NOAA scientists searching for new fish feed ingredients made a promising discovery earlier this year: sablefish raised on mealworms grow as large as those fed fishmeal, which is made with certain wild-caught fish. This is one of the latest studies in a collaborative effort to craft a balanced diet for farmed fish with no fish products. Their results, along with industry innovations, could equip aquaculture to meet the world’s growing seafood demand without increasing farmers’ dependence on forage species that serve as prey for larger fish.
The mealworm study, conducted by Bernadita Anulacion at the Northwest Fisheries Science Center’s Aqualab, compared the growth of a total of 168 sablefish fed one of three diets. The first group got their protein from plants and fishmeal. The second chowed down on a diet of plant proteins, mealworms, and fishmeal. And the third dined on plant proteins and mealworms. At the end of 10 weeks, all 168 were alive and had clocked roughly the same growth rate.
“We’ve made a lot of progress towards reducing aquaculture’s reliance on wild fish caught for feed in recent decades. We’re seeing better use of fish trimmings for feed, and feeds now commonly incorporate plant-based proteins,” said Ron Johnson, team leader of the NWFSC Fish Feed and Nutrition Team. “Now we’re looking at new alternatives and ways of combining ingredients that could completely eliminate fish products from aquaculture diets while still producing a healthy seafood product for consumers.”
Like their wild counterparts, farmed marine fish require a balanced mix of essential nutrients, amino acids, and fatty acids. Traditionally, aquaculture farmers mimicked diets found in the wild by serving fish feeds rich in whole fish, fish oils, and processing waste from commercial fisheries. That started to shift in the early 2000s.
Fishmeal and oils primarily come from small, open-ocean species like anchovies, menhaden, sardines, and mackerel. Each of these fish are sustainably managed in U.S. federal waters under the Magnuson-Stevens Act. But an over-reliance on these finite marine resources put a limit on how much the food industries, including aquaculture, could sustainably expand.
So scientists and the aquaculture industry turned their sights to alternative ingredients. Today, commercial feed contains proteins from soybeans, corn, peas, and wheat. Fish oils have also been supplemented with soybean, canola, and flaxseed oil.
Together, these products have substantially reduced the amount of raw marine materials in aquaculture feed. For example, fish-based ingredients in some Atlantic salmon feed has fallen from 90 percent in the 1990s to just 25 percent.