Towards Sustainable Aquaculture: A Brief Look into Management Issues

Abstract

Aquaculture’s role has expanded over the past two decades, with the industry contributing to nearly 50% of the overall fish production. Aquaculture production in Asia and Africa contributes a significant share of total global aquaculture output growth. Aquaculture supports livelihoods and income improvement in a number of states, despite the fact that economic situations have indeed been unfavourable and environmental concerns remain undeniable. To meet the growing demand for fish, aquaculture must expand. However, this expansion will not be sustainable unless management and planning are significantly improved. Local, national, and international management are needed to address the social, economic, and environmental problems. These provide the foundation to proper aquaculture management strategies. In considering the involved ecology, water quality, and genetics, aquaculture can have a detrimental impact on the environmental sustainability. This paper highlights the review on site selection with capacity evaluation, analysis of threats and risks, as well as certification and standards, which are all important considerations in achieving a sustainable aquaculture industry.

1. Introduction

Aquaculture has been suggested as a possible alternative for fisheries towards mitigating food security problems and preventing the loss of wild fish supplies. This industry has increased tremendously over recent decades, with less than 19 million tonnes in 1950 to 122 million tonnes in 2020 [1]. Although fish farming is often referred to a sustainable activity, it is associated with a number of potential ecological consequences. These include eutrophication of aquatic ecosystems, intensive use of land and water, ecotoxicity of ecological systems through the use of chemicals, and invasion of non-native species [2]. Hence, it is of the utmost importance to evaluate present aquaculture methods and find the most environmentally acceptable aquaculture production systems.

Concerns have been expressed regarding the sustainability of aquaculture as a result of its expansion without adequate management control [3]. Aquaculture must continue to expand in order to supply the rising demands for food. Planning and management from the local and international authorities are required for addressing aspects of economy, health, social, and animal welfare. These provide the guide in proper management in aquaculture. The continued use of aquatic resources for aquaculture will be expanded for the employees and traditional fish farmers to preserve their standard of living and means of subsistence. Though aquaculture can be utilised to eliminate poverty and unemployment, it is irresponsible to pull aside the environmental consequences from aquaculture. Lax management and incidents are two elements that contribute to the detrimental environmental effects of aquaculture [4]. In many parts of the world, shrimp farming has contributed to the destruction of mangrove forests, wherein the inland mariculture threatens the quality of freshwater [5]. Furthermore, wild fish as aquaculture feed is already a major source of concern. Oysters, clams, scallops, and mussels are filter-feeding organisms that are efficient nutrient absorbers and may exploit natural food sources in water, thus, removing unnecessary nutrients in the water [6]. Integrated multi-trophic aquaculture (IMTA) employs material excreted by one cultured species as intake for other cultured species under the same system. Consequently, the combination of cultured species which given feed in the right amount along with species which can synthesise feed via inorganic sources such as seaweeds would emerge a balanced feeding ecology, taking carrying capacity, site selection, and food safety into consideration [7]. Integrating species of plants together with aquatic animals can greatly enhance the aquaculture sustainability. Recent advances in science have unravelled a far better understanding of how aquatic environments function and the necessity for a sustainable management of these resources [8]. Aquaculture involves use of wild fish, water, and land to give optimal environment for cultured organisms. Aquaculture nonetheless affects the ecosystem, topography, soil, and water [9]. Despite the claims of other sectors of the productive economy, the ongoing exploitation of these resources by the aquaculture industry without concern for their sustainability will lead to their depletion. The culture unit provides the essentials for maintaining sustainability, which may be attained by concentrating on the system as well as its ecosystem to limit input and increase output through an integrated system [10].

