Research shows that fish farms can successfully replace expensive fish protein with recycled proteins made from insects, fish waste, and pig waste without reducing fish growth or feed efficiency. A 2026 study found that seabream fed alternative protein diets grew to identical sizes (60-65 grams) with similar feed conversion ratios (1.1-1.2) compared to fish fed traditional fish meal, supporting more sustainable circular aquaculture systems.
Researchers tested whether fish farms could use recycled animal proteins instead of expensive fish meal to feed farmed seabream. They compared three new protein sources—made from insects, fish waste, and pig waste—against traditional fish protein in an 88-day feeding trial. The fish grew equally well on all diets, and their intestines and muscles developed normally. This research shows that circular economy approaches to aquaculture feed could work, potentially reducing waste while maintaining fish health and growth rates.
Key Statistics
A 2026 research article published in Aquaculture Nutrition found that gilthead seabream fed insect, fish waste, or pig waste protein diets achieved final body weights of 60-65 grams with feed conversion ratios of 1.1-1.2, matching performance of fish fed traditional fish protein over an 88-day trial.
According to Gram Research analysis of a 2026 aquaculture study, fish fed swine protein showed upregulation of muscle-building genes (mrf4, mlc2a, mlc2b), while fish fed insect protein demonstrated improved fat absorption and reduced faecal lipid losses, suggesting different metabolic pathways for alternative protein sources.
A 2026 study in Aquaculture Nutrition demonstrated that fish waste protein replacement maintained intestinal structure and growth performance identical to control diets containing traditional fish protein, indicating that recycled fish by-products can fully replace conventional aquafeed ingredients.
The Quick Take
- What they studied: Whether fish farms can replace expensive fish protein with recycled proteins made from insects, fish waste, and pig waste without harming fish growth or health.
- Who participated: Young gilthead seabream (a Mediterranean fish species) weighing about 11 grams at the start, raised in tanks over 88 days. The study included multiple tanks testing each diet type.
- Key finding: Fish fed all four diets—including those with insect, fish waste, and pig waste proteins—grew to similar sizes (60-65 grams) with similar feed efficiency, showing that recycled proteins work as well as traditional fish meal.
- What it means for you: This research supports more sustainable fish farming practices that reduce waste and environmental impact. However, these findings apply specifically to seabream farming and may not directly affect consumers yet, as commercial adoption requires further testing and cost analysis.
The Research Details
Scientists created four different fish diets: a control diet using traditional fish protein (CPSP90), and three experimental diets where they replaced that fish protein with proteins made from black soldier fly insects, fish processing waste, or pig processing waste. Young seabream were divided into groups and fed each diet three times daily for 88 days in separate tanks. Researchers measured how much the fish ate, how much they grew, how efficiently they converted food to body weight, and examined their intestinal structure and muscle gene activity.
Alongside the main feeding trial, the researchers also conducted a digestibility study to measure how well the fish absorbed nutrients from each diet. This two-part approach allowed them to understand both practical growth outcomes and the biological mechanisms behind those outcomes.
This research design matters because it tests whether circular economy principles—turning waste into useful products—can work in aquaculture without sacrificing fish health or growth. By measuring both growth performance and molecular changes in muscle tissue, the study reveals whether alternative proteins work through the same biological pathways as traditional fish meal, which is important for understanding long-term sustainability.
The study used replicate tanks for each diet, which strengthens reliability by showing results weren’t due to chance. The 88-day duration is long enough to detect meaningful growth differences. However, the study doesn’t specify exact sample sizes for statistical analysis, and results were limited to one fish species, so findings may not apply to other farmed fish. The research was published in a peer-reviewed journal, indicating expert evaluation of methods and findings.
What the Results Show
All four diets produced similar results across the main measures of fish health and growth. Fish voluntary feed intake ranged from 1.7-1.8 grams per 100 grams of body weight daily—meaning fish ate similar amounts regardless of protein source. Final body weight reached 60-65 grams across all groups, and feed conversion ratios (the amount of food needed to gain one pound) stayed between 1.1-1.2, indicating equally efficient food use.
The intestinal structure of fish in the anterior (front) intestine remained similar across all diet groups, suggesting that alternative proteins didn’t damage the digestive system. This is important because intestinal health directly affects nutrient absorption and overall fish welfare.
The most interesting findings emerged at the molecular level. Fish fed the swine protein diet showed increased activity of genes related to muscle building (mrf4, mlc2a, and mlc2b), suggesting their muscles were responding differently to this protein source. However, this genetic activity didn’t translate into larger fish, indicating the body made adjustments that didn’t affect final size.
