Exploring the Integration of Rice and Aquatic Species: Insights from Global and National Experiences

Abstract

The objective of this article is to review the historical development of rice–aquatic species (RASp) integration and analyze the factors that affect its performance. Compared to rice monoculture, the integration of the rice–aquatic species system has a more significant impact on farm production, income, land (L), water use efficiency (WUE), net revenue, and labor use efficiency (LBUE) reduction. Although concurrent and alternate cultivations of rice–aquatic species increase unit water efficiency, concurrent cultivation requires 26% more water than monoculture. Furthermore, RASp farming promotes environmentally-friendly rice cultivation by reducing the use of pesticides (insecticides and herbicides), decreasing CH₄ emissions by approximately 14.8–22.1%, and enhancing water quality. These findings suggest that fish integration in rice fields could be integrated into extensive aquaculture. Finally, global cooperation is necessary to transfer knowledge about this technology, particularly from China, and more research is needed to evaluate the effects of rice–aquatic species integration in the context of climate change and practical water use efficiency. Additionally, a robust development program at the national and global levels, with regulatory and non-administrative bodies’ guidance and strategy, is needed to embrace the expansion of the rice–aquatic species practice.

1. Introduction

Around half of the total global population relies on rice (Oryza sativa L.) as a prime food source (about 3.5 billion people) [1,2,3], so rice plays a critical role in global food abundance [4]. However, rice cultivation consumes substantial amounts of fresh irrigation water worldwide [1]. It is primarily grown under flooded conditions, especially in areas with heavy rainfall, limiting its growth in arid and semi-arid regions [5]. Furthermore, the excessive use of fertilizers and pesticides in rice monoculture has led to imbalanced soil conditions and the emergence of new diseases and pests [6,7]. In the pursuit of maintaining rice monoculture yields, farmers are compelled to invest significant amounts of these inputs, reducing their overall income.

To ensure the sustainability of rice production and uplift the livelihoods of rice growers, agricultural diversification becomes imperative. By diversifying agricultural practices, farmers can strike a balance between rice cultivation and other crops, mitigating the environmental impacts of excessive input usage. Implementing innovative techniques, such as integrating rice with aquatic species (RASp), can optimize resource utilization and reduce reliance on vast amounts of water and synthetic inputs [7,8]. Agricultural diversification offers numerous benefits, including enhanced soil health, reduced pest pressure, improved water use efficiency, and increased overall resilience of farming systems [6,7,8,9,10,11]. Furthermore, diversification opens new income streams for farmers, reducing their dependence solely on rice production. Integrating livestock or aquaculture alongside rice cultivation can create additional revenue sources while promoting sustainable resource management [8,12,13,14,15,16,17,18,19].

Rice–aquatic species integration is a form of intensification where rice (R) remains the primary crop while aquatic species (ASp) become secondary products. This integration empowers efficient water use, offering a solution for sustainable food production [8]. RASp presents an innovative and holistic farming system that harnesses the ecological synergies between rice and aquatic species to optimize resource utilization, enhance productivity, and mitigate environmental impacts [8,9,10]. Implementing the rice–aquatic species farming system in lowland areas can sustain land productivity, increase farm incomes, enhance food quality in rural areas, and optimize (maximize) the utilization of agricultural resources [7].

Amidst the increasing pressures of population growth, climate change, and environmental degradation, sustainable agriculture has become critically important. RASp shows significant promise in contributing to global efforts to achieve the United Nations’ Sustainable Development Goals (SDGs), particularly those related to zero hunger [11,20,21]. The significance of this review lies in its comprehensive and data-driven approach to examining RASp’s potential as a sustainable production system. By analyzing the latest research and comparing RASp with monoculture practices, this review aims to offer valuable insights into the transformative possibilities of integrating rice with aquatic species. It will investigate the impacts of RASp integration on key aspects such as crop yields, total costs, water quality, water level, water storage, groundwater recharge, soil fertility, water use efficiency (WUE), land use efficiency (LUE), labor use efficiency (LBUE), greenhouse gases (GHG), and N₂O emissions, and compare them with monoculture. Furthermore, the review will discuss global and national experiences with RASp integration to provide a holistic perspective. Moreover, the study will identify gaps in current knowledge and research, paving the way for future investigations and innovation and addressing limitations in the realm of RASp integration.

2. Research Methodology

The study utilized a systematic and thorough approach to analyze peer-reviewed literature on rice–aquatic species. The analysis involved a qualitative evaluation of selected journal and conference papers. The authors reviewed and categorized each article based on its research focus and outcomes. The primary aim of this systematic review was to provide a comprehensive summary of current research and identify research gaps, leading to a more in-depth understanding of the research area’s present state. Figure 1 illustrates the methodology employed.

According to Tang et al. [10], are 25 models available for integrating rice–aquatic species (RASp). In this review, we conducted a survey using the keywords “fish-cum-rice” or “fish-rice” (RFSp), “rice-prawn”, “rice-shrimp”, “rice-tilapia”, “rice–carp”, “rice–crab”, and “rice–crayfish” to search online databases including ScienceDirect, China National Knowledge Infrastructure, and PubMed between 1986 and 2022 (Figure 2). All of these species belong to the aquatic species family. A total of 30,087 relevant studies were identified on ScienceDirect for rice–aquatic species (RFSp), including 2560 for “rice-cum-prawn” or “rice-prawn”, 7969 for “rice-cum-shrimp” or “rice-shrimp”, 3588 for “rice-cum-tilapia” or “rice-tilapia”, 4696 for “rice-cum-carp” or “rice–carp”, and 1860 for “rice-cum-crab” or “rice–crab”.

The publications were subsequently classified into nine categories. (1) use of aquatic species in rice farming systems [integration of fish and other aquatic animals in rice fields, types of aquatic species used in rice farming, and effects of aquatic species on rice yield and quality); (2) nutrient management in RASp (effects of nutrient management on aquatic plant growth, and optimizing nutrient levels for both rice and aquatic species); (3) ecological impacts of rice–aquatic species integration (effects of RASp systems on biodiversity, impacts on ecosystem services provided by rice fields, and conservation and management of rice field ecosystems); (4) water management in rice–aquatic systems (strategies for managing water levels in rice fields, effects of water management on aquatic species and rice yield, and irrigation practices for rice–aquatic systems); (5) rice–aquatic species integrated pest management (identification and management of pests in rice–aquatic systems, use of natural enemies and biological control agents, and integrated pest management strategies for rice–aquatic systems) (6) economic analysis of rice–aquatic species integration (economic viability of rice–aquatic systems, cost-benefit analysis of rice–aquatic systems, and economic incentives for rice–aquatic species integration); (7) sustainable rice–aquatic systems (best practices for reducing environmental impact and maintaining productivity, certification and labeling schemes for sustainable rice–aquatic systems); (8) impacts of climate change on rice–aquatic species integration (effects of changing climate patterns on rice yield and aquatic species growth, and mitigating the environmental impacts of climate change on rice–aquatic systems); and (9) crop diversification with aquatic species in rice farming (benefits and challenges of crop diversification in rice farming).

