshness matters enormously. Fish begin to degrade almost immediately after death, and starting with spoiled raw material produces low-quality meal with reduced protein and off-putting odors. Commercial operations typically process fish within hours of landing, or hold them in chilled seawater or brine to slow decomposition.
The Six Steps of Industrial Production
Commercial fish meal manufacturing follows a consistent sequence. Each step removes water and separates the valuable protein-rich solids from the oil and liquid fractions.
1. Cooking
Raw fish are fed into a steam cooker, essentially a long heated cylinder that raises the temperature high enough to coagulate the protein. This is the critical first step: it ruptures fat deposits inside the tissue and releases both oil and water that were physically or chemically bound to the flesh. The cooked mass comes out as a soft, solid mixture ready for mechanical separation.
2. Pressing
The cooked fish passes through a twin screw press, which squeezes the material and splits it into two streams. The solid portion, called presscake, retains 60 to 80% of the oil-free dry matter, mostly protein and bone. The liquid portion, called press liquor, contains water, dissolved proteins, vitamins, minerals, and fish oil. If the raw fish has very low fat content (under about 3%), the oil separation step that follows can be skipped entirely.
3. Oil Separation
The press liquor goes through centrifuges or settling tanks that separate it into fish oil and a watery fraction called stickwater. The oil is collected as its own valuable product. Stickwater still contains dissolved proteins and nutrients worth recovering, so it moves on to the next step rather than being discarded.
4. Evaporation
The stickwater is concentrated in evaporators that boil off excess water, producing a thick syrup known as fish solubles. This concentrate is then mixed back into the presscake before drying, which recaptures nutrients that would otherwise be lost and boosts the overall protein content of the finished meal.
5. Drying
The combined presscake and solubles are first broken up in a wet mill to create a uniform texture, then fed into a dryer. Two types are common: indirect steam dryers, which heat the material through contact with hot surfaces, and direct flame dryers, which blow hot air through the material. Steam dryers are gentler and preserve more nutritional value, while flame dryers work faster but risk overheating. The goal is to bring moisture down to about 10%, a level that prevents mold growth and microbial spoilage during storage.
6. Grinding and Packaging
Dried material passes through a vibrating screen fitted with magnets to catch foreign objects like metal fragments or fish hooks. It then enters a hammer mill that grinds it to a uniform particle size. The finished meal is weighed, packed into bags or stored in bulk, and shipped.
Making Fish Meal on a Small Scale
You don’t need a factory to produce fish meal. Small-scale and artisanal producers have been making it for centuries using sun-drying, and the basic principle is the same: remove enough water from fish flesh to create a shelf-stable product you can grind into powder.
Start with fresh small fish or fish scraps (heads, frames, guts from filleting). If the fish are longer than about 15 cm or thicker than 20 mm, split them open so they dry evenly. Salting helps draw out moisture and slows bacterial growth. A common traditional method is to pack the fish with dry salt in a container and leave them overnight, then remove them for drying the next morning.
For drying, lay the fish on raised wooden slatted tables or hang them on hooks in direct sunlight. Raised surfaces allow airflow underneath and keep the fish off the ground, which reduces contamination and speeds drying. Depending on climate and fish thickness, sun-drying takes anywhere from two to five days. You want the fish completely dry and brittle, snapping cleanly rather than bending. In humid climates or during rainy seasons, a low oven (around 70 to 80°C) or a simple solar dome dryer can substitute for open-air drying.
Once fully dried, break the fish into pieces and grind them. A grain mill, heavy-duty blender, or even a mortar and pestle works for small quantities. Sieve the ground material to get a consistent powder and remove any large bone fragments. Store the finished meal in airtight containers in a cool, dry place. Keeping moisture below 10% is essential: fish meal above that threshold is highly susceptible to mold and spoilage.
What Makes Fish Meal Nutritionally Valuable
Fish meal’s primary appeal is its protein density and amino acid profile. High-quality meal contains crude protein above 66%, with fat around 8 to 11%, ash (minerals) below 12%, and moisture near 10%. What sets it apart from plant-based protein sources is its concentration of essential amino acids that animals need but can’t produce on their own.
Lysine is the standout. Herring meal contains about 7.3% lysine, anchovy meal about 5.4%, and sardine meal about 5.9%. These levels are far higher than soybean meal or corn, which is why fish meal is so prized in poultry and aquaculture feeds where lysine is often the limiting nutrient. Methionine, another amino acid frequently deficient in plant proteins, runs around 1.8 to 2.2% across most fish meal types. The protein is also highly digestible, meaning animals absorb and use a large fraction of what they eat.
Preventing Spoilage and Combustion
Fish meal’s high fat content creates a real storage hazard. Lipids in the meal oxidize when exposed to air, generating heat. In bulk storage, that heat can build up enough to cause spontaneous combustion, which is why ships carrying fish meal have historically faced fire risks.
To prevent this, producers add antioxidants immediately after drying. The most widely used is ethoxyquin, a synthetic compound that slows lipid oxidation effectively and cheaply. It also stabilizes fat-soluble vitamins A and E within the meal, preserving nutritional value over time. Other synthetic antioxidants like BHT and BHA serve a similar purpose. Natural antioxidants exist but are generally less stable and more expensive, so synthetic options remain the industry standard for commercial production.
For small-scale producers, the combustion risk is minimal because quantities are too small for dangerous heat buildup. The bigger concern is rancidity. Storing your meal in sealed containers with minimal air exposure, in a cool and dark location, extends shelf life significantly. Freezing works well for small batches you plan to use over several months.
Equipment for Commercial Production
A full-scale fish meal plant requires a chain of specialized machinery: a feeding pit and screw conveyors to move raw fish into the system, a steam cooking machine, a twin screw press, centrifuges or decanters for oil separation, evaporators for concentrating stickwater, a disc dryer, cooling augers, a cylinder sieve, a crusher or hammer mill, and storage bins. These plants are designed for continuous operation, with fish entering one end and bagged meal coming out the other. Small to mid-size plants can process a few tons of raw fish per hour, while the largest facilities handle hundreds of tons daily.
The capital cost is substantial, which is why small-scale producers typically skip the pressing and oil-separation steps entirely and rely on simple drying and grinding. You sacrifice some oil recovery and yield efficiency, but the resulting meal is still a highly functional protein source for animal feed or garden fertilizer.