by
B. S. BHIMACHAR and S. D. TRIPATHI
Central Inland Fisheries Research Institute
Barrackpore, West Bengal, India
A REVIEW OF CULTURE FISHERIES ACTIVITIES IN INDIA
Abstract
Pisciculture, though an age-old industry in India, was practised only in a few States in Eastern India and was based on the empirical knowledge of the farmers. With the establishment of Fisheries Departments in the states extensive surveys of the fishery resources were initiated, but much headway in piscicultural research was not made until after Independence.
With the attainment of Independence and an emphasis on greater food production, fish culture activities were expanded to cover almost the entire country and research organizations established to scientifically investigate fish culture problems. Considerable advancement has since been made in various fields. A large number of fish seed collection centres have been established and the technique of spawn collection improved; survival rate during rearing from spawn to fingerling stage appreciably increased; mortality during transport of fish seed greatly reduced; swamps and other derelict waters reclaimed by eradicating or controlling the aquatic weeds; bundh breeding techniques of Indian major carps improved and activities expanded; and, both the Indian major carps and the Chinese carps successfully bred by administration of fish pituitary extracts. A large number of fish breeding centres have been established.
LA PISCICULTURE EN INDE - ETUDE GENERALE
Résumé
La pisciculture, quoique étant en Inde une activité séculaire, n'était pratiquée que dans quelques Etats de l'Inde orientale et était fondée sur des connaissances empiriques. Avec la création dans divers Etats de départements des pêches, des enquêtes approfondies sur les ressources piscicoles ont été entreprises, mais la recherche dans ce domaine n'a fait de réels progrès qu'après l'indépendance.
L'accession à l'indépendance s'est accompagnée d'un souci grandissant d'accroître la production alimentaire, aussi les activités piscicoles se sont-elles étendues à la quasi-totalité du pays en même temps qu'étaient créées des organisations de recherche chargées d'étudier de manière scientifique les problèmes liés à la pisciculture. Des progrès remarquables ont été faits dans divers domaines: un grand nombre de centres de collecte d'oeufs de poisson ont été établis et la technique de ramassage du frai a été améliorée; le taux de survie des alevins en cours d'élevage s'est notablement élevé; la mortalité des oeufs de poisson en cours de transport a diminué considérablement; des marécages et autres plans d'eau délaissés ont été récupérés par l'élimination ou le contrôle des plantes aquatiques; les techniques d'élevage des principales carpes indiennes dans les bundh ont été améliorées et développées; enfin, on a réussi à faire reproduire les principales carpes indiennes et les carpes chinoises en leur injectant des extraits de glande pituitaire de poisson. Un grand nombre de centres d'alevinage ont été créés.
RESEÑA DE LAS ACTIVIDADES PISCICULTURALES EN LA INDIA
Extracto
Aunque la piscicultura es una industria antigua en la India, sólo se practicaba en pocos Estados de la India oriental y estaba basada en el conocimiento empírico de los cultivadores. Con la creación de Departamentos de Pesca en los Estados se iniciaron amplios estudios de los recursos pesqueros si bien no se lograron grandes avances hasta después de la independencia.
Al alcanzar la independencia y concederse gran interés al incremento de la producción de alimentos, se ampliaron las actividades pisciculturales hasta abarcar casi la totalidad del país y se establecieron institutos de investigación para estudiar científicamente los problemas de la piscicultura. Desde entonces se ha hecho un gran progreso en distintos sectores. Se ha incrementado un gran número de centros de recogida de material íctico de repoblación y se han mejorado las técnicas de recogida de la freza; se ha incrementado la tasa de supervivencia durante la cría desde la eclosión hasta la fase de jaramugo; se ha reducido grandemente la mortalidad durante el transporte del material para repoblación; se han rehabilitado zonas pantanosas y otras aguas abandonadas mediante la eliminación o el control de las plantas acuáticas; se han mejorado y desarrollado las técnicas de cría bundh de las principales carpas indias, y se ha obtenido la reproducción de las carpas principales indias y de las carpas chinas mediante la administración de extractos pituitarios de pescado. Se ha establecido un gran número de centros de cría de peces.
India has vast culture fishery resources. There are innumerable small and large pond and tanks, jheels and bheels, swamps, and brackish-water lagoons and bheris. According to an estimate, 18,269,104 acres (7,307,642 ha) of cultivable waters exist in India (Anon., 1962b). Large areas of these potentially rich cultivable waters are at present lying fallow and could be made to produce considerable quantities of fish if developed on sound scientific lines. The production from existing cultivable waters could also be further enhanced by adopting improved techniques of fish culture.
Though an age-old industry, mentioned as early as 1127 A.D., fish culture has been mainly confined to the eastern states of Bengal, Bihar and Orissa. Here great potentialities for a fish trade have always existed, fish being the main diet of the rice-eating population of this region (Day, 1873; De, 1910). In the plains and deltaic regions of these states a large number of ponds have been dug within the past two centuries for construction work on railways and buildings, creating new waters. A large number of bheels and lakes, cut-off portions of river courses, also exist which have come into being due to natural causes. A net-work of major rivers providing the young of quick-growing carps, and the richness of the pond soil, helped the development of the industry. As the culturable carps (mainly catla, Catla catla, rohu, Labeo rohita, mrigal, Cirrhina mrigala and calbasu, Labeo calbasu) commonly called the major carps, did not breed in confined waters, the fishermen devised effective methods of collecting their spawn from the flooded rivers, the Ganga, the Mahanadi, and their tributaries during the monsoon months. Others explored ways of breeding them in confined areas by creating the flood conditions artificially and were successful in their attempts. Such ponds, where carps were made to breed, were designated bundhs. The eggs, collected from these bundhs, were and are still hatched in earthen pits in the vicinity of the bundhs where large-scale mortality is a common feature. The methods of transportation of spawn from the collection or production centres to the nearby ponds, or to markets also entailed heavy mortality.
No attention was ever paid to growing the spawn in nurseries before stocking them in the larger water bodies, which resulted in poor yield. To many, fish culture consisted of purchasing some spawn from the market, putting them in the pond and finally reaping a harvest at the end of the year. In brief, though an ancient industry, fish cultural practices in India lacked a scientific background. The empirical methods, as developed by the local fishermen, were often wasteful and faulty, thus seriously limiting production and returns.
In the later half of the nineteenth century and early in the present century attempts were, however, made to culture exotic food fishes to develop the supply of fish in regions which did not have a rich indigenous fish fauna. Though gourami (Osphronemus goramy) was introduced first in 1841 in Calcutta, it did not survive and was reintroduced in 1865 in Madras (Raj, 1916).
Early in the present century, with the organization of Fisheries Departments in certain states, attempts were made to extend fish culture practices to other parts of India and to develop these on scientific lines. Notable amongst these are the efforts of the Madras Fisheries Department. On the recommendation of Nicholson (1915) a large fish farm was established in the State at Sunkesula (Krishna District) (now in Andhra Pradesh) in 1911 with the object of (i) stocking barren waters, (ii) supplying of live fish direct to the markets, and (iii) distributing larvicides. In subsequent years a large number of ponds, tanks, moats and irrigation reservoirs were stocked with major carp fry and fingerlings, mostly collected from the river Godavari and inundated paddy fields in the deltaic region of the river.
Further attempts at introducing exotic fishes, O. gorami from Java and Mauritius in 1916 (Nicholson, 1918; Hornell, 1920) at Sunkesula and Cyprinus carpio from Ceylon to Ootacamund in 1939, met with some success. The nesting and breeding habits of gourami, Mystus aor and M. seenghala were studied (Hornell, 1922). Experiments were started as far back as 1918–19 to determine the relative values of different kinds of artificial food, such as ground-nut and gingelly oil-cake (Hornell, 1920) and a district by district survey of irrigation tanks and other inland waters was made.
Though traditional practices of culturing fish and prawns in embanked brackish waters exist in West Bengal and in the low-lying paddy fields of Kerala where mullets (Mugil spp.), prawns (Penaeus spp. and Metapenaeus spp.), bhetki (Lates calcarifer), pearlspot (Etroplus suratensis), etc., constitute a catch, systematic attempts to culture brackish-water fishes in fresh and brackish waters, to utilize the coastal saline swamps and low-lying areas in the deltaic regions, were first made by Madras Fisheries Department. Etroplus suratensis was introduced in the fresh-water tanks of Salem district and the gun powder factory ponds of Madras in 1915, and later bred at Sunkesula (Hornell, 1922). Experiments to determine the best species of mullets for stocking the fresh-water tanks, and the methods to be employed in conditioning and transporting them, were undertaken. From 1931 onwards, the Department made initial attempts to acclimatize and grow the white mullet or milkfish, Chanos chanos, in various departmental ponds, the fry being plentiful on both the east and west coasts during May-June and to a limited extent in November (Ranganathan, 1961). Unfortunately, proper management techniques with regard to the culture of mullets and chanos have not so far been developed.
