Reviving Ancient Practices: Modern Perspectives on Rice–Fish Culture ^†

Abstract

Rice–fish culture, an ancient agronomic practice, integrates aquaculture with rice farming, a sustainable solution for enhancing food security and agricultural productivity. The recent advancements and historical perspectives on rice–fish culture have increased its ecological, economic, and social impacts. The practice spans over 2000 years and has seen significant technological improvements, especially in regions like China, Thailand, and Bangladesh. Implementations of modernized rice–fish systems demonstrate increased rice yields, reduced pest and weed prevalence, improvements in soil quality, and higher profits for farmers. For example, in China, it was reported that a rice–fishing system produced 6000–7000 kg of rice and 1500–7500 kg of fish per hectare per year. Furthermore, the fish reduce herbivore insect abundance and weed abundance, effectively eliminating the need for pesticides. Despite its advantages, challenges such as water management, the availability of quality fish seed, and socio-economic barriers remain. By synthesizing findings from various studies, we will highlight the potential of rice–fish culture to contribute to sustainable agriculture and rural development, recommending strategies for optimizing its adoption and addressing existing constraints.

1. Introduction

Rice–fish culture is an integrated farming system where fish are raised in rice paddies, providing mutual benefits to rice and fish production. This method leverages the symbiotic relationship between rice and fish to enhance productivity, improve environmental sustainability, and increase economic returns. Overall, global rice–fish co-cultures are expected to increase farmers’ income by USD 175–197 billion, reduce the annual loss of nitrogen by 0.3 million tons, and avoid 7% of methane atmospheric emissions [1].

The classic process is illustrated in Figure 1 and begins with field preparation, which involves modifications such as deeper channels or ponds that serve as refuges for fish during dry seasons or harvesting. Water reservoirs and irrigation systems help maintain a stable water level [2]. Water reservoirs and irrigation systems are then set up to ensure a consistent water level. Once the rice is planted, fish (usually carp or tilapia) are introduced into the flooded fields. In this system, the interactions between rice and fish are symbiotic, with fish eating pests like insects and weeds, reducing the need for pesticides, while their waste enriches the soil with nutrients [2]. At the same time, rice plants provide shade and protection, creating a favorable environment for the fish. Proper water management is critical to maintaining water levels and supporting rice growth and fish survival. When it is time to harvest, rice is gathered first, leaving the fish in the channels. Afterward, the fish are either cultivated further or harvested, depending on their growth stage. This integrated system enhances productivity, promotes biodiversity, and reduces the need for chemical inputs, making it an eco-friendly and sustainable agricultural practice [2].

Several variations of rice–fish culture exist beyond the traditional method. For example, in a rice–duck–fish culture, ducks are added to the rice–fish system to eat pests and weeds, reducing the need for pesticides [3]. Their movement stirs up the soil, improving oxygen levels. Fish, such as carp and catfish, can, therefore, benefit from the extra nutrients in the water. Another variation is the use of shrimp instead of fish, implemented particularly in brackish water areas, near coastal regions [4]. The most commonly used species in this system is Macrobrachium rosenbergii (giant freshwater prawn). Shrimp feed on organic matter present in the paddy fields, contributing to the decomposition of plant residues and reducing nutrient loss [4].

An interesting variation is the introduction of the plant Azolla, a nitrogen-fixing aquatic fern, into the rice–fish culture. The nitrogen fixed by Azolla reduces the need for synthetic fertilizers, making this system particularly suitable for organic rice farming [5]. Moreover, Azolla can form a dense mat on the water’s surface, suppressing weed growth and preventing mosquito breeding. Fish can also consume the fern, while benefiting from the improved water quality and increased dissolved oxygen levels [5].

Each method offers unique advantages, providing unique approaches based on local environmental conditions, market demands, and available resources. As interest in sustainable food production grows, rice–fish culture remains a viable solution for promoting ecological balance and increasing agricultural resilience.

2. Methodology

The search was conducted using Scopus, a widely recognized scientific database, ensuring the inclusion of high-quality and relevant publications. The literature search was performed using the following keywords and Boolean operators: “rice-fish farming”, “rice-fish culture”, and “integrated rice-fish systems”. Filters were applied to include articles, reviews, and conference proceedings published in peer-reviewed journals. Studies focusing on rice–fish co-culture benefits, environmental impacts, economic aspects, and historical perspectives were prioritized. The findings were synthesized to present a balanced perspective on the ecological, agronomic, and economic impacts of rice–fish culture, considering various farming techniques and geographical contexts.

3. Historical Background

Rice–fish culture, the practice of cultivating fish in rice paddies, has a long and varied history across different regions, particularly in Asia. This integrated farming system has evolved over centuries, providing multiple benefits such as increased food security, pest control, and enhanced soil fertility.

