1. What Is in the Pellets That Fish Farms Use?
Farmed ocean fish in Japan, such as yellowtail and red sea bream, are often fed pellets made mostly of fish meal: small fish like anchovies, dried and ground into powder. Wheat flour, other plant ingredients, and vitamins are mixed in [1]. (Yellowtail is called buri in Japan, and red sea bream is madai.)
A research center in Ehime Prefecture, a fish-farming region in southwestern Japan, says fish meal usually makes up about 40 to 50% of this kind of feed [1]. So in a 100-gram scoop, around 40 to 50 grams could be ground-up fish. The number differs by species and by feed, so treat it as a typical range, not a fixed rule.
Fish meal is not just a Japanese habit. A U.S. government agency, NOAA Fisheries, explains that fish meal is a well-balanced source of high-quality protein, and that about 70% of fish meal and fish oil comes from small, open-ocean fish. The other 30% is made from scraps left over when fish are processed for people to eat [3].
2. Why Do Fish Farms Want to Use Less Fish Meal?
The main reason is money, and the reason behind the money is supply. Ehime researchers say most of the fish meal used in Japan depends on imports caught in South America, and its price is unstable [1]. A research institute in Mie Prefecture says more than 90% of the fish meal used in fish feed is imported, so swings in the world price strongly affect the price of feed [2].
Feed is also a huge part of the bill. The Ehime center says feed costs make up 60 to 70% of a farm's total expenses [1]. The Mie institute puts feed at more than 60% of the production cost of farmed sea fish [2]. When the price of the main ingredient jumps, a farm feels it right away.
So the question becomes practical: if fish meal is expensive and unpredictable, how much of it can be swapped for something cheaper without making the fish grow worse?
3. Did Yellowtail and Sea Bream Really Grow Just as Well on Less Fish Meal?
In the Ehime trials, yes. The center worked with government, universities, feed companies and fish farmers. In the fiscal year ending March 2019, they tested low-fish-meal feed on market-size fish in real farm net pens [1].
- Yellowtail: one-year-old fish got feed with 30% fish meal for three months, starting at the end of August. A comparison group got the usual 50%. Weight gain showed no difference between the two groups [1].
- Red sea bream: fish got feed with only 15% fish meal for five months, against 40% for the comparison group. The report says they grew equally well [1].
Another prefecture ran a similar test. In Mie, researchers fed red sea bream of about one kilogram a feed with 25% fish meal for 145 days in 2015, and compared them with fish on a store-bought feed containing 40%. Growth and death rates were about the same, the fish needed slightly less feed to gain weight, and the meat quality was judged about the same [2].
These are careful trials, but they are narrow ones: a few months, certain fish, certain sizes. They show that the idea can work. They do not prove that every farm can switch everything tomorrow.
4. What Takes the Place of the Fish Meal?
The Ehime center lists cheaper replacements from plants and from animal by-products [1]:
- Soybean meal: what is left after cooking oil is pressed out of soybeans.
- Corn gluten meal: what remains after the germ and starch are removed from corn.
- Feather meal and chicken meal: made from chicken feathers and leftovers from meat processing.
Most of these are parts people do not eat directly, so using them can also cut waste. Mixing many ingredients helps too: one ingredient alone may be short on some nutrient, but a blend can balance it out [1].
The same trend shows up elsewhere. NOAA Fisheries estimates that fish meal made up about 70% of salmon diets in the 1980s and about 25% in 2017. It lists plant options such as soybeans, peas and canola, and also yeast, insects and algae. It also notes that the U.S. approved taurine as a feed ingredient in 2018, which helps make plant proteins work more like the animal proteins fish are used to [3].
5. How Far Can Fish Meal Be Cut Back?
Nobody has a single answer. The trials above went down to 30% for yellowtail and 15% for sea bream, and the Mie institute also tested feeds with no fish meal at all, to see how they affect the flavor of the fish [2]. The details of that flavor work are in the report, and the short version we could read does not give the results.
What the sources do show is that the right amount depends on the fish, its size, the other ingredients, and how long it is fed. That is why researchers keep running trials one species at a time.
6. How Can You Look for Fish Meal Yourself?
You do not need a fish farm. If there is cat food, dog food, or ornamental fish food at home, read the ingredient list on the back. Ingredients are usually listed from the largest amount to the smallest. Look for fish meal, soy, corn, or chicken, and notice which comes first. If nothing at home works, if you visit a pet store, ask an adult first and read a label together.
If you want to read more, the Ehime and Mie reports are short and describe how long each trial lasted and what the feeds contained [1] [2]. A good question to carry away: if fish still need protein, how can farms get it while using the ocean's small fish more wisely?