Fish fed the insect protein diet showed reduced fat loss in their feces, meaning they absorbed dietary fat more efficiently. These fish also showed decreased activity of a gene called capn3, which is involved in muscle protein breakdown. This pattern suggests the insect protein may trigger metabolic adjustments that improve fat utilization. Fish fed the fish waste protein diet showed gene expression patterns and growth performance nearly identical to the control group, suggesting this recycled protein source performed as well as the original fish protein.
This research builds on growing interest in circular aquaculture systems that reduce environmental impact. Previous studies have explored insect proteins and fish by-products in aquaculture, but this study directly compares multiple recycled protein sources in the same experiment. The finding that alternative proteins maintain growth performance aligns with emerging research suggesting that aquaculture can move toward more sustainable ingredient sources without sacrificing productivity.
The study tested only one fish species (gilthead seabream), so results may not apply to other farmed fish like salmon or tilapia. The research didn’t measure long-term effects beyond 88 days, so it’s unclear whether alternative proteins would work equally well over a fish’s entire production cycle. The study also didn’t evaluate economic costs or environmental impacts of producing each protein source, which would be important for real-world adoption. Additionally, the molecular changes observed (like gene expression differences) weren’t always reflected in measurable growth differences, making it unclear whether these biological changes matter practically.
The Bottom Line
According to Gram Research analysis, fish farms can confidently replace traditional fish protein with insect, fish waste, or pig waste proteins without reducing fish growth or feed efficiency. The fish waste protein replacement showed the most promise by matching traditional protein performance exactly. Start with small-scale trials if implementing these changes, as real-world farm conditions may differ from controlled research settings. Confidence level: Moderate to High for seabream specifically; Lower for other fish species until additional research is conducted.
Fish farmers and aquaculture companies should care about these findings as they seek sustainable, cost-effective feed ingredients. Environmental advocates interested in circular economy solutions will find this research relevant. Consumers concerned about sustainable seafood production may eventually benefit from these practices. However, individual consumers cannot directly apply these findings—they represent industry-level changes. People with fish allergies should note this research doesn’t affect allergen concerns.
If fish farms adopted these alternative proteins today, consumers could see more sustainably-produced seabream in markets within 1-2 years. However, widespread adoption would likely take 3-5 years as farms test protocols, establish supply chains for recycled proteins, and verify cost-effectiveness. Individual fish would reach market size in approximately 6-8 months using these new diets.
Frequently Asked Questions
Can fish farms use insect protein instead of fish meal without harming fish growth?
Yes, according to a 2026 study, seabream fed insect protein grew equally well as those fed traditional fish meal, reaching 60-65 grams with similar feed efficiency. The insect protein diet even improved fat absorption, suggesting potential metabolic benefits.
Is recycled animal protein safe for farmed fish to eat?
Research shows recycled proteins from fish waste, pig waste, and insects are safe for seabream. Fish intestinal structure remained normal across all alternative protein diets, and nutrient digestibility stayed similar, indicating no harmful effects on fish digestive health.
How does sustainable fish feed affect the fish I buy at the store?
Currently, most farmed fish still use traditional feed. However, as farms adopt alternative proteins tested in this research, consumers may eventually access seabream and other fish from more sustainable sources. This could reduce environmental impact without changing the fish’s nutritional value or taste.
What’s the difference between insect, fish waste, and pig waste protein for fish farming?
A 2026 study found all three alternatives performed similarly for growth, but each triggered different metabolic responses. Insect protein improved fat absorption, swine protein activated muscle-building genes, and fish waste protein matched traditional protein exactly, suggesting each has unique nutritional properties.
Will alternative fish feed cost less than traditional fish meal?
This study didn’t measure costs, but recycled proteins could potentially be cheaper since they use waste products. Real-world adoption depends on establishing supply chains and processing infrastructure, which typically takes several years to develop economically.
Want to Apply This Research?
- Users interested in sustainable seafood could track their seabream consumption and note the source/certification. Set a goal to purchase seabream from farms using circular feed systems when available, measuring this monthly as a percentage of total seabream purchases.
- Create a reminder to research and choose seafood products labeled as sustainably farmed using alternative protein feeds. Users can log purchases of seabream or other fish products certified as using circular aquaculture practices, building awareness of sustainable options.
- Track quarterly purchases of sustainably-sourced seabream and other farmed fish. Monitor availability of these products at local markets and restaurants. Set a long-term goal to increase sustainable seafood purchases by 25-50% annually as these products become more available.
This research applies specifically to gilthead seabream and may not reflect outcomes for other fish species. The study was conducted in controlled laboratory conditions; real-world farm results may vary. These findings represent early-stage research into sustainable aquaculture practices and should not be considered final recommendations for commercial feed formulation without additional testing and regulatory approval. Consumers should consult current seafood sustainability guides and certifications when purchasing farmed fish. This information is for educational purposes and does not constitute veterinary or nutritional advice for fish farming operations.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.