Around 80 million tons of fish are grown in fish ponds and put on the market. Fish farming has become an important part of commercial fisheries. Today, the number of fish in the seas is rapidly depleted due to polluted seas, climate change, extinction of fish and overfishing. In fact, half of the fish we eat now, are grown in fish farms.
Fish farms, usually established for the purpose of raising marine fish, are located in the middle of the sea one mile off the shore. Fish farming is not permitted everywhere and in every bay of the sea. In addition to the state support for the establishment of a fish farm, it is necessary to obtain a lot of special permits. Fish farms are in large steel cages and descend deep. No more than 1.5 meters above the water. Red or yellow warning flashing lamps are mounted on them especially because they are dangerous for night cruising boats.
It should be kept in mind that fish farms are not a technological method for transcending natural boundaries, but on the contrary, they have a production process dependent on the continuation of fish stocks in the seas and the sustainability of the ecosystem. In this process, shaping the development of the sector in line with social and ecological demands is of great importance.
Fish Feed Used in Fish Farms
Some species of fish caught in the seas are fed to the feed factories to feed the fish grown in fish farms. For example, some small fish such as anchovies are used in fish-producing factories. In 2015, 58% of the anchovy caught in the sea was sent to fish flour and fish oil production. Anchovy, a food rich and inexpensive fish, is sent to fish farms instead of being put on the market, which means that the fish is expensive and cannot reach the public enough. Anchovy was produced as export in fish farms and became a source of feed for more expensive fish. As a result, anchovy hunting increases and the risk of fish becoming unavailable increases.
45% of the feeds of sea bream and sea bass produced in the farms are used as fish meal, 13% are fish oil and the remaining 40% are protein sources (soy, corn). To grow one kilogram of farm fish, more than 1.5 kilos of sea fish must be caught. It is necessary to catch 1.8 kg of wild fish to grow 1 kg of sea bass and 1.6 kg of wild fish to grow 1 kg of sea bream. Therefore, even though efforts are made to prevent carnivorous fish farming, other kinds of feeds are unhealthy. In an average fish farm, 12-13 tons of fish feed is consumed per day. The price of fish feed in kg is approximately $1. As can be seen from this table, fish farming is not very cheap.
Environmental Impact of Fish Farming (Aquaculture) Activities
Environmental Impact of Oxygen Consumption
Aquaculture studies limit the use of oxygen. The storage of organic wastes leads to an increase in the oxygen used by the sediment and consequently depletion of the oxygen in the bottom. As a result of the degradation of organic wastes by bacteria and other organisms, the concentration of O2 in the environment decreases and this may negatively affect benthic organisms. As the O2 content of inland lakes and ponds is more difficult to regenerate, it is necessary to pay more attention to a load of high nutrients in such ecosystems.
Phytoplankton and higher forms of algae and plants, as a result of the spread of limiting nutrients such as phosphorus and nitrogen in the inland waters, cause undesirable growth in water and cause eutrophication. While the amount of oxygen increases during the day as a result of photosynthesis, the carbon dioxide concentration increases and pH decreases due to the fact that photosynthesis stops at night and normal breathing continues. Increasing the amount of CO2 puts the life of water organisms in trouble and can also cause deaths.
The increase in water temperature causes a decrease in the amount of oxygen in the environment and a decrease in the amount of oxygen causes the balance of the ecosystem to deteriorate. Eutrophication and oxygen consumption are among the most important problems that cause deterioration of surface water quality. Decrease of dissolved oxygen due to nutrient intake and increase in undesirable aquatic organisms cause significant surface water quality problems.
Environmental Effects of Chemicals and Drugs
In aquaculture, chemicals are used to control diseases, increase water quality criteria and control aquatic plants. The chemicals used in aquaculture are antifouling, disinfectants (used for hygiene purposes), algaecides (algae killers), herbicides (herbicides), pesticides (all plant and insecticides), parasiticides (parasiticides) bactericides ( antibacterials).
According to a study on salmon farms in Norway, 18220 kg of antibiotics (oxytetracycline) were used. This amount corresponds to 210 grams per tonne produced. When antibiotics are given together with feed, 20-30% are kept in the fish body and 70-80% pass into the environment. 13 days after the treatment with oxytetracycline, which is a frequently used substance in bacterial fish diseases, a significant amount of antibiotic accumulation was found in fish caught near cages and at a distance of 400 miles and in mussels taken 80 m away.
In culture production, it is inevitable that medication treatment should be applied when disease occurs in the cultivated species. Preventing diseases is easier, less costly than treatment, and more reliable for public health and the environment. Measures to be taken to prevent diseases are an effective way to eliminate the drawbacks arising from drug use. Measures to be taken include vaccination, animal resistance to diseases, non-specific immunomodulators, probiotic and prebiotic use. In addition, to improve maintenance and feeding conditions, to prevent excessive stock density, to comply with hygiene rules are among the measures that can be taken.
If we have to use chemicals in cases of illness, we should use these chemicals according to veterinary or specialist prescriptions. We should avoid the use of random and irregular chemicals. Therapeutic chemicals should be given at the right dosage and time interval according to the conditions of use. Antibiotics should not be used randomly and alternate antibiotics should be used instead of the same antibiotic. Because antibiotics and other chemicals used in the treatment of bacterial diseases are bioaccumulated on various living organisms (fish, mussels, shrimps, lobsters) in the immediate vicinity.
