Unlocking Fish Growth: What is the best source of protein for fish?

October 7, 2025 •

4 min read

With feed costs accounting for 50-70% of total production expenses in fish farming, selecting the right ingredients is critical for profitability. This necessitates a deep understanding of what is the best source of protein for fish, which can be far more complex than simply picking one superior option.

Quick Summary

This article explores the diverse range of protein sources for fish feed, from traditional fishmeal to newer sustainable options, evaluating their nutritional value, digestibility, and cost-effectiveness for aquaculture.

Key Points

Fishmeal is not the only option: While historically the benchmark, traditional fishmeal is unsustainable and expensive, paving the way for alternatives.
Sustainability is a key driver: Growing demand for aquaculture requires sustainable protein alternatives like insect meal and plant-based proteins to reduce pressure on wild fish stocks.
Requirements vary by species: The ideal protein source and required percentage differ based on whether the fish is carnivorous, omnivorous, or herbivorous.
Blending sources optimizes nutrition: Combining different protein sources, such as soy and insect meal, often provides a more balanced and complete amino acid profile than using a single ingredient alone.
Processing improves plant digestibility: Fermenting or processing plant-based proteins like soybean meal can reduce anti-nutritional factors and improve their bioavailability for fish.
Economics drives formulation: The cost and availability of ingredients heavily influence feed formulation, making flexibility with multiple protein sources a crucial economic benefit for producers.

The Importance of Protein in Fish Nutrition

Protein is the most important and expensive component in fish diets, comprising roughly 16% of a fish's body composition on average. It is crucial for the formation of muscle, internal organs, and tissues, as well as for various metabolic processes. The protein requirements vary significantly between species and life stages. For example, carnivorous fish like salmon typically need higher protein diets (40-55%), while omnivorous or herbivorous species like tilapia or catfish may require less (18-45%), depending on their size and environment.

Unlike terrestrial animals, fish utilize protein much more efficiently as an energy source, which drives their higher dietary protein requirements. The quality of a protein source is determined by its amino acid profile, digestibility, and bioavailability. The ten essential amino acids that fish cannot synthesize themselves must be provided through their diet.

Traditional Protein Sources for Fish Feed

Fishmeal and Fish Oil

For decades, fishmeal and fish oil have been the gold standard in aquafeed due to their exceptional nutritional properties.

High-Quality Amino Acid Profile: Fishmeal contains an amino acid profile that is nearly perfect for meeting the nutritional requirements of most fish species.
High Digestibility: The protein in fishmeal is highly digestible, with values consistently exceeding 95%.
Nutrient Density: It is rich in essential nutrients, including highly unsaturated fatty acids like EPA and DHA, as well as minerals.

Despite its benefits, the industry's reliance on fishmeal from wild-caught pelagic fish raises serious sustainability concerns due to finite wild fish stocks. This has prompted a global push to find viable alternatives.

Terrestrial Animal By-Products

Rendered products from livestock processing offer a way to utilize waste streams and reduce costs.

Poultry By-Product Meal: A valuable alternative with an amino acid composition similar to fishmeal, particularly for species like rainbow trout.
Blood Meal: Can effectively replace a portion of fishmeal and has been shown to support positive growth in certain species like African catfish.
Feather Meal: After processing with steam to improve digestibility, feather meal offers a cost-effective, high-protein alternative.

While generally effective, the nutritional quality and inclusion levels must be carefully managed, as by-product meals can vary in composition and digestibility.

Modern and Sustainable Alternatives

Plant-Based Proteins

Plant proteins have become the most common alternative to fishmeal, driven by their lower cost and greater availability.

Soybean Meal: The most widely used plant-based protein source due to its high protein content (40-60%) and availability. However, it can contain anti-nutritional factors (ANFs) and is deficient in certain essential amino acids like methionine, which often requires supplementation.
Corn Gluten Meal and Wheat Gluten Meal: These are used in aquafeed for their protein content, though often require careful balancing with other ingredients to meet nutritional needs.
Algae and Aquatic Plants: Microalgae offer a highly sustainable source rich in protein and beneficial omega-3 fatty acids. Aquatic plants like duckweed and water spinach have shown promise as cost-effective options, particularly for herbivorous species.

Insect-Based Proteins

Insect meal is a promising, eco-friendly option that converts organic waste into high-quality feed.

