It has been reported that an estimated 51 species and 90% of large predatory fish have been lost due to overfishing. In 2005,
- 23% of the ocean’s wild fish stocks were lightly or moderately exploited and still offer some scope for further fisheries expansion
- 52% were fully exploited
- 16% were over-exploited
- 7% were depleted
- 1% were recovering from depletion and have no room for further expansion.
There are also an estimated 635,365 marine animals killed each year due to industrialized fishing as a result of the currently employed fishing practices, namely trawling and dredging. Aquaculture offers an alternative option to unsustainable fishing in marine and limnological settings. Moreover, aquaculture is a relatively efficient means to produce protein. Fish have a lower metabolic rate than terrestrial animals and in turn require significantly fewer micronutrients to grow. Salmon, which is the most intensively cultured fish, requires 1.2 pounds of input for every 1 pound of output. In comparison, chicken is produced at a 1.9:1 ratio, pork at 5.9:1 and beef at 8.7:1. It is also quite nutritious – low in fat and high in protein. Additionally, it provides valuable minerals and vitamins, and polyunsaturated fats, particularly Eicosapentaenoic and Docosahexaenoic acids which are most easily used by the human body. The World Health Organization (WHO) recommends consuming between 48-56 grams of protein per day: a typical 3 oz. serving of the most commonly consumed fish varieties provides 15-23 grams.
However, aquaculture will only reduce stresses on natural populations if farmed fish is readily accepted by consumers in order to shift demand away from wild-caught varieties. Such a shift in consumer demand is essential because of the high fixed costs associated with aquatic farming and the highly integrated nature of the commercial fishing industry in government subsidy programs and a relatively inelastic supply of labor, as well as the use of public resources for private economic benefit. If aquaculture practices become readily accepted there is a potential to reduce imported products and increase national economic opportunities if domestic production is increased. Emerging economies can use aquaculture to integrate themselves independently into the global market.
There is a lack of comprehensive guidelines to protect marine ecosystems and fisheries. These farming systems often use public land for the operations. If the environmental degradation is severe enough, the producers can claim economic loss and taxpayers will be required to pay for the clean-up. Furthermore, because the various genera, families, classes, orders and phyla of seafood are consumed and produced in various ways, it becomes necessary to regulate health claims and issue warnings when necessary. This is especially true as there are routine contaminations, rather than outbreaks.
As a result, there are a variety of environmental issues associated with aquaculture including:
- Loss of biodiversity
- Reduced fertility of wild fish
- False reports of population improvement caused by escapes
- Increased effluence in local waters resulting in eutrophication
- Reduction of water quality
- Loss of sea mammals and fowl targeted by aquaculturists
- Depletion of pelagic fish supplies used for fish meal
- Escape of non-native and potentially invasive fish
- Loss of ecologically sensitive areas due to land conversion
- Genetic alteration of wild stock
- Transmission of disease and parasites from farmed fish to wild species.
Fish may also contain dyes, antibiotics, PCBs, dioxin, and mercury caused by polluted water and/or human inputs. The same fish that is toxic to one person may not be harmful to another.
Current aquaculture practices will become unsustainable in the future due to the high input of pelagic fish [fish that grow and mature quickly/spawn and die young] in the fish-in-fish-out system. Furthermore, the fish are net consumers of commodity crops which have debatable health qualities and have become primarily GMO products in the United States.
Mansfield, B. (2011, March). Is Fish Health Food or Poison? Farmed Fish and the Material Production of Un/Healthy Nature. Antipode, pp. 413-434.
Welch, A., Hoenig, R., Stieglitz, J., Benetti, D., Tacon, A., Sims, N., & O’Hanlon, B. (2010, June). From Fishing to the Sustainable Farming of Carnivorous Marine Finfish. Reviews in Fisheries, pp. 235-247.