To reduce the number of publications, the authors initially refined the search by including the keywords “water quality”, “grain yield”, “quality”, “greenhouse gas emissions”, “nitrous oxide emissions”, “water use efficiency (WUE)”, “land use efficiency (LUE)”, “labor utilization efficiency (LBUE)”, “recharge”, “storage”, “flood”, “drought”, “soil”, “climate change”, “sustainability”, or “rice monoculture” from the previous search engine. This approach resulted in the selection of 20 to 110 publications, while the remaining publications were excluded.

The second refinement focused on adding the keywords “Asia”, “South Asia”, “Southeast Asia”, “Northeast Asia”, “East Asia”, “Australia”, “Africa”, “Europe”, “North America”, “South America”, or “Antarctica” to the initial search engine. The results showed that “fish-cum-rice” is practiced in the following countries or regions: “China”, “Hong Kong”, “Taiwan”, “Japan”, “Australia”, “Korea”, “Nepal”, “Malaysia”, “ Philippines”, “Indonesia”, “India”, “Odisha”, “Karnataka”, “Bangladesh”, “Myanmar”, “Cambodia”, “Thailand”, “Vietnam”, “Mekong delta”, “Senegal”, “Mali”, “Burkina Faso”, “Niger”, “Côte d’Ivoire”, “Guinea”, “Ghana”, “Nigeria”, “Togo”, “ Madagascar”, “Zambia”, “Iran”, “Italy”, “Hungary”, “Sri Lanka”, “Brazil”, “Uruguay”, “Caribbean”, “Laos”, “Malaysia”, “US”, “Canada”, “Danube Delta region”, “Louisiana”, and “Egypt”. However, rice–fish farming is not practiced in Antarctica.

Each database’s syntax was adapted to the search syntax. Exclusion criteria were applied to exclude records that were irrelevant to the scope of the review and did not match the search terms in the context of the search question. The review focused on thoroughly examining the benefits of rice–aquatic species cultivation (such as fish, shrimp, tilapia, carp, prawn, and crayfish) in terms of productivity, water efficiency, and food security, as compared to rice monoculture.

3. Rice–Aquatic Species Integration System (RASp)

Integrating aquaculture and rice cultivation is a promising strategy for maximizing land and water utilization, increasing production of both rice and fish, and achieving food security, especially in rural areas. This approach can also reduce costs and increase economic benefits and the quality of both rice and fish. The practice of stocking fish and shellfish in rice fields has been used for more than a thousand years in countries such as China, Indonesia, Thailand, Vietnam, Bangladesh, the Philippines, Myanmar, and Malaysia. The rice–aquatic species (RASp) is considered a globally important agricultural heritage system (GIAHS) and is commonly practiced in Southeast Asian countries. The integration of rice and aquatic species has resulted in remarkable agro-landscapes in countries like China, Thailand, the Philippines, Indonesia, India, and Bangladesh.

Additionally, fish production in rice fields can be categorized as either alternate or concurrent. In the alternate system, rice and fish are grown rotationally, as observed in coastal regions such as the gher and rice-cum-shrimp cultures in Bangladesh and Vietnam, respectively. After the rice crop in the monsoon season, shrimp is introduced during the dry season when saline water invades the rice fields. This alternating culture is a highly intensive rice–aquatic species integration [11]. Stocking densities for the alternate integration system were 10,000, 4500–10,000, and 1000–100,000 for monoculture, polyculture, and fingerling production, respectively. On the other hand, in the concurrent system, fish species, such as carp, catfish, prawn, and tilapia, are grown simultaneously with rice in the same space and time. The stocking densities for concurrent integration range from 3000 to 5000 for monoculture and 2000 to 26,000 for polyculture.

There are three types of concurrent rice–aquatic species fields: perimeter (at moderate elevation), central pond (pond located in the middle of the rice field), and trenches (on one or both sides of the rice field slope) [12]. Additionally, there are various other types of rice field trenches. The shape of these trenches has evolved from line-shaped (two equidistant transverses with a peripheral) to cross-shaped (intersecting) to circular-shaped made up of cross (latticed trenches), peripheral, diagonal, Y-shaped, and two-central longitudinal, as shown in Figure 3. The compensation rates for rice yield losses caused by trench construction were 95.89%, 85.58%, and 58.02% for line-shaped, cross-shaped, and circular-shaped trenches, respectively [13]. Therefore, the new trench shape helps to maintain rice yield without expanding the trench area. Typically, the trench covers approximately 10% of the rice fields [14].

3.1. Species, Feed, and Productivity (Profitability)

The traditional RASp includes rice-prawn/shrimp, snail, rice-tilapia, rice–carp, rice–crayfish, and rice–crab [15]. In China, P. sinensis is commonly reared in rice fields because of its high monetary value and its ability to produce high yields of rice and turtle without adversely affecting the quality of the water or soil compared to turtle monoculture [16]. However, C. carpio, C.auratus, and O. niloticus are the primary species stocked in rice fields in China [17,18]. B. gonionotus is frequently stored in polyculture with rice in paddy fields in southern Asia (India and Bangladesh) and southeast (Indonesia, Thailand, Malaysia, and Vietnam) Asia, while O. niloticus is the primary species in Ghana [17]. In Italy, C. carpio, C. auratus, and Tinca tinca are the most commonly distributed species. Prochilodus argentes, Leporimus elongatus, Pimelodus clarias, C. carpio, and T. rendalli are the most common species in both semi-intensive and intensive RASp integration in South America and the Caribbean. The most prevalent fish species in East & South East Hungary, India, and Indonesia, are common carp (C. Caprio). C. carpio, Ictiobus cyprinellus, and Ictalurus punctatus are the most common species in the United States (US). However, C. carpio, B. gonionotus, and O. niloticus are the main stocked species in rice fields in Cambodia, Laos, and Bangladesh, while L. rohita and B. gonionotus are the common species in Myanmar [18].

In India, the Indian Organic Aquaculture Project includes rotational cropping of organic rice and giant river prawns [16]. In south-western Vietnam, prawn farming dominates the Mekong delta, but other forms of commercial aquaculture, such as crab and mollusk farming, are also present in coastal areas, while freshwater fish farming in the inner section of the delta. In Myanmar, shrimp are produced in saline zones through alternating rice–aquatic species (RASp) integration, whereas little rice–aquatic species integration occurs in areas with fresh and brackish water [18,19]. The Macrobrachium species, Penaeus monodon, and other species, for instance, brackish water shrimps, are fish species that grow well in rice fields [15]. Tilapias can acclimate to changes in water levels and temperatures in rice fields to reduce the risks of ecological change, and they can also be cultivated in coastal brackish ponds [19,20,21,22,23]. In Bangladesh, tilapia can be grown as a variety of crops in systems with brackish water [19], while prawn and shrimp farming in rice fields are seen as an important component of the green economy and a technological policy for the integrated management of land, water, and aquatic species resources [24]. C. chanos, Mugil spp., and Penaeus spp. were utilized in brackish water. Other forms of integration include introducing livestock such as ducks (in Indonesia), Azolla (in China), chicken (in China), and pigs into rice–aquatic species in China, Indonesia, and India [25,26].