Black Soldier Fly (BSF) Larvae: Rich in protein and fat, BSF meal is a viable alternative that promotes a circular economy.
Nutritional Quality: Insect meals can have crude protein contents ranging from 42% to 74% and offer a balanced amino acid profile suitable for many species.
Environmental Impact: Insect farming requires significantly less land, water, and feed compared to traditional livestock farming.

Single-Cell Proteins (SCP)

Derived from microbes like yeast, bacteria, or fungi, SCP represents a novel and robust protein source. Fermentation can improve the bioavailability and nutritional profile of these ingredients, making them excellent fishmeal replacers.

Comparison of Protein Sources for Fish


Feature	Fishmeal	Soybean Meal	Insect Meal (BSF)	Microalgae
Protein Content	65-72%	40-60%	42-74%	30-70%
Amino Acid Profile	Excellent, near-perfect match for fish	Good, but often low in methionine; may need supplementation	Balanced, often rich in essential amino acids	Well-balanced
Digestibility	Very High (>95%)	Varies (77-96%), influenced by ANFs	High	High
Sustainability	Low, finite wild resource	Moderate, competes with human food	High, utilizes organic waste	High, renewable with low footprint
Cost	High and volatile	Generally lower than fishmeal	Varies, potential for cost-efficiency with scale	High, but decreasing with technology
Nutritional Constraints	Few (potentially high phosphorus)	Anti-nutritional factors (ANFs)	Potential nutrient imbalances at high inclusion levels	Inconsistent nutrient profiles if not carefully managed

Finding the Optimal Protein Blend

Recent research indicates that a mixture of different protein sources is often more effective than relying on a single ingredient. This approach allows formulators to create a balanced amino acid profile, overcome the limitations of individual ingredients, and reduce costs. For instance, combining a high-quality fishmeal with a plant-based protein like soybean meal and supplementing with specific limiting amino acids (e.g., methionine) can produce an excellent diet.

Flexibility in feed formulation is also a key benefit. As the market price of ingredients fluctuates, manufacturers can adjust the blend to maintain a cost-effective and nutritionally complete feed. This moves the aquaculture industry towards more sustainable and economically viable practices without compromising fish health or growth. The NOAA Fisheries website provides additional information on feed alternatives and sustainability initiatives in aquaculture.

Conclusion: No Single 'Best' Source, but Strategic Blending is Key

While high-quality fishmeal historically served as the definitive benchmark, the question of what is the best source of protein for fish no longer has a single answer. The optimal protein source is context-dependent, relying on the specific fish species, their life stage, and the economic and environmental goals of the operation. By strategically combining diverse protein sources—including sustainable options like insect meal, plant proteins, and microalgae—aquaculture can transition from a reliance on finite marine resources to a more resilient, cost-effective, and environmentally responsible model. The future of fish nutrition lies not in a single ingredient, but in the intelligent blending of multiple alternatives to meet evolving demands.

Frequently Asked Questions

Protein is vital for fish growth and tissue repair, providing essential amino acids needed for muscle and organ development. Fish also use protein as a primary energy source, which contributes to their high protein dietary requirements.

Yes, some fish species, especially omnivores and herbivores like tilapia, can be raised on completely plant-based diets, provided the feed is carefully formulated. It often requires supplementing with limiting amino acids like methionine and lysine to ensure optimal growth.

Anti-nutritional factors (ANFs) are compounds found in some plant-based proteins, like soybean meal, that can hinder nutrient absorption and affect fish growth. Processing techniques like fermentation are used to reduce these factors.

Yes, high-quality fishmeal is still considered the benchmark for aquafeed due to its excellent amino acid profile and digestibility. However, its use has been significantly reduced and is often blended with alternative protein sources to improve sustainability.

Insect meals, particularly from black soldier fly larvae, are a highly promising alternative to fishmeal. They offer a high protein and fat content with a balanced amino acid profile. They are also a more sustainable and eco-friendly option for aquafeed.

Yes, fish have varying protein requirements based on their feeding habits. Carnivorous fish need higher protein levels (40-55%), while omnivorous fish and herbivorous fish require less, typically in the 18-45% range.

Mixing different protein sources can create a more balanced amino acid profile, overcome the nutritional limitations of individual ingredients, improve digestibility, and provide greater flexibility to adjust to fluctuating ingredient costs.