Rice–fish culture in China can be traced back approximately 2000 years, making it one of its oldest known agricultural practices [6,7]. Historical records and archeological evidence suggest that this practice was well established in regions such as Zhejiang Province during the Neolithic Age (6000 BC), where freshwater fishing and rice cultivation were closely linked [8]. However, at this time, the technology for controlled water management in paddy fields had not yet been developed. The system was not only a method of food production but also a significant cultural practice, being recognized as an agro-cultural pattern [7]. In China, the practice has been recognized as a Globally Important Ingenious Agricultural Heritage System (GIAHS) by the FAO and UNESCO, highlighting its significance in biodiversity conservation and sustainable farming [6]. It is also rapidly developing, with fish yields reaching up to 750 kg/ha and rice production increasing by up to 47.3% [9].

The rice–fish system spread through other Asian countries, such as Japan, beginning in the early 1840s in the Saku basin, Nagano Prefecture, and expanding significantly during World War II due to government subsidies for boosting food production [10]. Due to this, the practice reached its peak in 1945 but declined post-war with the introduction of chemical pesticides and more intensive modern fish farming methods [10]. Despite this decline, large-scale rice–fish operations still exist in some regions of Japan, such as the Saku basin [10].

In northeast Thailand, government and non-government agencies have recently encouraged the implementation of rice–fish cultures. The practice has been adopted, with varying success, among small-scale farmers, with wild fish often constituting a significant portion of the yield (20–80%) [11]. This is due to most of the paddy rice fields in Thailand being dependent on rainfall, lacking enough water to sustain both fish and rice production [11]. However, wild swamp fish tolerate these conditions, and traditional systems for their management and capture have significantly expanded in tandem with rice farming [11].

Rice–fish culture demonstrates the enduring potential of integrating aquaculture with agriculture for sustainable food production. Its historical significance and modern recognition as a GIAHS highlight its value in enhancing biodiversity, food security, and soil health despite regional challenges and shifts in farming practices.

4. Benefits of Rice–Fish Culture

In recent years, rice–fish culture has seen a resurgence in various parts of Asia, including China, Indonesia, and Thailand, driven by its ecological benefits and the need for sustainable agricultural practices [12].

In fact, it has been shown that a rice–fish co-culture increases biodiversity, reduces pests and weeds, and enhances soil and rice quality. Wan et al. [1] reported that the co-culture implementation reduced herbivore insects by 24%, weeds by 58–68%, and increased economic value by 10.33%. Other authors such as Cui et al. similarly showed that the implementation of the rice–fish culture resulted in a rice yield increase of 4% and nitrogen-use efficiency of 6%, effectively reducing nitrogen losses and methane emissions [1]. In Thailand, implementing a rice–fish co-culture resulted in a 25.40% higher economic value with a positive change in temperature and humidity regulation [13]. A summary of the benefits resulting from a rice fish co-culture is present on

Table 1. Rice–fish cultures and their resulting benefits.

Location	Rice Yield *	Fish Yield	Other Benefits	Ref.
China	4.14%	---	Decreased herbivore insect abundance by 24.07%; reduced the need for pesticides by 23.4%; profit increased by 10.33%.	[1]
Thailand	4–25%	400–600 kg/ha	Decreased weed abundance by 58–68%; profit increased by 25.40%.	[13]
India	~30%	500 kg/ha	Decreased herbivore insect abundance by 24%.	[1]
China	8–47.3%	225–750 kg/ha	Decreased withering rate by 53%; decreased damage to Chilo suppressalis by 53%.	[9]

* Rice yield increase when compared to an average rice monoculture.

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Rice–fish co-culture has been shown to improve rice milling quality, nutrient content, and appearance. However, the level of improvement depends on the rice variety [14]. Suitable rice varieties need to be screened for rice–fish co-culture system, as the rice grain yield often differs from a regular rice monoculture. The authors Li et al. [14] tested 33 rice varieties to select suitable rice varieties for rice–fish co-culture systems, with 11 found to be suitable for a rice–fish co-culture. These 11 varieties showed a high yield and strong lodging resistance while in rice–fish co-culture and included the varieties Yexiangyou 9, Huangguanghuazhan 1, Huangguangyouzhan, and Qingxiangyou 033 [14].

However, some recent studies have pointed out that even though rice–fish co-culture systems generally reduce greenhouse gas emissions, they may increase methane emissions by 29% [1]. This is reportedly due to decreased oxygen concentration in the water, which, in the case of rice–fish systems, can reach an 18% decrease [1]. The decrease in oxygen may create oxygen-free zones where methanogen microorganisms thrive. The reduced decomposition of organic matter in anaerobic conditions and the increased sediment disturbance by the fish also supply the methanogenic organisms with more substrates such as acetate and hydrogen. Cui et al. theorize that utilizing certain more sophisticated technologies, such as aeration, could assist in controlling methane emissions as they would introduce oxygen to the water [1].

