I. PHYSICAL FACILITIES
The Government of India, through the Indian Council for Agricultural Research (ICAR), continued to support the further development of infrastructural facilities. The furniture has been procured for the international hostel. The hatchery building is almost completed except the airconditioning work. The express power line for uninterrupted supply of electricity is being commissioned.
II. RESEARCH INVESTIGATIONS
A. Disciplinary Research
While inter-disciplinary researches are progressing, different laboratories have been working on projects of disciplinary nature, the main features of which are as follows.
1. Nutrition Laboratory
Fish feed formulation and nutritional bio-energetics of Asiatic carps
Protein requirement of catla fingerlings was ascertained in a laboratory experiment of 60 days' duration at 25 C to 30 C. Using synthetic diets containing casein, gelatin, dextrin, vitamin and trace elements, dietary protein levels of 30, 35, 40 and 45 per cent were experimented with. The best growth trend was noted as 40 per cent protein level. Soybean oil was used as the source of fat.
Field trials on testing four experimental feeds observed promising in laboratory conditions has been initiated in experimental ponds of 0.006 ha. The feeds are being tested on all the three species of Indian major carps, i.e. catla, rohu and mrigal in replicates of three. Conventional ground nut oil cake and rice bran, also pelletised as the other experimental diets, serve as control. The work is progressing.
Four diets using plant protein, rice bran, fish meal, vitamins, minerals and trace elements with 30, 33, 36 and 39 per cent protein levels were tested on grass carp fingerlings at 30–34 degrees centigrade. Maximum growth was obtained with feed containing 36 per cent protein.
For digestibility studies, half-hourly faecal collections appear more suitable as there is neither any leaching nor contamination of such samples as compared to overnight collections. Crude protein digestibility of a mixture of groundnut oilcake and rice bran was 71.5 per cent when analysed from half-hourly samples as against 50.3 per cent from overnight faecal collection.
2. Genetic Laboratory
With a view to finding out the ploidy level of female common carp x male rohu and female common carp x male mrigal hybrids, their chromosome numbers along with those of the parent species were determined. The hybrids were found to occupy the intermediate position.
In order to establish genetic markers for the identification of stocks of Indian major carps, muscle estrases and serum protein (transferrin) were studied. The muscle estrases in mrigal is trimer, while in catla and rohu it is tetramer. The transferrin is observed to be a monomer in the above three species.
Genetic engineering studies have made a good progress as the first gynogenetic (G1) mrigal, about 2.5 kg in weight and three years in age, was bred and G2 progeny obtained. Triploids and tetraploids of rohu have also been produced and are being studied as to their genetic value.
Rohu-catla hybrids are viable as they attained their first maturity when three years old and were bred successfully through hypophysation. Rohu-catla hybrid was back-crossed with male rohu. Reciprocal cross of catlarohu was also obtained. Further hybridization was achieved by crossing mrigal females with common carp males. Reciprocal cross was also obtained.
3. Aquatic Microbiology Laboratory
Experiments were conducted on the utilization of fermented water hyacinth in fish ponds. The plastic pool trials included aspects such as bacterial communities, plankton, and primary production. Fish growth indicated a high rate of leaf processing leading to plankton abundance. Preliminary studies on the nitrogen fixation levels and associated parameters were initiated. The ranges of nitrogen fixation rates in the water medium were 3.70 ug N. cubic meter/ha in the farm pond and 13.30–16.70 ug N/cubic meter/ha in rural pond with high blue-green algal populations (Anabaena and Oscillatoria).
Three representative ponds, viz., a natural rural pond (1 ha.), an excavated pond in a village (0.2 ha.) and a rearing pond (0.1 ha.) at CIFA were selected for preliminary analyses of nitrogen fixation levels and related studies.
The nitrogen fixation level in water was measured as 0.80, 3.60 and 15.30 ug N/cubic meters/ha in the three ponds respectively, showing a high degree of activity in the farm pond and a very low level in the rural pond. An increase in the heterotrophic bacterial population in the sediment was observed during the period April to September whereas it remained more or less constant in water. The aerobic nitrogen fixers increased in water but showed a decrease in sediment. Anaerobic nitrogen fixers increased both in water and sediment. The number of bacteria was generally high in the farm pond indicating a high level of production and fixation.
4. Aquatic weed management laboratory
Formulated feeds with 25 per cent and 35 per cent leaf protein of water hyacinth were fed to the fry of rohu, catla and mrigal. During a six-week period of observation, the fishes were found to accept the feed and grow well. The growth was comparable to that attained with the conventional feed mixture of ground nut oil cake and rice bran. Rohu and mrigal exhibited comparatively better growth than catla. Rohu and mrigal fry showed the best growth with feed containing 25 per cent leaf protein.
5. Ichthyopathology and fish health protection laboratory
A short-term training programme was organized on fish disease diagnosis for the State Fisheries Officials on 2–13 March 1987, covering the nature of pathogen, mechanism of disease outbreak, influence of environmental parameters, techniques and procedures of disease diagnosis, fish health management, preventive and curative control measures, etc. Several field programmes were also organized to diagnose the diseases and on undertaking control measures.
