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Department of Thematic Studies Environmental Change
MSc Thesis (30 ECTS credits) Science for Sustainable development
Chao Han
What is the most sustainable
system for fish production in the
Amazon Basin?
2 Copyright
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Abstract
There is a need of increasing fish production due to the rapidly growing population. The Amazon basin has around 1 million km2 of freshwater area, and a substantial part could be an
ideal base for the development of the fish rearing industry. Currently, small-scale fish farming and fishery is commonly observed in the Amazon Basin, but these systems can negatively impact the environment, for example, via eutrophication and overfishing. Here I compare several fish production systems reported for the Amazon Basin to evaluate what is the most sustainable system that should be preferably implemented in that region. I also analyzed the potential of expanding fish farming at the Amazon basin, including a suggestion of the kind of the Amazonian water type and the fish species that should preferentially be recommended as the most appropriate for sustainable production. Blackwater and clearwater main tributaries have been pointed out as the most appropriate areas for fish farming and are recommended as the potential base of fish farming. As there is an existing market for the fishes Colossoma macropomum (Tambaqui); Arapaima gigas (Pirarucu) and Piaractus mesopotamicus (Pacu),
these have been pointed out as the main species to start a sustainable fish production. The analysis of the fish production systems was performed in a way to allow a proper combination of the water self-purification mechanism and the fish culture industry. My main suggestion for sustainable fish production is that:
a) fish rearing location should be changed on a yearly basis in order to decrease the local environmental impact. Water self-purification mechanisms are suggested as the main process to help to ameliorate the environmental impacts of fish farming.
b) Tree seeds and fruits from 26 types of trees that naturally grow in the Amazon basin should be used for fish feeding, especially for tambaqui and pacu.
Keywords: Amazon Basin, Environmental Impact, Self-purification mechanism, Sustainable fish farming,
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CONTENT
1. Introduction ... 5
2. Background ... 6
2.1. Adequate Fish for aquaculture ... 7
Colossoma macropomum (Tambaqui) ... 9
Arapaima gigas (Pirarucu) ... 10
Piaractus mesopotamicus (Pacu) ... 11
2.2 Adequate food for feeding fish ... 12
2.3 Solution of fish farming effluent ... 13
2.4 Filtration activities ... 14
3. Methodology ... 16
3.1 Study area ... 16
3.2 Method selection ... 16
4. Results & Analysis ... 19
5. Discussion ... 24
5.1 Sustainable aquaculture ... 24
5.2 Aquatic environment selection ... 25
5.3 Fish feed replacement ... 25
5.5 Overfishing issue ... 22
6. Conclusion ... 27
7. Acknowledgements ... 28
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1. Introduction
The yearly world aquaculture production increased from 180,000 to 480,000 tons (Subasinghe, 2017) from 2000 to 2013. However, there is still a tremendous gap between total production and fish consumption demand. Aquaculture in South America has increased dramatically in recent decades, and there is still great potential to increase fish production (Valladão et al., 2018). The Amazon basin possessed over 1 million km2 of freshwater resources a certain
amount of freshwater area could be an ideal place for developing the fish rearing industry (Castello et al., 2013).
A wide variety of fish are commonly produced in the Amazon Basin by fish fishery activities like Tambaqui; Tambacu; Pacu; Surubim; Matrinxa and Pirarucu (IBGE/SIDRA, 2014). These species have been confirmed of having great flavor and texture, especially tambaqui (Porto et al., 2018). As the increasing need of aquaculture production in Brazil, the production of tambaqui and pacu have increased 336% from 2001 to 2010 and it still has a growing trend (Borges et al., 2014). Other wild fish species, that are commonly not considered for production, could also be potentially a fish source (Junk et al., 2007).
Traditional ways of fish farming produce high levels of nutrient emissions to the aquatic environment such as nitrogen and phosphorus (Gomes & Silva, 2009). These nutrients could stimulate algal blooming and eutrophication (Verdegem 2013). Is has also to be highlighted that fish farming activities commonly use commercial fish feed which has a negative impact when the leftovers fish feed goes into the natural water flow. Traditional fish farming also requires a variety of basic infrastructure and pond construction. When the fish density become higher in the fish farming pond, it will discharge additional wastewater towards the environment.
To make the aquaculture more sustainable, most studies focused on different treatments of the fish farming effluent, such as using nitrogen removal techniques or wetland fish farming techniques (Crab et al., 2007; Zhang et al., 2011). Regarding sustainable aspects, there is not one clear study that evaluated possibilities to make fish farming in the Amazon Basin more sustainable. In this paper, I intend to evaluate different Amazonian aquaculture systems in order to identify some that have the lowest environmental impact. The idea of ‘sustainable fish farming’ should include the following aspects: a) replacement of commercial fish feed; b) finding the most environmental-friendly way to grow the target fish species; c) the exploration of the potential fish farming area after evaluating the current freshwater resources at the Amazon Basin; d) applying water purification mechanism to reduce the original cost of fish farm management.
The application of the sustainable fish farming concept in the Amazon Basin could bring up several benefits for the local society and also contribute to its preservation, as it would provide a direct profit by natural environments. More fish production could potentially be delivered to the local urban areas also stimulating the local economy and promoting a decrease in impacting fishery activities (Almeida et al., 2009). This way of fish farming would require fewer commercial fish feed and use more of the natural resources which could substantially decrease
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the environmental problems caused by intensive conventional fish farming (Gomes & Silva 2009). Most importantly, avoiding overfishing could potentially be beneficial to the whole biodiversity from the Amazon Basin. This study contributes to the knowledge of aquaculture and also sustainable food production-related journals, for example, “Aquaculture Research and Development” and “agroecology and sustainable food systems”.
This thesis aimed to assess the potential of sustainable fish production in the Amazon basin evaluating and comparing systems for fish production that are described in the literature in order to propose the best sustainable solution. This evaluation has also focused on a system that would avoid the use of commercial fish feed and minimizing the effluent pollution caused by fish farming activities.
2. Background
According to UN projection, the global population is growing and will reach 9.5 billion by 2050 (United Nations, 2015). The growing population also comes with intense urbanization which indicated the increasing demand for food. Food production needs to increase rapidly in order to meet up the global food needed in 2050 (Dooley, 2018). Fish is a great protein source, compared with other protein resources such as beef, pork, and lamb, it has comparatively lower fat content. Besides, using fish as the main protein source is beneficial to human health, it also can effectively reduce the rate of catching diseases (Donaldson, 2018) and greenhouse gas emissions, as cattle are one of the main sources of human-induced GHG (O’Mara, 2011). The fishery industry has long been considered one of the most important fish production sources since 1950. However, the world capture fisheries (including inland and marine fisheries) have become stable for each year’s production since the 1990s, fluctuating around 90 million tons per year (FAO, 2018). Specifically, the UN has indicated that global marine fish stock decreased from 90% to 69% in 2013. Governments from all countries should effectively regulate their fisheries and prevent over-fishing issues (Neumann et al., 2017). As the fish consumption ever grows, there is a need to increase global fish production and aquaculture seems to be one of the best solutions.
