False Salvation: The Truth About Global Marine Aquaculture
2017, High School, Prose
Imagine swimming in the ocean, just offshore. You are surrounded by beautiful, clear water — until suddenly everything changes. Before your very eyes, the once pristine water changes into a filthy wasteland. The ocean floor is covered with trash and dead marine organisms. Fish swim so closely packed together that you can barely move, and the water is so murky that you can only just catch a glimpse of what’s ahead. The organisms around you are sluggish, moving slowly due to lack of oxygen, and the surface of the water is coated with algae.
Contrary to what you may be thinking, this area is not a toxic waste dumping site. It is an area in which aquaculture, or the act of raising fish and other aquatic species for food, is taking place. Aquaculture is the fastest growing sector of food production: it has grown from less than one million metric tons (MMT) in 1950 to 55 MMT in 2008 (Townsend 2012). Roughly 40% of fish consumed worldwide come from fish farms, and farmed salmon production exceeds wild salmon catch by 70% (Naylor et al. 2005). Aquaculture often takes place in freshwater, but it is common in oceans as well. In general, marine aquaculture is used to raise mollusks, shrimp, and fish, such as tuna and salmon (Townsend 2012). Aquaculture was created as a means to solve the pressing problem of overfishing by farming fish in order to take pressure off of wild populations. However, aquaculture comes with many problems of its own. While some forms of aquaculture can be sustainable, in general, the current trends show that the costs of fish farming far outweigh the benefits.
The primary issue that results from aquaculture is increased eutrophication and algal blooms. Nitrogen and phosphorus are limiting nutrients, which means that the present quantity of these nutrients controls the amount of plant growth in an area. When extra nitrogen and phosphorus are released into a body of water, algal growth increases. The algae consumes large amounts of oxygen, leaving little behind for other organisms to use. Since these organisms cannot breathe, they die, and as decomposers use oxygen to break down the waste, it becomes even more difficult to breathe. Eventually there is so little oxygen that the area becomes a dead zone (Diana 2009). This process is known as eutrophication, and can often occur due to the increased nutrients that result from fish farming. According to a 2007 study, 72% of the nitrogen and 70% of the phosphorus in food used to feed farmed species is not retained by those organisms, and 9.5 kilograms of phosphorus and 78 kilograms of nitrogen are released per ton of fish farmed (Cao et al. 2007). These extra nutrients frequently lead to eutrophication. For example, China’s Bohai Sea, which is often used for shrimp farming, is soon to become a dead zone due to pollution. Aquaculture is a major reason for this disaster: phosphorus levels in the shrimp farming areas of the sea are 900 times higher than they are elsewhere in the water (Cao et al. 2007). To stop the kind of eutrophication and algal blooms that are occurring in the Bohai Sea, many farms use herbicides and pesticides to control algae. However, the chemicals from these compounds just end up polluting the water more, making conditions even worse for the organisms that inhabit the area (Baker 1998). Algal blooms can also be toxic themselves, and the poisons can spread outside the farmed zone and hurt wild ocean species as well as farmed ones (Baker 1998). In fact, cage systems interact significantly with other ocean areas, releasing large amounts of waste: the average percent of waste found in farmed waters is about 2.56%, while in non-farmed waters it tends to be below 1.5% (Cao et al. 2007). Waste levels are also higher in areas in which so-called “trash fish” are used as feed, which brings up another important point: threats to wild populations.
While the negative effects of aquaculture may seem localized, they can actually have extremely far-reaching effects on wild marine populations. One of the most prevalent issues is the use of small fish to feed larger farmed fish. Wild species such as anchovies and herring, sometimes referred to as “trash fish,” are often caught and ground up into fish meal in order to feed the farmed species (Baker 1998). This destroys biodiversity and can drastically alter ocean food chains, disrupting entire populations of wild marine organisms. It is also much less efficient, as more energy would be gained if humans just ate the smaller fish as opposed to feeding them to bigger fish and then consuming those bigger fish (Earle 1995). In addition, if escapees from aquaculture areas enter locations in which they do not naturally occur, the escapees themselves can be a form of pollution. These escapes are almost inevitable, especially from open lots in the ocean. In fact, escapes from fish farms cause 39% of global aquatic species introductions (Naylor et al. 2005). These escapes are problematic for many reasons. First, interbreeding between wild and farmed species can reduce genetic diversity, as most farmed species are very similar genetically (Naylor et al. 2005). A reduction in genetic diversity means that populations are more vulnerable to extinction, as there are few mutations or differences that allow some member species to survive potential extinction events, such as food or oxygen shortages. In addition, interactions between escaped farmed fish and wild fish can stress the wild populations, leading to increased mortality of the wild fish (Naylor et al. 2005). The escapees can also out-compete wild fish, and most importantly, they can spread pathogens and diseases to both wild fish populations and human populations.