An incidence of severe ulcerative disease symptomatically more or less similar to the South Asian cases has been recorded in Catla catla causing mass mortality of the species in carp polyculture ponds. Bacterial forms similar to Aeromonas hydrophila and Staphylococcus aureus have been isolated invariably from the ulcerated areas. Treatment measures based upon drug sensitivity tests consisting of chloramphenicol has significantly checked the spread of the disease. No bacterial forms could be isolated from kidney, heart, blood, etc. Virological examinations of the samples are underway.
Outbreaks of argulosis in brood fish ponds were recorded and effectively cured by application of 0.25 ppm malathion (activity ingredient) in the pond in combination with dip treatment of fish in 500 ppm potassium permanganate solution. Complete healing of the deep lesions was achieved after seven days of the treatment. However, a second treatment after a week was also taken up to prevent recurrence.
LC 50 toxicity values of malathion were found to be 2.5 ppm and 4.5 ppmn for L. rohita and Anabas testudineus fingerlings respectively for 96 hours.
B. Inter-disciplinary Research
1. Broodstock management and fry/fingerling rearing
Studies on the effect of water replenishment and aeration on maturation of broodstock were undertaken in eight ponds of 0.1 ha each, stocked at 1500 kg/ha with prospective spawners of catla, rohu, mrigal, silver carp and grass carp in the weight range of 1 to 5 kg. They were fed with formulated feed (protein level of 30 per cent) at 3 per cent of their body weight daily. Of the eight ponds, three ponds were aerated and in three ponds, water was replenished keeping the other two ponds as control. The preliminary study found that addition of about 20 per cent of original water volume twice a month for four months helps in better gonadal development than aeration for five hours each day using surface aerators.
In the Institute's Hatchery Complex, by using well water, C. mrigala was induced-bred on 30.04.87 much ahead of the normal breeding season (between the end of June and mid-August).
2. Management studies of undrainable ponds
The laboratory and field trials on finding out an effective piscicide indicated that half the recommended dose of bleaching powder (5 mg/l chlorine) in combination with the nitrogenous fertilizer, urea (5 mg/l ammonia) could effectively kill all the aquatic animals including large murrels in a much shorter time. The principle involved is the accentuation of chlorine effect on fish kills with liberated ammonia. This method has distinct advantages like reduction in bleaching powder requirement, imparting fertilization value by the combined treatment and thereby reducing the total cost involved to a larger extent.
Provision of additional feeding area in the form of submerged substrate for periphyton development has shown trends of better growth in rohu as against those in ponds without the additional submerged substrate in experiments on monoculture of rohu.
3. Catfish culture: Mystus spp.
Juveniles of Mystus seenghala were procured and stocked in a 0.08-ha pond @4000/ha in the first week of May 1987. An experiment conducted on the temporal variations in feeding activity revealed that the species is nocturnal in its feeding habits. Another experiment on the food preferences of the species is in progress.
III. TRAINING ACTIVITY
A. Secondment of Junior Scientists
Under the secondment programme of Junior Scientsts, Mr. Zulkafli bin Rashid from Malaysia completed his one-year training and produced a technical report on the nutrient status of water and sediment in nursery and rearing ponds of carp.
B. Assistance to the Bangladesh National Centre
The RLCI experts have assisted the Bangladesh National Centre in Mymensingh in organizing training programmes on composite fish culture for extension officers.
C. Other Training Programmes
The Farm Science Centre conducted six on-campus and one off-campus training programmes in various aspects of aquaculture involving 102 and 10 persons, respectively. It undertook one on-campus and six off-campus training courses in home science for 10 and 69 participants, respectively. The Agronomy Section also trained 60 persons in its off-campus training programme.
The other programmes of the Farm Science Centre included the continuing Land-to-Lab Programme, the Prime Minister's 20-point programme and the Project on Science and Technology for Women.
The activities under the above Project for women is being carried out in five villages involving a total of 50 women-participants. Demonstration programmes on carp seed raising technology have been launched.
Under the Trainers' Training Centre, six training courses were organized on various aspects of inland aquaculture involving 50 in-service personnel from the States of Orissa and Arunachal Pradesh.
A one-month training course on aquaculture for 13 Central/State officials of Fisheries Departments was organized under USAID. In addition, an Orientation Course on the preparation of final reports for World Bank Projects was organized for seven State Officials for a one-week period.
IV. INFORMATION ACTIVITY
The computer room at RLCI has been air-conditioned and 165 input data sheets have been filled up to initiate AQUIS. Efforts are being made to collect more data input sheets from sister organizations in the country.
Meanwhile, two scientists have been trained in computer programming under government sponsorship one on basic programming and the other on FORTRAN.
The computer is expected to be fully operational by 1988 as soon as the spare parts arrive.