The intensive fish farming technology is always conducted in cages, which also require extra labor to manage the culture process and extra input of human-made fish food. Intensive fish farming has the highest level of productivity compared with other types of fish rearing methods and is more auto-mechanized compared with semi-intensive and extensive culture systems. Semi-intensive aquaculture requires more control over the natural environment, always by treating the wastewater and effluent, but it produces larger quantities of food. Under some specific ecological and environmental conditions, this way of fish farming can substantially increase the total production of a natural fishery in certain areas (Asche, et al. 2008).
Extensive aquaculture is the most basic fish farming technique with the last energy and food input during the fish farming process. Extensive aquaculture can be conducted in the ocean,
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natural lakes, and rivers. Fish are mostly fed and nurtured by the environment but with multiple mesh enclosures for easier catching in the harvest season.
Currently, fish production at the Amazon floodplain heavily rely on small-scale fisheries1 and
intensive fish farming2 (Castello et al., 2011; Pinaya et al., 2016). Small-scale fishery means
catching wild fish in natural aquatic systems. However, the wild fish catch is not a feasible way for large scale supply of fish biomass due to the high cost in terms of human power and also due to the risk of overfishing (Cavole et al., 2015).
The mall-scale fishery is closely correlated with local income and nutrition sources (Béné et al., 2007). In the Amazon region, people paddle their canoe to fish at different places such as floodplain lakes, channels, and main rivers. This kind of fishing is done by the use of cast nets, purse, and drag nets (Coomes et al., 2010). The commercial fishing efficiency at the Amazon Basin is dependent on location, boat size, skippers, and therefore it is not possible to evaluate the fish stock at different locations (Almeida et al., 2003). The yield for different fish species is dependent on the period of the year and therefore, the production from this kind of fishery is less stable compared with traditional fish farming methods such as intensive and semi-intensive systems.
Semi-intensive fish farming has already been applied to many Amazonian fish species. According to Ono et al. (2003), at the semi-intensive fish farming system, Pirarucu can reach up to 10 kg of body weight in the first year of growth. Despite the increase of total production, with a larger density of pirarucu in this production system, there is a greater stress load that makes this species more prone to diseases. A study of the different parasites in various tissues of pirarucu has been conducted and confirmed that this way of fish farming can have a detrimental influence on the fish quality itself (Araújo et al., 2009).
2.1. Adequate Fish for aquaculture
Based on the existing and available knowledge from the literature, only very limited fish species are suitable for sustainable fish farming at the Amazon Region, because of the area limitation and food demand. There have been big concerns related to the invasive species that may cause interbreeding and even diseases spreading (FAO 2005) and therefore foreign species such as
Oreochromis niloticus (tilapia) should not be considered for selection. In this way, only native
species should be considered for fish production in the Amazon region.
I prioritized the most common edible fish as the most suitable fish species for fish farming, also considering the rearing period and potential of natural food sources (tree seeds). IBGE/SIDRA (2014) reported the aquaculture production ranking, which was used as a basis for fish selection,. Three types of local fish that accounted for most of the aquaculture production share in this report have been selected as the target species according to the total production and availability
1 Catching existing fish in the wild
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of rearing in the wild (Table 1). The reasons for this choice have been due to a focus on fish species that can live in natural environments and simultaneously be reared by fish farming activities. Species that included the following features were exempt from the selection: long growing period (over 2 years), local ornamental fish species, fish that are not edible and endangered. It should be highlighted that possibly and very likely other species could potentially be appropriate for fish farming activities, but at an early stage, it would be more appropriate to stimulate the implementation of species that are locally known and that have already an existing local market and would have a potential market for export, as these are well-known species.
Table 1. Tambaqui; Pacu; Pirarucu basic information for fish farming (Gomes et al., 2006; Costa et al., 2016; Jomori et al., 2003)
Type of fish
Cultured period
Fish farming
density(x/m2) Farming area Reproduction
System
Tambaqui 12 farming months
5, 10 and 15
fish m2 Pond Nov-Dec
Intensive
Pacu 1-2 years 1.35 fish/m2 pond Nov-Mar
Semi-intensive Pirarucu Phase 1: 3-4 months Phase 2: 9-10 months 1 fish/m2 flooded forests, rivers, lakes, and coastal drainages Waiting for spontaneous spawning intensive
Tambaqui (Figure 1), pacu (Figure 2), and pirarucu (Figure 3) are among the main consumed fishes by Amazonian people (Saint-Paul, 2017). Tambaqui and pacu have omnivore behavior. During the flooding seasons, most of the fishes fed on terrestrial origin items such as a wide variety of fruit and insects (Martinelli, et al., 2006, Oliveira et al., 2006), items that take up a great portion of their diets. Pirarucu is one of the most popular fish farming species in the Amazon Basin as it is considered to have an excellent taste of meat and high market value (Almeida et al., 2013). Under natural living conditions, pirarucu has a very complex reproduction process, more labor observation and special care would be needed when pirarucu comes to the reproduction period. However, even with these characteristics, pirarucu, together with tambaqui and pacu should be considered the most appropriate species for fish farming.
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Colossoma macropomum (Tambaqui)
Colossoma macropomum (Tambaqui) is a common farming species throughout South America
and is the second-largest scaled fish at the Amazon basin (after Arapaima gigas). In the wild, it reaches over one meter in length and 30kg in weight (Goulding & Carvalho, 1982).
Tambaqui is an omnivorous fish that feeds fruits and seeds, while the juvenile always feeds on zooplankton, insects, and decaying vegetation (Saint-Paul, 1986; Lovshin, 1995; Valladão et al., 2018). The adult tambaqui possess the powerful jaw which makes it be able to crush and grind the hard shell of different fruits and seeds such as palm nuts and rubber tree seeds. This could potentially be very interesting for local farmers, as they would not need to rely only on the commercial fish feed and they could also apply other feed resources such as rubber tree seeds that are naturally produced by the forest. Besides, tambaqui is suitable for most of the environments from the Amazon Basin regardless of dissolved oxygen concentration and it also has a remarkable adaptation ability (Saint-Paul 2017).
Figure 1. Colossoma macropomum (Tambaqui) Source:
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Arapaima gigas (Pirarucu)
Arapaima gigas is known as ‘giant of the Amazon River’, it is the largest scale fish at the Amazon Basin, which can reach 200 kg in weight and around 3 m length in the wild (Bezerra et al., 2013). This fish is carnivorous and always fed on different fishes, juveniles, insects, and also fish larvae. Pirarucu does not need to be reared in a pond with high oxygen concentrations, as this species is an air-breathing creature and very suitable for low oxygen farming (Lima et al. 2015). Intensive fish farming techniques have been used as the main production method for the fishery in the wild (Castello, 2015). Pirarucu is a very versatile fish, as it has a high quality of meat with no thorn, and with a low level of fat content. Besides, the leather of the fish can be used in the footwear and clothing industry as well.