Since fish are packed so closely together in aquaculture environments, it is easy for them to spread diseases to one another. Therefore, antibiotics are often applied to the lots in order to attempt to stop the spread of disease. However, the prolonged use of antibiotics selects for antibiotic-resistant bacteria. These bacteria can either spread to wild fish stocks, causing a population collapse, or spread to human populations and sicken many people (Hopkins et al. 1995). Though aquaculture is meant to relieve pressure on wild fish stocks while still providing safe food for humans to eat, it is actually hurting our oceans, as many marine organisms are becoming ill due to drug resistant bacteria created on fish farms. It is true that not all areas pack organisms as closely together, which reduces the need for antibiotics. However, as intensive fish farming uses high densities of organisms and therefore relies on heavy use of antibiotics, it is the most cost-efficient and thus the most common practice (Hopkins et al. 1995). Chemicals such as hormones and dyes are also often released into the water in order to change the color of the fish or otherwise change its appearance or size (Hopkins et al. 1995). These chemicals cannot be contained in open ocean lots, meaning that they are able to exit the aquaculture area and pollute wider areas of the ocean, once again hurting wild fish stocks.
While aquaculture endangers many different marine areas, the threat to estuaries is perhaps one of the most distressing. Estuaries are areas where river and ocean waters meet, and are extremely important breeding grounds and nurseries for aquatic organisms. One type of estuary is a mangrove swamp, a tidal wetland filled with many mangrove trees. These trees have thick, tangled roots, which make them ideal nurseries for marine organisms. However, it has become increasingly common to destroy mangrove swamps in order to create shrimp farms. This causes a loss of estuarine nurseries and severely threatens wild populations, as they no longer have a safe place to rear their young (Cao et al. 2007). The benthic habitat, or the floor sediments of the estuary, is also frequently destroyed by aquaculture, once again threatening wild species that inhabit those areas or use them as breeding grounds (Baker 1998). Without access to estuaries, it is very difficult for many organisms to repopulate. If aquaculture continues to destroy estuarine habitats, wild marine organisms will begin to die out, as they will be unable to breed successfully.
While all of this may make it seem like aquaculture is a terrible, hopeless process, there are in fact ways to improve it. It likely is possible that aquaculture can be sustainable and reduce the pressure on wild fish stocks, but it needs to be reformed and regulated in order to allow that change to occur. The FDA has stated that there are inadequate methods to meet the needs of aquaculture, but this could change if new strategies are developed (Hopkins et al. 1995). For example, current methods allow some of the negative effects of fish farming, such as eutrophication and algal blooms, to be mitigated with proper wastewater treatment. However, it is highly demanding to use this type of treatment and develop other sustainable aquaculture processes, so new treatment technology is needed in order to increase efficiency (Cao et al. 2007). In order to get rid of pathogens, people have attempted to use chemical methods, but this often ended up causing more harm than good, as the chemicals only increased pollution levels. Instead, experts recommend using microorganisms to destroy pathogens or the implementing an integrated aquaculture system (Cao et al. 2007). Integrated aquaculture is a type of aquaculture in which the waste products are used to benefit other species. For example, waste from a fish farm can be used to fertilize vegetable fields onshore. The EPA recommends this treatment, as well as other sustainable methods such as reducing reliance on herbicides and pesticides, raising fish in tanks as opposed to in open water in order to reduce escape and stop the spread of pollutants and diseases to wild populations, and using protein that does not come from “trash fish” to feed farmed species (Baker 1998).
The idea of avoiding using other fish as feed for farmed species is echoed by Sylvia Earle, renowned marine biologist and author, in her 1995 book. Earle claims that most species that are farmed are not viable candidates for cultivation. For example, attempts to raise huge organisms such as swordfish and and tuna are not sustainable, as it requires unbelievable amounts of energy to feed them. When an organism consumes another organism, only 10% of the energy contained in the prey is transferred to the predator. So by consuming farmed tuna instead of just consuming the fish fed to that tuna, humans gain less energy and contribute to unsustainable aquaculture, further polluting our oceans. According to Earle (1995), the best thing to do is eat lower on the food chain in order to increase energy efficiency and decrease reliance on farming of big fish — because, as she says, feeding the world on cultivated tuna is about as likely as feeding the world using farmed panthers.
By now, it should be clear that aquaculture is not, in its current state, the solution to the problem of declining wild fish populations. In reality, despite the problems of overfishing, there are times where buying wild fish can be more sustainable than buying farmed fish. For example, the state of Alaska uses fish quotas to keep salmon fishing at sustainable levels. The state has seen a great deal of success with the program, and it is likely that buying wild Alaskan salmon is more sustainable than buying farmed salmon. So if you’re ever torn between buying farmed salmon or wild salmon, check to see where each came from — the more sustainable option could surprise you. Each farm or fishing area has different regulations, and it is important to do research on each in order to select the option that will affect our oceans the least. In addition to making personal purchasing choices, it is important to advocate for regulation of aquaculture. It is absolutely possible to make aquaculture sustainable: all that is needed are the appropriate tools and mitigation techniques. Aquaculture has the potential to improve both the lives of humans and aquatic organisms — but we need to push to make it better first.
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