2. Aquaculture Threats for the Environment

Aquaculture utilises water as a culturing medium, hence, the survival of aquaculture organisms is dependent on the water quality—for example carbon dioxide (CO₂), ammonia (NH₃), pH, and dissolved oxygen (DO) [11]. Aquaculture activities have an impact on water quality due to the feed waste and excretion from the cultured organisms, which eventually affects the organisms being cultured. Different culture systems affect the environment in different ways because of the differing management practices and waste (faeces, indigestible solids, uneaten feed) [11]. Common practices include the release of materials—such as dissolved nutrients, uneaten food, faeces, and dead fish—to water bodies containing aquaculture cages. Cage aquaculture discharges untreated nutrients and toxins into water bodies, which has ecological consequences. Additionally, the escape of farmed fish from cages can pose genetic and ecology threats to wild fish populations though competition and interbreeding. It is risky for escaped farmed fish to reproduce in the wild because their offspring have a high mortality rate [9]. A typical aquaculture effluent includes dissolved or suspended particles, as well as nutrients such as nitrogen, which contribute to eutrophication commonly happened in the cage culture. In intensive culture systems involving high densities, substandard water quality might pressure the cultivated species, making them more prone to disease. Other than the above, antibiotics also contribute to a significant proportion of chemical waste which is able to deteriorate the water quality [12].

Table 1. Average load of nutrient during cultivation of certain farmed fish (kg/tonne of product).

Common Name	Total Phosphorus (TP)	Total Nitrogen (TN)	Total Suspended Solid (TSS)	Biochemical Oxygen Demand 5 (BOD5)	Reference
African Catfish	5.3	13.4	468.2	39.8	[15]
White Shrimp	86.8	93.73	287.06	11.0	[16]
Atlantic Salmon	19.9	33.0	220.5	90.0	[17]
Nile Tilapia	24.1	15.0	609.3	38.3	[18]
Rainbow Trout	76.5	31.2	290.2	83.3	[19]

displays the volumes of wastewater from numerous cultivated species. On the basis of species cultured weight, variable concentration (mg/L), volume of water, and other estimation-relevant factors for which kg/tonne values were not explicitly provided, derivations were developed. The values provide an approximation of the waste loads resulting from the cultivation of several aquaculture species. Aquaculture technology advancements have enabled the production of previously uncultivated, high-value species in developing states besides a growing need for food and other input which affects the environment. In their pursuit of environmentally friendly production of food, priority has been given by researchers to the species with high market demand such as catfish and tilapia [13]. Several attempts have been made to classify the numerous environmental concerns posed by aquaculture. In Figure 1, a succinct description of the environmental concerns caused by aquaculture is provided. The impacts are more drastic in lakes as the water source becomes stagnant when the alterations in microbial populations and the toxicity of released chemicals increased [14].

There are both organic and inorganic components in aquaculture wastewater, which stimulate the environmental load in which the wastewater is discharged. Poor water quality is frequently caused by anthropogenic factors other than aquaculture [16]. This is especially true for mollusk aquaculture, which is more frequently used as a waste treatment. Bivalves and mollusks may extract nutrients from moderately enriched waters more effectively than from heavily enriched waters [20]. Unless there is a significant proportion of total suspended solids, pond effluent has a lesser effect on receiving waters than domestic wastewater. However, due to eutrophication, large-scale aquaculture and clustered smallholder farms constitute a threat to potential development of aquaculture in a region in which they are located [15]. Shrimp cultivation in wetlands is no longer economically viable due to nutrient enrichment [16]. Eutrophication occurred in the river body as a result of direct waste discharge from the shrimp farms among the surrounding population.