Figure 2. Arapaima gigas (Pirarucu)
Source: http://protec.ufam.edu.br/2018/02/27/hidrolisado-proteico-de-subproduto-de-pirarucu-arapaima-gigas-preparado-com-protease-de-aspergillus-flavofurcatis/
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Piaractus mesopotamicus (Pacu)
Pacu is an herbivorous fish that feeds on a variety of resources such as fruits, flowers, leaves, and even tree seeds (Merola, 1988). It is distributed in many countries in South America and it is well known for its flavor (Borghetti and Canzi, 1993). This species can reach 3-7kg of weight in the environment. It is adequate for the fish culture because it is considered to be highly adaptive to different kinds of environments and temperature, compared with other tropical fish species, (Pullela 1998). Besides, pacu is quite adaptive and does not have specific requirements for rearing, and it is also suitable for farming in environments with low oxygen availability. Pacu consumes nuts and tree seeds, which means it will be easy to find fish feed replacement in the forest (Galetti et al., 2008). Finding feed replacement can lower the cost of fish feed and make the fish culture process becoming more sustainable.
Figure 3. Piaractus mesopotamicus (Pacu)
Source:https://www.researchgate.net/publication/308265681_The_combination_of_aquaponics_systems _and_grey-water_recycling_-_Introduction_of_the_Greyponic_system-/figures?lo=1
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Using commercial fish feed does not fit the aim of developing fish farming in a sustainable way, because commercial fish feed contains an extra amount of N and can have a negative impact on the environment (d’Orbcastel et al., 2009). Therefore, finding a local replacement for commercial fish feed is crucial for a sustainable system.
Lucas (2008) and Anderson et al. (2009) evaluated the nutritive value of several Amazonian seeds such as carbon hydrate, protein, nitrites and combined it with information about the nutrition needs of the targeted fish species. They pointed out a list of local tree seeds that could be used for this purpose. Over 30 types of seeds that could potentially replace fish feed had been included. There is still a need for adjustments and tests in order to evaluate the best feeding source, but it is very clear from existing literature, that local tree fruits and seeds are appropriate to be used as feeding sources for fish aquaculture. According to the research conducted by Gomes & Silva (2009), the information on nutrition needs for tambaqui fish farming was collected and compared to natural tree fruits and seeds.
In some fish rearing system, tambaqui was fed by commercial fish meal (Table 2). It should be highlighted (Table 2), that every kilogram of fish feed contains 30 grams of dicalcium phosphate 320 grams of albumin, which are quite positive in terms of nutrition the growth of tambaqui. However, it is unavoidable that fish feed leftovers could harm the environment. Phosphate and albumin would add extra elements to the water body which may lead to the deterioration and eutrophication of the waterbody (d’Orbcastel et al., 2009).
In natural systems, tambaqui can potentially feed on different natural resources such as plankton and tree seeds as its natural diet was considered in consisting of 78-98 percent of fruits (Lucas, 2008). It is evident that tambaqui sometimes can be fed by rubber tree seeds (Goulding 1982),
Table 2. Main constituents of commercial fish feed. (Gomes & Silva 2009)
Ingredient g kg−1 Albumin 320 Gelatin 77 Corn starch 441.3 Soybean oil 60 Cellulose 60 Dicalcium phosphate 30 Vit/min supplement 5 Ascorbic acid 0.5 NaCl 5
Chromic oxide III 1
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as the rubber tree is pretty abundant in the Amazon basin (Schroth et al. 2004). Rubber tree seeds had high amounts of protein and carbohydrate being 30% and 20% of its content respectively (Table 3). These two components are the main energy and nutrition resources for tambaqui growth. Compared to the commercial fish feed, rubber seed has lower phosphorous contents, which could consequently decrease the Phosphorus release towards the environment. Besides, the rubber seed is coming from the rubber tree that naturally grows in the Amazon forest area. In this case, the cost of fish feed could be highly reduced. In addition, there is still a variety of fruits or plant seeds that can be used for feeding Tambaqui (Lucas, 2008), including seeds from 27 woody angiosperms and 4 herbaceous plants. These species provide the tambaqui inland aquaculture with more options of fish feed.
Table 3. Main constituents of rubber seed. (Schroth et al. 2004)
Constituent (wt%) Moisture 9.1 Residual oil 6.2 Carbohydrate 19.9 Protein 30 Ash 6.5 Fibre 8
Pacu is considered one of the most important edible native fish at Amazon Basin (Queiroz et al,. 2005). It has been farmed commercially for many years and fed with formulated fish feed (Takahashi et al., 2011). In nature, pacu was mainly fed by fruits of the palm tree in the wet season, it has been confirmed that over 70% of food residue in the guts is palm tree fruit constituents (Galetti et al,. 2008). Palms are diverse and abundant, and could sometimes be dominant at the Amazon Basin (Vormisto et al., 2004), which indicated pacu have plenty of food resources in the wild. Similar to tambaqui, Pacu could also be fed completely by natural fish feed such as tree seed and fruit.
2.3 Solution of fish farming effluent
Fish rearing activities of tambaqui, pacu, and pirarucu can discharge extra amount of phosphorous and ammonia in the environment (Gomes & Silva 2009; Zadinelo et al., 2015; Bernardi et al., 2018). Gomes & Silva (2009) followed wastewater effluents of tambaqui growth at different rearing ponds and they observed that relatively high levels of P and N release in all rearing ponds. These authors observed that the average weight gain and total yield of fish reared in a fertilized (with extra urea and superphosphate) pond were 20% higher than from Natural water ponds, however, the fertilized pond could have a higher release of N and P. It can be assumed that fish farming using processed pond will have a more negative impact on the environment. Compared with using processed pond system, using freshwater resources can discharge less emission of N and P.
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Local people in Amazon basin have set cages in the freshwater resources such as reservoir and lakes for fish farming, and they fed fishes using commercial fish feeds (Fisheries, F.A.O 2011), the food residue of the commercial fish feed will discharge unwanted extra nutrition and cause water body pollution (d’Orbcastel et al., 2009). However, very little detailed research has been reported in the scientific literature.
Fish farming effluent is a topic that needs to be properly addressed in a sustainable fish production system. The commonly used way for fish farming effluent treatment is constructed wetland technology and reuse of wastewater (Naylor et al., 2003; Turcios and Papenbrock, 2014). However, in the Amazon Basin, the construction of man-made wetlands will pose other environmental threats towards the forest.
One study from Jia et al. (2015) suggested that water self-purification mechanism, relying on plant adsorption, natural sedimentation, biological process, etc. could be applied for the fish farming industry. The Amazon Basin itself has a high diversity and abundance of the aquatic environment, densely colonized by aquatic macrophytes that could, therefore, be used as a water self-purification mechanism for a sustainable fish farming program.
The self-purification mechanism is a strategy to use natural processes that clean the water body maintaining its pristine condition when impurities coming from outside the environment (Ostroumov, 2003). This mechanism can remove or lower the level of nitrogen and phosphorus, which can be a useful tool to solve the water body pollution such as eutrophication.
The function of water self-purification covers a wide range of physical, chemical, and biotic processes (Wetzel, 2001). Some of the major functional processes of self-purification mechanism are:
2.4 Filtration activities
The evaluation of water self-purification systems should always include physical, chemical, and biological factors and processes.
