Offshore aquaculture

Offshore aquaculture is a new way of farming fish in the ocean. Instead of keeping fish farms close to the shore in calm, shallow water, offshore aquaculture places farms in deeper, more open waters farther away from land. This lets fish live in conditions closer to their natural habitat, with stronger ocean currents and more nutrients flowing through.

One reason people support moving fish farms offshore is to protect the environment near the shore. Inshore fish farms can sometimes harm the ocean floor and cause harmful algae growth because food and waste from the fish build up in one place. When farms are moved offshore, the ocean currents help carry away waste, which can be better for the environment.

However, there are also concerns with offshore aquaculture. Some worry about the use of certain medicines in farming and the chance that farmed fish might escape and spread diseases to wild fish. Even with these concerns, offshore aquaculture offers a way to grow more fish to meet the world’s growing demand while reducing conflicts with other ocean users.

Background

Aquaculture is growing quickly because there are fewer fish in the wild and it is a good business. In 2008, about half of all fish people ate came from aquaculture, and it has been growing by about 6.6% each year since 1970.

In 1970, a grant from the National Oceanic and Atmospheric Administration brought together scientists and engineers to see if farming fish far from shore was possible. Now, it is possible to grow fish, shellfish, and seaweeds far from land using special technology. However, big challenges remain, like making sure the fish pens can survive storms and figuring out how to work far from shore.

Technology

To survive in the rough ocean far from shore, fish farms need to be stronger than those closer to land. Scientists are working hard to make these farms cheaper and easier to care for.

Right now, some fish farms use floating cages on the surface, like those used for salmon. But offshore farms often use special deep cages that can sink and rise in the water. These big cages hold many fish and are tied to the ocean floor. They have floating markers on the surface that help feed the fish and store tools. This kind of farming is happening in places like the Bahamas, China, and Spain. Keeping the cages underwater helps reduce waves and makes it safer for boats.

Using the ocean for more than just fish farming can help the environment. For example, a old oil platform off the coast of California is being used to grow mussels and other sea creatures. Scientists are also studying ways to mix different kinds of sea animals and plants together so they help each other grow. This could solve some problems with offshore farming. Some people dream of mobile cages that move with ocean currents, but there are still many rules to follow before this can happen.

Space conflicts

As the oceans become more used for many purposes, there are more disagreements about who can use them. This happens because natural resources in the ocean belong to everyone, and many groups want to use the same space. Some of these groups include tourism, people who catch fish for fun, and industries that catch fish to sell. There can also be problems when placing machines that make energy from the sea.

These conflicts can become harder to solve because many ocean areas are far away and hard to watch and control. However, people can sometimes pick spots that are far away to avoid these problems. This lets them run big operations that save money. For countries that don’t have good spots close to the shore, like Spain, offshore systems offer another choice.

Ecological impacts

See also: Aquaculture of salmon § Issues

The effects of offshore aquaculture on nature are still not fully known because this method is mostly being studied.

Many worries about offshore aquaculture are similar to concerns about farming fish closer to the shore.

Pollution

One worry with farms close to shore is that extra nutrients and waste can harm the seafloor. Moving farms farther out into deeper water helps spread these nutrients more. But even in deeper water, some nutrients and waste still go into the environment. Future offshore farms might be bigger and create more waste. It is not yet clear how much waste the ocean can handle.

Wild caught feed

Like farms closer to shore, many offshore farms use wild-caught fish to feed the fish they are farming. If this continues, there might not be enough wild fish to support it.

Fish escapes

It is important to keep fish from escaping in offshore farms because they cost a lot. But as these farms grow, some fish might escape. This could affect wild fish, even if the farmed fish are from the same area. Special cages are used to protect against damage and predators like sharks. However, some small fish eggs can still pass through the cage material.

Disease

See also: Fish diseases and parasites

Farming fish farther out seems to cause fewer diseases than farming closer to shore. But new types of fish are now being farmed in deeper water, and we still don’t know much about how diseases might spread between these farmed fish and wild fish.

Using static cages far apart may help prevent diseases from spreading. But new moving cage technology might create new challenges for disease control. The need for live fish for feeding and breeding can also spread diseases between different kinds of fish.

Employment

Aquaculture is often supported by governments to create jobs and income, especially when wild fisheries are limited. However, this might not be the same for offshore aquaculture. Offshore aquaculture requires a lot of equipment and supplies, so it will try to save money by using machines instead of people. As offshore aquaculture grows, more jobs may appear in processing plants rather than in the actual fish farming areas.

Prospects

As of 2008, Norway and the United States were leading in creating designs for offshore fish farms.

In 2010, the Food and Agriculture Organization noted that many believed fish farming would need to move farther from the coast to meet the world's growing need for seafood. They encouraged creating better technologies and helping developing countries access them. Some members also warned to be careful about possible negative effects of moving fish farming offshore.

In 2002, the European Commission suggested moving fish cages farther from the coast and encouraged more research and development of technologies for offshore farming. By 2008, several European countries, including Norway, Ireland, Italy, Spain, Greece, Cyprus, Malta, Croatia, Portugal, and Libya, had offshore fish farming systems in operation.

In the United States, moving fish farming to areas beyond state control can create regulatory challenges. As of 2010, all commercial fish farms were located in waters close to the shore, under state control. However, five research and commercial projects in New Hampshire, Puerto Rico, Hawaii, and California were in federal waters. In June 2011, a bill called the National Sustainable Offshore Aquaculture Act of 2011 was proposed to create rules and research programs for sustainable offshore fish farming in federal waters.

Current species

By 2005, offshore aquaculture was used in 25 countries, both for testing and for business. Most of these farms grow fish that eat other fish, called finfish. In the US and the Bahamas, special cages that can go under the water are used to grow valuable fish like moi, cobia, and mutton snapper. These cages are also being tested for growing other fish like halibut, haddock, cod, and summer flounder in New Hampshire, and amberjack, red drum, snapper, pompano, and cobia in the Gulf of Mexico.

Growing shellfish like scallops and mussels in offshore farms is becoming more popular. Shellfish are grown on ropes or floating rafts in nets. Mussels can handle rough ocean conditions well. Unlike fish, shellfish don’t need regular feeding, which can save money. The University of New Hampshire has studied farming blue mussels in the open ocean. They found that in cleaner offshore waters, mussels grow more meat and have thinner shells.

Global status

In offshore aquaculture, fish farms are placed in deeper, more open waters farther from the coast. This method allows fish to live in conditions closer to their natural habitat, with stronger currents and more nutrients. Currently, most developments are in exposed areas rather than fully offshore. Experts say that more research and development are needed to fully use the opportunities in deeper waters.