Nutrient levels in receiving waters are typically high when animals are fed due to uneaten feed, faeces, and other metabolic byproducts [18]. The discharge of nutrients caused by a poor plan can be contained, depending on the prevailing conditions in waterbodies. Consequently, aquaculture industry assessments will be carried out to ensure that these farms are run in an environmentally responsible manner as a result of these uneaten feed, faeces, and other metabolic byproducts. Other organisations utilise the water wherein the cultured animals are raised as a shared public resource for agricultural, or leisure purposes [16]. Future agricultural systems must be increasingly self-sufficient, not just in terms of farm biosecurity but also possible disease impacts, both in terms of water utilisation and fertiliser discharge minimisation. The responsibilities of fish meal producers in facilitating the local aquaculture industry toward the development of more sustainable production systems will be of the utmost priority. Open ocean aquaculture has been suggested to meet the expanding worldwide gap between aquaculture supply and demand; yet, the question of whether this potential will be realised remains uncertain. Likely, a variety of technologies, involving appropriately managed wild-catch fisheries, and-based facilities, and the location of farms will be necessary to meet the rising demand for aquaculture [16]. Despite a growing trend among farmers to embrace internationally approved and responsible aquaculture techniques, many major farms continue to employ feeding practices that did not lead to continuing sustainability. Examples include the lack of a tracking system for water quality related to feeding and the lack of feed utilisation indicators [17]. This is a consequence of the lack of organised initiatives for sustainable aquaculture. Hence, the implementation of sustainable farming is solely dependent on the technical help supplied by feed manufacturers plus, the education community of each state. For example, in the shrimp industry, feeding trays have become a popular method for decreasing feed waste and organic matter and nutrient wastes through to the environment [19].

Shrimp aquaculture has had a severe influence on coastal ecosystems due to the destruction of mangroves and the resulting changes in biodiversity such as control erosion, unfavourable water quality, and damaging the breeding sites for aquatic life [16,21]. Mangroves grow along estuaries and beaches in around 124 states with tropical or subtropical climate [22]. In the 25 years between 1995 and 2020, a total of 36,000 km² of mangroves were lost throughout all five continents. These mangroves were deforested for recreation, tourism, infrastructure building, and aquaculture purpose (mainly for shrimp pond). The construction of shrimp ponds necessitates the destruction of mangroves, and past experience has shown that an excessive number of farms clustered along the coast leads to decreased productivity, disease outbreaks, and the failure of the projects. The removal of mangrove for shrimp aquaculture could lead to global warming [23]. Recruitment has been disrupted as breeding sites and nursery zones have been destroyed, and native aquatic species populations have either migrated or killed totally, making it difficult to transition from aquaculture to fishing as a means of survival [24]. Therefore, these above-mentioned issues underscore the need to consider alternatives for survivability of coastal ecosystem by implementing sustainable aquaculture practices.

3. Selection of the Site and Assessment of Carrying Capacity

Several strategies will be employed to attain the ecological and environmental sustainability of aquaculture. The right location of a farm to reduce unwanted impacts is an essential strategy. The foundation of sustainable aquaculture will be comprised of proper design of the hatchery, selection of site, as well as proper management [25]. Policy is also essential in this process, since it regulates entry into the aquaculture industry and provides areas that are appropriate and sufficient of determining the environmental effects of aquaculture. In most states, the aquaculture sector lacks a legislative framework governing environmental quality. Carrying capacity is the maximum load of cultured species that the environment can sustain without deleterious effects on the ecosystem, system used for culture, and stocks [26]. The cultured biomass in an aquaculture system provides input–output relationships in which the inputs are additive and the outputs are subtractive. Carrying capacity has a cultural dimension and is therefore typically dynamic [27].

Determination of limits and standards using improved and innovated concept for site selection is the first step to policy formulation in order to avoid excessive carrying capacity [28]. For instance, when aquaculture creates no negative effects in an environment and maximum production limitations are met with social satisfaction, the carrying capacity assessment is reached [29]. As a result, sustainability is realised due to the fact that community satisfaction is attained through sufficient economic rewards derived from eco-friendly technology, which also provides a place for additional resource users. Following the determination of the carrying capacity, it is possible to establish aquaculture facilities with capacities that correspond to the carrying capacity. Carrying capacity is also used for aquaculture planning, and the assessment of acceptable aquaculture zones [30].