Biological filters consisted of the use of different animals and plants, being the first one invertebrate filter feeders, animals that fed on suspended organic matter and other food leftovers from fish farming or other human activities. The filter feeders in self-purification systems are mainly used during the cleaning process to increase sedimentation and suspended solid reduction (Wahab et al, 2017). The use of aquatic macrophytes is another constituent of the filtration activity, as they have a high rate of assimilating nitrogen and phosphorus (Christiansen, 2014). Macrophytes can also assimilate nitrate that originates from other human activities. Amazon basin is abundant of macrophytes in freshwater systems such as floodplain and other tributaries (Silva et al., 2013). As the function mentioned in the previous paragraph, it can be used as a tool to ameliorate the freshwater condition in the Amazon basin. In terms of biological process, hydrobiont (the organism that lives in water) can contribute to the removal of
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suspended particles and chemical pollutants from the water body, in some cases, cladocerans are able to filter 40ml of water per individual per day (Wetzel, 2001). Benthic animals are present in river bottom sediments and consume high amounts of organic matter and even biogenic pollutants (Ostroumov, 2003). Besides, benthic organisms can sometimes serve as a binder to connect chemical pollutants and biogenic substances as the accumulation of the pollutants (reference). Regarding the removal of C, N, and P, which are the culprits of the water system eutrophication, it can be removed from the water body by different processes. The imago insects can play an important role in the removal of C, N, and P, when the insects complete their larva period, they will be able to take away the nutrients from the water surface. According to Wetzel (2001), the emergence of imago insects can take away 0.5 g C/m2 per year from the
water surface. Fish and bird-eating processes can also be a way to decrease the amount of N, and P (Ostroumov, 2003) from the water column. In the fish farming area, most nutrients will be consumed by fish eating processes. However, there are still nutrients leftover that could be a threat to the environment.
In terms of physical processes, a large range of dilution, adsorption, sedimentation, and evaporation (Ostroumov, 2006) have been used for this purpose. Fish farming activities always produce a huge amount of excremental feces of the fish, which are difficult to collect and reuse. Physical sedimentation decreases particles in the water column and incorporates fish waste to the sediment of the river bed, it would be consumed by organic matter degradation. In some integrated agriculture-aquaculture systems the mud of the fish farming area could be used as a source of nutrition to the plants (Yi et a., 2002). The absorption can happen when there are suspended particles which could be a help for diluting the water body (Ostroumov, 2003).
Very little of experimental research has been conducted of chemical self-purification mechanism. It has been shown that photochemical degradation can accelerate the degradation speed of organic matters from fish farming wastewater, including protein, fat, and sugar (Spencer et al., 2009), however further research about the photochemical degradation process needs to be done in the Amazon basin area.
The natural water purification process could be an effective method to solve eutrophication problems from different water bodies (Ostroumov, 2005). Self-purification means that the water body itself can contribute to the reduction of pollutants, this mechanism also could be regarded as a way of ecological regulation. The self-purification system of the water body is a complicated mechanism that includes physical, biological, and also chemical processes. (Ostroumov, 2010).
To the best of my knowledge, only a few studies have been carried out to examine the function of water self-purification in the Amazon Basin. It is also very difficult to decide and monitor the impact factor of this mechanism. Although the Amazon Basin is shrinking to 80% of its original total area, it still has a huge amount of freshwater resources (Davidson et al., 2012). By taking advantage of the water self-purification mechanism, the fish yield in Amazon Basin can increase in a sustainable way.
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3. Methodology
3.1 Study area
The Amazon river basin covers 7,351,000 km2 in South America, which is the largest rainforest
in the world (Junk et al. 2007). The flooded forest scatters the whole Amazonia, spreading its tributaries and its branches, consisted of lakes, igarape, and seasonally flooded area, covering an area that varies from 14 to 29% of the total Amazon Basin (Castello et al., 2013). Besides, the Amazon Basin has the world’s largest diversity of freshwater fish species (Reis et al. 2003), so it has a great potential for the development of the fish farming industry with enough water resources and abundant fauna. The Amazon water bodies can be divided into white, clear, and black waters (Sioli, 1950).
There is a high diversity of aquatic environments at Amazon basin, including wetlands, igarapes3 (streams), igapos4, varzeas5, and lakes. The wetlands in Amazon Basin varies from
seasonal and permanent and have a rich biodiversity that supported by a wide range of animal and plants. 12% of Amazon’s wetlands is overlapped with the Amazon floodplain, presenting unstable water storage and consistency (Melack & Hess, 2010). A number of Igarapes with steady water flow has been enclosed and used as a small-scale fish farm in Amazon Basin Costa et al., 2016). The characteristics of Igapos are similar to the floodplain, also created by seasonal inundation for several months in a year, it always formed with black water and with a yearly variable water storage and flow (Haugaasen & Peres 2006).
Even though the Amazon Basin has a variety of aquatic environments, currently only a few of them are used as the local fish farming base (Costa et al., 2016; Valladão et al., 2018). Most fish rearing activities are conducted in human-made or natural ponds, otherwise, the fish production is coming from wild fisheries (Coomes et al., 2010). Although some parts of the pristine Amazon Basin water resources have already been destroyed by human activities such as dam construction in the Amazon Basin area (Latrubesse et al., 2017), this is still just a minor part of the available freshwater area. If a minor part of natural water resources were sustainably used for fish farming, the Amazon Basin could have a great amount of fish production per year with the least impact on the environment.
3.2 Method selection
This paper was based on a review of the existing literature and data collection as the empirical work. The material included peer-reviewed literature and some grew literature, like reports from the Food and Agriculture Organization (FAO). The searching process had a focus on major topics and to gather information for each of them, a combination of literature selection, information/data collection was performed according to the topic. This procedure was performed with a focus on the aim of assessing potential sustainable fish production in the Amazon Basin, regarding the freshwater system, fish food replacement, and solution for the
3 Branches of the Amazon mainstream, characterized by low-depth and always flows in forest 4 Blackwater-flooded forest
17 aquaculture effluent.
The concept of sustainable fish farming has been brought up many years before (Reinertsen and Haaland, 1995), and has been applied in Japan, Norway, Australia, by focusing on the source of feed ingredients, breeding approaches, topography, etc.(Olesen et al, 2011; Cheshire and Volkman, 2004; Yokoyama 2003). However, to the best of my knowledge, sustainable fish farming has never been applied at Amazon Basin according to current literature. This is the first evaluation of sustainable fish farming at the Amazon Basin, which will combine literature from different areas such as fish farming techniques; fish food replacement and effluent solution.