Fish in the RASp field consume rice weeds, and insect pests, while prawns primarily consume algae, insect larvae, and worms. In China, supplementary feed for the fish may consist of wheat bran, wheat flour, oilseed cakes (rapeseed, peanuts, soybeans, for instance), grasses, and green fodder, and in Malawi, maize bran and napier grass [27]. Li et al. [28] have suggested that the best way to achieve high-quality and high-yielding rice is to combine indica rice with fish that receive both organic and inorganic fertilizers. This method has proven most effective in humid regions with paddy soils containing low total nitrogen content (TN 1.5 g/kg), where an increase in rice yield is attributed to aboveground biomass, soil potassium (K⁺), soil bulk density, water TN [29], rice planthopper, and soil redox potential (Eh). Applying the RASp integration system has dramatically reduced the quantities of chalky rice in the subtropical zone while increasing the proportions of brown rice, milled rice, and head rice. However, RASp did not have any discernible effects on other grain quality traits in the temperate zone [28].

Table 1. Productivity of crops in rice–aquatic species culture among different countries in relation to rice monoculture.

	Productivity (kg/ha/Season)			Fish Species	Reference
	Rice Mono-	Fish	Rice
Bangladesh	4702	259	5261	C. carpio, B. gonionotus, O. niloticus	[30]
	4188	485	4736		[31]
	-	1453	2257	Prawn & fish	[32]
	-	827	2352		[33]
	-	1080	3800–5000	B. gonionotus, O. niloticus	[34,35]
Indonesia	-	300–890	6380–7780	C. carpio, B. gonionotus	[7,36]
China	7915–10,319	1900–2500	8300–12,000	C. carpio, B. gonionotus	[15,37]
		372	6290	C. carpio var. color	[38]
India	5560	1230	5800	Rohu, Catla, Silver carp, Common carp, & Mrigal	[39]
	-	1144	3300	C. catla, C. carpio, C. mrigala, L. rohita	[16]
	3362	980	3629	C. catla, L. rohita, C. mrigala, C. carpio & M. rosenbergii	[40]
	-	1300–2000	3000–3600	B. gonionotus, C. catla, C. mrigala	[41]
Ghana	-	201	4410	Nile tilapia (O. niloticus)	[17]
Vietnam	-	325–1218	2182	Mud Carp, Chub, Carp	[42]
	-	1024–2200	5700–6806	C. carpio, B. gonionotus, O. niloticus	[35,43,44]
	-	326	4209		[45]
Thailand	-	173	363		[46]
	-	900–1100	-		[47]
	4700	300	3600	O. niloticus, C. striata, C. carpio, B. gonionotus, C. cirrhosus, P. jullieni, C. batrachus	[48]
Japan	4061–5319	345	4871–6381	Carassius complex, Goldfish	[49]
Nepal	3370	354	3670	Common carp (C. carpio)	[50]

shows that the integration of RASp can lead to an increase in rice productivity ranging from 4.14 to 16.64% [7,15,16,17,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50].

The highest fish outputs were observed in food fish, followed by carp fry and catfish fry (Clarias gariepinus), while the lowest -yield was obtained from grass carp. Fish and rice productivity varied depending on factors such as ridge width or ditch width, the species cultured, regular food varieties (e.g., plankton, periphyton, and benthos), intensive or extensive farming, and the stage at which they were harvested. China had a fish yield of about 0.372–2.5 t/ha, followed by Vietnam (2.2 t/ha), India (1.1–2.0 t/ha), Thailand (0.175–1.1 t/ha), Bangladesh (0.259–1.45 t/ha), and Indonesia (0.89–1 t/ha), Ghana (0.2 t/ha), Japan (0.345 t/ha), and Nepal (0.354 t/ha) [14], as shown in Table 1. The combination of multiple species of fish tended to increase rice and fish productivity, particularly in India, where the combination of B. gonionotus, C. catla, and C. mrigala resulted in higher productivity compared to other species combinations.

Rice–fish farming in the coastal areas of Kerala (Pokkali fields) produced a fish yield of 229 kg ha⁻¹ and a rice yield of 2.4–4.4 t ha⁻¹ of salt-tolerant high-yield rice varieties [51]. In Vietnam’s coastal areas, rice–fish farming yielded 2–3 t of rice, 50 kg of shrimp, and 150–200 kg ha⁻¹ of fish [52]. The gher system in Bangladesh consists of shrimp and fish culture with a yield of 280–450 kg ha⁻¹, depending on water exchange, followed by boro rice with a yield of 0.50–1.40 t ha⁻¹, or 3.2–7.7 t ha⁻¹, respectively. The system also yields 200–250 kg of shrimp and 150–175 kg of fish per hectare [53]. In rice–brackish water shrimp farming in five coastal provinces of the Mekong Delta, the average yield was 640 kg ha⁻¹ of shrimp and 3.5–4.0 t ha⁻¹ of rice [52].

These outcomes indicated that the yield components varied depending on the RASp model used, geographic distributions, the quantity and content of feed nutrients, types and amounts of organic and inorganic fertilizers used, and the density of aquatic organisms. Notably, rice yield significantly increased in the subtropical and tropical zones.

3.2. Water Quality, Soil, and Requirement for Water Levels

Depending on the water resources available, the integration of rice and fish systems can be achieved in various ways, such as irrigated, deepwater, rain-fed, and coastal systems [54]. Bashir et al. [55] suggest that the ideal conditions for RASp cultivation are a pH range of 6.5–9, 10 ppm CO₂, 5–7.5 DO (dissolved oxygen), 30–90 cm water level, 25–30 cm water transparency, and a temperature of 25–30 °C. RASp integration enhances water quality and abundant microorganisms, leading to improved performance, quality, and growth of tilapia muscle [56]. In addition, the levels of TN, ammonia-N, and TP in the water of catfish and shrimp ponds were substantially lowered by RASp [57]. Although rice cultivation in the catfish and shrimp ponds reduced respiration rates in the water and sediment, the respiration rates of the fish and shrimp remained unaffected [57]. The integration system improves the fertility of the soil and reinforces sustainable crop production [37,58]. Feng et al. [59] reported a 70–79% reduction in nutrient concentration in water samples in the co-culture compared to fish-monoculture, indicating that integrating aquatic species in rice fields can lessen environmental pollution. However, Li et al. [57] distinguish nine herbicides in 68 RASp and 30 sediment samples in the RASp integration in six provinces of China, posing ecological threats to the daphnia, fish, and algae.