The total market for aquaculture space is anticipated to increase because of the sector’s rapid expansion, particularly in Asia, with the utilisation of coastal slopes that are affecting the ecosystem. Local considerations pertaining to a site’s ecological sustainability and the size of the market are two common selection criteria for selection sites [31]. Accessibility to infrastructure and supporting facilities is a consideration in deciding the location of aquaculture operations, which has environmental, transportation, and economic implications. Because of the short-term aspect of this management strategy, aquaculture progress will be hampered even more, as it has a limited geographic scope and wider implications on environmental sustainability in the remote location [32]. Carrying capacity is evaluated throughout the whole site selection procedure, beginning with the calculation on capability and giving special attention during selection. Since the process needs to begin at a specified time, it adheres to spatial and temporal aspects, plus evaluating the complete range of available space before determining aquaculture-suitable locations. The assessment of carrying capacity must be adapted to the proposed target species and system as it is an ongoing system. Additionally, the estimation of carrying capacity is still necessary for the extension of established species to new places.

4. Hazard and Risk in Sustainable Aquaculture

Risk involves three key concepts which are: uncertainty of outcome, probability of unwanted event to happen, as well as impact when the unwanted event occurring [33]. An analysis of risk is an objective, systematic, standardized, and defensible method of assessing the likelihood of negative consequences occurring due to a proposed action or activity and the likely magnitude of those consequences, or simply defined as ‘science-based decision-making’. Risk analysis will then involve the assessment of risk posed by a threat or hazard. Hazard has the potential to cause loss or harm, example: pathogens (pathogen risk analysis), aquatic organisms that are newly introduced into an environment (genetic risk analysis, ecological risk analysis, invasive alien species risk analysis), and chemicals (social risk analysis and food safety risk analysis, and environmental risk analysis) [34].

Consequently, regardless of how well a system is managed, accompanying risks and hazards exist for every aquaculture system. In aquaculture, the biological nature system is a risk that causes market volatility, scarcity, and multiple objectives. Meanwhile, diseases, natural catastrophes, inadequate outputs, equipment malfunction, harmful algae bloom, silt buildup, poor water quality, dissolved oxygen consumption, fish death, capacity constraints, and fish escape are all examples of potential aquaculture uncertainties [35,36]. These hazards associated with aquaculture involve pollution, genetic issue, climate change, habitat structural changes, occupational hazard, and food security [37,38]. The hazards can have a broad impact on the environment, the population, and human health [39]. However, risk management is recommended as the most effective means of preventing loss and waste [40]. Risk is linked to activities and results, regardless of how it is interpreted. Biological, environmental, and economic factors can all pose threats to aquaculture development [35].

The sustainability of aquaculture supply is contingent upon the environmental sustainability of production, the condition and function of ecosystems that support production, as well as the economic and social sustainability of production and processing operations. The direct and indirect implications of aquaculture systems to the environment, particularly those associated with energy source, pose threats to environmental sustainability [38]. This energy source represents a combination of feed inputs, which are mostly fossil fuel-based indirect inputs in the form of fertilisers and pesticides, as well as direct inputs in the form of electricity and fuel usage. The continued use of fossil fuels and electricity as sources of energy is detrimental towards the sustainability of the aquaculture industry, and mankind overall [35]. Utilising resources—such as land, water, and fertilizer—efficiently is essential to maintaining the sustainability of the environment. Lowering the usage of these resources is necessary to provide a healthy environment in a sustainable manner. Despite dramatic shifts in production and consumption patterns, the growing demand for energy will likely worsen land-use conflicts between the aquaculture sector, and ecosystem restoration, thereby intensifying environmental deterioration. Work vessels are equipped with capstans or a crane for monitoring and inspection purposes in cage culture risk management. The workers are responsible for the monitoring, cleaning of dead fish from the cages, and regular detection of the parasite load on a sample of fish [36].

In aquaculture, hazard identification can be conducted using robust techniques to establish qualitative and quantitative elements of the hazards presented for decision making with policy formation. The phase of risk management is a collaborative evaluation of every available and appropriate social, economic, and environmental policy by authorities as well as stakeholders [41]. System mismatches can be rectified through the risk communication stage since it permits reevaluation and readjustment of the process. However, flaws in human perception may need the participation of multiple individuals to make the decision [42]. Therefore, it is desirable for employees to be included in the enterprise-level risk management process so that choices may be made via means of exchanges between management and employees. The risk assessment will indeed assist governing bodies in deciding whether aquaculture is socially and environmentally acceptable. In the risk matrix analysis, magnitude is ranked below impact, hence impact is examined rather than magnitude.

