Preface Freshwater aquaculture is an age old tradition in many countries like Australia, China and Japan. Even today, fish remains one of  cheapest sources of animal protein. Capture fisheries and aquaculture together form an important food producing sector with a special projection on its prime role in eradication of protein deficiency and malnutrition among rural poor. Global aquaculture production has already crossed 80 million tons and in spite of all problems, there has been a steady growth in this sector. This comprehensive publication “Handbook on Freshwater Aquaculture” is the collective effort of a wide array of eminent people associated with Indian aquaculture. Special emphasis has been given to aquaculture and its prospects and problems in rural India especially the lesser known areas of Northeast India. The book covers almost all important aspects of freshwater aquaculture, both traditional and modern aquaculture techniques, water quality issues, integrated farming practices, environmental, socio-economic and livelihood issues. It is expected that the book will prove to a source of useful information for the needs of students, scholars, farmers and researchers.

Introduction In recent years aquaculture has become the fastest growing food production sector in the world with 10% annual growth rate in comparison with 3% for livestock and 1.6% for capture fisheries. FAO (2000) estimates that by 2030, over half of the fish consumed by the world’s people will be produced by aquaculture. It is not only the demand for animal protein but the high returns associated with aquafarming when compared with agriculture or animal  husbandry that has accelerated the growth of aquaculture. Thus, in the last two decades aquaculture with greater emphasis on shrimp farming made fast strides among Asian countries including India. The culture of carps in freshwater and shrimps in brackishwater are the two main culture practices followed in India. During nineties around 10% of 2.7m ha. brackishwater area has been put under farming along with a number of other supporting and ancillary units viz.; hatcheries, feed mills, processing and packaging industry etc.

Fish is the most important source of protein for the people of Northeastern India where almost 100% people are fish eaters. So fish culture is very popular in this region. There is a huge demand for fish here and the most popular aquaculture practice is pond culture. The state of Tripura particularly progressed well in fish production and became self sufficient in fish seed production. The state is blessed with 22,895 ha of water bodies where more than 50% (12,895 ha) of area is used for aquaculture purpose. Composite fish culture and integrated aquaculture are very common here. These fish ponds are very productive both in eco-physiological and faunistic point of view. Most of the farmers have a pond area of less than one hectare for fish culture and are unable to go for any supplementary feeding. Average fish productivity is estimated as 1800 kg/ha. Preliminary experiments conducted in the Institute showed that timely application of the fertilizer and/or restricted supplementary feeding improves total production.

Introduction In present times aquaculture is being practiced using both conventional or non-conventional methods with considerable variations. Aquaculture can be termed as – extensive, semi-intensive and intensive based on operations and involvements. An increase in the intensity of aquaculture requires an increase in capital as well as operational costs. Here we will examine the three main levels of aquaculture used in various habitats and later consider the conventional methods of aquaculture. Different Levels of Aquaculture Fish culture practices can be classified into three different kinds or levels on the basis of the intensity of aquaculture in terms of capital as well as operational costs. The chances of crop failure often increase with increasing intensity of aquaculture, which may involve: 

Fish production of the country has improved considerably in the post-independent India with the total production going up from 7.52 lakh tons in 1950-51 to 90.4 lakh tons in 2010-11, with an average growth rate of 4.35% per year after 1990. The real jump has come from inland aquaculture sector. Production from inland waters which used to be less than 30% of the total till sixtees, gradually rose at a fast pace and crossed the 50% mark by the end of 20th century. The present contribution of inland sector to the country’s total fish production of 52.09 lakh tons is 58% recording an average annual growth rate of 8.4% per year after 2011. This increase in contribution from inland sector is because of the quantum jump in production from freshwater aquaculture, made possible mainly due to development of technologies of hypophysation of Indian Major carps and composite fish culture during late fiftees and sixties respectively. Development of these two technologies, along with their wide extension through Fish Farmer’s Development Agency, initiated by Govt. of India in latter part of 1970s, have in fact revolutionised freshwater aquaculture scenario of the country. It is presently contributing to over 70% of the total fish production  from inland resources of this country.

Fish culture is an age old tradition modified and improved by several scientific inventions. Farmers can easily take up fish culture in village ponds, tanks or any water body and can improve their financial position substantially. Pond aquaculture is the most common method of fish culture throughout the world. For successful aquaculture of fish, molluscs, crustacean and even aquatic plants, the water and soil in which fish are grown should have favourable conditions for their growth which, in turn, is intimately linked with several physical, chemical, biological characteristics of water and management practices adopted. Physical and chemical characters of the soil and water will affect the primary and secondary production of water bodies. The survival and production of fish in a pond is dependent on the primary and secondary production. Primary production depends on the water quality parameters. Phytoplankton make carbohydrate using sunlight and releases oxygen. This is the major source of energy and oxygen in the ecosystem. Zooplankton which feed on the phytoplankton form major source of food for the fishes.

Background In simple term, what agriculture is to land aquaculture is to water and can be defined as the art, science, and business of cultivating plants and animals in water. Considering scope of inland aquaculture in the present discussion would be limited mostly to grow desirable fish/prawn (hence forth termed as fish) in fresh water ponds and to some extent to their seed production in hatcheries. The important activities in aquaculture includes deliberate interventions during the rearing process or life cycle of the stock, management of the culture system and production process so as to increase survival and production of stock. Since, the main goal of aquaculture is to maximize the fish production per unit land/water resources per unit time which primarily depends on the degree of management and intervention. The important forms of intervention and management practices are regular stocking, fertilization, feeding, liming etc. The degree of care taken or effort put in these aspects would determine the level of production.