The water depth required for successfully integrating the RASp system varies depending on different factors. Traditionally, rice monoculture employs shallow water, whereas RASp integration requires deeper water. In tropical conditions, continuous flooding of 2.5 to 7.5 cm of water is believed to provide an ideal environment for rice growth [60,61]. However, when rice fields are used for fish farming, deeper water is required. A deeper section of rice fields, called a fish refuge, is preferred by farmers for successful fish growth, with the ideal water depth for fish being 65–70 cm [62]. In Northeast India, the water level ranged from 1–3 cm in April, 10 cm from April to May, 51 cm on 15 August, and 24 cm at the time of fish harvesting in November [63]. In Bangladesh, prawn and small fish cultivation were maintained at water levels of around 30–40 cm in rice fields and 100 cm in ditches [64], while a water depth of 21 cm was needed for fish culture in rice fields [65]. In China and Bangladesh, the RASp integration was used at a depth of 20 cm [9,66], while in Vietnam, an average water level of 27 cm was observed in RASp integration [45]. In Thailand, the water level in RASp fields ranged from 15 to 35 cm throughout the rice growing season [48]. Hence, regional practices may differ slightly based on various factors.

In the coastal regions of Bangladesh, rice yield was not significantly affected by the depth of water (50 cm or 70 cm), while a higher yield of fish and shrimp was observed at the deeper depth of 70 cm. On the eastern coast of India, two water depths were identified: (1) a diversified farming system based on rice–fish integration for rainfed lowland (up to 50 cm water depth), and (2) a multitier farming system based on “rice–fish-horticulture-livestock” for deepwater (50–100 cm water depth) conditions. Sinhababu and Mahata [67] reported on the amount of rainwater harvested and its use in rice–fish diversified farming systems in rainfed lowlands in India. The 1300 m² pond refuge harvested 1820 m³ of water, corresponding to an average water depth of 140 cm. After five years of on-farm rice–fish farming in coastal saline areas, Sinhababu et al. [68] observed a 50% reduction in water salinity in fish refuge ponds.

A major obstacle to the widespread adoption of the RASp integration system is the lack of access to sufficient water [30,61]. Insufficient water, drought, and irregular rainfall can adversely affect fish growth in rice fields. In shallow water, fish experience increased stress, which can negatively impact their survival, growth, and reproduction [69]. Low water levels have a significant impact on the total fish biomass produced in rice fields [70]. Therefore, implementing the RASp integration system is difficult when the water supply is limited.

On the other hand, flooding or excessive water is one of the primary concerns that the RASp integration system has. When rice ecosystems flood, fish may escape, and wild, predatory fish may enter, leading to lower yields due to predation and disease transmission. The water quality in rice fields is also affected by floods as land-based pollutants contaminate it, hindering fish growth and production. The financial limitations faced by small-scale farmers in developing nations prevent them from constructing sufficient dikes in their rice fields, leaving them at risk of flooding [62]. The height of typical dams is about 25–30 cm, and the same width [62], and it’s important to note that financial constraints are the main reason why these farmers cannot build dikes to the proper height and width. Rice fields with low and narrow dikes are at a higher risk of flooding, particularly for small-scale farmers in developing countries who cannot afford to build higher dikes [62]. Furthermore, sluice gates, which could help manage water levels efficiently, are often absent in rice fields. As rice is the primary crop in the RASp integration system, fish farming must adapt to the water availability and needs for rice production. To prevent fish from escaping or fleeing during floods, stronger dikes with fencing and netting can be constructed around rice fields [31].

3.3. Land Use Efficiency (LUE), Labor Use Efficiency (LBUE), and Water Use Efficiency (WUE)

In a study conducted by Dwiyana and Mendoza [7], it was found that rice–aquatic species (RASp) systems increased LUE by 1.74 times compared to rice monoculture. Additionally, the rotational fish culture (ROTF) system had an even higher LUE of 2.58 times than rice monoculture. However, rice monoculture was found to have a higher LBUE (USD 3.07 per man per day) than rice–aquatic species integration (USD 2.69 per man per day), according to the same study [7]. On the other hand, the LBUE achieved with ROTF integration was higher (USD 4.16 per man per day during the rainy season and USD 4.74 during the dry season) than that of rice monoculture. Among various rice–aquatic species systems, fish yield was found to be the highest. In Karnataka, India, the integrated RASp system was discovered to generate an additional 41.4% of jobs and also had a higher LUE than rice monoculture [71].

The concurrent cultivation of RASp in China requires approximately 26% more water than rice monoculture. Therefore, these models are not recommended for use in regions with limited or insufficient water supplies [72]. In the Philippines, the trench refuge and pond refuge regimes have been found to increase water requirements by approximately 23.3% and 26.3%, respectively, compared to rice monoculture [73]. According to

Table 2. Comparison of rice and fish WUE (water use efficiency) values under various farming systems (FS).

Farming	Crop	Type of Study	WUE (Kg/m3)	Reference
Agriculture (river water)	Rice	Crop production & land use a	0.74	[74,75]
		Experimental a	0.85–1.6	[76,77]
		Review a	1.09	[78]
Aquaculture	Fish	Assessment a	0.21–0.37	[79]
		Review a	0.36	[80]
		Experimental a	0.207	[26]
Integrated	Rice–aquatic species	Assessment b	1.21	[31]
	Pig–rice–catfish	Experimental b	4.31	[26]

Note(s): ^a: WUE calculates by dividing the yield by the amount of water consumed. ^b: The WUE is calculated in integrated systems by dividing the yield (rice + fish + any other species) by the total amount of water consumed by all participating enterprises.

, which presents data from various sources [26,31,74,75,76,77,78,79,80], the water use efficiency (WUE) for integrated fish in rice fields is reported to be 1.21 kg/m³, which is at least 10% higher than the WUE for rice monoculture (0.85–1.60 kg/m³).

The taller rice plants provide shade to fish during the hot season, reducing thermal stress and potentially decreasing water evaporation [81,82]. Moreover, the integration of pig–rice–aquatic species increases WUE by approximately 39% compared to rice monoculture and 28% compared to rice–aquatic species. This suggests that incorporating more enterprises into paddy fields results in higher WUE values.

No recent studies have been conducted to measure the water use efficiency (WUE), land use efficiency (LUE), and labor use efficiency (LBUE) of integrated rice and fish cultivation. Therefore, it is recommended that more recent research be conducted to assess these efficiency measures.

