Solutions to Unsustainable Salmon Farming Practices

Onshore aquaculture is a sustainable alternative to open-net salmon farming, where salmon are contained in nets placed directly into the ocean.

Hannah Brumby: Geology

Justin Parker: Building & Construction Technology

William LaVoice: Natural Resources Conservation

Gabbie Furtado: Animal Science

In the last twenty years salmon consumption has skyrocketed, increasing by nearly 250% (FAO). Today the bulk of production comes from salmon farms (OurWorldInData). The EU, the US, and China make up over seventy percent of the global market for Atlantic salmon and consumption is increasing in each place (Williams 2017). Unfortunately salmon farming has proven to be both economically and environmentally unsustainable. Yet production has not stopped due to the high demand. In order to meet people’s demand for salmon, a transition to more sustainable farming practices needs to take place.

Aquaculture is often seen as a solution to problems such as overfishing and economic stagnancy, but it also creates new problems, causing detrimental impacts to the water and ecology surrounding the salmon farm. These effects include decreasing biodiversity, elevated mercury levels in wild fish, and introgression. These effects are generally localized, but have the potential to create long-lasting damage to the affected ecosystem. Because of this, there is debate over whether or not investing in salmon farms would be an overall beneficial alternative to fishing for wild salmon.

Aquaculture is defined by the National Aquaculture Act of 1980 as the breeding and raising of marine animals in controlled environments.  Sea-cage salmon farming in particular affects us as a community in many different ways. With such a drastic change to the local ecosystem comes a change in availability to people.  The increase in algae and build up of waste surrounding the farms leads to poor air and water quality, making the area unlivable for people. The escaping of salmon and introgression can affect the quality and quantity of wild salmon that you buy at the market.  These farms also attract predatory animals, such as sharks, to the area due to the large number of easy prey. In addition, the large increase in salmon production actually causes more problems for the economy than it solves. The increase in salmon available drives the market price down, creating a lack of income for our local fishermen.  They now have to increase the amount of fish they catch to make up for the loss of income, essentially adding to the overfishing of wild salmon.

Introgression is caused by escaped fish due to a breach in nets from marine salmon farms is causing a decline in wild salmon’s local population size. Introgression is a common issue caused by marine salmon farms. The nets used in open water farming operations are often difficult to maintain. Rips in the netting occur quite often due to storms or other sea life trying to get the salmon, like sea lions or seals. These escaped fish intermingle with the wild populations, resulting in introgression, increased competition, and transference of parasites and diseases. It is the process of gene flow from one species gene pool to another’s. Introgression is like when a red sock gets caught in a load of white laundry, causing the rest of the clothes to turn pink. The farmed salmons’ genetics will “stain” the gene pool of the wild salmon.  Because of this, introgression causes variation in the recipient wild salmon’s gene pool. This is problematic because farmed salmon have lower genetic variation that wild salmon, which in turn causes the wild salmon’s genetic variation to shrink. Shrinking genetic variation can lead to populations of any species, land or aquatic, to die out. The outcome of this cycle is detrimental, and results in lower population sizes of local wild salmon (Karlsson, Diserud, Fiske, Hindar, 2016).

Run-off from marine salmon farms is more expensive to clean up than the production of salmon is worth. Folke, C., Kautsky, N., & Troell, M. (1994) found that if the polluter-pays principle applied here, the “production cost exceeds the highest price paid for farmed salmonoids…”. This is quite shocking considering the massive scale we are producing salmon on. The only way the industry can persist is by ignoring the pollution they are causing. In Nordic countries production of salmon breached 250,000 pounds in the year 1994 (Enell, 1995).

A good solution to this problem is moving salmon aquaculture on shore using closed-circuit systems, or recirculating aquaculture systems.  Salmon farmers should be implementing strategies to collect the fish waste, which can effectively be used as fertilizer in other agriculture fields or possibly used as feed for shellfish aquaculture.  Currently, every ton of salmon produced in aquaculture creates about 92.6 to 145.5 pounds of nitrogen waste and 15.9 to 23.1 pounds of phosphorous waste (World Resources Institute). Excess nitrogen and phosphorous waste in the water are the leading cause of an algal bloom if they are in high concentrations (n.d).  In 2015, the United States used almost 5 billion pounds of fish, making the country the second largest consumer (NOAA, 2011). This means that in order to meet the demand of the U.S., there was a minimum of 231,500,000 pounds of nitrogen waste and 39,750,000 pounds of phosphorous waste produced to feed a single country.  This kind of waste buildup leads to massive eutrophication due to the excess nitrogen being introduced to the environment without purpose. On-land fish factories have created filter and disinfectant systems that have proved effective in minimizing their environmental impact on the surrounding area. They are able to use water flow to collect the solid wastes and UV radiation and other techniques to disinfect the waters prior to pouring it into the ocean (Miller & Semmens, 2002).  Some companies are also implementing aquaponics, a system that uses the fish feces and wastewater as a nutrient source for hydroponics (2010).  Hydroponics is the growth of plants without soil in water containing dissolved nutrients (Santos et al., 2013).  Aquaponics, a combination of aquaculture and hydroponics, allows the recycling of nutrients to be used by the plants being used in the system. This decreases the total amount of waste produced when compared to a purely aquaculture system.