With this, it will be simple to quantify the potential environmental repercussions of aquaculture, including pollution, erosion, damage of ecosystems, excessive nutrient, and rising water consumption [40]. Risk analysis for food safety, genetics, infection, social hazards, and environment helps to ensure aquaculture’s sustainability by minimising the industry’s environmental impact as illustrated in Figure 2. Pathogen risk analysis is conducted to investigate the possibility of harmful disease from imported species. Furthermore, the pathogen risk analysis is evaluated from the possible outcomes of exposure in threatened species, the risks that come with every pathogen when products are permitted in, and finally, the potential entrance of aquaculture products with acceptable risks [43]. Before proceeding to the following phase, the assessment of food safety risks should first evaluate the hazards connected with the product.

Interbreeding between cultured fish and wild stocks is linked with genetic risk in aquaculture, considering that farmed fish have been deliberately grown or genetically designed for specific traits. Genetic risk analysis would include strategies to reduce possibility of escape and increasing reproductive capability [44]. Moreover, the position of fish farms, efficient quarantine, and human access contribute to the risk of escape. An ecological risk assessment revealed that hybridisation between tiger grouper and giant grouper increased the growth rate of the commercial grouper species, but if released into the open ocean, it would present a threat to the native grouper [45].

The social risks associated with aquaculture are the danger of investment failure and the restriction of other commercial activities. Aquaculture’s social risk can be evaluated by evaluating its consequences, scope, and accessible records. Investment loss in aquaculture is a risk that cannot be entirely avoided, given that aquaculture engages with biological and environmental topics. Several households in low-income countries have suffered substantial losses [46]. Thus, aquaculture’s social risks can be mitigated by proper site selection and management.

5. Certification for Sustainability

Certification is a nonaligned third-party evaluation of quality standards intended to certify a company’s claims of satisfying standards. In fact, standards are sets of elements that are useful towards the aquaculture industry, and society. The foundation of standards includes the formulation of standards, the approval and implementation for certification, and the identification of actions and outputs. Sustainability, food safety, animal welfare, and community responsibility seem to be the most important features for obtaining certification in aquaculture [47]. These criteria are interrelated from the perspective of the public. It is natural for consumers to believe that good aquaculture practice will lead to improved, healthier, and safer products that are less harmful to the environment and that boost animal welfare. For cage culture, it is important for the daily inspections to be conducted in accordance with official aquaculture standard to guarantee that the cages are in working order as well as to examine the welfare of the fish to reduce the impacts to the environment. This situation has prompted aquaculture industry stakeholders to place a greater emphasis on their products’ safety, health, environmental responsibility, and animal welfare. A government that is strongly committed to promoting food safety, environmental sustainability, and animal welfare can be a great contribution to both society and the environment [48].

The legitimacy of certification depends on the use of the scientific method with honesty and responsibility by both small scale and large aquaculture companies. For certified products, traceability is important; therefore, it is essential to maintain records of product movement in order to ensure responsible trade. These issues can only be met by international third-party certification schemes, which provide operationalisations of sustainability in tandem with comprehensive guides, enable companies to convey their standards and values to more customers, and give concerned customers confidence by giving explicit criteria and monitoring by independent bodies [47]. These can be carried out by authorities’ institutions such as The Aquaculture Stewardship Council (ASC), fisheries and ASC Chain of Custody (CoC), Department of Fisheries (DoF), Shrimp Seal of Quality Organization (SSOQ), Shrimp Farmers Association (SFA), Shrimp and Fish Foundation (SFF), Frozen Food Exporters Association (FFEA), Aquacultural Certification Council (ACC), Global Aquaculture Alliance (GAA), and the World Wildlife Fund (WWF) which are generally run by the government or private organisations.