3.4. Greenhouse Gas (GHG)

Cultivation of fish in rice fields has demonstrated a significant reduction in methane emissions (by about 14.8–22.1%) and nitrous oxide (N₂O) emissions (by about 9%), despite rice monoculture increases the emissions of greenhouse gas (methane (12%) and nitrous oxide) by 2.5% from the total GHG. This is due to water mixing at different levels by the movement of fish species and livestock, which boosts the DO level in the field’s standing water [83,84,85,86].

On the contrary, co-cultivation systems have been shown by several studies to result in a 26% increase in CH₄ emissions compared to monoculture systems [83,87,88,89]. However, the inclusion of fish, crabs, and crayfish in RASp (rice–fish, rice–crab, and rice–crayfish) significantly lessens N₂O emissions [89,90]. A rice–crab integration method minimizes seasonal N₂O emissions by 19.7–28% [89]. Additionally, the rice-cum-crayfish model reduced CH₄ emissions by 18.1–19.6% but increased N₂O emissions by 16.8–21.0% compared to rice monoculture model [91]. Co-culture RASp systems can reduce N loss from NH₃ volatilization and nitrate leaching while also promoting nitrogen use efficiency (NUE) through a reduction in N fertilizer applications [90]. Feng et al. [92] found that adding phosphorus to the RASp had no effect on CH₄ emission while adding K significantly increased CH₄ emission from the RASp by 18.4%. Combining P and K increased CH₄ emission from the RASp six-fold, with no effect on N₂O emission. In Germany, where the average temperature is 25 °C, the rice–carp model released the most methane, with an average of 13.6 mg m⁻² h⁻¹, followed by the rice–carp/tilapia model, which released 12.1 mg m⁻² h⁻¹ on average, and the rice monoculture model, which released 10.7 mg m⁻² h⁻¹ on average [69]. Methane production is often higher in rice paddies with higher temperatures due to the growth of methanogens [93,94]. Yu et al. [29] estimated that CH₄ emission increases with temperature, precipitation, soil DOC (dissolved organic carbon), soil MBC (microbial biomass carbon), and soil dehydrogenase activity, while it (CH₄ emission) decreases with soil Eh, soil nitrate, soil ammonia, soil urease activity, water pH, and aboveground biomass. N₂O emission depends on soil SOC (soil organic carbon), soil MBC, soil Eh (redox potential), soil nitrate, soil ammonia, soil urease activity, soil dehydrogenase activity, and water DO.

Several studies have shown that co-culture systems can significantly reduce the global warming potential (GWP) of rice production. For example, in southern China, the GWP of rice-Gibel carp integration was 4611–4754 kg CO₂ ha⁻¹ lower than that of rice monoculture (5391–5977 kg CO₂ ha⁻¹) [95]. Similarly, in China’s Jianghan District, rice–crayfish integration had a GWP of 3847–7205 kg CO₂ ha⁻¹, lower than the rice monoculture value of 5828–8478 kg CO₂ ha⁻¹ [90]. Xu et al. [96] reported a reduction in GWP of 11.1–21.1% with the rice–crayfish integration model compared to rice monoculture. However, in the northeastern part of China, rice–crab integration (both juvenile and megalopa) had a GWP between 9293 and 9811 kg CO₂ ha⁻¹ higher than rice monoculture (7275 kg CO₂ ha⁻¹) [88]. Previous studies conducted in East Asia have consistently found that co-culture systems effectively reduce CH₄ emissions and global warming potential (GWP) from rice paddies [90,93]. However, research conducted in South Asia showed that the RASp model resulted in a significant increase in CH₄ emissions ranging from 26% to 112% and GWP by 11–22% [69,83,88,94]. This difference could be attributed to variations in mean annual temperature and precipitation across different geographic locations.

The results indicate that CH₄ and N₂O emissions vary based on factors such as the type of aquatic species used in the co-culture system, fertilizer usage, mean annual temperature, and precipitation levels. Further research is needed to better understand the overall production and emission of CH₄ and N₂O, particularly under conditions of changing water levels, feed input, species and fertilizer types, RASp stocking density, and varying temperature and precipitation.

4. Benefits of Rice–Aquatic Species (RASp) Integration

4.1. Social-Economic Benefits

Integrating rice and aquatic species farming can significantly reduce the cost of rice production, as fish eat pests and insects and improve soil fertility, reducing the need for more feed and fertilizer. This approach increases rice yields by 8–26% and reduces pesticide use by 23.24% compared to rice monoculture [7,39]. Moreover, the use of chemical fertilizer is reduced by 24% in RASp, despite similar production yields, due to low labor requirements [9]. This method also increases farmer income by 40–57% during the dry and wet seasons, respectively [7,30]. Dwiyana and Mendoza [7] found that stocking two species of fish in the rice field produces 1 ton of rice at USD 39.89 (cash cost) and USD 54.44 (total cost), which means increasing the productivity by 40 to 57% during the dry and wet seasons, respectively. While Dewan [97], in his examination, displayed an average 164.4–198.2% increase in the benefit of fish in rice fields.

Integrating aquatic species with rice also provides a more diverse and healthier food supply than monoculture farming. In China, “rice–crayfish” integration reduced the cost of fertilizers and pesticides by 50% and 79.5%, respectively [37], and boosted the net economic budget for the ecosystem by 26.9–75.6% over rice monoculture [98]. Wang et al. [88] reported that the rice–crab culture also enhanced the ecosystem economic budget by USD 3412.66/ha for megalopa crab, USD 2757.47/ha for a juvenile than the USD 2229.49/ha for rice-monoculture. Tong [98] and Feng et al. [59] reported that the overall net income from RASp integration systems was as high as 115% of the overall revenue in fish-monoculture.

Additionally, RASp co-culture systems induce the motivation of farmers to adopt this method, as it provides double income sources from fish and rice, perhaps because of the lower cultivation costs with double income sources such as fish and rice, which induced the motivation of 70,000 farmers in Bangladesh to adopt rice co-culture systems with the support of non-governmental organizations (NGOs) [81,99]. Investigations in Bangladesh, Indonesia, and the Philippines revealed that integrating fish in rice yields net returns of 56%, 50%, and 207%, respectively [99,100,101], compared to rice monoculture. The net economic benefit of RASp is enhanced by the great value of aquaculture species [102].

Farmers can benefit from additional income opportunities by integrating rice–aquatic species with fish markets. However, the success of this integration depends on factors such as market demand, transportation infrastructure, and processing facilities. It is crucial to ensure sustainable fishing practices that do not harm the ecosystem or other species. Fish market prices vary significantly throughout the year, and introducing fish to the market simultaneously with harvests from various rice farms can negatively impact pricing. In contrast, fish pond owners can time the harvest and sale of their fish more flexibly, making them less vulnerable to drought, unlike farmers who need to prepare their fields for the upcoming season and cannot delay the sale of their fish.

4.2. Environmental Benefits

The significant environmental benefits of including fish in the fields of rice comprise (i) biodiversity, (ii) the use of resources and nutrients, and (iii) groundwater recharge, water storage, and climate.