In Turner Falls, Massachusetts, there is an aquaculture facility focused on raising Barramundi, a freshwater perch from Australia  (White, 2018). This farm raises about 2 million pounds of fish a year with only 15 pounds of solid waste produced a day. This waste can then be sold for use as agricultural fertilizer.

Waste runoff is greatly reduced using an onshore facility since management of the waste is greatly increased.  In closed-circuit tanks, solid waste is filtered out of the water in order to maintain water quality and reduce waste fragmentation, minimizing likelihood of disease in salmon (Miller and Semmens, 2002).  Waste fragmentation is the breakdown of fish waste which then dissolves into the water. An on shore system minimizes waste runoff when the farm dumps its water into the environment as management will have removed the majority of solid waste during water circulation.  The dissolved waste of fish farms is primarily made of nitrogen (ammonia, nitrite and nitrate), phosphorous, and organic matter. In a sea-cage farm, these waste products cause the eutrophication (excess nutrients that cause an algal bloom and lack of oxygen) of the area.  For this situation, aquaponics becomes very useful as the plants would remove the excess nutrients from the water. If this is not possible, a biofilter is a great substitute (Miller and Semmens, 2002). A biofilter will “grow” a film of microorganisms that are able to extract and use the excess nutrients in the water as it runs through the filter, improving water quality without need to replace as much (2010).

In a closed-circuit system, fish farms are even able to filter out pathogens such as viruses, which can be a big cost to sea-caged fish.  This is accomplished using UV radiation and dissolved ozone. After the solid waste is removed, UV radiation can be used at low levels to kill viruses, which are next to impossible to control in open water.  This procedure is considered low maintenance and low risk (Miller and Semmens, 2002). Dissolved ozone is a more risky treatment as low levels in water and air can be toxic to the fish and people respectively.  However, it does help with reducing the organic material in the water and kills most pathogens (Miller and Semmens, 2002).

In order to encourage this move, we would need to put a waste tax on fish farms, ultimately making onshore aquaculture cheaper and environmental impacts lessened.  Policy that restricts the amount of waste runoff allowed needs to be put in place and governmental incentives should be offered in order to help current ocean-based operations transition to on-shore facilities.  One of the National Oceanic and Atmospheric Association’s (abbreviated as NOAA) policies is to ensure that all of their decisions and policies work toward protecting wild fish and their environments (NOAA, 2018).  However, based on the research, this is not being upheld. With the new policies in place, the companies would only be allowed a maximum amount of waste runoff, determined by what the environment is able to use without eutrophication occurring.  Anyone found to exceed this amount would be heavily fined with the tax used to fix the problem created.

However, this would become costly for these companies as keeping waste runoff to such a low amount could prove virtually impossible without a way to capture the waste in the water.  This is why government help or reward for transitioning to an onshore facility would be ideal. If government programs could offer companies grants or reimbursements that cover a large portion of the costs to move on land, that would be incentive enough for companies to start changing as costs of a closed circuit farm tend to be one of the biggest factors in choosing to stay in the water.  This could also work for new aquaculture companies as starting a closed circuit system without any financial help could be a large reason why people choose the sea-cage strategy.

Another way for government programs to help encourage the move to land aquaculture would be to educate the consumers on why this farming strategy is superior, increasing a market for closed-circuit farmed fish.  If enough people understand that this is the least environmentally harmful way to supply fish, they will begin to shop for that market specifically, helping increase the demand and easing the financial burden of making the switch to this new management system.  Educating the people running the aquaculture of how making the switch would help financially in the long run would also encourage the change in facility. With on shore management, there is a decrease in viruses and parasites with proper equipment and management as well as potential for additional product using aquaponics or collecting the feces to sell as fertilizer in other agricultural fields.

