ARS Strategies To Benefit Aquaculture Industry

Although the global aquaculture industry produced 73.8 million tons of fish and shellfish, with an estimated first-sale value of $160.2 billion in 2014, the United States is still the leading global importer of fish and fishery products. Ninety percent of the seafood we eat comes from foreign waters, and half of that amount is from aquaculture. Thus, there is significant opportunity to increase U.S. aquaculture production.

Aquaculture refers to the breeding and raising of fish and shellfish. These practices can sometimes stress the environment by adding nutrients to waterways, such as ponds, lakes, rivers, and oceans. Scientists with the Agricultural Research Service (ARS) are working diligently to find ways to mitigate any negative environmental impacts from aquaculture.

Raising Fish in a Closed System

One way to produce more fish products is in land-based, closed-containment aquaculture systems. In 1989, ARS scientists at the National Center for Cool and Cold Water Aquaculture (NCCCWA) in Leetown, West Virginia, conducted the first of several research projects to develop recirculating water systems to help producers provide more fresh seafood for market. ARS also provides funding to The Conservation Fund’s Freshwater Institute (TCFFI), in Shepherdstown, West Virginia, to develop these kinds of technologies. Recirculating water systems can help increase the amount of fish available to markets while solving some of the problems inherent in open-water fish farms.

In such systems, large tanks are erected and filled with fresh water that is constantly moving, filtered, and reused. In fully functional commercial operations, tanks are used to hatch fish eggs, raise those newly hatched fish to fingerling size, and grow those young fish to market size.

“With recirculating aquaculture systems, fish farm expansion is no longer highly constrained by competition for limited water resources, fish farm sites, or strict regulations on pollution discharge,” explains Steven Summerfelt, director of aquaculture research at TCFFI. “In addition, nutrients can be reclaimed, fish escape can be prevented, and disease interaction between farmed and wild fish can be minimized.”

After more than 20 years of research and refinement, this concept is now used widely in nurseries for salmon culture around the world. It is poised to present commercial aquaculture with a successful business model for land-based production of market-size fish. Recirculating systems, such as those pioneered at TCFFI, use as little as 4 percent new water each day, which means that a complete water exchange takes place once every 25 days. This miserly use of water is an environmental plus. It also allows recirculating aquaculture systems to be located in many places where traditional aquaculture wouldn’t work, increasing access to local seafood even in landlocked markets.

NCCCWA scientists maintain a broodstock development program in which fish are produced in recirculating systems designed by Summerfelt and his team. Broodstock are sexually mature individuals of a cultured fish species that are kept separately for breeding purposes. In 2008, a new facility based on this technology was completed in Leetown. It houses the entire lifecycle of the NCCCWA broodstock, which are evaluated for production efficiency.

Similarly, ARS scientist Brian Peterson at the National Cold Water Marine Aquaculture Center in Franklin, Maine, leads a breeding program to improve yields, production efficiency, and product quality in Atlantic salmon. Broodstock for the program are reared entirely in recirculation systems; however, in partnership with the Maine Aquaculture Association and Cooke USA, performance is evaluated on progeny that are raised in commercial net pens. This information is used in the breeding program, which supplies superior broodstock to the industry.

Oysters and the Estuarine Environment

While closed systems are on the horizon, aquaculture in natural open systems is still the norm, especially for bivalve shellfish. Open systems can have environmental impacts, such as the addition of excess nutrients to the water. Excess nutrients can lead to algal blooms and reduce the amount of oxygen available to fish.

ARS scientists are looking at the impact of bivalve shellfish aquaculture on the environment. While bivalves like oysters, mussels, and clams excrete nutrients, producers do not add food to the system. Instead, the bivalves feed on algae by filtering surrounding water, providing an environmental bonus. 

The shellfish culture industry on the west coast of the country represents oyster, clam, and mussel growers from Alaska to California and generates an estimated $100 million in gross annual sales. Still, domestic production does not meet national demand.

In Newport, Oregon, ARS ecologist Brett Dumbauld and collaborators are working to determine the impact of bivalve aquaculture on estuary grasses and other habitats as well as on water quality. Dumbauld, who is with the aquaculture program in the ARS Forage Seed and Cereal Research Unit, investigates the impact of oyster aquaculture in estuaries such as Willapa Bay, in Washington State.

In west coast estuaries, eelgrass, Zostera marina, is protected by federal and state regulations. “Seagrasses and reef-forming bivalve shellfish serve a variety of important ecological functions in estuaries,” says Dumbauld. These include enhancing biodiversity, providing nursery habitat for fish and invertebrates and refuge from predators, filtering water, and controlling erosion. Although oyster aquaculture reduces eelgrass presence in Willapa Bay, the overall reduction is less than 1.5 percent, according to Dumbauld’s studies, which used aerial photography and ground measurements to map and model eelgrass presence across the estuary landscape. Eelgrass levels in most individual oyster beds didn’t vary much from year to year, but eelgrass levels did vary with oyster harvest technique. “Beds with chronically low eelgrass levels were mechanically harvested,” says Dumbauld. “Mixed and hand-harvested beds were most variable, but some had well over the predicted amount of eelgrass present.”

“Our studies show the eelgrass habitat is resilient to oyster aquaculture as a disturbance, and we found no persistent negative effects at the landscape scale in this estuary,” says Dumbauld. He is currently investigating how fish use shellfish culture sites and eelgrass in these estuaries.

ARS research on recirculating aquaculture systems and on the impacts of bivalve aquaculture provides the aquaculture industry at large with the necessary information to provide more seafood to U.S. consumers while also preserving the aquatic environment.—By Sharon Durham, ARS Office of Communications.