4.2.1. Biodiversity

The preservation of biodiversity is a critical component of environmental stewardship, particularly given the threats to both terrestrial and aquatic ecosystems posed by population growth and food demand. Human activity has significantly disrupted biodiversity through environmental pressures and water contamination, making the management of aquatic habitats a unique challenge. Mono-shrimp farming, for instance, has caused severe damage to coastal biodiversity by harming flora and fauna [40]. Conversely, the integration of recirculating aquaculture systems (RASp) can help maintain genetic diversity in aquatic organisms while also offering benefits for farming efficiency and long-term nutrient use [103]. In rice fields, for example, introducing livestock through RASp has been found to promote biodiversity by creating a habitat for various aquatic flora and fauna, including fish that can eat disease-carrying mosquitoes [82,104,105,106]. Studies [35,107,108] have shown that RASp integration does not harm a large number of fish or aquatic biodiversity in rice fields and can even result in adaptable and successful co-cultivation, increasing aquatic organism biodiversity. In China, fish-integrated rice fields have a high ecological service value due to their unique farmland and environmentally friendly planting practices [105].

4.2.2. Water Resources, Nutrient

By allowing aquatic species and plants to share water resources, integrating rice–aquatic species (RASp) can significantly increase water resource utilization efficiency. In the hot season, rice growth can provide fish with more shade, reducing thermal stress and creating a water temperature suitable for fish growth [82]. Aquatic organisms facilitate the transfer of feed and organic matter from anaerobic to aerobic processes, lightening the soil, boosting the supply of plant nutrients stabilized by clay particles, improving soil permeability, and enhancing oxygen levels. By controlling insect and pest attacks on rice crops, aquatic species also reduce the need for pesticides [109]. RASp promotes a dynamic nutrient cycle in rice fields, with the excrement of aquatic species and livestock serving as a source of organic fertilizer that enhances the field’s carbon content, improving the C:N ratio. Rice crops benefit from nutrients derived from aquatic species and livestock feces, accelerating nutrient cycling [110]. Fish can use excess nitrogen from rice fields to produce proteins, which can be sold on the market to strengthen the economic situation of rural counties [41,111].

4.2.3. Groundwater Recharge, Water Storage, and Climate

Rice–fish cultivation can potentially benefit groundwater recharge, water storage, and climate change mitigation efforts [112]. In Thailand, integrating RASp increases water storage by 16,682.3 THB ha⁻¹ year⁻¹ compared to monoculture, which only stores 295 THB ha⁻¹ year⁻¹ [47,48]. Additionally, groundwater conservation increases from 9540 to 13,992 with the implementation of the RASp integration system [47,48]. By cultivating both fish and rice simultaneously, households can boost their income and well-being while reducing environmental harm and enhancing climate change resilience. Agricultural cultural heritage sites are often highly ecologically vulnerable because of their high population density, heavy reliance on the land, isolation, and lack of modernization, and could benefit greatly from the adoption of rice–fish cultivation practices.

Climate change affects rice–aquatic species integration, a farming system that combines rice cultivation and aquatic species. Climate change alters the hydrological cycle, leading to changes in water quality and availability. Extreme weather events like floods, droughts, and typhoons damage rice fields and aquatic habitats, reducing crop yields and fishery productivity. Temperature changes affect pests and diseases, negatively impacting rice and aquatic species. In recent years, a decline in precipitation has led to a proportional decrease in rice fields available for harvest. Climate change has caused changes in seasons and increased the frequency and severity of flood and drought events. However, RASp integration can counteract some of these effects. Crop evapotranspiration and water evaporation in RASp can increase surrounding humidity and improve precipitation and rainfall, particularly in dry regions where mesoscale convection can occur [113]. The large contact surface between air and water in paddy fields and the trapezoid-shaped trench around rice fields also contribute to mass water evaporation, which can regulate temperatures and absorb heat in the summer. Moreover, integrated RASp, such as rice–crayfish, can reduce the global warming potential (GWP) compared to rice monoculture, while rice-crap cultivation increases GWP from paddy fields.

According to the analysis, dry areas suffer from the absence of rice and fish integration due to drought, while flood-prone regions are vulnerable to damage. Hence, integrating RASp can be a potential solution to combat these issues by carefully choosing fish species based on specific geographic conditions. Adapting to these impacts requires resilient farming strategies, such as improving water management, diversifying crops and species, and enhancing renewable energy use.

5. Case Studies

5.1. Worldwide Case Studies

According to the literature review, most global rice–aquatic species farms are concentrated in South and East Asia. Still, there have been some developments in Africa, as shown in Figure 4 and

Table 3. Years of well-established rice–aquatic species in different countries.

Location	Starting Year	Reference
East Asia	In China, about 2000 years ago, in the era of the Han Dynasty	[43,45,49,62,88,111,112]
	The 1950s in Korea
	1943s in Japan
Southeast Asia	The Ciamis area of West Java, and Indonesia, even before 1860	[5,36,43,45,46,47,48,54,62,66,100,101]
	Over 200 years ago in Thailand
	1954–1974 in the Philippines
	1928 in Malaysia
	Kerala, Sri Lanka, Cambodia
	1975 in Vietnam’s Mekong Delta
South Asia	In India dates back almost 1500 years ago	[30,31,32,33,39,55,62]
	1980 in Bangladesh
Australia	Started in Southern New South Wales with carp in the rice field	[62]
Africa, the Middle East, and West Asia	1900 in Madagascar	[27,62]
	1953 in Malawi
	1992–1993 in Zambia
	1989 in Senegal
	1970 in Egypt
	1997 in Iran
Europe	At the end of the 19th century in Italy	[62,73,76,113]
	In the early 1900, in Hungary
	Danube Delta region
South America and the Caribbean	1940s in South America (10 countries) and the Caribbean (8 countries) Such as Brazil, Haiti, Panama, and Peru	[62,114]
US	1954s in The United States (US)	[62]

[5,27,30,31,32,33,36,43,45,46,47,48,49,54,55,62,66,73,76,88,111,112,113,114].

RASp integration has been an excellent source of nutrition and food security for farming communities worldwide, dating back to the Han Dynasty in ancient China around 2000 years ago [45,88], followed by India [39], Bangladesh [31,35], Vietnam [35,42,45,52,98], Egypt [59], Indonesia, Lao PDR [100,115], The Philippines [54,66,100], Cambodia [10], Malaysia, Myanmar [18], Thailand [46,47,48,62], Hungary [112], Sri Lanka [114,116], Korea [117], and Kerala [51,105]. RASp is most prevalent in regions with deepwater and rain-fed rice cultivation [117].

