Is Aquaculture Sustainable?
According to the United Nations, “sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” As the world’s population increases, there is great need to embrace ecological, human, and economic practices that will sustain our planet and its citizens.
Fish is recognized as a healthy food source and a recommended part of a balanced diet. Since the 1990s, yearly production from wild capture fisheries has leveled off at just around 90 million metric tons. During this same period, aquaculture production has continued to increase and is projected to match the annual production of wild capture fisheries by 2030.
Aquaculture plays a key role in providing food for a growing population, but the question remains can the aquaculture industry accomplish this in a sustainable manner. Many articles have highlighted problems with aquaculture practices. Some of these issues include:
- Aquaculture production requires fish feed which places stress on forage fish populations. The conversion ratio of 3 lbs. forage fish to 1 lb. of salmon is not efficient.
- Fish grown in net pens can have a detrimental effect on the local environment if large amounts of uneaten food or waste material accumulate on the bottom. The excess nutrient material can lead to oxygen depletion in the water and increased stress on local aquatic species.
- Antibiotics and chemicals used to maintain fish health and treat fish diseases can leach into the environment.
- Farmed fish can escape into the natural environment and breed with native populations causing changes in genetic diversity.
Some of these popular beliefs about unsustainable aquaculture can be challenged. Dr. Jesse T. Trushenski, an Associate Professor with the Center for Fisheries, Aquaculture, and Aquatic Sciences at Southern Illinois University Carbondale, shares a presentation where she describes how aquaculture is actually sustainable.
Dr. Trushenski points out that:
- Fish beat terrestrial livestock in both feed conversion and dress-out.
- Feeding fish in aquaculture systems provides challenges because of their complex nutrient needs that are dependent on fish meal and oils derived from wild forage fisheries. However, the fish in to fish out ratio (FIFO) is actually more efficient than shown in simplistic examples. The FIFO is actually 0.3, meaning 3 pounds of farmed fish can be produced from one pound of wild fish.
- More efficient utilization of marine feed resources is leading to improved fish feed formulations.
- Farmed salmon actually provides more omega-3 than wild salmon when compared on a weight basis. Omega-3 helps contribute to good health.
- The benefits of eating fish far outweigh the risk from contaminants in these foods.
- U.S. Food and Drug Administration approval of drugs for use in aquaculture is very stringent and limits the use of antibiotics.
Traditional agriculture is the largest consumer of available freshwater resources. Up to 70% of the “blue water” withdrawals (i.e., water from rivers and lakes, groundwater and glaciers) are used to support agriculture (see figure). About 40% of the world’s food supply depends on irrigated lands. With the world’s population expected to grow from the current 7.4 billion to an estimated 8.3 to 10.9 billion by 2050 (United Nations News Centre, 2013), there will be continuing pressure on water supplies.
Global Agriculture Water Withdrawal (Source: Globalagriculture.org)
Advances in recirculating aquaculture and aquaponics help alleviate the demands on water usage. For a good introduction on recirculating aquaculture, see A Guide to Recirculation Aquaculture – An introduction to the new environmentally friendly and highly productive closed fish farming systems (FAO and Eurofish, 2015).
JD Sawyer of Colorado Aquaponics talks about the benefits of aquaponics and how it provides a sustainable food production system. Aquaponics recycles the waste water from fish tanks into vegetable grow beds. The plants use the waste as a nutrient source and help to filter the water so that it can be returned to the fish tanks. Aquaponics uses only about 5-10% of the water used for traditional land-based agriculture.
Growing seafood in a sustainable manner is not only good for the environment, but makes good business sense too. The demand for seafood with sustainable certification now accounts for 14% of the market, compared to 1% a decade ago. The global sustainable seafood market is now valued at $11.5 billion while the growth in demand for sustainable seafood is 10 times that of conventional seafood.
- A Guide to Recirculation Aquaculture – An introduction to the new environmentally friendly and highly productive closed fish farming systems, Jacob Bregnball, FAO & EUROFISH International Organisation, 2015
- Global Agriculture Water Report
- Making fish farming more sustainable
- Reeling it in: global sustainable seafood market hits $11.5bn
- “World population projected to reach 9.6 billion by 2050 – UN report”. UN News Centre. June 14, 2013. Retrieved June 16, 2013.
New Disease Threatens Tilapia
Tilapia has emerged as an important farmed fish helping to feed a growing world population. Global production of tilapia has soared from approximately 1.2 million metric tons in the year 2000 to over 4 million metric tons in 2012 (Fitzsimmons, Creozi, and Tran, 2014). Production of tilapia now surpasses other popular farmed fishes, such as catfish and salmon.
Diseases and parasites pose threats to aquaculture and can have devastating effects on fish populations. Recently the outbreak of a new disease has caused mass mortality in tilapia and poses a threat to the tilapia industry. As recently as 2005, the Sea of Galilee, Israel, yielded 316 tons of tilapia to fishermen. However, by 2009 only 8 tons were harvested. Tilapia farmers were also affected and reported losses of 20-30% of the fish in their ponds. Similar mass die-offs of tilapia were experienced in Ecuador. This disease seems to only target tilapia.
A team of international researchers characterized the disease as a virus. Detailed genetic examination of diseased tissue from affected tilapia showed that the virus was a new type of disease, which the scientists named tilapia lake virus (TiLV). The researchers observed that the disease symptoms included “lethargy, endophthalmitis, skin erosions, renal congestion, and encephalitis.” The disease is transmittable within tilapia populations.
Given the importance of the tilapia industry, which is valued at $7.5 billion yearly, there is urgency in finding a way to mitigate this new disease that has such devastating effects on tilapia populations. Researchers are actively looking for ways to control this disease, including a possible vaccine.
- Characterization of a Novel Orthomyxo-like Virus Causing Mass Die-Offs of Tilapia
- The Scary Thing About a Virus That Kills Farmed Fish
- Tilapia Global Supply and Demand in 2014, Kevin Fitzsimmons, Brunno Cerozi, Loc Tran, Adelaide, Australia, 10 June 2014 presentation