Aquaculture and Mariculture: Growing Fish For Food

This piece is focused on the farming of commercial species of fish, and the ocean-based variant known as mariculture. For many, wild-caught seafood is not an option. With increasing demands on wild stocks, aquaculture of some form or another has to step in. There are both good and bad aspects to aquaculture, but it has taken a greater role in supplying the world with seafood.

Increasing Role for Aquaculture

According to the National Marine Fisheries Service, half of all seafood consumed by humans is produced by aquaculture. According to the UN FAO, carp, salmon, tilapia and catfish are the most important types of fish raised. China produces more than half of all farm-raised fish, much of it being carp species. Here in the US, farm-raised seafood accounts for only a small fraction of our consumption, the vast majority of our seafood is imported.

A major factor as to why farm-raised fish is so important is that fish tend to use more of their feed to produce meat. When compared to land animals raised for food, only chicken can come close to salmon. Again, quoting from NMFS it takes 1.2 pounds of food to produce 1 pound of salmon. It takes chicken 1.9 pounds and beef a staggering 8.7 pounds of food to do the same. To take advantage of this ability of fish to effectively convert food into meat, there are several types of containment systems used in fish farming.

Some Aquaculture is Better Than Others

Fish farm

Not all fish farms and fish farming techniques are equal, some fish do better than others in certain farms. Also, overcrowding in an attempt to maximize yields can lead to the same problems with health and quality that plague the beef and poultry industries. I prefer wild caught seafood, but I have eaten plenty of farm-raised fish, some of it very good, some not so great.

Much of what I see within my price range, especially frozen salmon and trout, are small pieces that either taste fishy or have a muddy taste. I cooked some farm raised steelhead from Peru last month. Not only were the fillets mostly skin, what little meat there was tasted like I raised it in my aquarium. The only resemblance it had to the wild caught steelhead I’ve had in the Pacific Northwest was that it was pink.

On the other side of the spectrum, I recently cooked some farm raised barramundi (Asian sea bass) by Australis Aquaculture. I had never tried this species before, it tasted clean and mild. Although I wanted bigger fillets, it is worth trying again.

With several different ways to raise fish it can be difficult to know where your fish is coming from. Not only which country its country of origin, but how it was reared and what was it fed. Below is some information on the different types of aquaculture used in fish farming.

Fish Farming Methods

Fish farming is a general term for all types of rearing food fish in some type of enclosure. The most common types of containment include fish ponds, fish cages, recirculated water systems or integrated systems known as aquaponics. Most of these methods are employed to rear a single type of fish in a given containment. However a composite method can also be used to raise several species of food fish in one containment area.

On a world-wide scale, the most common farm-raised fish are various types of carp and tilapia, which are usually farmed using “extensive” methods. This is a low intensity/low input method that is best for these types of vegetarian fish, allowing the fish to eat whatever grows in the habitat.

The most valuable species farmed in terms of dollar value is Atlantic salmon, which is usually raised using “intensive” methods. These fish are artificially fed using pellets of fish meal, fish oil, soy, corn or other products and are raised in large, dense numbers. A high ratio of fish within the feed, especially if it contains natural pigments, is one metric for better quality farmed salmon. The US produces surprisingly little farm-raised Atlantic salmon, producing more catfish, trout, tilapia and shellfish. Other species farmed on a small-scale include sturgeon, red drum, cobia and cod.


chinese fish pond aquaculture

This is the oldest type of fish farming, with some methods dating back to ancient times. They range in size and complexity, but all must maintain proper oxygen and ph levels to keep the fish healthy and yields high. Waste from the fish can be used to great effect as a fertilizer for crops but can become a major source of pollution if not taken care of. Intensive fishponds require much higher water quality than extensive farms, making this method very water-intensive, up to a million gallons per acre, annually.

Recirculating Aquaculture Systems and Aquaponics

Love The Wild Red Trout with Salsa Verde
Red trout raised by RAS Aquaculture

Recirculating Aquaculture Systems (RAS) are advanced techniques that limit wastage by recycling the water used in the system. Large facilities can recycle their water several times before discharging, which limits potential pollution to local waterways. Many types of fish and shellfish are raised in this closed-loop system, graduating to larger holding tanks as they reach market size. Atlantic salmon are increasingly being raised in recirculated systems. In some cases, this recirculating system is augmented by raising several species that help clean the water for the others.

In Aquaponics, fish like tilapia or barramundi are grown in large tanks, where they eat algae. The wastewater from these tanks is then used to grow crops, typically herbs, with hydroponics which filters the water for the fish. It is innovative, with numerous projects using some form of aquaponics across the globe. However, it can be difficult financially, with several large-scale projects often failing.

Sea Cages/Mariculture

salmon farm

Raising fish in cages can be done in a variety of settings with many different types of fish. When these cages are used for marine species, it is known as mariculture. The cages are placed in the ocean either coastal or offshore. Intensive farming of Atlantic salmon in fish cages can have tens of thousands of fish living in tight quarters. Young bluefin tuna are often corralled into these cages and fed until ready for market – essentially a tuna ranch.

Fish cages can also be situated in ponds or reservoirs filled with fresh or salt water. The fish are raised in cages and fed artificially until they reach harvest size. Marine species include mullet, sea bass, and salmon plus shellfish like oysters and prawns.

Aquaculture is here to stay, love it or hate it. As fish farming and aquaculture have gained a bigger share of our seafood consumption, criticisms have arisen. An upcoming post will touch on the criticisms associated with large-scale fish farming.

For the latest (2016) statistics on US Aquaculture by NOAA check out this report.