The total area of RASp co-cultivation has reached 1.67 × 106 ha, representing 4.48% of the total rice planting area in China [38]. In 2016, the area covered by rice–crayfish was 4.2 × 105 ha [37], while RASp reached 2.37 × 106 ha in 2019 and 2.53 × 106 h m² (a square hectometer) in 2020 [118,119]. This premise is becoming increasingly popular. RASp integration is practiced on 1 M ha, 0.8 M ha, 0.23 M ha, and 0.01 M ha in Indonesia, Vietnam, India, and Thailand, respectively. In Bangladesh, 20–30% of the total area of paddy fields, 10.14 million ha, is suitable for RASp integration [64]. However, in Korea, the presence of weeds, diseases, and pests makes it challenging to manage and control RASp, resulting in less than 1% of all paddies being organic rice paddies [117].

The RASp has gained increasing attention from the farming community in recent decades, primarily due to its promising economic returns.

Table 4. International experiences on rice–fish production practice.

Location	Principle Findings	Reference
China	The addition of Azolla (utilized as bio-fertilizer, fixed about 450 kg of N/ha annually, substitute 50% urea) to fish-rice culture increases fish yield by 70% more than without Azolla.	[120]
	In RASp, plantings with a high density (20 cm × 30 cm) yield more rice than those with a medium density (30 cm × 30 cm) or a low density (40 cm × 30 cm).	[121]
	Integrating rice and aquatic species intensively is an effective method for decreasing hypoxia in culture ponds.	[57]
Vietnam & China	Fish have the potential to effectively combat pests and diseases, as evidenced by their ability to decrease the population of herbivorous insects and weeds, as well as reduce the use of pesticides by 23.4–65%. Fish also lowered the abundance of invertebrate predators by 19.48% while increasing the richness and biomass of the ecosystem by 67.62% and 62.01%, respectively. Moreover, co-cultivating fish with rice in a recirculating aquaponic system (RASp) improved soil fertility and led to a 10.33% increase in economic value compared to monoculture.	[43,122]
Bangladesh	The RASp cultivation was seen as more gainful (remunerative) than rice monoculture regarding net return and benefit-cost ratio. Depending on the efficiency and productivity, tilapia or common carp can be cultured with rice using the suggested fertilizer.	[123]
Bangladesh and Vietnam	Fish farming has traditionally been done in rice fields that are either medium-flooded (50–150 cm) or deep-flooded (150–250 cm).	[35]
Myanmar	Concurrent rice–aquatic species (RASp) integration could maintain rice production relative to rice monoculture, with the added benefit of fish as a more nutritious food and higher value commodity, however, despite the fact that this has not yet been tested on a large scale.	[124]
India	Around USD 900 earnings can be created from 1 ha RASp integration, while USD 720 can be obtained from rice monoculture, whereas the income from the RASp integration is roughly 26.1% higher than monoculture.	[39]
Louisiana/US	Increase the yield of both Procambarus clarkia and Oryza sativa when they are cultivated together in the same field.	[125]
Nigeria	Fish–pig–rice integration reduces waste and input and increases productivity.	[26]

displays relevant international studies and research conducted on the subject [26,35,39,43,57,120,121,122,123,124,125].

However, the investigation overlooks several crucial factors, including the practical determination of WUE, appropriate plant–plant and row–row distance, feed quantity, water level, and the impact of climate change. Rice yields in East Asia and South Asia increased by 2.2% and 4.3%, respectively, but decreased by 6.7% in Southeast Asia and remained unchanged significantly in Europe [29].

Farming fish in paddy fields could lead to an increase in rice production by 8–25%. Favorable associations were found between rice yield and increases in above-ground biomass, soil total potassium, soil bulk density, and total water nitrogen. In contrast, negative associations were found with soil Eh and the presence of planthopper rice [29]. The impact of co-culture models on rice yields was time-dependent, with longer periods of co-culture resulting in increased yields [29]. Crayfish is the most important form of aquaculture in Asia [126].

According to FAO [127,128], there are 167 million hectares of rice fields worldwide, of which 134 million hectares are suitable for fish-integrated paddy rice. However, only 1% of this area is currently utilized for fish farming [111], leaving 99% of the area suitable for integration untapped. Introducing aquatic species into rice fields has the potential to significantly increase food production. If all suitable areas were utilized for rice and fish farming, an additional 125.96 million tons of rice and 46.90 million tons of fish could be produced annually [8]. This suggests that growing aquatic species in rice fields could increase food production by up to 27%.

5.2. National Case Studies

Egypt has a long history of rice cultivation and is known for its high-quality rice production [129]. Integrating rice and aquatic species is an important aspect of sustainable agriculture in Egypt. Over the years, Egypt has successfully implemented several national rice–aquatic species integration case studies, some of which are highlighted in

Table 5. History of rice–aquatic species integration in Egypt.

Main Findings	Reference
Limited tests were applied to rice–carp at the beginning of the 1970s with reinforcing results.	[130]
The rice–aquatic species cultivating region extended significantly utilizing reclaimed salt-impacted lands and, in 1989, reached a peak of 225,000 ha. As rice costs increased, however, high-yielding varieties (HYVs) were embraced, and reclamation areas were utilized for rice monoculture. By 1995, the area containing RASp integration had shrunk to 172,800 ha. Regardless the 1995 fish production from rice fields represented 32% of the total aquaculture production in the country.	[131]
In 1997, 73,500 tonnes of C. carpio were produced from the addition of 58,000 ha of cultivable area.	[132]
Determine which fish species (C. carpio or O. niloticus) are most suitable to stock rice fields. At the conclusion of the experiment, the average body weight of C. Carpio rose from 11.7 g to 154.5 g, while that of O. niloticus climbed from 26.2 g to 176.8 g. It was advised to cultivate tilapia rather than C. carp in rice fields because of the high selling price of tilapia.	[133]
In 2008, a significant increase in the aquaculture industry from rice paddies began. This brought in a limitation of freshwater shortage joined, and the high-water requirements for rice farming necessitated the integration of fish farms with rice ranches. Public authority farmers provide free supplies from the fingerlings of common carp to support this farming approach in Egypt. In 2009, the full production reached 37,700 t from fish in rice fields.	[134,135]
Fish output in rice fields climbed from 10,000 t in 1999 to 34,000 t in 2014, with tilapia representing around 48% of the total performance and catfish and common carp making up the remaining 50%.	[136]
The production declined from 34,000 t drastically to 17,500 t, 13,535 t, 7700 t, 11,800 t, and 15,893 t in 2015, 2016, 2017, 2018, and 2019 respectively.	[137,138]

[130,131,132,133,134,135,136,137,138].

Overall, integrating rice and aquatic species (RASp) has been a successful strategy for sustainable agriculture in Egypt. It has not only increased the income of farmers but has also provided a source of protein for local communities and reduced the use of pesticides and herbicides. The constant reduction of the lands designated to the co-culture is gotten back to the paddy season is not adequate for producing market-size fish. Therefore, juvenile fish raised in rice fields are relocated to other aquaculture systems for further growth. During the rice harvesting season, when the fields are drained, the fish are confined to the ditches and trenches, making it easier to collect them [139].