Interactions of Wild Species and Fishes Escaping Fish Farms
Cultivated species can become dominant in natural environments by escaping from farms. These culture fish, which are difficult to adapt to natural environments, also hybridize with natural stocks and may lead to the emergence of new breeds that are difficult to live in the ecosystem. One of the consequences of these escapees is the degradation of the gene pools of our natural stocks.
In order to avoid these problems, necessary precautions should be taken in the aquaculture facilities in order not to escape to nature. For this, double nets should be used in cages or cages should be checked frequently and tears should be repaired. In aquaculture in the ponds, the necessary precautions should be taken in the exit waters and culture species should be prevented from escaping to nature.
Dead Fish Wastes
Fish deaths caused by disease, poisoning or a technical problem in aquaculture units are waste material. These wastes must be removed from the environment by burying or burning with lime. These dead fish waste should not be disposed of in the aquatic environment or elsewhere.
The visual pollution created by aquaculture is being reacted by other sectors. These responses are particularly focused on net cage production in sea and freshwater. During the aquaculture activities, all kinds of precautions that will not cause visual pollution are taken.
In this context, bags and other wastes of feed used in aquaculture are regularly removed from the facilities. In addition, the structures on the land are designed in harmony with the environment in which they are located and the exterior facades are painted in accordance with the environment.
Environmental Effects of Fish Feed
In parallel with the developing world population in recent years, the expansion of aquaculture production causes important socio-economic benefits but also causes significant ecological changes. The type and area of ecological change depend on the method of aquaculture production, the amount of production, the physical, chemical and biological characteristics of the coastal area. Due to their location, aquaculture farms are established in natural areas away from industrialization and urbanization. Unlike other animal breeding enterprises, such enterprises are directly intertwined with the environment and it is not possible to separate the breeding area from the natural environment with a limit.
In recent years, these enterprises, which have increased rapidly in capacity and number, have spread to wider areas in parallel with the rapid increase and have started to discharge more to the environment by using more water, feed, and chemicals with the modernization of production activities and the advancement of technologies. As a result of this, aquaculture enterprises have started to get reactions from some circles and they have been accused by the tourism sector especially because they think that they harm the environment. In the accusations made, such enterprises are shown as completely harmful and in the eyes of foreigners, aquaculture enterprises are attributed targets to the environment as enemies. Rather than confronting the aquaculture and tourism sector, they should share and support their fields of activity in harmony with each other.
Aquaculture is the production of marine and freshwater organisms, which are suitable for consumption, economic value, commercially, by providing optimum ecological conditions in natural and artificial environments, starting from egg production and keeping all life stages of the organism under controlled conditions. Aquaculture helps to increase food production, create better nutrition opportunities and improve public health, increase income, increase foreign exchange input, reduce pressure on natural fisheries, and contribute to the production of low-cost marine sites. The opinion accepted by all authorities is that the production of hunting will not increase significantly.
Aquaculture will play an important role in closing this gap. In addition to the socio-economic benefits of aquaculture, there are many other benefits. These benefits help reduce the pressure on fishing. As a result of the development of hatcheries, the natural fish stocks are increased and the stocks are maintained. As aquaculture needs clean and quality water, it helps to increase environmental awareness. They contribute significantly to the economies of the countries.
A farming system with all these benefits will, of course, have an impact on the environment. This effect is much lower than the effects of human activities such as agriculture, settlement, industry, infrastructure facilities. With the increase in aquaculture, intensive problems have started to occur with other sectors using coastal area. The most important accusation brought by these sectors to aquaculture is the allegations that the enterprises pollute the environment without relying on any data. Studies have shown that the impact of aquaculture on the environment is not permanent and will disappear in a short period of time. When the pollutant factors of the seas are considered, the pollution dimensions created by the pollutants such as domestic, industrial, sewage and bilge waters are much more important.
Although it is accepted that aquaculture has a little negative impact on the ecosystem in studies conducted to date, some researchers have reported that environmental degradation has been reported in fish farming enterprises in Europe and shrimp enterprises in Southeast Asia and Latin America. As a result of the rapid increase in aquaculture production in recent years, it is expected that the amount of solid and dissolved wastes left by aquaculture enterprises will increase.
Positive Effects of Fish Feeds on Environment
In addition to the negative effects on the environment, the feeds that are obliged to be used in fish farming (especially in intensive farming) have many positive effects. In particular, its contributions towards the fish farming and supply of fish that the natural environment cannot meet as well as the situation where the need for aquaculture can be met without requiring hunting types that are unconscious, endanger the continuity of populations, and cause the extinction of the species by reducing the expectation of fishery products acquired by hunting should not be ignored.
- Contribution to Sustaining Natural Balance
The production of shelled and aquatic plants in eutrophic waters prevents the increase of nutrient organic substances in the waters. In contrast, aquaculture studies in oligotrophic waters provide increased productivity due to organic and nutrient element excretion.
- Meeting the Nutritional Needs of Other Creatures in the Living Area
The remnants of the feeds used in fish feeding and the metabolic wastes resulting from nutrition meet the nutritional needs of many other species including decayed feeds and ensure the enrichment of areas that are highly deprived of phytoplankton and zooplankton.
- Prevention of Destruction of Other Fish Species in the Region
In intensive cage farms, other fish species that were previously found naturally in the region but are in danger of extinction due to lack of nutrients are fed with the remainder of the fish feed. This provides the increase and continuity of that natural population.