Several procedures were conducted in order to ensure a high-quality literature review, the evaluation of different systems for fish production performed queries in the web of knowledge databases: Web of Science, Google Scholar, ScienceDirect, Society for conservation biology, Wiley Online Library and Linköping university Online Library. In terms of Amazon freshwater site selection. Keywords and expressions chosen to establish database queries were: keywords and expressions chosen to establish database queries were: “fish farming” or “aquaculture”, “freshwater ecosystem” AND “Amazon Region” or “Amazon Basin”. The queries searching time range was selected from 2009 to 2019, because this was the decade that the global interest and awareness of sustainability has highly increased. It was not the aim of this study to make a meta-analysis or a systematic review of this topic, but rather to identify the most appropriate papers that directly connect with the main aim of this thesis. It is not possible to identify all relevant articles using the same term for once only. The queries were defined by the combination of two or more keywords listed before, resulting in identification between 22 to 86 articles on the Society for conservation biology. In addition to the database searching, a number of articles were located through the reference lists in relevant articles, the searching results were analyzed according to several criteria, First, the sources had to be primary source research, any source that focused on secondary source research were removed in the first round, second, the sources have to be from a peer-reviewed journal and I excluded the rest that is not, third, I reviewed all the titles and abstracts of the results to make sure that articles are in line with the purpose of my research that based on research aim and also removed all those articles which are, a) focused on other subjects such as the physiological feature of fish species, b) focused on fish species in other regions instead of the Amazon Basin. When examining the data from the articles, I searched for statements that demonstrated a proper research procedure conducted, and the data provided is correlated with my purpose (detailed freshwater type and water quality type). As the high impact factor of this journal (4.842) and high citation times (149 times) promised its reliability and validity, research of Castello et al. (2013) was used as the main reference for this thesis as it detailed explained, in a comprehensive way, the variety of aquatic environment of Amazon Basin adequate for fish production. I could not find others articles or book with such deep analysis. Castello et al (2013) enumerated some specific water types that match the fishes living condition, Further fish species monitoring will be required in future research. There are various water types such as tributaries and branches that are not suitable for fish farming. They are needed to be classified and analyzed by the water condition (flow speed, area, contaminant), in order to make sure the environment is appropriate to conduct fish farming activities.
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Regarding local fish farming effluents, the keywords chosen for quires were ‘environmental impact’, ‘aquaculture management’ AND ‘Tambaqui’, ‘Pacu’, two or more keywords could result in 112-682 journal articles on Wiley Online Library. Articles were selected in a similar way with the previous query, I removed secondary source research and focused only on peer-reviewed journal, ensured the journals I used had the most updated publication date, articles going back no further than 2009. During the examining process, I acquired a huge number of irrelevant articles, such as papers related to microelements need of fishes (Araújo et al., 2016), and also growing parameters of juvenile phase (Fiúza et al., 2013). After reading all these articles’ keywords and abstracts, I excluded all these articles that are not in line with my original purpose. This part of the review only focuses on fish farming effluent in the local farming process. According to these criteria, information related to fish farming pollution was based on Gomez and Silva (2009), which was the main article related to the aquaculture water environment comparison in Amazon Region. These authors conducted experiments in different ponds (natural and human processed ponds), and, as expected, they found out that the release of nutrients and pollutants is much lower in natural than in human processed ponds.
Using commercial fish feed will not fit the aim for sustainably developing fish famring, because Commercial fish feed contains high extra amounts of N and can have a negative impact on the natural environment (d’Orbcastel et al., 2009) and as this would not fit the principles of sustainable fishing. Therefore, finding the replaced by natural and local feeding sources of commercial fish feed is crucial. The keywords for this query were ‘fruit consumption’, ‘local fish’, ‘Amazon Basin’, the keywords led to 586 journal articles in Wiley Online Library, articles are selected according to the following aspect, 1. Original research paper, 2. Peer-reviewed journal, 3. Contains the target fish species such as Tambaqui, Pacu and Pirarucu. A variety of articles mentioned the relationship between tree seeds, fruit, and local fish consumption (Correa and Winemiller, 2014; Arantes et al., 2017), which also linked the local frugivorous fishes with the changing environment at Amazon Basin, Lucas (2008) elaborated thoroughly about all kinds of seeds at Amazon Basin, and observed that over 30 types of seed are included, the detailed nutrition of seed and could potentially be used for feeding fish in aquaculture, the replacement feasibility of fish feed needed to be tested in the future research.
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4. Results & Analysis
Local people in the Amazon Basin used fishery as their main fish production sources and gradually developed fish farming techniques (Junk et al., 2007). Amazon locals use different farming systems such as intensive and semi-intensive system as the major fish farming techniques (Fisheries, F.A.O 2011). Currently fish production in the Amazon floodplain heavily rely on small-scale fisheries6 and intensive fish farming7 (Castello et al., 2011; Pinaya et al.,
2016). Small-scale fishery means catching wild fish in natural aquatic systems. However, the wild fish catch is not a feasible way for large scale supply of fish biomass due to the high cost in terms of human power and also due to the risk of overfishing (Cavole et al., 2015).
Castello et al. (2013) were used as the main reference for aquatic environment selection for this thesis as it detailed explained, in a comprehensive way, why the most adequate Amazonian type of water are black and clearwater types and that inundated area in the flooding season are the most appropriate aquatic environment for fish production. Blackwater rivers have usually a slow speed, flowing through swamps and sometimes wetlands covering an area of 21,600 km2
in the whole Amazon basin. Blackwaters have lower nutrition levels than white and clearwater and have acidic pH (Janzen, 1974; Ríos-Villamizar et al., 2013). Clearwater tributaries have appropriate dissolved oxygen and relatively low level of suspension solid, the pH level is neutral which is a suitable living place for many fish species (Ríos-Villamizar et al., 2013), and those occupy an area of 48,500 km2 (Castello et al., 2013). These areas could be considered as
the most appropriate place for natural fish farming in comparison to white waters. In the black and clear water bodied water conditions like flow speed, area, and presence of contaminants have to be taken into account in order to make sure that the environment is appropriate for fish farming activities.
Information related to fish farming pollution is covered by relatively vast literatures. However, their fish species in focus usually are salmon and tilapia (Wang et al., 2012; Baccarin and Camargo, 2005). As effluent information is very limited and absent for pacu and pirarucu. Literature was found about tambaqui, one of the targeted fish species in this study, the study from Gomes and Silva (2009), authors have conducted experiments in different ponds (natural and human processed ponds), and, as expected, they found out that the release of nutrient and pollutants is much lower in natural than in human processed ponds.
As a result from the search for “treatment”, “fish effluent”, “feed ingredients’’, resulted in some studies indicating that the leftover of commercial fish feed accounted for one of the main sources of fish farming effluent (Aboutboul et al., 1995, Kuhn et al., 2010). The commercial fish feed contains high amounts of N and can have a negative impact on natural environments (d’Orbcastel et al., 2009) and as this would not fit the principles of sustainable fishing, the commercial fish should be replaced by natural and local feeding sources.
Frugivorous fish plays an important role in dispersing seeds in the Amazon Basin (Parolin et
6 Catching existing fish in the wild
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al., 2013). Diet assessment of fruit-eating fish like tambaqui indicated that Tambaqui and Pacu accounted for up to 35% seed dispersal of lianas and trees during the flood season (Anderson et al, 2009). Lucas (2008) evaluated several kinds of available seeds at the Amazon Basin and observed that over 30 types of seed could potentially be used for feeding fish in aquaculture. The commonly used way for fish farming effluent treatment are constructed wetland technology and reuse of wastewater (Naylor et al., 2003; Turcios and Papenbrock, 2014). However, at the Amazon Basin, the construction of man-made wetlands would have an extra energy demand, and this system may not have a high performance in removing nitrogen (Chen et al., 2009; Liu et al., 2015). One study from Jia et al. (2015) mentioned that water self-purification mechanisms, relying on plant adsorption, natural sedimentation, biological process, etc., could potentially be applied to the fish farming industry. The Amazon Basin itself has a highly diverse and complex aquatic environment, highly abundant in aquatic plants, and water self-purification mechanisms could be a potential method for the sustainable fish farming program. Once the most suitable rearing system is selected, the sustainable fish farming program could be further analyzed by field tests.
