Offshore cage culture systems have a variety of positive attributes. For instance, they experience high water flow and flushing of the system. Additionally, offshore areas can be sited away from navigation lands and typically have better water quality than nearshore systems, which are often negatively impacted by run-off, other non-point sources, and point sources. Compared to nearshore culture methods, offshore cage culture does not detract from the aesthetic value of the coast. The U.S. Department of Commerce is encouraging development of offshore aquaculture because of these attributes.

Along with the numerous opportunities that offshore culture presents, there are several constraints to developing these systems in the PNW. First, the technology is still being developed. Although there are several research projects studying offshore cage culture, many questions and issues must be addressed. There are high costs associated with developing an offshore cage culture system. Additional costs such as labor and accessibility are concerns since regular monitoring and maintainance of the system is required. These high cost systems favor the use of high value species.

Some people question if offshore development should occur since other countries may be able to use inshore areas to culture the same species for less money than a US offshore venture. One alternative is to lower costs by using offshore systems to culture shellfish instead of finfish, which would require less labor and feed costs.

Winter storms in the Pacific Northwest can threaten the integrity of the systems and may cause great physical damage and monetary losses. One method to lessen the impact of rough seas is to submerge the entire system. Some people in the industry believe that cages in the PNW must be submerged 20–30 feet to reduce the impact of the surge. Because of the dynamic marine environment, offshore cage culture may not be appropriate in the PNW except for in the Straits of Juan De Fuca.

Many people in the aquaculture industry believe it will take about 20 years to develop the technology to create productive systems using offshore cages. (Photo from NOAA Central Library, Aquaculture Information Center)

University of Delaware Links to Marine Offshore Cage Culture
Links to numerous websites related to this technology

Articles

Marine Aquaculture Zoning
Written by Kristen M. Fletcher and Erinn Neyrey from Mississippi/Alabama Sea Grant Legal Program

NOAA Article
Describes the first offshore cage culture operation in Puerto Rico

Organizations and Companies

Amiflex Marine
British-based company that designs cages

Bonnar Engineering / Dunlop Oil and Marine
Ireland-based company that designs cages

Ocean Spar Technologies, L.L.C.
Engineering consulting company based on Bainbridge Island, Washington, which focuses on the aquaculture industry

Offshore Aquaculture Consortium
Focus on the Gulf of Mexico

Stirling University/Malta Mariculture Ltd (MML)
Cage culture project in the Mediterranean

Land-based marine aquaculture systems have several advantages. Technology is rapidly advancing in this field and the cost of equipment, such as chillers and pumps, is decreasing. A land-based system allows the water quality to be controlled more easily via filtration. The weather has a lesser impact on land-based systems and animals than on those exposed to the elements like offshore cage culture. Compared to net pen systems, land-based systems can diminish the risk of disease introduction to the natural waterways. Finally, there is little to no effluent produced in a recirculations system, which is especially important to maintain the integrity of the natural environment.

However, there are several drawbacks for pump ashore systems. Coastal land is expensive. Energy costs are high to run pumps, motors, chillers, heaters, etc. If a facility is located further inland there are higher costs associated with pumping the water further. There are also high overhead, labor, and capital costs associated with this type of system.

Despite the obstacles, there have been successes and opportunities to develop land-based culture systems. Onshore tank farms in Tasmania and South Korea have had success growing flatfish; however salmonid onshore tank farm production has not been profitable.

Land-based systems can be used to grow low quantities of high value species for the ornamental or live fisheries markets. In these markets a high quality individual is valued more than a high quanity of medium or low quality individuals. There has been successful use of recirculation systems in the Pacific Northwest. Hatfield Marine Science Center is currently utilizing water from Yaquina Bay to conduct a feeding/nutrition study of clownfish. The water is filtered and heated prior to introduction to the system and is used to counter evaporative losses. (Photo by: James P. McVey)

Links to Pump Ashore/Land-based Culture Websites

AquaNic Recirculating Aquaculture Systems Links
Website has links to books and free publications related to recirculating systems

Site Assessment for Land-based, Temperate Marine Aquaculture
Website focuses on Western Australia

Aquaponics and Tilapia Short Course
University of the Virgin Islands offers a 7 day course on recirculation/aquaponics systems
Please note that this website may move to a different URL each year.

Virginia Tech's Aquaculture Program
Brief summary of topical projects

AquaNic Discussion Site
Subject is Recirculation Aquaculture Systems

Submerged line culture is often the preferred method for culturing bivalve species such as mussels and oysters. Some aquaculturists describe the greatest advance in oyster culture has been to move the oysters off the bottom so sediment will not impact their ability to filter feed. Oyster culture is often performed using longline, rack, and tube culture methods. The advantage of submerged line culture is that the animals are suspended in the water column and are able to obtain food (plankton) more easily. In addition, submerged line has advantages over on-bottom culture since siltation and exposure to benthic animals is reduced. (Photo by James P. McVey)

Links to Submerged Line Culture Websites

More Information

British Columbia Shellfish Growers Information Resource System

Articles

New South Wales fisheries office examines the aquaculture potential of blue mussels

Download a PDF
Massachusetts Aquaculture Grant, Submerged Coastal Offshore Mussel Aquaculture System (SCOMAS)

Download a PDF
Shallow Water Resource Use Conflicts: Clam Aquaculture and Submerged Aquatic Vegetation

Companies and Organizations

British Columbia Shellfish Growers Association

Makai Ocean Engineering, Inc.
Company designs aquaculture systems

Pacific Coast Shellfish Growers Association

Net pens are often used for salmon culture. Washington's waterways continue to contain net pens whereas the only net pens in Oregon are in Young's Bay. There is increasing interest to convert net pens from salmon culture to halibut, sablefish, or lingcod culture. Finding a suitable and permittable site to use net pens is one of the major limitations for net pen culture. In addition, environmental and economic concerns associated with net pens have fostered research into alternative technologies and systems. (Photo by: James P. McVey)

Links to Net Pen Culture Websites

Articles

The Net-pen Salmon Farming Industry in the Pacific Northwest
NOAA Technical Memorandum NMFS-NWFSC-49

Article on the NETSystem and Ocean Spar project

Salmon Nation Article
Mentions the Net pens in Young's Bay, Oregon

Tide Pool Article
Article from 1999 discusses the Net Pens in Young's Bay, Oregon

Companies

MariCulture Systems
Washington-based company that offers alternatives to net pen culture

Future Sea Technologies
British Columbia-based company that designs and sells aquaculture systems

It is often expensive to find solutions to technical problems associated with marine aquaculture. There are often high costs associated with initial investment of equipment and labor followed by high costs for feed and continuous maintenance. The figure to the left shows divers performing maintenance and testing the integrity of a net pen.

The high costs associated with aquaculture systems has forced the industry to explore cost-cutting technology. For example, researchers at Grays Harbor College are interested in collaborating with organizations that create waste heat (e.g. power plants and natural gas companies) to reduce the cost of heating water via electricity. The researchers hope for a joint venture that utilizes warm water to facilitate faster growth of freshwater species such as koi, crayfish, and catfish. Finally, there is some limited freshwater aquaculture of warmwater species using geothermal heat in the PNW. There may be opportunities to develop this resource further. (Photo by: James P. McVey)