Other states followed Madras in matters of fishery research as Fisheries Departments were established, but little headway in piscicultural research was made. However, fairly exhaustive surveys for the development of fisheries were conducted in Bengal (Gupta, 1908; Naidu, 1939), Punjab (Dunsford, 1911), Uttar Pradesh (Eyde, 1923), Baroda (Moses, 1947), Mysore (Bhimachar, 1942) and Hyderabad (Rahimullah, 1944). Several pamphlets and bulletins were published by these departments to popularize fish culture. In Bengal, improvements in carp cultural methods were suggested by Sen (1941) and Hora (1943a-f, j and i; 1945d) in a series of articles to popularize and bring pond culture on scientific lines. Hora (op.cit.) suggested the extension of these practices to various parts of the country, and advocated the manuring of ponds and the removal of predators to increase production from culture ponds. The chief requirements of fish farms were formulated (Hora, 1945b) and suggestions were made to develop the salt water bheris of Bengal for fish culture (Hora and Nair, 1944). Studies on the diseases and mortality of fish in tanks and ponds, and transport of fish fry, engaged the attention of Khan (1939a and b, 1941, 1943b, 1944). The nesting and breeding habits of Osphronemus goramy were studied by Jones (1939), Kulkarni (1943) and Bhimachar et al., (1944), and its cultural possibilities by Spurgeon (1945) and Kulkarni (1946). However, the slow growth of the fish was perhaps the main reason for its not supporting a commercial fishery. Possibilities of murrel (Ophiocephalus spp.) and pearlspot culture were discussed by Hora (1945c), Bhaskaran (1946), Rahimullah (1946), and Chacko and Kuriyan (1947a and b). The Advisory Board of the Indian Council of Agricultural Research in its memorandum of 1944 directed the development of pond culture and also sponsored fisheries research by financing ad hoc schemes by state governments and universities which helped the study of the hydrobiology of certain inland waters and of the bionomics of the major food fishes of Madras and Bengal.
Utilization of sewage for fish culture attracted the attention of others (Moses, 1941), and a Symposium organized by the National Institute of Sciences of India in 1944 threw more light on the possibilities of utilizing the Calcutta sewage for piscicultural purposes. Effects of Calcutta sewage on fish (Nair, 1944a) and possibilities of developing sewageirrigated fisheries in salt lakes (Bose, 1944) were discussed. Fowler (1944) drew attention to the biochemical aspects of sewage irrigation while Nair (1944b) suggested the raising of alternate crops of paddy and fish in the same field. However, it was felt that more work was necessary before recommending large-scale use of sewage for fish culture.
Studies on the bionomics and spawning of carps were made in the Punjab (Khan, 1938b, 1942, 1943a and 1945; Husain, 1945) and Bengal Fisheries Department (Das, 1917; Muzumdar, 1939; Ahmad, 1944, 1946; Hora, 1945a; Das and Das Gupta, 1945) and in the University of Calcutta (Mookerjee et al., 1944a and b; Mookerjee, 1945). The National Institute of Sciences of India organized a symposium in 1945 on the factors influencing the spawning of carps which brought to light various view points. The most important of them, which was to revolutionize carp culture in the years to come, was the suggestion made by Khan (1945 op. cit.) emphasizing the role of internal secretions in precipitating spawning which may be brought about by changes in the meteorological and chemical conditions. These factors were further studied in the Punjab and Bengal and also in Madras.
Biological control of mosquitoes which act as vectors in the spread of various diseases viz., malaria, filaria, dengue, etc., also received the attention of various workers (Wilson, 1917; Hora, 1927, 1937; Sen, 1937; Roy, 1938). Hora and Mukherji (1938) drew up a table for the identification of Indian fresh-water fishes and made certain observations on the relative utility of the probable larvivorous fishes of India. Although two exotic larvivorous fishes, Lebistes reticulatus and Gambusia affinis, were introduced into India in 1909 (Prashad and Hora, 1936) and 1928 (Gopinath, 1943) respectively, little work either on the indigenous or exotic species was done until the late thirties. Khan (1938a, 1943c) in the Punjab, Fraser (1938) in Poona, Hora and Nair (1938) and Job (1941a, 1943 and 1944) in Bengal and John (1940) in Travancore-Cochin worked on larvicidal fishes and advocated their culture. Etroplus suratensis and E. maculatus (Sebastian, 1942) and Horaichthys setnai (Job, 1940) were further added to the list of larvicides. Interest in the control of guinea-worm disease was evinced since Megalops cyprinoides (Setna and Kulkarni, 1940) and Ambassis spp. (Job, 1941b) were found to feed principally on Cyclops, which act as vectors in the spread of the disease. The Government Fish Farm at Chetput, Madras, was established specificially for the culture and distribution of larvicidal and cylopscidal fishes.
Soon after Independence, emphasis was laid on greater food production; fish culture activities were expanded to cover almost the entire country, and the industry developed at the hands of both the Governmental agencies and private pisciculturists. Any large-scale program for the development of fisheries has necessarily to be based on the solid foundation of scientific research. The Government of India established the Central Inland Fisheries Research Station (now Institute) at Calcutta in 1947 to conduct scientific investigations for a proper appraisal of the inland fisheries resources of the country, and to evolve suitable methods directed towards their proper conservation, management and development. As the Government of India assumed direct responsibility for fisheries research under the present constitution of India, this Institute became the main centre for inland fisheries research. Local problems are still being investigated by the State Fisheries Departments, and this Institute maintains a close liaison with these and with the Universities doing similar work. The Institute established its Pond Culture Division at Cuttack (Orissa), in view of the facilities afforded by the State Fisheries Department to work at a number of fish farms in and around Cuttack, to evolve suitable scientific methods in regard to management of culture fisheries.
The problems of culture fisheries being many and varied, it was not possible to study all aspects simultaneously; top priority was given to improving techniques of collecting and rearing major carp fry, investigating carp culture practices to achieve maximum survival rate from spawn to fingerling stage, reducing mortality during transport, eradication of aquatic weeds from fish ponds, and inducing spawning of carps by artificial flooding of ponds and by injection of pituitary gland extracts(Bhimachar, 1959). Experiments to determine the suitability or otherwise of certain exotic species for culture in different parts of India were also undertaken. The increased need for fish seed for cultural purposes made a heavy demand on the Calcutta spawn markets, hence the Institute, alive to the need for quality fish seed for this purpose, organized the Fish Seed Syndicate in 1950. The object was to procure quality fish seed from surplus areas to supply to deficit states; this gave great impetus to the pisciculture industry. The Syndicate has, since its establishment, done excellent work and is today the biggest fish seed trade organization in the country. It has not only effected considerable improvement in the transport of fish seed by rail and air, but also carries out large-scale rearing of fry in well prepared nurseries. Other organizations, viz., the General Marketing Company, the Eastern Fisheries Corporation, and the West Bengal Government-sponsored Fishermen Cooperative Society (now defunct) also sprang up and started undertaking export of fish seed on smaller scales.
Rahman (1946) suggested that collection of carp spawn should be considered a technical job and expert catchers be registered, to save the wastage due to new men taking to this business. In the empirical method of collection there were serious drawbacks causing heavy mortality of spawn, either during collection itself or in the nursery ponds (Alikunhi, Chaudhuri and Ramachandran, 1952). Hence certain improvements were suggested, such as the proper fixing of the net so as to offer the least resistance to fast-flowing waters, changing the form of the receptacle (gamchha), removal of spawn from the gamchha at regular intervals, and keeping the sieve submerged in water when sieving the collections. It was also recommended that overcrowding during temporary storage in pits, hapas or hundies and any sudden change of hydrological environment should be avoided.
The growing need for carp fry necessitated searching for natural breeding grounds and new spawn collection centres. Carp spawn is now collected from the rivers on a very large scale by Governmental agencies in Uttar Pradesh, Madhya Pradesh, Bihar, Gujarat, Maharashtra, Orissa, Andhra Pradesh and Madras States in order to stock the public waters and meet the demand for fry by private pisciculturists. However, the non-availability, or low percentage of major carp fry in the collections in many states necessitates its import from Calcutta markets. About 10,000 to 15,000 fishermen are engaged privately in collecting spawn in West Bengal, Bihar and Orissa.
Despite the intensive collection of carp fry in certain sections of some rivers, a regular survey of such resources has been made only in a few cases(David, 1959; Ibrahim, 1961). No data are available, in most cases, of the quantities collected from year to year. A concerted effort is now being made by the Central Inland Fisheries Research Institute to prospect areas of quality fish fry occurrence, and towards standardizing the collection equipment and procedure (Anon., 1965).