Table 4. Main fish farming techniques in the Amazon Basin. (Arbeláez-Rojas et al., 2002; Gomes et al., 2006; Junk et al., 2007; Valladão, 2018). N/A= data not available
Farming Techniques
Fish feed Densities Location Pollution Type
Fishery Natural fruits N/A natural lakes and rivers
N/A Extensive
Farming
N/A N/A N/A N/A
Intensive Farming Artificial fish feed 10-50 fish/m3 Cage ； igarapé channel
Discharge into the natural water body Semi-intensive
Farming
Artificial fish feed
1-9 fish/m3 Pond；Reservoir Discharge into the natural water body
Fisheries were considered as the main method to acquire fish in the Amazon region. Fishermen could apply over 15 types of fishing tools to catch fish in the wild, including harpoons, hooks, different types of nets, etc. (Junk et al., 2007). The fishing potential in the Amazonian was regarded inexhaustible in the last decades, due to the fact that many aquatic environments in the Amazon basin were brown and black water, which have low nutrient content and relatively low fish density (Molnar et al., 2000). As the growth of population, the continuous fishery will not meet the demand of local protein needs and it may lead to overfishing issues (Campos et al., 2015). Over the last years, there has been an increase of aquaculture in reservoirs, lakes, and rivers performed by local fish farmers. Fishery is still considered as a source of protein for local people, besides, very limited fish farmers use raceways to farm tilapia and rainbow trout (Fisheries, F.A.O 2011).
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farming and semi-intensive fish farming8 (Valladão, 2018). These ways of fish farming mainly
rely on the human-made fish feed and discharge wastewater towards the environment. In Brazilian Amazon, fish farmers use small fish cages to raise tilapia and local fish species such as tambaqui and pirarucu. This method has been applied to the whole country and became popular in all major reservoirs (Fisheries, F.A.O 2011). Aquaculture was also conducted in small dams in Amazon Basin, which can help to increase fish production. However, the ecological barrier was shown in fish farming dams and cause species richness and diversity alternation (Sousa et al., 2018).
Selecting one existing cultivation system in Amazon Basin will not help to completely prevent aquatic pollution. Traditional way of fish farming can have negative impacts on the environment, especially due to fish feed inputs and effluent discharge. The environmental impact on fish feed input depends on a high feed conversion ratio, low economic feed conversion ratio will cause more residual nutrition accumulated towards the waterbody which can lead to eutrophication and acidification (Nhu et al., 2016). Nutrient release emission through effluents was the main reason for the eutrophication of water bodies, most specifically due to the release of phosphorus during the production process (Gomes & Silva, 2009). There is a need to find another way to increase protein production with the least environmental impact. Solution for a more sustainable fish farm
As the whitewater tributaries create much turbulence, which will pose threat to fish farm management, whitewater will not be considered as the option for this program, The background of the freshwater system in Amazon basin indicated that the floodplain from the main tributaries from blackwater and clearwater could be ideal areas for the expansion of fish farming, the water flow is relatively slow and easy to enclose an area for fish farming.
According to the background, the sustainable fish farming program should start with the species that currently edible and easy to farm. Tambaqui, Pacu, and Pirarucu are already appreciated edible fish species at Amazon Basin and are easier to cultivate, as many fish farmers currently are cultivating these species (Fisheries, F.A.O 2011). Therefore, I choose these three species as the target fish for expanding fish production at Amazon Basin.
Fish farming in the enclosed area discharges phosphorous and ammonia to the environment, as there are quantities of fish feed leftover and fishes’ metabolic emissions. (Zadinelo et al., 2015; Bernardi et al., 2018). Using natural fish feed such as plant fruits and seeds has lower phosphorus compared with commercial fish feeds, which could effectively reduce the fish farming waste towards the environment, however, extra labor work on tree seeds collection is needed. The water self-purification mechanism could also be a feasible solution to deal with the relatively high nutrient levels from this fish production, as it will contribute to pollution reduction by naturally conducting physical and biological processes. Here I decide to combine replacing fish feed and using water self-purification as the strategy for sustainable fish farming. I also suggest that it would be better to change the fish farm area every 3 years. For the floodplain in the Amazon basin, in dry seasons, selecting different locations with abundant
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water resources and use only several of them setting an enclosure to develop fish rearing activities. Changing the location every 3 years to let the fish farm places doing the self-purification process by the floodplain itself. For the tributaries and other rivers, it is better to start the location from the upstream of the river, since that the water movements can transport the pollutants to the downstream, the waterbody from upstream to downstream can do the self-purification simultaneously. (Mobile fish farming strategy) In the moving water body, it is also required to alter the fish farm location per year or 3 years, in order to avoid the irreversible degradation of the water body. During the culture process of feeding enclosure in the stream and floodplain, this research encourages using natural resources such as tree seed and fruits instead of using the commercial fish feed.
Potential fish production
I did a very conservative estimate of fish production in the Amazon. In case only 0.5% of flood plains area from the blackwater and clearwater environments and only from the major Amazon Basin tributaries are used for fish farming, the area available for sustainable fish aquaculture would be 1.18×105 km2.
Using tambaqui as the main target species, each adult fish considered as 0.8kg of market weight (Costa et al, 2016), and a conservative fish density of 5 individuals per square meter (according to Table 1), it is estimated that the fish production would be 5.25*105 tons per year after the
following formula:
𝑇 = 𝐴 × 𝑊 × 𝐸𝑠 × 𝐷𝑠 × 𝐺 where:
T: Estimated production per year (tons) A: Potential area for fish farming (km2)
W: Water coverage percent (%)
Es: Estimated fish farming expansion area percent (%) Ds: Density of target fish (fish/m2)
G: Market weight per fish (kg)
T=1.18*1011m2*22%*0.5%*5*0.8= 5.25*105 tons
As above calculated, using 0.5% of freshwater resources in the Amazon basin could have 525,000 tons yield of tambaqui production. According to data from the World Bank, the production could take up around 3/4 of the total production of Brazil (722,560 tons).
Overfishing issue
As mentioned in the last section, fishing activities in the low-income area accounted for the most of fish production, also contributed to the local nutrition sources and cash-income (Bene et al. 2007). However, local people usually are not commonly aware of the impact of overfishing. According to Petrere (1978), in the 1970s, the Colossoma macropomum (Tambaqui) was the most common fishery species in the fishing harbor of Amazonia freshwater fisheries, Manaus, and accounted for 40% of the total fishing production. In the following decades, tambqui percentage of total fish production has fallen to only 10%. This figure continuously fell to 5%
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at the end of the 20th century (Batista & Petrere 2003). As the growth of the population since the 1970s, the fishing intensity has grown much higher than before (Campos et al., 2015), which indicated the fishery managers need to take steps to keep the fishing industry survived and avoid the tambaqui being further overexploited.