According to CAPMAS [140], Egypt has a total rice area of 1,305,540 acres, which produces 4.5–5 million tons of rice. Around 100,000 acres of this area are used for fish cultivation in rice fields, yielding 15,893 tons in 2019. If the entire rice area is utilized for rice–aquatic species integration, it is estimated that Egypt could produce an additional 867,341 tons of rice and approximately 208,890–680,000 tons of fish.

6. Sustainable Rice–Aquatic Species

Sustainable rice–aquatic species (RASp) are becoming increasingly popular due to their ability to decrease the environmental impact of rice farming while increasing productivity. To ensure sustainability and maximize benefits, farmers can implement several best practices. Firstly, maintaining proper water levels in rice fields can reduce nutrient loss, prevent weed growth, and conserve water resources. Secondly, using organic or natural fertilizers like compost or animal manure can improve soil health and decrease the need for chemical fertilizers, which can harm aquatic life and water quality. Thirdly, integrated pest management strategies can help control pest populations without using harmful chemicals.

To meet sustainability criteria, certification and labeling schemes like the Sustainable Rice Platform (SRP), Fairtrade, and Organic certification have been developed. These schemes provide standards and certification for responsible and sustainable production practices, promoting transparency and encouraging continuous improvement. Certification can also help farmers access new markets and increase their income. In conclusion, implementing best practices and obtaining certification can help maintain sustainability and maximize the benefits of sustainable rice–aquatic systems, improving farmers’ livelihoods and reducing environmental impact.

7. Constraints and Challenges

Despite the numerous benefits highlighted in this survey regarding the use of RASp (rice with aquatic species), several challenges remain for scientists to address. RASp farming requires deeper water depths than traditional rice cultivation, making it more suitable for areas with ample water supply, such as rainy regions [62]. However, this limits the use of short-stemmed, high-yielding rice varieties, favoring drought-tolerant strains grown with water from fish farming. Incorrectly modifying the fish-to-rice ratio can lead to low yields for both crops.

Ensuring sufficient nitrogen and phosphorus is crucial, added in limited quantities through feed to prevent pollution [141,142,143]. Intensive culture in rice fields is necessary to meet the required fertilizer levels. The lack of technical skills, guidance, and labor support for RASp hinders its adoption. Global collaborations are needed to transfer technical expertise and provide institutional support, training facilities, and extension services, as seen in successful examples from China.

RASp farming requires a larger initial investment for installing bunds, drains, and shelter in rice fields [62]. Geospatial and environmental data knowledge can optimize resource use [144,145]. Access to low-interest credit from government agencies, national banks, and non-governmental organizations could encourage resource-poor farmers to switch to RASp farming.

Lastly, the insufficient research and innovation to improve management and cultural practices is a significant constraint on RASp farming in Egypt. Therefore, agricultural policymakers and agronomists must champion the benefits of combining aquaculture with rice and explain these advantages to rice-growing communities to promote farming with aquatic species. By addressing these challenges and supporting RASp with the necessary resources and knowledge, we can unlock its potential to contribute significantly to sustainable and resilient agricultural systems.

8. Future Prospects

To enhance future research on rice–aquatic species cultivation, several international areas should be considered. (1) Develop advanced technology for disease and pest control in RASp farming. (2) Improve irrigation systems to mitigate flood and drought impacts. (3) Incorporate smart technology into integrated agriculture between rice and aquatic species (RASp). (4) Investigate the connection between gas emissions and the quality of aquatic species in integrated farming. (5) Optimize fertilization rates, methods, and feeding practices for maximum productivity and safety. (6) Select appropriate rice species for fresh and brackish water usage. (7) Develop climate-resistant strains of rice and fish. (8) Evaluate the climatic impact on different rice breeds, fish species, and livestock. (9) Determine the impact of RASp integration on GHG emissions, water quality, and biodiversity. (10) Practically measure water use efficiency in the field.

On a national level, in addition to the above points, the following areas should be considered for future research. (1) Evaluate the ecological and environmental value of rice–aquatic species farming. (2) Develop fish aggregating and harvesting techniques, as well as optimal rice planting patterns in rice fields. (3) Prioritize RASp integration efforts in areas with abundant water resources. (4) Promote intensification and diversification to boost fish production and profitability when feasible. (5) Establish appropriate prices for rice, livestock, and fish products. (6) Provide optimal supplies of seed, fodder, and technical expertise for maximum productivity. (7) Facilitate knowledge transfer and experience sharing. (8) Provide necessary technical and guidance support.

Further scientific investigation is needed for feed quantity and quality, system optimization, fertilizer and pesticide applications, plant–plant and row–row distance, water levels, climatic effects on co-culture, and adoption suitability. Addressing these areas will contribute to sustainable RASp farming globally and nationally.

9. Conclusions

The survey confirms that integrating aquatic species in rice fields is an effective water-saving practice, boosting crop yields and mitigating water scarcity risks globally and locally. However, concurrent rice–aquatic species (RASp) integration requires more water than rice monoculture, making it unsuitable for water-limited areas. Despite this, RASp systems offer numerous benefits, including improved farm production, revenue, land and water resource use, and lower GHG emissions.

China excels in land and water use proficiency, but RASp co-culture needs a climate-resilient policy framework. Climate change affects rice–aquatic systems, necessitating strategies, such as water management improvements and crop diversification. Sustainable RASp systems are vital for food security and rural livelihoods, emphasizing practices such as maintaining water levels, using natural fertilizers, and integrated pest management. Certifications like SRP, Fairtrade, and Organic support sustainability and market access.

To maintain product quality, regulating the intensity and spread of joint farming and feed application on a large scale is essential. Training, workshops, problem-solving, long-term business plans, technical support, and public–private partnerships are needed to enhance RASp’s role in sustainable food production. More research is required to expand future production and promote policies for sustainable food production through rice–aquatic species integration.

At the local level, overcoming obstacles like technical expertise, production expenses, and water scarcity is crucial for RASp adoption. Persuading rice farmers to use integrated RASp will boost their incomes and local food availability, enhancing overall food security. Encouraging integrated RASp farming nationwide can boost the food supply.

For water-rich regions, there is no reason to oppose expanding integrated RASp. Although there are limited water resources, drought-tolerant rice strains can be grown with water from fish farming. This review proposes globally increasing fish integration in rice fields, focusing on high-production, rainfed regions. Specific coastal practices: adopt Bangladesh’s gher system, and promote rice shrimp farming in Vietnam and India. Seasonal approach: rice in monsoon, shrimp in the dry season, simulating saltwater influx. Emulating successful rice strains from India’s Kuttanad Wetland Agriculture System can benefit areas near the sea. These practices enhance the integration of fish and aquatic species in rice fields, providing ecological and agricultural advantages.