Hora (1943a, e, 1945d) invited attention to the adopting of scientific methods of fish culture similar to agricultural practices, involving the use of at least three different kinds of ponds, nursery (60 × 40 × 4 feet, 20 × 13 × 1.3 m), rearing (100 × 80 × 5 feet, 33.3 x 26.6 x 1.6 m) and stocking (over half an acre in area, 0.2 ha, and about 6 to 10 feet, 2 to 3.3 m deep). However, efficient operations are only possible when the ponds are specially constructed for fish culture. Some states in India are experiencing great difficulties in the construction and designing of fish farms. Information is now being gathered on different soil conditions, water retention, surface features, etc. As digging ponds on flat land costs more than putting cross dykes in an already existing water body, the latter possibilities are being explored. In Orissa and Tripura where a large number of swamps exist, the Fisheries Departments undertook experiments on the removal of silt and aquatic weeds and dividing a big water sheet into a number of small, long and manageable ponds by cross bundhs. These experiments have proved that this is a much more economical way to construct ponds (Mitra, 1956a, b, 1957).
Till recently, no regard was ever paid to the intensity of stocking spawn and the preparation of ponds; this usually resulted in a poor survival rate. Exceedingly high rates of mortality of fry in nursery ponds (90 to 98.7 percent) have been reported from Orissa State (Alikunhi, Chaudhari and Ramachandran, 1955b). The causes of mortality in the nursery ponds have been listed by Alikunhi et al., (1952, 1955a and b). To obtain maximum survival of fry, spawn has to be reared in small nursery ponds to the stage when the major carp fry could be segregated easily from undesirable species and stocked in larger ponds for further growth and fattening. As the fry are very delicate, easily susceptible to diseases and predationnial and with specific feeding habits, the nurseries have to be specially prepared. In perennial nurseries, management practices to increase the survival of young carp fry include: (i) drying the pond bottom to expose the soil to the sun for proper mineralization, (ii) removal of excess organic debris to prevent production of toxic gases and spread of epidemic diseases, (iii) removal of aquatic weeds, which not only harbour predatory aquatic insects, but deprive the water of nutrients for the production of the zooplankton forming the food of the fry, and also upset the ecological balance by supersaturation of oxygen (Alikunhi et al., 1951) or production of toxic substances by mass decay, (iv) eradication of predatory and weed fishes, which either feed directly on carp fry or compete with them for planktonic food (Alikunhi and Jhingran, 1951; Alikunhi, 1956, 1957).
3.2.1 Control of aquatic weeds and water blooms
Although the cheapest way to remove aquatic weeds from nursery and rearing ponds is by manual labour, anhydrous ammonia at 15 ppm N can also be used for their control. This also kills the predatory and weed fishes and fertilizes the pond with a nitrogenous fertilizer (Ramachandran, 1960). The water blooms can be controlled by repeated application of raw cowdung (Alikunhi, 1956) or covering the water surface with Lemna (Alikunhi et al., 1952) as is commonly done in Bengal.
3.2.2 Eradication of predatory and weed fishes
The role of predatory and weed fishes in spawn collection nets has been discussed by Karamchandani (1957) and their subsequent transfer to nursery ponds along with carp spawn is bound to affect the survival rate. Derris root powder at 4.6 ppm and Endrine at 0.1 ppm have been used to kill predatory and weed fishes effectively (Alikunhi, 1957; Barrackpore, 1964). Recently, some local plant poisons, such as powdered seed kernel of Croton tiglium (3 ppm), powdered seeds and dried leaves of Mallitice piscida (2 ppm and 10 ppm respectively) custard-apple seeds (Anona squamosa) and Euphorbia thirucalli, have been found to be quite effective and useful. Laboratory and field trials conducted to find a suitable agent for detoxification of Endrine-treated waters have indicated that though lime, sodium hydroxide, potassium permanganate, sulphuric acid and cowdung could serve the purpose, ordinary charcoa at 50 ppm appeared to be more suitable, as well as economical. It has also been observed that the presence of rich organic matter in the soil, or a thick algal bloom in the water mass, accelerated the natural detoxification phenomena (Barrackpore, 1964, 1965).
3.2.3 Manuring of ponds
The main food of spawn and fry being zooplankton (Alikunhi, 1952, 1958; Mitra and Mohapatra, 1956), a sustained high level of zooplankton production is essential during the rearing period. Artificial fertilization is used to increase productivity by making more nutrients available to the lower levels of the food chain, especially bacteria and phytoplankton. Perennial nurseries generally tend to be slightly acid, and therefore require to be corrected by addition of lime. Even in seasonal nurseries, lime at 200 to 300 lb/acre (222 to 333 kg/ha) is usually spread over the dry pond-bed to ensure the fullest utilization of additional manure. The pond owners are usually advised to use the same fertilizer which they are using for their lands, but being soluble in water its nutrient contents are immediately available, unless the water contains suspended soil colloids or considerable soluble iron which ties up the phosphates. Hence smaller applications are necessary for ponds than for soils. Application of manure prepared by composting water hyacinth, banana petioles, arum stem, Hydrilla verticillata and Ceratophyllum has been advocated by Saha (1953). Green manuring, by growing Sesbania sp. on the pond beds and crushing it after ten to fifteen days, is practised in the farms of Orissa. Experiments at the Pond Culture Division of the Central Inland Fisheries Research Institute showed that heavy manuring with cowdung in experimental cement cisterns resulted in the production of a rich crop of zooplankton within about two weeks. The application of raw cowdung gave a better result because the nutrients present therein were more readily available than in cowdung manure or dry cowdung, (Alikunhi, 1957). The high production, however, lasted for only a short while and it was found difficult to maintain it over a long period. A large-scale field experiment showed that spaced manuring with an initial dose of 1,000 lb/acre (1,111 kg/ha) of cowdung followed up ten days later by five more supplementary doses, each of 2,000 lb/acre (2,222 kg/ha), every third day maintained a fairly high level of plankton production. The same quantity of manure applied in a single dose did not maintain similar high production (Calcutta, 1957). While organic manures have been used for a considerable time, the use of inorganic fertilizers is still experimental. Application of 18-8-4 N-P-K at 500 kg/ha have given very good results both in the preparation of nursery ponds and also in short-term rearing experiments (Barrackpore, 1965).
In addition to major nutrients, small quantities of manganese, zinc, copper, boron, cobalt and molybdenum are also needed for growth. The soils in India show deficiencies of boron, manganese and zinc in a number of instances, and while the effect of such deficiences has been studied to some extent on crop plants, little is known about their effect on fish growth or fish food. Preliminary experiments conducted in the cement cisterns at Cuttack have indicated that addition of manganese lead to a definite increase in the quantity of plankton produced (Barrackpore, 1961).
3.2.4 Assessment of food
The fry feed selectively and their feeding capacity is quite considerable (Alikunhi, 1952). Therefore, stocking density should be based on the quantity of such food items available in the environment. The former belief that major carp fry feed exclusively on unicellular algae has been disproved, and it is now known that the density of zooplankton in a nursery pond should be the basis to determine the intensity of stocking. A qualitative and quantitative estimation of plankton content is, therefore, necessary. A simple method of quantitative sampling was developed during the course of these investigations. A small conical plankton net made out of standard No.21 bolting silk, or fine muslin, open at both ends was fixed on to a circular metal frame 9 to 12 in (22 to 30 cm) in diameter and with a short handle, and a glass tube 3 to 4 in (7 to 10 cm) long and 1 in (2.5 cm) in diameter was tied to the lower tapering end. Samples of water are collected by a person standing in knee-deep water near the edge of the pond and stretching out his arm towards the centre of the pond. The surface of the pond is first slightly disturbed to disperse or mix the algal scum, if any, and the mug for collecting the sample then held with its mouth downward to about 6 in (15 cm) below the surface of water and gradually tilted to collect the water. If the plankton sediment obtained after filtering about 12 gallons (55 litres) of water and addition of a few drops of strong formalin is light brown or pale yellow in colour, i.e., with zooplankton predominating, and about quarter of an inch (6.4 mm) or more in height, i.e., over 3.0 cc in volume, the pond may be considered to be sufficiently rich for a stock of about 500,000 fry per acre (200,000 per ha) (Alikunhi et al., 1955a). Mitra and Mohapatra (1956) considered an initial availability of 0.1 to 0.3 cc of zooplankton per fry as essential, and further observed that occurrence of phytoplankton blooms produces detrimental results, especially when zooplankton is poor and blooms persist for long periods.
3.2.5 Control of predatory insects
Predatory aquatic insects multiply rapidly between poisoning and stocking and have been found to take heavy toll of fry as soon as the latter are released in the pond (Khan and Husain, 1947; Ganguly and Mitra, 1961; Gorai and Ray Chaudhuri, 1962). Anisops spp. can kill half inch (12.7 mm) fry, while Laccotrephes spp. and Ranatra spp. can kill even larger fry. The olive beetle, Cybister spp., and its larvae are highly predatory, and able to destroy fingerlings up to 2 in (5 cm) in length (Alikunhi, 1957). Larger insects and larvae can be controlled by gently dragging a fine-meshed cloth-net and destroying those collected.
