Limit wild fish use as feed

Choose sustainable feed ingredients

Instead of using wild sources, fishmeal can be made from scraps of fish (both wild and farmed) processed for human consumption. Ingredients from plant and animal agriculture—like soy and poultry—are also used to make high protein ingredients.

More recently, insects, algae, and single-cell organisms have been tested to provide many of the same nutrients to farmed fish as more traditional ingredients do. Many of the major feed manufacturers are investing in the development of these alternative feeds and some fish farmers have found success using them.

All feed ingredients have some environmental footprint, so choosing aquaculture feeds that are both good for farmed fish and have minimal impacts on the ecosystem is important.

Farm omnivores 

Not all fish are carnivores. Some, like catfish and tilapia, can be raised on diets with very little or no fishmeal or fish oil. In some industries, no supplemental feed is required. Fish and shrimp raised in extensive aquaculture systems, and shellfish (like mussels and oysters) feed by filtering plankton and other naturally-produced organisms out of the water.

By farming species that do not require significant amounts of animal protein or oil in their feed, aquaculture can reduce its reliance on wild fisheries.

Improve feed conversion efficiency

Feed Conversion Ratio (FCR)—the ratio of how much a fish eats to how much weight it gains—is the most common metric of feed efficiency. In the past, feed efficiency was poor, but technological advances have reduced the FCR of most commonly farmed species including salmon, shrimp and tilapia.

In the best cases today, FCRs of close to 1:1 are possible. However, feed use can still be one of aquaculture’s biggest environmental impacts.

By closely monitoring how much farmed fish eat during feeding and making feeds that are easily digestible, aquaculture should continue to improve the conversion efficiency of feed so that it requires less feed to grow fish successfully.

Sustainable sourcing of broodstock

Where do farmed fish come from? In most cases, farmers maintain groups of mature fish known as a broodstock. These fish provide eggs and/or juveniles for the purpose of being raised to market. This method is preferred to a practice called ranching, which takes fish from the wild and grows them for eventual sale.

Not only do ranches rely on wild populations, in some cases the fish they take are still juveniles, meaning they have not had the chance to reproduce in the wild. For example, young eels are caught and then farmed to supply unagi to sushi bars. Similarly, young bluefin tuna are ranched for the highly profitable but resource-intensive industry. This practice has contributed to the depletion of wild stocks of both of these species.