Availability of quality fish seed is the critical and basic input for successful fish culture operations. Till the sixties, a major part of the seed required for culture was being collected from the riverine sources, which had several disadvantages. Indian major carps viz. Catla, Rohu & Mrigal and Chinese carps viz. Silver carp & Grass carp mature in the pond but do not spawn or lay eggs in standing waters. Usually they breed or spawn naturally in flowing rivers during monsoon months. In artificial breeding, certain inducing agent (hormone) is injected to fish for successful spawning. In India, the first successful induced breeding of carp was achieved through use of pituitary hormone in 1957. Increased seed production of fish today is a direct result of improved technologies of breeding, hatching and rearing. Three decades ago, earthen “pit” hatcheries were used for hatching eggs around bunds. Today large commercial hatcheries exist, where all activities such as raising of brood stock, breeding and fry rearing can be undertaken. This has certainly marked the growth of the industry. Commercial Chinese hatchery facilitates not only large-scale production of fish seeds but also improves the survival percentage of seed.

Introduction Packing and transportation forms an important component in fish trade whether live fish, fish seed, fresh fish, iced fish or dried fish. There are few reasons necessitating packing and transportation.     ·    The movement of fry/juvenile for stocking into farms or restocking into natural environment.     ·    The movements of fish to markets for sale selling/consumption.     ·    The movements of ornamental aquarium live fish for trade.     ·    The movement of aquatic animals for research purpose.

The aquaculture sector showed an overwhelming growth of 468% during the last two decades and is presently playing a key role in the changing Indian economic growth. The contribution from aquaculture is 21.6% by volume and 49.3% by value to the total fisheries exports. Inland fisheries sector had shown consistent growth of over 5% per annum over the period of 1999-2005. High demand of aquaculture products in the world has forced the aquaculturist to change the culture system from extensive to intensive. This has led aquaculturist to lose millions of dollars due to fish mortalities associated with fish disease and related conditions. Out break of disease has been considered as a major stumbling block in intensive aquaculture practices. Disease is a very complex interaction between three important factors, namely the susceptible fish, the disease causing agents (pathogen) and the environment. These three factors are most important and must be considered in any fish disease outbreak. The environment in which the causative agent of diseases and their host fish interacts, may favour one or the other. Changes in the environment, whether natural or artificial, may shift the balance from one side to the other and will often determine whether the host will survive or succumb. Understanding and managing the stress and their causative factors are thus the key factors for successful aquaculture.

Introduction Pearls have been favourite jewel of humanbeing since ancient times. Pearl is a natural gem and is produced by living organisms, the pearl oysters and mussels (Molluscs), unlike other precious stones. It is perhaps, the only gem that does not require the treatment by lapidary. According to our Indian system of gemmology, of the nine maharatnas (Heera, Mukta, Manikya, Pravala/Munga, Gomeda, Indra-neela, Vaidurya, Pushyaraga, and Panna) pearl (Mukta) is only next to diamond (Heera). The science of pearl culture has not been widely popular, however, the art and trade form has reached the zenith. With the turn of the last century, the demand for pearls increased, but their supplies from the existing fishing grounds have diminished due to overexploitation and pollution. Such a situation necessitated tremendous research attention in the following decades with support from state and trade sectors, the world over. This led to the evolution of culture pearl technology as a booming aquaculture enterprise in Japan and China. These two countries have a monopolistic control over pearl trade.

Introduction Aquaculture has been shown to offer high potential to fill the gap between supply and demand for fish and fish products to mitigate the problems of malnutrition with ever increasing world population. Globally, aquaculture has been growing rapidly in the last decade, approximately at 10-15% per year. The total aquaculture production, which was 26.7 million metric tonnes in 1996 increased to 37.5 million metric tonnes in 2001, in which tropical countries have been particularly contributing well, with the Asian component exceeding 80% (Ayyappan and Jayanthi, 2004). The country has varied and enormous aquatic resources (coastline: 8041kms, EEZ: 2.02 million sq. km., river & canals: 171334 km., brackish water area: 1.422 million ha., reservoirs: 2.050 million ha., ponds: 2.855 million ha., beels & oxbow lakes: 0.788 million ha) (Gopakumar, 2000). The North-Eastern region of India is endowed with rich diversity of aquatic and biotic resources, which needs judicious and scientific exploitation for diversification of farm practices so as to mitigate the problem of demand and supply of quality food.

The North Eastern Region of India possesses unique potential for fishery activities. The region represents all agro-climatic zones ranging from warm water drainage system to cold water conditions facilitating freshwater fishing and is identified as the hot spot of freshwater biodiversity. So far about 267 fish species have been reported to be present in the region, which is approximately 33.13% of the total Indian fresh water fishes (Munilkumar and Nandeesha, 2007). The total land coverage of the region is 2.55 lakh sq. km. which is about 7.76% of the country, out of which 70% is hilly terrain (Mahanta and Tyagi, 2003). The main fishery resources of the region comprises of rivers (18,968 km), reservoirs (8,019 ha), beels/lakes (1,48,491 ha) and tanks and ponds (42,782 ha) (Ghosh and Ponniah, 2008). The North Eastern Region of India with its large fish eating population, needs planned sustainable development of its existing as well as potential fishery resources. A challenging environment for fisheries development prevails in the region by way of very high demand and price of fish. Given the socio-economic conditions and vast fishery resources of the region, there is a strong chance for diversion of work force to productive sectors like fisheries thus transforming the economy of the region and further socio-economic development.