Figure 4 The pirarucu population density in 41 communities of lower Amazon Region and associated population status (Castello et al., 2014)
Pirarucu is the largest freshwater fish in the world, which originated from South America. As one of the most popular edible fish species, pirarucu has decreased substantially due to overfishing at Amazon Basin, it also confronts with the threat of extinction in some of the local communities. In the study of Castello et al. (2015), they investigated the Arapaima gigas population density in 41 communities of the lower Amazon region (Figure 4). The population density in 76% of selected research communities is depleted. The pirarucu in 19% of communities is even extinct. Only very few of the communities have a well-managed pirarucu population density. There had been a discussion of the reasons for pirarucu depletion, floodplain deforestation or overfishing? However, according to research conducted by Castello et al. (2014) and Ngor et al. (2018). They suggested that the overfishing is the main reason for the depletion of pirarucu, not deforestation of the floodplain.
The overfishing issue can have a variety of impacts on the environment. The frugivorous fishes were important protein and income resources of the local people of Amazonia. In the past five decades, frugivores hav been overhunted, which have led to the disruption of the mutualism between fruit-eating fishes and plants (Correa et al., 2015). There are over a hundred types of frugivorous fruit-eating fishes in South American wetlands eating fruits and taking care of the seed dispersion (Horn et al., 2011). As the ongoing overfishing of the frugivores fish in the Amazon basin area, the seed dispersal quality and quantity can be compromised, which have a huge impact towards on the local ecological system (Correa et al., 2015).
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5. Discussion
5.1 Sustainable aquaculture
The traditional way of developing the fish farming industry is to converse the original land or water resources to introduce aquaculture, which always has impacts on the environment and can cause ecological damage (Fuchs et al., 1999). This way of fish farming in the Amazon basin can gradually discharge pollutants to the natural environment which may cause irreversible environmental issues, it will also disrupt the natural resilience function. Several components formulate a sustainable aquaculture system, the combination of farming systems, resource usage (including land, water, energy), and suitable aquaculture inputs (seeds, feeds, infrastructure, and labor) (Fisheries, 2014). In this fish farming expansion research, I have analyzed the potential of fish culture expansion at the Amazon Basin area, also considered the current fish farming technology, overfishing issue, and pollutants possibility. Construction of fish farming facilities will pose a threat to the Amazon natural environment, for example, construction waste. In this case, this research suggests a mobile fish farming strategy, and also recommends that the water self-purification mechanism should be combined with fish rearing techniques and also change some of the ongoing traditional commercial fish feed, this way can help to reduce fish farming effluent and cost of fish meal. The implication of self-purification mechanism will contribute to the sustainability of local fish production and also increase the fish production, the idea proposed fits the original aim of this research, which is to compare with different aquaculture systems to find out what is the most sustainable system for fish production at Amazon Basin. In this case, the local economy could be improved since fish yield has been one of the major income sources in the Amazon Basin (Junior et al., 2018).
The original aim of this thesis is to find out the most sustainable system for fish production in the Amazon Basin. The concept of sustainable aquaculture can refer back to 20 years, a variety of literature have proposed ideas to make aquaculture more sustainable and eco-friendly. Fish feed can be produced using substitute protein such as soybean, corn gluten instead of human-made fishmeal, which could help to increase the feeding efficiency and discharge less food leftover to the environment (Morikawa 1999). Integrated farming systems such as aquaculture-agriculture combination are also applied for sustainable development, this system uses aquaculture effluents and excavated muds as fertilizers to enhance agriculture productivity and avoid over-enrichment of the waterbody (Frankic & Hershner, 2003). Besides, using nitrogen removal techniques or wetland fish farming techniques (Crab et al., 2007; Zhang et al., 2011) also contribute to aquaculture sustainability. For the best of my knowledge, there is no available published paper in the literature focusing on a sustainable fish farming system at Amazon Basin like it is proposed in this paper, compared with previous sustainable aquaculture studies, this research proposed sustainable aquaculture idea that suits only Amazon Basin and focused on four sectors: Fish selection; Water resources type; Water self-purification mechanism and using the natural fish feed, the elements of each sector have been evaluated respectively in individual studies. Fish species such as Tambaqui, pacu and pirarucu are verified that can be reared by different fish farming system, and the information about rearing environment and habitat is already available (Gomes et al., 2006; Costa et al., 2016; Jomori et al., 2003). The ideal kind of water ideal for the fish population and the living condition has been previously evaluated
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(Goulding, 1980; Castello et al., 2015; Castello et al., 2013), but are not specifically related to fish farming in natural environments. Therefore, fish farming activity in the natural flooded forest needs to be further evaluated in the future. In terms of water self-purification mechanism, the incorporation of this mechanism with fish farming activities had been introduced before and evaluated by several pieces of research, but mainly in lakes and reservoirs, but and not specifically in the Amazon region(Yan et al., 1998; Jia et al., 2015; Han et al., 2015). Implementation of this mechanism has never been conducted in the Amazon Basin area. The replacement of commercial fish feed with natural tree fruits and seeds were proved to be a very accessible and feasible strategy, but the fish growth rate and speed could be different (Roubach and Saint‐Paul, 1994), indicating that tambaqui could be fed by natural fruits and seeds with the suitable protein content. However, this study mentioned over 20 types of natural tree seed, the exact amount of protein content and feasibility of using certain type tree seeds need to be deeply evaluated in further research.
5.2 Aquatic environment selection
The water environment for aquaculture expansion was evaluated based on relevant literature. Black and clear water types were selected as the target area for conducting fish farming activities (Castello et al., 2015). Seasonally fluctuating water levels heavily influence the dynamics of fish population and also related fish production in the Amazon basin, the rise of water level could trigger a sudden increase of fish population as a number of spawn and other fish species will flow into flooded area due to the rising water level (Castello, 2008). As spawns and fishes flow into the newly flooded area, the growth speed of spawns and fishes will increase because the newly inundated area will have fewer competitors of plant-based food resources such as tree fruits, seeds and algae (Goulding, 1980). Despite the inundated area has an abundant fish population in the rising water level period, it may potentially not be suitable for sustainable fish farming activities, for the steady water resources could not be guaranteed all year round and the flooded area could not be predicted and located all the time. In this case, the chosen inundated water area should carefully be chosen in a way that it has always available some water making that area suitable for sustainable fish farming activities.