The Bengal farmers separate notonectids and carp fry by spraying mustard oil in the hapas. Various vegetable oils were therefore tried. Linseed and mustard oil were found to be the most effective, but the former was slightly toxic to the young fry as well as to zooplankton. Owing to their high viscosity, vegetable oils spread very slowly on the water surface. Emulsions were, therefore, prepared by addition of soap wastes or ordinary cheap washing soap solution, which facilitated easy spreading of oil as a thin film over the water surface. A quantity of soap equal to about one-third the weight of oil was sufficient to make a satisfactory emulsion. Under field conditions, oil at 50 lb/acre (55 kg/ha) of water surface yielded satisfactory results. The notonectids are killed within half an hour, and Ranatra spp., are also affected (Pakarasi, 1953). Higher doses, however, kill water boatmen, Cybister spp., larvae of other beetles and bugs as well. The operation should be performed on a windless day to be effective. As many of the beetles and bugs can fly out of water and migrate from pond to pond repopulating the cleared ponds, the stocking operations should follow twelve hours after the spray operation.
Experiments with oil of Alexandrian laurel (Calophyllum inophyllum, a vegetable oil common in Malabar and Orissa, water dispersible gammexane (0.1 ppm) which kills notonectids and prawns, and pure gamma isomer of benzene hexachloride (0.1 ppm), etc., have all proved to be quite effective, cheap and useful, as they do not affect the fish fry and zooplankton adversely to any great extent. Recently, Srivastava and Konar (1965) have reported that 0.5 ppm of DDVP (0:0 Dimethyl - 2:2 - dichlorovinyl phosphate, manufactured and sold as ‘Nuvan’ by Ciba Ltd., Switzerland) in the emulsifiable form effectively kills Nepa, Sphaerodema, Ranatra, Dytiscus, Dytiscus larvae, Hydrophilus and dragonfly nymphs in the laboratory within 6 to 58 hours. Ponds otherwise quite suitable and with a fairly high density of zooplankton have given poor survival of carp fry when they were not cleared of predatory insects.
3.2.6 Supplementary feeding
In systematic fish culture it is usual to add supplementary food to obtain higher yields, as the water may support only a limited crop of zooplankton even after fertilization. Additional advantages that accrue from supplementary feeding are (i) a higher density of stocking for better use of available natural food, (ii) better growth on a mixed diet, and (iii) residual manurial value of the feed. Preliminary experiments have shown that carp fry grow decidedly better when equal quantities of zooplankton and artificial food, rather than an excess of artificial food alone, are given, and that they consume more of the zooplankton than of the artificial diet in a given time. For the first two days, however, the fry hardly make any use of the artificial food. Laboratory experiments have shown that they feed avidly on rice bran and ground-nut oil-cake, or a mixture of the two, as soon as they start feeding. It is, therefore, clear that for the successful rearing of fry, the nursery ponds should be rich in zooplankton at the time of stocking, and that from the second or third day after stocking, the natural food, i.e., zooplankton should be supplemented by artificial food such as rice bran and oil-seed cake. Under field conditions the fry have to be fed once or twice a day with rice bran and, or, oil-cake. These are more easily assimilated by the delicate fry if they are in a finely powdered state, when they will also remain suspended in the water column for a much longer period (Alikunhi, 1957). The artificial feed to be given to carp fry in nurseries is a 50:50 mixture of rice bran and mustard-oil cake starting with thrice the weight of the fry at the time of stocking for the first five days, increasing to four and five times in subsequent five day periods (Barrackpore, 1961).
Recently, laboratory experiments have indicated that dried and powdered shrimps and notonectids, certain cereals and pulses and fat-free proteins, individually or in a suitable combination, were more nutritive than oil cakes and brans which have been so far used as artificial feeds in pond culture (Barrackpore, 1965). Further observations are, however, in progress.
Some laboratory experiments were carried out at the Indian Statistical Institute, Calcutta, to study the effects of antibiotics and vitamins on carp fry particularly with a view to enhancing their survival during the period of fast growth and heavy mortality. These experiments have shown (i) that both antibiotics and vitamin B complex, with vitamin B12, significantly enhanced survival rate in comparison with untreated controls (Das and Krishnamurthy, 1961a), (ii) that vitamin B complex without B12 did not have a significant effect (Das and Krishnamurthy, 1961b) and (iii) that cobalt nitrate with goat's stomach extract (1 ppm cobalt nitrate and 5 cc extract), a cheaper source of vitamin B12 as the micro-organisms in a ruminants' paunch synthesize B12 in the presence of cobalt, significantly enhanced survival rate (Das, 1959).
Fry are reared in the nurseries for a period of about two weeks where they attain a size of about 25 to 30 mm and have to be removed to larger rearing ponds. Different species develop different feeding habits; the food requirements of the fry increase appreciably and they need greater space for movement for proper health and growth. At this size carp fry can be easily distinguished from predatory and weed fishes. The preparation of rearing ponds is no less essential though less elaborate.
The advanced fry are grown in the rearing ponds to 100 to 150 mm length and stocked at 20 to 30,000 per acre (8 to 12,000 per ha) without feeding and 50,000 to 60,000 per acre (20 to 24,000 per ha) with feeding.
Experiments on intensive production and various stocking rates and ratios are in progress. Experiments to enhance the production of fish by liming, manuring and artificial feeding were carried out by stocking 3,750 fingerlings/ha in one of two combinations viz., catla, rohu and mrigal or catla, rohu and common carp (Cyprinus carpio) in the ratio of 4:3:3. The trials showed the better growth of common carp, and that the total production in ponds with common carp combination was higher than with mrigal combination. Catla grew better in ponds treated with oil-cake as manure than in ponds where oil-cake was used as an artificial feed.
Transport of spawn and fry in earthen pots (hundies) on slings from seed collection centres for stocking in cultivable waters has been in practice since very ancient times in India (Job, 1951). The transport of fish seed of all culturable species over long distances without mortality has always been a problem. Although there were various indigenous practices intended to prevent mortality, these were inadequate. It was, therefore, necessary to find more effective ways of transporting large quantities of fish seed for meeting the increasing demand in remote areas. While maintenance of dissolved oxygen balance in the medium for transportation of spawn and fry is very important, inimical gases like CO2 and NH3 resulting from metabolic products and decomposition of dead young are also important as they cause mortality. Increasing concentrations of ammonia affect the young so adversely that they are unable even to utilize the dissolved oxygen present. Khan (1941) studied the oxygen requirements of C. mrigala while Basu (1950; 1951b; 1952) studied the physiological requirements of the eggs, larvae and fry of Indian carps and Motwani and Bose (1957), the active respiratory rates of L. rohita. Viswanathan and Tampi (1952) determined the oxygen consumption of Chanos in relation to size, while Job (1957) worked out its routine active oxygen consumption. Basu (1952) showed that spawn and fry of catla, rohu and mrigal consume the maximum amount of oxygen between pH 6.0 and 7.9 at 36° to 37°C and that dissolved oxygen below 0.5 ppm is fatal to both spawn and fry, whereas they can live for 24 hours or more with 0.5 to 1 ppm of O2. But even at this concentration 2.5 to 5 ppm of CO2 is lethal to spawn and 10 to 15 ppm to fry (15 to 40 mm long); at 2 ppm of O2 and above, the lethal limit of CO2 is increased to 100 ppm for spawn and 225 to 250 ppm for 15 to 40 mm long fry. These results suggest that during transport of spawn and fry, if the maximum oxygen level can possibly be maintained at 2 ppm in the medium, there is less chance of mortality within 100 and 250 ppm CO2. Saha et al., (1956), however, observe that spawn can withstand dissolved CO2 and dissolved free ammonia up to 20 ppm and 2.5 ppm respectively.
Spawn has been generally transported within and outside Bengal in earthen pots with water from the collection ground and a few grams of finely pulverized red soil sprinkled over the surface of the water. Periodic scraping of the bottom of the container, by means of a cloth rolled into the form of a rope, to throw out the bottom mud and occasional shaking of the entire medium during transit are a common sight. At intervals of four hours the water is changed and red soil added; the traders believe that without this there would be a heavy mortality. Basu (1951a) reported that these soil particles help in attracting the negatively charged spawn infected with bacteria to the bottom of the container and keep them buried under the soil, keeping pollution localized. In a series of experiments undertaken in the Technology Laboratory of the Directorate of Fisheries, West Bengal, on the mortality of spawn and fry of Indian major carps, it was proved beyond doubt that water collected from spawn collection centres as a medium of transport had no specific effect; tank water being as good as the spawning ground water. Similarly, specificity of red soil also could not be established, ordinary soil in finely pulverized condition having the same effect. However, addition of pulverized soil, in general, increased the survival period, possibly due to the presence of some chemical ingredients needed for spawn (Saha and Chowdhury, 1956). Mortality occurred almost instantaneously in acid water, but by adjusting the pH to 8.5, spawn could be transported for about 56 hours by rail with only a three to four percent mortality. As earthen containers are liable to break, other containers of galvanised iron or tin were devised but transport in these involved constant care and attention of attendants who had to accompany the consignments. To avoid such difficulties experiments with closed containers were undertaken in the Orissa, Punjab and Madras Fisheries Departments to transport fish fry with and without oxygen packing. Mitra (1942) seems to be the first amongst the Indian workers who foresaw the possibilities of fry transport in closed containers with oxygen under pressure. Khan (1946) devised an oxygenated container for 30 to 200 fry and fingerlings (depending on their size). Raj and Cornelius (1949) successfully transported mirror carp fingerlings from Ootacamund to Kumaon (Uttar Pradesh) in an improvised 10 gallon petrol can with oxygen under pressure. Ganapati and Chacko (1951) made a comparative study by transporting C. chanos (5 to 8 cm), M. cephalus (2 to 8 cm) and E. suratensis (5 to 8 cm) in tin carriers with and without oxygen.
