**2. Integrated rice-aquaculture farming (RAF)**

in highest population in the world, it is expected that India may become the highest populated

The size of the population depends on its number and the ratio of available bearable resources. The population size also is contingent on the way resources are used and disseminated between the populations. To meet the demands of forever growing human population, major agricultural fertile lands are getting converted into residential areas. The total available land area in India occupies 2.4% of total land area of the world. Added fertile land area exists in India than any other country except the USA and Canada, which are holding more water area [1]. Because of the availability of more arable land and water, India became an agriculture-based country. From ancient days, major Indian populations live in villages and revolve mostly around agriculture and allied activities. It is well exemplified with the statistics of Indian population since 1947; it is tripled due to improvised and sub-standard conditions in India [2]. However, due to enormous increase in population along with increased poverty, modernization and more effectively globalization and medication, majority of the adjacent villages of small towns and all most all large and moderate villages located around cities were urbanized. Urbanization

The food scarcity is the predominant factor that influences the growth and economy of the overpopulated country. Supplementation of nutritious food to the forever growing human population in a nation like India or overall worldwide is at most target of governments or World United Nations. Though the agricultural land area is getting reduced due to overpopulation in the world, it is the focus to produce sufficient or more amount of nutritious food to meet the demands of population. The conventional methods of agriculture may not produce or increase the food productivity. Alternative methods are in focus to produce high amount

Since ancient days the traditional cultivation methods were contributed for the food and living safety throughout the world. But at the present day, farming is completely linked to high yield by usage of many varieties of pesticides. This type of farming certainly pollutes the environment and drags the farmer into debits due to high investment on crops in the case of crop failures, which ultimately cause suicides of the farmers and their families in developing countries like India. One of the reasons for this is majority of the farmers are focusing only on one crop at time where there is a high degree of uncertainty. Besides this, the usage of excess amounts of pesticides and fertilizers causes imbalance in ecosystem and alters the natural environment, which ultimately influences the flora and fauna of that area, including soil microbiota [3], which may cause drastic change in the livelihood and may also be one of the responsible factors causing severe change in natural cycle and seasons such as reduced rainfall, increase in the temperatures and short or prolonged yearly seasons besides health hazards in the consumers. To overcome the above circumstances, integration of various agricultural enterprises, viz., cropping, animal husbandry, fishery, forestry, etc. has great potentiality in the agricultural economy. The usage of expertise of conventional methods in

The conventional methods of agriculture are completely successful and are developed by farmers for different environments which maintain rich biological diversity [4–6]. According to

country by 2050 as per World Population Data Sheet of 2009.

12 Aquaculture - Plants and Invertebrates

caused drastic conversion of arable agricultural land into modern housing.

combination of modern methods is well explained in many studies [4–6].

of food by using available agricultural land.

Integrated culture is not new and exists naturally. The natural ecosystem itself is a big example for integrated culturing where a number of flora and fauna living together in the same area of land. Coming to the natural integrated system in the rice fields, besides fish species coming from outside through water, crabs grow by making burrows within the field. The best well-known natural example for integrated rice and aquatic species (ASp) is rice and freshwater crab culture. The freshwater crab *Oziotelphusa* (*Oziotelphusa*) *senex senex* enormously grow naturally in rice fields in India. Since its natural occurrence in the rice fields, this crab is popularly named as 'Indian rice field crab'. This crab is a good source of protein and is available throughout the year with no cost. The name 'poor man's protein' is also popular for this freshwater rice field crab since most farmers (poor villagers) consume it [12, 13]. Though the farmers do not focus on naturally occurring integrated rice systems like crab within the rice fields for commercial purpose, they understand the importance of more than one culture within the same field. One more thing that the farmers focused on is commercially important species and benefit out of its yield along with the main crop.

The culturing of ASp in the rice fields is originated from the farmers, who were experienced with fish along with prawns, crabs and other invertebrates grown naturally (ASp moves from ponds to rice fields through irrigated water) in the rice fields without adding any ASp seed in the irrigated field. The observation takes the farmers to culture ASp in the rice fields initially without any selection of the ASp. Later farmers are motivated to grow selected ASp with rice by following conventional methods based on the conditions of the local environment. In the ancient days, the farmers tasted the yield of integrated rice-ASp culture. In the beginning, it was called as rice + fish culture [14, 15]; later, it became rice-aquaculture. The uncontrolled entry of outside ASp into the integrated culture field and leaving the cultured ASp to outside the field are problems even today, but capture system of rice-ASp culture was introduced to overcome this problem [16]. In this system, cultured ASp purely depends on the naturally available feed in the field. But in general, farmers supplement feed for growing organism from outside. However, continuum in the transition from pure capture culture to a capturebased production system is gradual and is described by Halwart [17].

Integrated rice and aquatic species culture have lot of scopes and achievements of high productivity in terms of carbohydrate and protein with proper management methods and controlling systems. The selection of culture species plays a crucial role in productivity, besides environmental conditions and proper management at the time of culturing. However, the farmers are in practice to cultivate the integrated rice and aquaculture in many areas of Asian countries and some of the African countries.