Multiple issues threaten to exclude small-scale aquaculture (Figure 3) from the globalisation of aquaculture business for example, requirements for market access, hazards and expenses associated with quality standards throughout production [48]. The applicability of certification in small-scale aquaculture company is questionable. The standards are primarily applied in cultured organisms which have high market demands, resulting in a negligible market share for developing countries, along with numerous problems concerning fair trade requiring responses [49], classifies these obstacles considering environmental, social, and finance issues.

Sustainability is not a measurable quantity; consequently, its direction must be determined through indications [50]. The aquaculture supply chain is governed at both the regional and international levels through regulations that are mainly focus on controlling disease, food safety, and conservation [51]. The arguments and essential criteria for accomplishing sustainability, food safety, animal welfare, as well as social responsibility through aquaculture are summarised in

Table 2. Mitigation guideline for sustainability certification.

Aspect	Requirement
Environment	Implementation of environmental assessment during selection of site in order to reduce hazards Water usage with a conservation leaning Prevention of fish escapes and importation of exotic aquaculture species Adoption of state’s aquaculture policy and plan Limited utilisation of drugs and chemicals
Food safety	Site selection free from pollution Usage of contaminant-free feed with approved composition Adhere to Hazard Analysis and Critical Control Point (HACCP) Cultured species must be free of pathogens Usage of approved therapeutants
Animal welfare	Knowledge on cultured species welfare and management among the workers Cleanliness of culture environment for pathogen control Restriction on antibiotic management with withdrawal period Consideration of pathogen-free species Limitation of injury to cultured animals in the production process with minimised suffering during slaughter
Social welfare	Compliance with labour and wage standards Participation of all stakeholders in the surrounding community Cluster of small-scale farmers for fetish certification

. With alternative certification, a wide library of data is provided as indicators for sustainability in aquaculture that can be compiled, despite the difficulties and high expenses associated with data collection.

6. Conclusions

Aquaculture is a fast-expanding industry in the production of food, accompanied by a rise in both the industry’s intensity and its workforce. The expansion has been accompanied by operators’ negligence that cause issues related to the environment. Aquaculture has the potential to harm genetic diversity, general ecology, human health, natural resources, and water quality. Sustainable aquaculture is essential for decreasing aquaculture’s risks in order to maintain safety of food product for human consumption. Serious and concrete measures should be taken to prevent adverse effect of aquaculture towards the environment. To achieve sustainability, the first step is to choose areas with the capability to manage both aquaculture biomass and waste. Continuous management with planning of cultivation, site selection, and carrying capacity assessment is required. It is essential to comprehend the hazards associated with running aquaculture facilities in a state while evaluating sites for aquaculture by taking into account the disease transmission as well as other issues. Aquaculture risk assessment must be undertaken and collaborated upon by the community to increase local knowledge. Utilisation of stakeholders’ opinions is a contentious issue among scientific communities. However, community members’ knowledge can be quite valuable. When regulatory bodies plan for aquaculture, the ecosystem approach to aquaculture can also be used to create sustainable aquaculture. This method is scientifically sound since it ensures sustainability by management and improving livelihoods. The recommended aquaculture methods will have a large and favourable impact on aquaculture production all over the world while also positively improving environmental sustainability. For the implementation of these measures, key players—including international agencies, researchers, policymakers, government and non-governmental organisations, and fish farming societies—must be actively engaged. To facilitate the recommended adaptation solutions, social, economic, and ecological concerns must be identified and addressed. Because aquaculture can have negative environmental consequences, it is indeed crucial for evaluating and anticipating the consequences for alleviation steps to be taken under acceptable bounds. Regulators must continue to monitor aquaculture sites and take appropriate action when necessary to support ecological sustainability, appropriate food quality, social welfare, and environmental health. Thus, an empirical study is required to comprehend the interconnected processes of enhancing aquaculture productivity and environmental sustainability.