For successful transportation, concentrations of toxic substances like CO2 and NH3 should be kept low, or alternatively they should be removed as soon as formed. Srinivasan et al. (1955) studied the effect of secondary sodium phosphate at 1.5 g/l in the transportation of fingerlings of L. fimbriatus, C. reba, B. sarana, C. catla and C. mrigala in open and oxygen-filled containers. They concluded that replenishment of oxygen is the main problem; removal of CO2 alone did not help in any way in the open containers, but it had a beneficial effect in closed containers where fry could be transported for 48 hours with 0 to 2 percent mortality. Saha et al. (1956) used permutit, activated charcoal, amberlit and pulverized earth at 2.5 parts/100 parts of water for the removal of carbon dioxide, ammonia and poisonous gases, and found that permutit was the worst absorbent as it removed dissolved oxygen also, though it removed the maximum of ammonia. Pulverized earth, and amberlit and charcoal were found to be effective for any transport up to 72 hours, and beyond 72 to 80 hours, respectively. In their experiments secondary sodium phosphate reduced the transport period by 24 hours in comparison to control, probably due to the sudden change of pH.
The credit for introducing polythene bags on an economic basis goes to the Department of Fisheries, Bombay, which successfully transported major carp fry 20 to 25 mm in size, from Calcutta to Bombay in 1955 in two polythene bags measuring 840 mm x 610 mm and having a thickness of 0.0625 mm placed in 18 litre empty kerosene oil tins and partially filled with water so as to take the shape of the container. After putting in the fry the bags were pressed to the level of water to expel the air. Oxygen from a cylinder was released slowly in each bag until it was blown up to the top of the tin container. The bags and tins were closed and put into cardboard cartons with pieces of paper in between the tin and inside of each carton to serve as insulation. In a 12 hour air journey, the mortality was 2.25 percent and 3.5 percent in the two bags which contained 1,200 and 2,300 fry respectively (Ranade and Kevalramani, 1956).
This method has come to stay as the only means of large-scale transport on an economic scale except that the cardboard cartons are not used now. Large consignments of carp fry are despatched every year to various destinations within the country by rail and air.
While carp fry can now be safely transported, transport of carp fingerlings (50 to 100 mm) is still a problem. Effective methods of transporting these have been developed in Madhya Pradesh in 40 gallon (180 litres) capacity galvanized iron drums. An opening 48 cm x 30 cm is cut along the main body of the cylindrical container through which fingerlings are introduced into it. To avoid rolling of the drum, four small iron brackets are fixed opposite to the opening on the outer surface of the body. A mortality of about 5 percent has been observed in such containers (Anon., 1955).
The transport of adult fishes, especially major carps is a problem confronting most fishery workers. Since these are generally required for breeding, it is essential that they are transported with the least shock and injury. The best equipment that is now recommended for this purpose is the splashless tank with attached aeration equipment developed by the Fisheries Extension Unit, Hyderabad (Mammen, 1962a). Open canvas containers (1 m x 1 m x 1¼ m) are already being used in Punjab and Madhya Pradesh for transporting major carp breeders.
Culture of salt-water fishes is not practised intensively in India. Estuarine mullets, prawns and pearl-spot are taken into the brackish-water bheris of West Bengal and paddy fields of Kerala along with tidal water. Unfortunately, no serious attempts were ever made to collect or segregate the fry of desirable species for stocking, hence any large-scale transport activity is lacking. Fry of M. tade, M. parsia, M. cephalus and M. corsula are collected from estuaries, coastal swamps and creeks for stocking the fresh-water ponds in coastal districts of West Bengal. Experiments conducted to transport them without mortality have shown that earthen hundies give better results than tin carriers, and that 200 fry (15 to 30 mm) per earthen hundi with 22 litres of water can be safely transported for a period of about four and a half hours (Sarojini, 1958).
The failure of Chanos culture in South India is adduced largely to difficulties in transporting the fry. The present practice consists of conditioning the fry in nurseries for 24 hours after collection and later acclimatizing them in tin carriers containing four buckets (28 litres) of sea water. By a process of removal of one bucket and addition of one bucket of fresh well-water, the salinity is reduced to nearly that of fresh water in a period of about 12 hours. When these fry, about 250 to 400 in number and ranging from 13 to 17 mm in size, are transported in a tin carrier, a mortality of 15 to 30 percent is usual after a six hour train journey. The Fisheries Extension Unit, Mandapam Camp (South India), has recently reported that as many as 150 fry could be transported in 175 cc of water for 24 hours without any mortality when packed in a small plastic bag, 20 cm long and 12 cm wide, with oxygen under slight pressure. The oxygen consumption of Chanos fry is calculated to be as low as 0.0002 cc per fry per hour (Mammen, 1962b). Dealwood boxes measuring ca. 55 cm x 32 cm x 33 cm were constructed with vertical and horizontal partitions to receive 40 such bags, thus transporting 6,000 fry at a time (Rao, 1961). Successful methods of transporting Chanos fingerlings may help in promoting its culture as their survival rate in ponds is not high now (Mammen, 1962b).
The productivity of fish ponds is considerably reduced by infestation of weeds and obnoxious algal blooms. Various methods have been tried, but the problem has neither been tackled on a systematic basis, nor have the economics of the various measures adopted been considered seriously.
From smaller water bodies, clearance of weeds by manual labour is possible and economical too, but in larger and thickly infested ponds, tanks, bheels, jheels, etc., effective weed control can be achieved only by chemical, chemical-cum-manual, or mechanical-cum-manual clearance.
Amongst the floating weeds, water hyacinth (Eichhornia crassipes), is the greatest menace in the fishery waters of Bengal, Bihar, Orissa and Assam. While manual clearance is the most economical method for smaller ponds and tanks, treatment by the chemical weedicide 2,4-D, seems to be the best for larger bodies of water (Philipose, 1963; 1964; Ramachandran, 1963).
Common marginal weeds, Typha, Colocasia, Sagittaria, Cyperus, Scirpus, Juncus, Ipomoea and Jussiaea, and emergent weeds such as Trapa, Limnanthemum, lotus and lilies, can be controlled effectively by cutting the shoots under water repeatedly at intervals with hand scythes.
Generally, it is the submerged weeds, Hydrilla, Vallisneria, Nechamandra, Ottelia, Ceratophyllum, Najas, Utricularia, etc., which are the most obnoxious. Shading by floating weeds like Pistia, Salvinia, Azolla or Lemna, and production and maintenance of permanent algal blooms check these weeds effectively but these methods may not be practicable in larger expanses of waters or swamps. Here dragging metal chains or rakes, with the help of hand-mechanical-or power-driven winches may be useful (Mitra, 1956b).
Sodium arsenite at 4 to 6 ppm, depending upon the density of infestation, has been found to be the most effective and economical chemical treatment for submerged weeds. Although poisonous, it does not kill fish at this dosage but must be used carefully and cattle and human beings should not be allowed to use the water for drinking or any domestic purpose for about 10 to 15 days after treatment. However, two treatments per annum are sufficient. Addition of 10 ppm of copper sulphate after lowering the pH to 6.0 acts as a weedicide for Hydrilla and Chana, the vegetation completely decaying and settling to the bottom in about 25 days (Banerjea and Mitra, 1954; Mitra, 1959). Effective control of submerged weeds by using anhydrous ammonia according to a prescribed technique has been advocated by Ramachandran (1962). With 12 ppm of nitrogen, it is practically non-poisonous to livestock and can be used for sectional treatments and maximum concentrations easily achieved in the zones of thick infestations. Possibilities of biological control of weeds by stocking such ponds with grass carp (Ctenopharyngodon idella) are being explored.
Algal blooms can be controlled with 125 ppm of commercial sulphuric acid in 24 hours without affecting zooplankton (Khanna, 1960) and in neutral or slightly alkaline waters with 0.25 to 0.5 ppm of copper sulphate. Copper sulphate at 2 to 3 ppm in slightly alkaline waters or sodium arsenite at 3 to 5 ppm completely controls the filamentous algae.
The economics of the various methods adopted for controlling the weeds have been discussed by Philipose (1963) and Singh (1962) has found the possibility of utilizing aquatic weeds as composts for manuring agricultural fields. Yard experiments gave higher fruit yields with Najas, Hydrilla and Ottelia while Eichhornia compost gave consistently lower yields than the control (no treatment). Experiments are underway to evolve a suitable compost prepared by mixing different weeds according to their mineral contents.
