As human population grows, the demand and need for fish will grow alongside it (FAO, 2007). As such, despite developments in fishing technology, the demand for fish will almost certainly exceed sustainable levels. Aquaculture is poised to fill the gap between fish needs and sustainable fishing, and to be scalable to meet future demands (FAO, 2007).

Aquaculture is already economically viable, with 40% of all food fish and 22% of all trade in fish already raised in aquaculture facilities, mostly from developing countries (World Bank, 2007). However, some forms of aquaculture are far from sustainable.

The most pressing environmental issues are antibiotic-resistant strains of germs due to widespread use of antibiotics and the collapse of aquatic ecosystems around aquaculture facilities. Some other issues that must be resolved include the escape of genetically modified fish into the wild and the need to feed the fish in aquaculture facilities (Aquaculture: fulfilling its promise, 2007). Our goal is to develop guidelines for creating an aquaculture industry that is both free from as many environmental dangers as possible and scalable to meet growing fish demand in the future in an economically viable way.

Meeting fish demand through aquaculture will involve replacing the consumption of wild fish with that of farmed fish. For the purposes of this plan, we looked at two general types of fish farming: cage farming and intensive farming.

Extensive Aquaculture

Cage farmingis comparatively simple to set up and maintain because there is no need for advanced water quality control systems. However, this reliance on nature for water management causes environmental problems, notably algae blooms caused by the concentrated waste and nutrients (Aquaculture: fulfilling its promise, 2007). The severity of these risks depend on site selection, whether the captive population is limited to the carrying capacity of the body of water, and levels of pollution from nearby sources such as industry. Ocean waters near the shore with good tidal flushing are most suitable for this type of aquaculture, and more exposed sites and attention to cage density can prevent risks to the environment (C. Goudey, personal communication, November 20, 2007). Other strategies to lessen the risk of environmental damage use shellfish, sponges, or other filter feeders to improve water quality (Shin, 2005). Also, it may be possible to use mobile cages to reduce the effects of unhealthy waste concentration (MIT Sea Grant, 1998). The first option would work well for countries where the right species are already native to the area, while the second option would allow landlocked nations or nations with little coastline a chance to develop aquaculture, as the mobile cages could be deployed in international waters. The current economic feasibility of mobile cages is unclear. While we are not currently able to provide an answer, we believe that should sufficient commercial and governmental pressure develop, means of reducing the cost of mobile-cage aquaculture would arise.These two options should provide most nations a means of performing this type of aquaculture while preserving the environment.

Intensive Aquaculture

We also encourage the use of intensive, closed-loop systems for aquaculture. In these systems, almost all the water is recycled, with at most 5-10% of water being replaced each day (Changing the face of the waters). This also means that escape of genetically modified stock is much more difficult and that with careful monitoring antibiotic-resistant diseases can be contained,allowing the safe use of genetically modified fish and antibiotics. Furthermore, as the water is in a closed loop, the wastefrom the fishwill not impact the surrounding environments. The ability to stack shallow tanks makes intensive farming particularly well suited to flat fish such as flounder (C. Goudey, personal communication, November 20, 2007). The primary downside is the complexity of the recycling systems.However, intensive aquaculture provides an opportunity for landlocked nations to become involved, and stacking tanks allows for large numbers of fish in a single facility.

Genetics and Feeding

There is a growing fear that genetically modified fish escaping from cage farms could seriously impact the surrounding environment. Aquaculture broodstock (fish selected for breeding) is often chosen to create fish with traits optimized for aquaculture.However, these traits are often less useful, if not harmful, in the natural environment.There is a fear that escaped fish from farms may displace native species, either through interbreeding or putting too much pressure on the local ecosystem (The threats and benefits of G.M. fish). But thisclaim is not well supported. Though some farmed fish may interbreed with wild fish, there is little evidence that these new genes are harmful (C. Goudey, personal communication, November 20, 2007). However, the risk still exists, so we recommend mixing randomly selected wild fish with the broodstock, to minimize the differences between the two groups.

Great work is being doneto find replacements for wild-caught fish in farm feed. "Soybean meal can replace all or most animal meals in the feeds for the majority of cultured omnivorous freshwater fish" (Quick facts). We encourage such efforts, as they may prove key toending aquaculture'sdependence oncapture fisheries. We also recommend using low trophic level farmed fish to feed higher trophic level fish.

Solving the Problem on a Global Scale

To solve these problems, we propose that developing countries use cage farming to raise large numbers of low trophic level fish, using plants as feed and our previous suggestions to prevent negative environmental impacts. These fish would be used both as a source of protein for locals and as food for higher trophic level fish farmed in more wealthy nations. The money from exporting fish would allow the developing countries to keep the fish farms operating, helping supply food to their citizens. In this manner, developing nations would get both food for their citizens and a new revenue stream, while developed nations could continue to consume higher trophic level fish with very little negative environmental impact. Implementing this plan would involve encouraging companies in developed countries to move to high trophic level farming and to purchase farmed feed fish from developing nations. In the United States, the National Oceanic and Atmospheric Administration (NOAA) is already authorized under the Merchant Marine Act to provide loans to help build aquaculture facilities (NOAA, 2007), which could help motivate corporations. By controlling the types of facilities it grants loans to, NOAA could encourage the creation of high trophic level farms that use only sustainable feed. We also urge the creation of an international team of aquaculture experts to assist nations with farm design and placement, ensuring the most environmentally friendly farms possible and making them even more economically feasible for developing nations.

There still remains the question of scale. Farms have produced anywhere from 63,000 to over two million pounds of tilapia per year (Sell, 1993). At an average per capita per year consumption of about 35 pounds, a single farm could feed as many as 50,000 people (Availability and consumption of fish). This would allow the entire population of the Maldives, more than 350,000 people, (Maldives information, 2007) to be fed with as few as eight large fish farms.

Final Notes

In some cases, it may be possible to produce even better systems for particular nations. In India, for example, some cities have integrated their waste water treatment and aquaculture systems so that human waste is used as feed for the fish (Changing the face of the waters). However, such specialized multitrophic solutions are dependent on many factors, including local climate and the species involved, and are thus hard to create general guidelines for. While such systems can be very useful, designing them is a task best done on a case-by-case basis.

NOAA recently released a 10-year plan for aquaculture in the United States (NOAA, 2007). We agree with its goal of increased usage of farming, particularly the use of aquaculture to rebuild stocks of wild fish. As the plan seems to be focused more on production and research goals, we feel it is compatible with our plan and encourage its adoption.