5.3 Fish feed replacement
This proposal indicated that commercial fish feed should be replaced by natural fish feed such as tree fruits and seeds. Some publications indicated that the extra phosphorus constituents are needed because the added amount of phosphorus helped the fish to obtain the optimum growth and nutrient body retention (Morales et al., 2018). The nutritional requirements of tambaqui larvae growth are sufficient, but not much information related to nutritional requirements for the growing stage of tambaqui is currently available (Rodrigues, 2014). However, tambaqui growth rate related to P and N still needed to be further evaluated. Replacement of commercial fish meal can help to reduce the P discharge towards the water body, which can contribute to long-term sustainable aquaculture. Despite the environmental concerns of commercial fish feed, the growing price of fish feed also needed to be considered. Using natural fruits and seeds as the fish meal will completely cover the cost of commercial fish feed in aquaculture. The collection of tree fruits and seeds by the local population could open up a new income for them. Currently, the tree seeds that are collected by local people are used for forest restoration or
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direct local market selling. However, tree seed collection for aquaculture has never been promoted at Amazon Basin. The seed collection hasn’t applied to many species (Weber et al., 2001; Knowles et al., 1995), therefore, the seed collection process will require extra labor charge and time. Besides, the flooded season will surely hamper the seed collection process, which added up the extra burden on the collection of seeds and fruits (Oghenekome, 2004). 5.4 Minimize fish farming effluent
Previous studies about sustainable fish farming are mainly concentrated on the treatment of effluent and at the same time, minimize the environmental impact of fish farming (Frankic& Hershner, 2003). Other techniques are also effective for decreasing fish farming wastewater such as reuse of water from the fish pond and the development of filter technology. It is inconvenient to introduce large-scale fish farms and aquaculture infrastructure because of the vulnerability of the Amazon basin. Constructing a dam and its related facilities have already posed threat to the local ecological environments and disadvantages are continuously being exposed (Castello et al., 2013). Here, this research introduces the natural water self-purification mechanism that has never been used in the aquaculture area. This water mechanism only relies on nature elements such as gravity fall, absorption, microorganisms, fishes and even insects (Ostroumov, 2005). Without human resources input, this mechanism working only require two things, enough time and space, which makes it extremely suitable for its implementation in the Amazon Basin area. Fish farming activities always have a variety of pollutants in the wastewater which has a detrimental impact on the environment (Gomes & Silva 2009). Connecting the fish farming and water self-purification function would potentially reduce the wastewater treatment cost, and at the same time, increase the fish production without other environmental impacts such as eutrophication. The water self-purification utilization could be more effective when the mobile fish farm was set in the upstream, because the water flow can gradually transport the pollutants towards downstream, during the process of transportation, pollutants will be separated to a different area by natural settling process, which helps to conduct water self-purification in the different area simultaneously and receive a better result.
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6. Conclusion
(1) The Amazon basin is an abundant area of freshwater resources, and the most suitable for expanding fish farming are floodplains from blackwater and clearwater. Further research about the implementation of fish production in small streams should be conducted in order to open up another big perspective in terms of productive areas.
(2) Overfishing could bring a negative impact towards Amazonia’s ecological system including the food chain and the dispersal of tree seed (plant regeneration could be affected). Developing sustainable fish farming could be a solution to reduce the unfriendly environmental fishery activities.
(3) Tambaqui and pacu are suitable for the fish farming expansion project due to its adaptation to several habitats. Both species can be fed by natural substitution such as rubber tree seed and 26 more seeds option. Pirarucu could also be pointed out as a potential candidate, but finding the food replacement for pirarucu should be the priority before expanding pirarucu fish farming scales.
(4) Water self-purification can be applied to the fish farming industry, including physical (absorption, sedimentation), chemical (photochemical degradation, redox process) and biological (filtration process and removal by animals).
(5) The expansion of fish farming activities in the floodplain should start at dry seasons and changing location yearly for the water self-purification. In the main tributaries or rivers, the fish farming expansion should start from the upstream, in order to disperse the pollutants and help the water body to do self-purification simultaneously in both upstream and downstream.
(6) There is a huge potential to increase the Amazonia fish yield in a sustainable way. Farming 0.5% of the clear and black water floodplain area in consumption could add a huge amount of fish production of the Brazilian fish farming industry. The amount of fish biomass that would be produced by applying this sustainable concept in only 0.5% of the floodplain area of the Amazon basin could be 5.25*105 tons per year, a value that equals to 3/4 of the current
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7. Acknowledgements
Foremost, I would like to express my gratitude to my advisor and also supporter Assoc. Prof. Alex Enrich Prast, who has continuously supported my Master thesis study and research process. He first raised the original idea of my study and helped a lot with the researching and also academic writing. I really appreciate his enthusiasm and broad knowledge about the Amazon Basin area.
Besides, I also really appreciate Doctor Angela Sanseverino’s help for the discussion and also information about fish farming regulation searching. Her help is really important for the background information collection in the research.
My sincere thanks also go to Program Director Teresia Svensson, who helped me a lot with the thesis course arrangement and finding the perfect advisor for my Master thesis.
Finally, I must express my appreciation to my parents for all support and continuous encouragement through my 2 years of study. The completion of the thesis will absolutely not possible without them. Thank you so much.
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8. References
Aboutboul, Yossi; ARVIV, Roy; VAN RIJN, Jaap. 1995, Anaerobic treatment of intensive fish culture effluents: volatile fatty acid mediated denitrification. Aquaculture, 133.1: 21-32.
Arbeláez-Rojas, G. A., Fracalossi, D. M., & Fim, J. D. I. 2002. Body Composition of Tambaqui, Colossoma macropomum, and Matrinxã, Brycon cephalus, When Raised in Intensive (Igarapé Channel) and Semi-Intensive (Pond) Culture Systems [Composição Corporal de Tambaqui, Colossoma macropomum, e Matrinxã, Brycon cephalus, em Sistemas de Cultivo Intensivo, em Igarapé, e Semi-Intensivo, em Viveiros]. v. 31, n. 3.
Anderson, Jill T., Joe Saldaña Rojas, and Alexander S. Flecker. 2009 "High-quality seed dispersal by fruit-eating fishes in Amazonian floodplain habitats." Oecologia 161.2 (2009): 279-290.
Almeida, I.G., Ianella, P., Faria, M.T., Paiva, S.R. and Caetano, A.R., 2013. Bulked segregant analysis of the pirarucu (Arapaima gigas) genome for identification of sex-specific molecular markers. Embrapa Amazônia Oriental-Artigo em periódico indexado (ALICE).
Almeida, O.T.D., Lorenzen, K. and McGrath, D.G., 2003. Commercial fishing in the Brazilian Amazon: regional differentiation in fleet characteristics and efficiency. Fisheries Management and Ecology, 10(2), pp.109-115.
Almeida, O.T., LORENZEN, K. and McGrath, D.G., 2009. Fishing agreements in the lower Amazon: for gain and restraint. Fisheries Management and Ecology, 16(1), pp.61-67.
Anderson, J.T., Rojas, J.S. and Flecker, A.S., 2009. High-quality seed dispersal by fruit-eating fishes in Amazonian floodplain habitats. Oecologia, 161(2), pp.279-290.
Anderson, J.T., Nuttle, T., Rojas, J.S.S., Pendergast, T.H. and Flecker, A.S., 2011. Extremely long-distance seed dispersal by an overfished Amazonian frugivore. Proceedings of the Royal Society of London B:
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Arantes, C.C., Castello, L., Stewart, D.J., Cetra, M. and Queiroz, H.L., 2010. Population density, growth and reproduction of arapaima in an Amazonian river‐floodplain. Ecology of Freshwater Fish, 19(3), pp.455-465. Arantes, C., Winemiller, K., Petrere, M., Castello, L., Hess, L. and Freitas, C., 2017. Relationships Between Forest Cover And Fish Diversity In The Amazon River Floodplain.
Araújo, C.S.O., Gomes, A.L., Tavares-Dias, M., Andrade, S.M.S., Belem-Costa, A., Borges, J.T., Queiroz, M.N. and Barbosa, M., 2009. Parasitic infections in pirarucu fry, Arapaima gigas Schinz, 1822 (Arapaimatidae) kept in a semi-intensive fish farm in Central Amazon, Brazil. Veterinarski Arhiv, 79(5), pp.499-507.