As stated earlier, the collection and supply of quality fish seed to meet its increasing demand posed a problem in the expansion of fish culture activities. Attention was, therefore, paid to inducing the carps to breed in bundhs, by artificially flooding them as is practised in the Midnapore and Bankura Districts of West Bengal, and also breeding them by administration of pituitary gland extracts.
The factors inducing spawning of carps in rivers and bundhs were discussed at a symposium in 1945 and since then several workers have further studied the problem with a view to popularizing the practice of bundh-breeding in other parts of the country. Heavy rains, submerging partially or wholly, the shallow adjoining spawning grounds (Ganapati and Alikunhi, 1950; Ganapati et al., 1951; Khanna, 1958), low alkalinity (Saha et al., 1957), together with many other factors, like lunar periodicity, etc., were shown to stimulate the breeding of carps.
In Madhya Pradesh, special attention has been paid since 1949 to the study and location of spawning grounds in the riverine stretches and bundh type of tanks, and during the past decade to the construction of dry bundhs and the breeding of carps in these. The carps have been observed to breed in standing waters, over hard, stony, soft or clay substrata, with water temperatures ranging from 26° to 33°C and pH from 7.2 to 8.2 (Dubey and Tuli, 1961). Breeding in about 35 perennial tanks and reservoirs comparable to wet bunds has been established. The first successful experiment in dry bundh-breeding was carried out in 1958, and since then many more bundhs have been constructed by the Department and the farmers. The practice of dry bundh-breeding is to collect mature and maturing breeders from perennial reservoirs during May and June, keep the sexes segregated in small ponds till the first monsoon showers; then to introduce selected numbers of these breeders, in the proportion of one female to two males, into the dry bundh as soon as sufficient water has accumulated there; then to wait and watch for their breeding. Eggs are collected with gamchha at the end of the spawning activity. Hatching hapas are ordinarily fixed in the breeding bundh itself. Studies on some of these bundhs by Alikunhi et al. (1964a) are of interest as breeding of carps has also been observed in ordinary ponds. These authors have reported repeated breeding in dry bundhs without removal of the water (unlike bundh-breeding in West Bengal) and made suggestions for improvements in bundh breeding by advocating new hatching techniques, removal of overgrowth of grass from spawning grounds to facilitate collection of eggs, removal of weed fishes to enhance survival, and better selection of breeders which are free from injuries and in healthy condition to ensure 100 percent breeding. They also suggest the fixing of hatching hapas in relatively clearer waters, where silt and oxygen would not be limiting factors, use of bleaching powder at 1 ppm for killing fairy shrimps (Streptocephalus and Branchinella) and, draining and refilling of ponds for subsequent breeding to avoid fairy shrimps and fry from earlier spawnings during collection. The selection or construction of a dry bundh has been described in which spawning grounds could be prepared in such a way as to flood them at different water levels for individuals of different sizes and species. Methods for achieving successful breeding on a commercial scale have been recommended.
Considerable experience in the construction of dry bundhs has been gained in Madhya Pradesh during recent years and while many existing bundhs have been improved, latest constructions are generally masonry structures with arrangements for overflow of excess water and complete draining of the bundhs. Apart from the bundh itself, a dry bundh unit now consists of storage ponds for breeders, an observation post with arrangements for storage of necessary equipment, and a set of cemented hatcheries with a regular supply of water for handling a very large number of eggs at a time.
Collection of spawn from rivers has manifold disadvantages. The collection centres being situated in remote, inaccessible areas and the period of spawn availability being short and dependent on various weather conditions, the resources are never exploited to the maximum advantage. Further, the rearing of river spawn being of a mixed quality, is uneconomic. Though bundhs do yield quality spawn, they are few in number and the production is limited compared with the demand. However, the need to induce the major carps to breed in confined waters was realized as far back as 1937, when Khan made an unsuccessful attempt to induce spawning in Cirrhina mrigala by injecting mammalian pituitary gland (Khan, 1938b). No further attempts were made till the mid-fifties when a number of experiments were simultaneously carried out in the Zoological Laboratory of the Mysore University and the Pond Culture Division of the Central Inland Fisheries Research Institute. Clarias magur and Heteropneutes fossilis, two air-breathing cat-fishes were successfully induced to spawn in the Mysore University (Ramaswami and Sunderaraj, 1956, 1957 a-c; Ramaswami and Lakshaman, 1959). Chaudhuri (1960) successfully bred the carp minnow, Esomus danricus, and the catfish, Pseudotropius atherinoides, by intraperitoneal injection of carp pituitary gland in 1955 and 1956 respectively.
During the 1957 breeding season, the major carps, Labeo rohita, Cirrhinus mrigala and Labeo calbasu, and the medium-sized carps, Cirrhinus reba, Labeo bata and Puntius sarana were for the first time successfully induced to breed by pituitary treatment at the Central Inland Fisheries Research Sub-Station at Cuttack, Orissa (Chaudhuri and Alikunhi, 1957). During these experiments both intraperitoneal and intramuscular injections were successfully tried and the fish bred in clear tap water, accumulated rain water and stagnant pond-water, some six to eight hours after injection. However, in certain instances a second injection at an interval of eight to ten hours was necessary. It is significant to note that only fish pituitary glands were used, and that intramuscular injections required a much smaller dose than the intraperitoneal. In the majority of cases of successful spawning, fertilization was almost hundred percent and hatching as high as 95 percent. It was noted that the doses depended on the size and stage of maturity of the gonads of the breeders. However, the determination of dosage was still not well developed. Further experiments were continued at the Cuttack Sub-Station to determine the dosages and standardize the technique. Mammen and Sulochanan (1962) and Badami and David (1964) successfully bred catla at Mettur and Tungabhadra reservoirs respectively. The Fish Breeding Centre established at the farm below the reservoir by the Tungabhadra Fisheries Board is undertaking extensive induced breeding work on Indian major carps, particularly catla, which clearly indicates that this work can very well be done successfully at other centres. Chaudhuri (1964) has outlined the methods followed in inducing spawning of Indian major carps by pituitary injection. Suggestions have been made to use homoplastic pituitary glands removed from live or recently-killed fishes or from fishes well-preserved in ice. Simple methods to remove the gland, by removing the top of the cranium or by cutting the head longitudinally into two equal halves, have been described. Techniques of preservation, preferably in alcohol, preparation of gland suspension and injection, calculation of dosages, etc., have been discussed in detail. An initial dose of 2 to 3 mg/kg of body weight to the female fish, followed by a second injection at 5 to 8 mg/kg of body weight after 5 to 6 hours, together with a dose of 2 to 3 mg/kg of body weight to the males (generally two in number for each female), gave highly successful results. Earlier, Chaudhuri (1959) had already described the methods of distinguishing the sex of breeders of Indian major carps. Great stress was, however, laid during all these years on temperature range and for successful results optimum temperatures were considered to vary between 74° to 87°F (23.3° to 30.6°C).
The two Chinese carps, Ctenopharyngodon idella and Hypophthalmichthys molitrix, introduced lately into India were also successfully induced to breed for the first time in ponds at the Cuttack Sub-Station during July 1962 when these were just three years old (Alikunhi et al., 1962, 1963). The techniques of breeding adopted were essentially the same as those followed in the case of Indian carps but due to the limited stock of breeders of the two species and also the need to arrive at the correct dosages, the injected fish, as soon as they started spawning, were taken out, stripped and the eggs artificially fertilized. However, the response of the Chinese carps to pituitary injections is identical with that of the Indian carps. The fecundity of C. idella compares with that of C. catla and of H. molitr with that of C. mrigala. The induced-bred, pond-reared silver carp, H. molitrix, attained sexual maturity when only about one year old, and could be bred successfully by pituitary extract injections (Alikunhi et al., 1965).
The breeding season of the Indian major carps is short, and optimum weather conditions, such as cool, rainy days with relatively low temperatures, are limited to a very few days during this period, so the scope of induced breeding is very much restricted, even when a good stock of breeders is available. It is therefore obvious that if suitable weather conditions are provided, breeding could be induced almost every day during the monsoon months. Alikunhi et al. (1964b) have made preliminary observations on commercial breeding of Indian carps at controlled temperatures in an air-conditioned laboratory. As eggs produced in the air-conditioned laboratory did not hatch satisfactorily under field conditions, it was considered necessary to hatch the eggs also under laboratory conditions.