Salmon fishing and open ocean farming as it is now is not sustainable. There have been many species of fish that have been overfished to near extinction, one of the most notable being the Atlantic Cod. This fishery is what brought early settlers to this part of the world. There is even a wooden cod hanging up in the Massachusetts state house, as a symbol of the fish’s importance. Now, the massive cod fishery that once fed this area has been reduced to about one percent of its former size and may not ever recover (Ropiek, 2014). Salmon could suffer the same fate as the Atlantic Cod. By bringing the salmon farming operation on shore, this would alleviate the pressure and our dependence on the wild population of salmon. With the salmon farms being an onshore operation, there can be a greater availability of fresh salmon without the costs and environmental impacts of shipping long distances. Over 90% of the seafood that americans eat is imported (2015). A decrease in the distance it takes for the finished product to reach the consumer will result in a cheaper, fresher product for the consumer.

Critics argue that farmed salmon is overall much more unhealthy than wild-caught salmon, as farmed salmon contains significantly higher levels of saturated fat than wild-caught salmon. For the most part, the debate boils down to issues regarding the diet of farmed salmon. While wild-caught salmon consume a diet consisting mostly of krill and other invertebrates, farmed salmon consume a diet of specially-formulated fish pellets made mostly out of vegetable and fish matter, and containing additives that enhance digestion, flesh pigmentation, growth, etc. (2019). Many are frightened by the idea of “enhancing” the farmed fish, but the truth is that most of the additives in salmon feed are made from natural ingredients and emulate natural processes. For example, the attractive pink-red color in the flesh of farmed salmon is achieved by incorporating yeast, algae, and crustacean products such as krill and shrimp into the salmon feed, since the salmon don’t receive those nutrients in a farm as they would in the wild (2019). However, there is some merit to the argument against salmon farming with regards to the feed used. According to NPR, 90% of the fish that is caught and used for fishmeal is actually safe for human consumption. This means that the use of the twenty million tons of fish that are taken out of the ocean per year is potentially misdirected (Leschin-Hoar, 2017). In other words, humans could be eating that fish instead of feeding it to salmon. With overfishing becoming a looming global problem, some fish farms, such as Verlasso, are taking steps to reduce the amount of fish consumed by their salmon by supplementing their diet with plant matter (Weise, 2013). The salmon remain as healthy as ever. This is just one example of the direction that aquaculture is heading in, which is one of improved fish health and more sustainable sourcing of fishmeal. As we move forward into the future and develop more sustainable ways to feed and raise salmon for food, terrestrial aquaculture systems are the next logical step for the salmon farming industry.

And of course, the classic counterargument against establishing more recirculating aquaculture systems is that it is too expensive. One also may argue that it is better to keep salmon farming as-is, and continue to establish salmon farms that utilize ocean water and dump waste into the oceans because the impacts aren’t as negative as the cost of building and maintaining recirculating aquaculture systems. In reality, the idea that recirculating aquaculture systems are inherently more expensive than net-cage systems is an industry myth. An international summit on fish farming in land-based closed-containment systems, held in 2013 and attended by global experts on aquaculture, explored these ideas. According to models created by experts from the Conservation Fund Freshwater Institute, net-pen systems and land-based systems have approximately the same cost of production. And while the carbon footprint of land-based systems were projected to be slightly higher than net-cage systems, the overall carbon footprint was actually lower for land-based systems when taking into account freight shipping costs for importing net-cage salmon from other countries. (Summerfelt and Christianson, 2014). When taking into account these factors as well as the fact that closed-system aquaculture reduces disease, contamination, and impact on the local ecosystems surrounding salmon farms, terrestrial aquaculture appears to be the direction in which the United States should be heading.

Salmon consumption is increasing at a fast pace globally, and at the same time, our oceans are being polluted and overfished. If human beings are to continue enjoying salmon as a staple in their diets, it will be imperative that we establish alternative methods of growing and raising salmon for consumption. While conventional salmon farming practices suffice, they also contribute detrimental impacts to their surrounding environments such as sediment eutrophication, sea lice, and introgression from escaped salmon. On top of this, the current sources of fish used to produce salmon feed are being overfished as well. It is without a doubt that the future of salmon farming lies in the creation of terrestrial aquaculture systems, which reduce waste produced by the salmon farm and allow for better conditions that can grow healthier and tastier fish.


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  1. تعویض سیستم و کامپیوتر آماده امروزه بیش از قبل رایج شده است. پیشرفت تکنولوژی ما را ملزم به بروز بودن کرده است. تعویض قطعات قدیمی کامپیوتر مانند پردازنده و مادربرد می‌تواند اولین گزینه ما باشد.

    یافتن فروشگاهی که در حال مطمئن بودن، تضمین بابت فروش قطعات استوک کامپیوتر نیز ارائه کند بسیار مشکل است. نور استوک مفتخر است یکی از بزرگترین مراکز خرید و فروش قطعات دست دوم در ایران باشد. همچنین امکان فروش قطعات کامپیوتر به ارگان ها نیز وجود دارد.

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