A rice–fish culture also results in social and nutritional benefits. It increases food security, providing a complementary, nutritious diet rich in carbohydrates, proteins, minerals, and vitamins, while generating higher food yields [15]. Furthermore, additional revenue from agrotourism may be possible, improving livelihood by diversifying income sources [15].

5. Challenges and Constraints

Implementing a rice–fish culture presents challenges and constraints that can impact its success and adoption. These challenges can be broadly categorized into environmental, economic, and social factors.

The more limiting factors are the environmental ones. Effective water management is crucial for a successful co-culture, as inadequate water supply and quality can constrain rice and fish production [11]. In Thailand, rainfed rice fields are the most common type. This means these fields only exist during wet seasons, and their water supply depends solely on rainfall, which is unsuitable for fish farming [11]. This limits which regions can benefit from this co-culture, as it may be impossible to implement in some.

Small-scale farmers may face economic challenges as a pond fish culture requires a significant initial investment. This initial investment encompasses not only the infrastructure but also the fish feed, the water management systems, the fertilizers, other chemical products, and other labor costs. Furthermore, some regions may require the farmers to obtain permits for aquaculture activities or compliance with environmental regulations, which can add to upfront investments [16]. Moreover, fish farming is usually perceived as economically riskier when compared to traditional rice cultivation [16].

Social challenges include a lack of education, services, training, and cultural barriers. Farmers need extensive training and hands-on experience in techniques such as fish nurseries, stocking density, and species selection to implement a rice–fish culture successfully [15]. In some regions, there are cultural and social barriers, such as low scholarly levels among farmers and a lack of consideration for women’s roles in decision-making [11].

Moreover, ethics regarding animals must be taken into account. The optimal fish stocking density is 15,000 fish/ha [17] for the best yield and, therefore, profit. Overcrowding can cause stress, aggression, and injury among fish due to limited space and competition for resources like oxygen and food. In fact, fish deaths are common in these co-cultures, with Amur carp and common carp rice co-cultures having a survival rate of 72–85% [18]. It may also compromise the ecological balance of rice–fish systems, risking long-term sustainability in favor of short-term economic gains. Additionally, in many regions, rice–fish cultures are traditional systems. Overcrowding might push these systems toward industrial models, eroding cultural values tied to sustainable practices. In the European Union, the maximum stocking densities in organic aquaculture are regulated under Regulation (EU) 2018/848 [19], and for carp and other freshwater fish in ponds or natural lakes, the limit is stipulated at 150 kg/ha, which translates to roughly 75 fish per hectare in the case of carps (2 kg per fish). This brings to light that even though maximum profit is reportedly obtained at 15,000 fish/ha [17], it may not be the best for the animals. Furthermore, these regulations limit the application of a rice–fish co-culture in the European Union in the case of organic aquaculture.

Rice–fish culture faces significant environmental, economic, and social challenges despite its potential benefits. Effective water management, high initial investments, and the need for farmer education and training are critical barriers to its widespread adoption. Therefore, addressing these constraints is essential to unlock the full potential of this sustainable agricultural practice.

6. Conclusions

Rice–fish culture is a sustainable farming practice that enhances productivity by integrating aquaculture with rice cultivation. Rice–fish culture offers a clear advantage over conventional monoculture systems by enhancing rice yield (up to 47.3% in some cases), with fish contributing to natural pest control, thereby reducing pesticide dependency by up to 24%. Additionally, weed abundance can decrease by 58–68%, minimizing herbicide use.

Beyond its ecological benefits, rice–fish culture enhances soil fertility and nitrogen-use efficiency, reducing fertilizer requirements and lowering nitrogen runoff, a major environmental concern in rice farming. The presence of fish contributes to sediment mixing, improving nutrient distribution and soil aeration. Such features make rice–fish culture highly relevant for climate-smart agriculture, as it not only boosts productivity but also mitigates methane emissions when properly managed.

Despite its significant potential, the widespread adoption of rice–fish culture is constrained by several challenges. Environmental factors, such as the need for effective water management and the suitability of specific regions, often limit its implementation. Economic barriers, including high initial investment costs for infrastructure, fish seed, and water management systems, make it particularly challenging for small-scale farmers. Social constraints, such as limited access to education, training, and services, and cultural barriers further hinder its adoption in some regions.

With the proper support and commitment, rice–fish culture can become a cornerstone of sustainable agriculture, contributing to biodiversity conservation, rural development, and global food security.