Further results have been achieved during the past years. The interval between the first and the second injection has been reduced to three to four hours, instead of the usual six hours, with satisfactory results. Fish have been made to spawn even at 38°C, but the fertilization, hatching and survival to fry stage in this case was very poor. Fishes were induced to breed in Assam as early as April, as they were ripe by the end of March. Studies on the effect of synthetic hormones on the gonads and spawning of fish are being conducted. Studies on the storage of fish sperm at low temperatures in different diluents showed that Cyprinus carpio sperm remained alive and active even after 72 hours at 0°C when kept in Frog Ringer's and Holtfreter's solution with 1 percent glycerine, but they died after 50 hours when the temperature was maintained at 9°C. Similarly sperms of L. rohita survived for 21 and 50 hours respectively when kept in the above diluents at 0°C. Experiments on the effects of feeding vitamin E (Ephynal) on the gonadial maturity of fishes indicated a slightly better growth, maturity and slightly higher average weight of ovary per gram body weight of treated fishes over controls. The effect of Rontgen rays on the eggs and fry of C. carpio and their further development is under study (Barrackpore, 1965).
To disseminate the knowledge gained at the Cuttack Sub-Station in the induced breeding of carps, brief training courses for the State Fisheries Officers and the Fisheries Extension Officers have been conducted almost regularly from 1958 onwards. Reports have been received regarding the success in such experiments from Orissa, Andhra Pradesh, Madhya Pradesh and Uttar Pradesh. For the last two years, the Pond Culture Division has provided technical assistance to establish fish breeding centres in various states. This Division is also distributing fry of the major carps and common carp to deficit states in India for introduction into various waters; it is also distributing Chinese carp fry to all the states for studies on rearing and growth in the different environments.
Research work in the Indian Universities and elsewhere on the structure of the pituitary gland of different species has further helped to understand the physiology of breeding (Das and Khan, 1962; Ramaswami, 1962; Lal, 1964). Success in induced breeding has opened up a new line for research, that of producing different strains of fish with better qualities of flesh and growth. Hybrids produced by crossing indigenous fishes are being reared at Cuttack, and it has been observed that the hybrid of rohu-catla grows better than catla, and that catla grows better than the hybrid of Labeo fimbriatus and Catla catla (Barrackpore, 1964). Much more work is required along these lines.
The first exotic food fish to be introduced after Independence was the controversial Tilapia mossambica, which was brought to India almost simultaneously by the Madras Fisheries Department and the Central Marine Fisheries Research Institute in 1952. It soon became popular in the South and was introduced into a large number of ponds, tanks and even reservoirs in Kerala. However, it was soon found that the population in ponds was stunting. Experiments in the Pond Culture Division at Cuttack proved that tilapia is a predatory fish in nursery ponds and competes seriously with mrigal, and to some extent with rohu, in the stocking ponds, affecting their growth. It is, therefore, not considered to be a compatible species for culture with carps. Experiments to culture tilapia males alone in stock ponds have also not yielded very encouraging results, as a few females inadvertently gained entry into these ponds and spoiled the experiments. Culture of tilapia along with murrels gave some encouraging results and the work regarding the size and ratio of fingerlings and fish to be stocked is in progress. With heavy manuring and artificial feeding, repeated netting of tilapia ponds has yielded 5,780 kg/ha/annum.
The Prussian strain of Cyprinus carpio introduced into the Nilgiris did not breed successfully in the plains, hence another strain of this species was brought to India in 1957 from Bangkok. This strain bred freely in the plains where the temperatures were considerably higher than on the hills. However, in recent years even the Prussian strain, Cyprinus carpio var. specularis (mirror carp), has been acclimatized and now breeds freely at various places in the plains in India. Mirror carp were transplanted from the Nilgiris to Kumaon (1947), thence to Himachal Pradesh (1955), Kashmir (1956), Sikkim (1957), Punjab (1958), Madhya Pradesh (1959), Bihar (1960) and Rajasthan (1960). With the introduction of mirror carp to Himachal Pradesh, this area has not only become self-sufficient in fish production, but a leading state in supplying young fish for stocking to other states. This State has now undertaken the stocking of Gobind Sagar Lake (Bhakra reservoir) with mirror carp juveniles from the Deoli Fish Farm (Anon., 1962a). A large number of lakes in Kashmir sustain a crop of mirror carp, which is sold in markets as a coarse fish.
In the plains there is still a great shortage of carp seed, hence culture of common carp has been suggested. Common carp fry have been distributed by the Cuttack Sub-Station to various states where many articles have been written and pamphlets distributed to popularize this new fish. Simple techniques have been developed at Cuttack to breed the common carp in cloth hapas on a commercial scale, giving up the use of kakabans and cement cisterns. Such hints have been outlined by Alikunhi (1960) and circulated to all state governments. Studies on the fecundity, hatching, rearing and growth of the fish have been made. Under Indian conditions, this species is reported to grow faster than mrigal and rohu, and almost as well as catla, but in terms of weight its production equals the combined production of rohu and mrigal.
The common carp attains maturity when it is 15 to 20 cm long and six to eight months old; it lays about 130,000 to 230,000 eggs/kg of body weight. Unlike in temperate countries, it breeds in the plains of India almost throughout the year with peak periods from mid-January to the end of March, and during July-August. Breeding is either limited, or there is almost no breeding, when the temperature goes very high during summer or very low during winter; however, the same fish can be made to breed three or four times in a year at an interval of two or three months. Hydrilla or Naias have been found to serve as suitable egg-collectors and are introduced into hapas in the proportion of twice the weight of the female fish. The period of incubation ranges from 36 to 72 hours depending upon the prevailing temperature and the fry are ready for stocking on the fourth or fifth day after spawning. Common carp attains an average weight of about a kilogram in a year. Various combinations of common carp with indigenous and exotic carps are being tried to find the best ratio in which these could be stocked in ponds.
In order to increase the variety of quick-growing cultivable species of fish, and to conduct observations on the use of grass carp for controlling rapid growth of weeds in tropical warm water ponds, experimental consignments of fingerlings of silver carp and grass carp were brought to India for the first time in 1959 (Alikunhi and Sukumaran, 1964). The carp have not only been induced to breed in India, but also used for culture in view of their remarkable growth and biological utility in Indian conditions. Observations on their feeding habits have shown that the silver carp is predominantly a phytoplankton feeder, while the grass carp feeds avidly on Hydrilla, Lemna, Azolla, etc. Ponds where silver carp and catla were stocked together recorded less production than ponds where silver carp were grown alone, but a little more than where catla alone were reared. This proves silver carp to be a superior fish to catla in regard to growth, and is also otherwise preferred to catla as it is less bony and more tasty. Grass carp, stocked at the rate of 50 to 60 fish weighing 70 to 90 kg per acre (=0.405 ha), were found to utilize duck-weeds at the rate of about 2 kg/fish/day. Unlike in China, silver carp, both males and females, attained maturity in India when about two years old, 54 cm long and about 1.8 to 2.4 kg in weight. Though grass carp males matured at about the same age, size and weight as the silver carp, the females did not (Alikunhi et al. 1965). Since 1962, stocks of these carps have been built up by induced breeding at Cuttack for further studies, and they have also been distributed to almost all the states of the Indian Union for experiment and propagation.
As about 2,000 square miles of culturable coastal tracts are available in India, there is vast scope for the development of brackish-water fish culture on a commercial scale (Panikkar, 1952). Attempts in Madras and Kerala have yielded a good deal of information and have been a step towards organizing the industry on scientific lines, and more attention is now being paid to brackish-water culture possibilities. The existing practice of fish culture in the deltaic areas of West Bengal is part of a slow process of reclamation of the land for conversion into rice-fields; this has been described by Pillay (1958) and Pakrasi et al. (1964). However, the industry is still backward and much research work is needed to make fullest use of these water bodies. The Central Marine Fisheries Research Institute, Mandapam Camp, also undertook the study of the growth of Chanos in an experimental farm constructed there for the purpose.
Pillay (1954) outlined suggestions for the improvement of the bheri culture of Bengal. Unsatisfactory water supply due to greatly diminished tidal range, inadequate and haphazard stocking, no attempts at the removal of predators, lack of food production and the limited period of growth, are some of the causes responsible for the low production from bheris. To increase production, it is necessary to prevent predatory and uneconomic varieties of fishes gaining entry into these ponds, and to fertilize them to grow more fish food. Experimental studies have been made to determine the growth requirements of blue-green algae (Pillai, 1954; Bose, 1960), the effects of salinity on nitrogen transformation (Mandal, 1962a), and the type of fertilizer for brackish-water soils (Mandal, 1962b).
Ecological studies of brackish-water bheris (Pillay, 1954; Pillay, Vijayaraghavan and Thakurta, 1962) have been very useful for understanding the biotic interaction. Each species of alga has been found to have its own salinity and water-depth preferences; higher water temperatures and salinity are conducive to greater production of benthic algae, and soil nutrients appear to be of greater significance than the nutrients in the water for the production of the benthic flora.
Ecological studies of some of the tidal lagoons, with a view to finding their suitability for development into salt-water fish farms, as well as the construction requirements, selection of species, production of food, and supplementary feeding in Chanos culture, have been discussed by Tampi (1959; 1960).
The Brackish-water Fish Culture Section of the Central Inland Fisheries Research Institute, have located suitable grounds and methods of collection. Shooting nets and hapa nets are now being introduced for collecting the fry. Fry of bhetki (Lates calcarifer) are available during May to October in Thakuran and Matlah rivers; M. parsia in Muriganga, Matlah, Thakuran and Saptamukhi rivers almost throughout the year; M. tade during September-October in and around Kakdwip; and M. corsula during July to October. Preliminary investigations on the culture of mullets and Chanos were initiated in the brackish-water farm at Keshpur, near Chilka, and a remarkable growth of M. cephalus, M. troschelli and Chanos chanos, observed.
The use of paddy fields for carp culture was suggested by Hora and others, and certain preliminary experiments were made (Hora, 1943 g, h, 1951; Chacko and Ganapati, 1952; Iyengar, 1953). However, experiments conducted in Bihar, Uttar Pradesh and Andhra Pradesh in recent years have not given significant results. Experiments conducted at the Indian Rice Research Institute's plots at Cuttack between 1957 and 1960 by the Pond Culture Division have indicated that there is not much scope for this work in India, particularly where there are no irrigation facilities or the fields are liable to flooding.
Utilization of sewage for fish cultural purposes have been considered since the Symposium of 1944, though no serious attempts were made to investigate the problems. However, Ganapati and Chacko (1950) suggested the construction of a sewage fish farm, while Saha et al., (1958) studied the physico-chemical properties of Calcutta sewage in relation to its use in sewagefed bheris, and suggested dilution of raw sewage with fresh water to bring down the concentration of inimical ingredients below lethal limits before introduction into a fishery. Gopalakrishnan and Srinath (1963) suggested the use of treated domestic sewage (activated sludge) as a fertilizer for fish ponds in view of its easy transportation in the dried form and storage for use at the farm whenever necessary. Laboratory experiments to determine the effect of sludge on growth of fingerlings of C. carpio, C. mrigala, C. catla indicated that the sludge has a direct influence on increasing the growth of fish and production of plankton due to the release of nutrients into the water. The sludge had a more pronounced effect on the growth of mrigal, which may be due to their habit of consuming more of the decaying organic matter from the bottom.
Interest in prawn culture in fresh-water ponds has developed only recently. Experimental consignments of Macrobrachium rosenbergii and M. malcolmsonii were collected from Godavari and transported from Rajahmundry to Hospet (Tungabhadra Dam) and Cuttack. The prawns stocked in the ponds at Cuttack in the nurseries grew well and bred. Juveniles of M. malcolmsonii have been stocked in various tanks and reservoirs of Mysore State during January-February, 1965, and their growth rate, etc., are being studied. Attempts to breed M. rosenbergii in the laboratories of Central Inland Fisheries Research Institute, Barrackpore, were successful and during the course of this work, various interesting observations on the breeding behaviour were also made (Rao, 1964).
The paddy fields bordering the Vembanad Lake in Kerala and those situated alongside the tidal rivers in the Sunderban area of West Bengal are used extensively for the cultivation of prawns for some period during the year. The prawn fry, along with certain other species of fish, are impounded in these fields which are converted into vast enclosures with masonry sluicegates (Menon, 1954; Gopinath, 1955; Panikkar and Menon, 1955; Pillay and Bose, 1957; Pillay, 1958). These methods of prawn culture are far from intensive, and there is much scope for improvement. Suggestions to culture prawns on scientific lines by selective stocking, manuring of ponds, extension of rearing periods, etc., have been made by these authors, but nothing has been done so far in the field to achieve greater production.
Except for a few studies on the habits of Gambusia affinis (Chacko, 1948), Aplocheilus lineatum (Chacko and Ganapati, 1949a) and larvicidal propensities of Carassius auratus Chacko and Ganapati, 1949b), no further work was done on the larvicides. Some state governments, however, did continue to collect and distribute larvicides and cyclopscides to the Blocks and Panchayats to control filariasis and guineaworm.
Culture of murrels (Ophiocephalus spp.), though started in Madras at Sunkesula (Nicholson, 1918) and at Madhopur in Punjab in 1917 never became important. The culture of pangas catfish, Pangasius pangasius, for the control of molluscs (Hora, 1952, 1953) has been suggested, but without any scientific background with regard to suitable sizes for stocking, timings of stocking, and any information on the forage-predatory fish ratio. Some preliminary experiments with tilapia as a forage fish for Channa (Ophiocephalus) striatus were, however, carried out, but no large-scale murrel culture can be advocated at present in view of the scarcity of knowledge.
Khan (1944) made some observations on the parasitic diseases of carps in ponds and suggested definite treatments. Considerable work has been done on the control and prevention of parasitic diseases in ponds in recent years. The symptoms and control measures for diseases caused by Ichthyophthirius multifilis Gyrodactylus sp., Argulus spp., Isoparorchis hypselobagri, Ligula sp., and Saprolegnia parasitica have been discussed by Gopalakrishnan (1964) in a Symposium held under the auspices of the Zoological Society of Calcutta on Recent Advances in Parasitology. Biological methods for the control of Ligula and Isoparorchis hypselobagri have been suggested.
Fish mortality in ponds and tanks has been recorded by various workers. A common practice to prevent sudden mortality in fish ponds followed by fish farmers in Bengal is to cut banana plants into pieces and float them over the ponds, or crush and extract the plant's juice and mix it with pond water. Basu (1958) investigated the problem with a view to understanding the basic scientific principles involved, and found that though the juice had an acid pH (5.2 to 5.7), it contained considerable amounts of methyl orange alkalinity. The addition of the juice thus lowers the pH of the water slightly but considerably increases its buffering capacity, preventing mortality due to increased concentration of carbon dioxide.
Apathy of the public, lack of financial patronage and shortage of trained personnel, are some of the chief reasons for the backward condition of piscicultural programs in the country in spite of the existence of Fisheries Departments in many states. Only relatively recently has public attention been drawn to fisheries development and pond culture came to be recognized as a relatively easy and quick means of increasing food supplies. Various State Fisheries Departments have organized extension services through which technical and financial help is given to the farmers to improve existing fish culture techniques, and to bring unused areas under cultivation. Reclamation of derelict ponds and tanks was undertaken by cooperative societies organized for the purpose, thus adding greatly to the area of water under pisciculture. ‘Demonstration fish farms’ to impart knowledge concerning improved methods of fish culture, ‘nursery farms’ or ‘fish seed farms’ to supply quality fish seed in remote areas at nominal rates, and ‘experimental or research farms’ to study problems of local interest, have been established throughout the country. Exhibitions are arranged on various occasions and propaganda and publicity conducted during such occasions have given a great impetus to fish culture programs, as individual fishermen and cooperative organizations constantly come forward for further government help.
The paucity of trained personnel for implementation of fish culture programs was met by initiating training courses at selected centres. A training section was established at the Central Inland Fisheries Research Institute in 1948 where a ten months' course of instruction in inland fisheries with special emphasis on fish culture was organized which has now been raised to a twelve months' course. During the last 17 years 380 candidates have been trained at this Institute, including 17 under the Colombo Plan. The eighteenth session of the training course with 44 candidates, including three foreigners, is at present in progress. Training centres have also been established in the states as well to impart short-term training, generally six months, to undergraduates for manning subordinate services. Occasionally, short-term training courses are arranged for block development officers and village level workers. The lack of text-books presented great difficulties to the teaching of fish culture. The situation was helped by Rao and Prasad (1953) and Rao (1963), who compiled the existing information on inland fisheries and oceanography.
With the establishment of the Central Inland Fisheries Research Institute and the availability of experimental data to effect improvements in fish cultural practices, it was found necessary to build up an agency to ensure the proper application of these results in the field. A Central Fisheries Extension Service, with the object of functioning as a liaison between the research laboratories on the one hand, and the fisheries departments and the fishermen and fish farmers on the other, was established by the Government of India in 1953; this has since expanded and now covers almost all the states. The extension units distribute suitable pamphlets, guide the fish farmers on methods of scientific fish culture, and arrange exhibitions and film shows with the idea of educating the public.
In 1959, the National Development Council stressed the need for assisting village communities in building up community assets such as fish ponds and other inland waters, which indirectly meant utilization of man-power resources. The role of panchayats (village councils) in certain other functions, such as regulation of collection of fish spawn, cannot be over-emphasized. The annual conferences on community development held at Mysore and Srinagar in 1959 and 1960 respectively, and also the working group on panchayats, recommended that the task of fish culture in village tanks should be entrusted to panchayats, which should be entitled to make use of the income from fisheries. This has further helped the expansion of fish culture activity. In fact, in Orissa and Andhra Pradesh good progress has been made by panchayats in undertaking fish culture in tanks owned by them.
The figures of actual production of fish from cultured waters are not available, but the magnitude of the production can be roughly estimated from the fact that 267 million carp fry and fingerlings and 1,400 million spawn were collected and 0.947 million acres (0.3841 million ha) of water stocked with them during the First Five Year Plan (1951–56), and during the Second Five Year Plan (1956–61) the production of fry and fingerlings for stocking tanks and ponds rose to 1,800 million (Anon., 1962b).
