An organized effort will be made to determine the role of specific nutritional deficiencies upon the susceptibility of carp and catfish to specific challenge doses of specific warmwater fish pathogens which cause major problems in commercial fish production. Plans were developed and approaches designed to measure the effect of clinical and subclinical deficiencies of pantothenic acid upon the virulence and pathological effects of Flexibacter columnaris in young carp. Low, intermediate, and high levels of pantothenic acid will be fed to replicate groups of young carp held in the recycle system under controlled environmental conditions and then challenged with a measured dose of live bacteria, administered as a swab or as a bath. Morbidity and clinical damage will be assessed and related to the nutritional state of the animal. Clinical measurement of tissue levels of pantothenic acid will be used to measure biologically available vitamins in the fish. A similar set of experiments will be conducted with sheatfish fed different levels of ascorbic acid and then challenged with Aeromonas hydrophilae. An improved method for assay of ascorbate derivatives in fish tissues was reviewed and will be used for clinical assay of the nutritional state of the fish for this critical water soluble vitamin.
Work will also focus upon detection and identification of specific fish pathogens encountered in commercial fish production in pond waters, in intensive culture in raceways and cages, and in the nursery ponds and the recycle system. The decision was made to delay the establishment of a virology laboratory and tissue culture system. The Haki personnel would rely upon the virus detection and prophylaxis capability of the Veterinary Services Institute in Budapest for this work. Staff limitations and predicted cuts in support funds and personnel at Szarvas indicate that more progress would probably be made in fish health work if the personnel currently on hand would concentrate on bacteriology and parasitology rather than attempt to set up an adequate tissue culture and virology research group. The main thrust now will focus upon prevention of disease and improvement of general fish health through improved environmental controls and improved fish nutrition. Clinical methods to evaluate fish health were discussed, and appropriate measures will be initiated to assess nutritional state of the fish. Erythrocyte transketolase activity techniques were planned to assay for thiamine status; serus transaminase activity techniques were planned to assay for pyridoxine status; blood serum and anterior kidney total ascorbate and stable vitamin c2 storage levels assays were outlined; and erythrocyte rragility tests to measure tocopnerol nutritional status were reviewed. Other clinical methods to assess nutritional state of fish reared under different environmental conditions and under different feeding regimens were outlined. These will be incorporated into the fish health research programmes of each unit of the division.
A major effort will be mounted to develop catfish technology for a joint venture between Haki and the Bikal state farm. Haki will provide the scientific supervision plus the dry diet mix which will be incorporated with pasteurized fish wastes from the new fish processing plant at Bikal to form the feeding rations for sheatfish reared in the warm thermal waters available at the Bikal site. The system at Haki will be used to accelerate spawning of the brood stock in the recycle system, and the larvae will be reared to fingerling size in this controlled environment. Larvae and fry will be taught to feed in the troughs early in the spring, thus saving one year in the production cycle. New and better fry to fingerlings formulations will be developed and tested. Fingerlings will be transferred to the commercial system for grow-out and marketing. Fish wastes from the processing plant will be used to supply the majority of the protein required by these carnivorous fishes. The commercial catfish production will be a joint venture between the Scientific Research Division and the Pilot Fish Farm of the Haki centre and will involve many of the skills of the personnel assembled there from both divisions.
The hydrobiology group is also involved in planned research programmes for utilization of liquid manures to promote natural food organisms for fish. The chemical movement of nitrogen, carbon, and oxygen in natural and in fish farm production waters will be studied. New thrusts have been planned for more effective polyculture systems utilizing more fully the various food organisms present in natural or in managed waters.
Testing of technology developed by the research division or pilot plant at cooperatives and state farms in Hungary is planned.
This team will concentrate on finalizing the lipid requirements of carp. New plans were made to broaden the research effort into more specific studies of the role of the required polyunsaturated fatty acids (PUFAs) of the omega-3 type in the establishment, maintenance, and function of the vital phospholipids of respiring cell membranes. The Biological Research Institute of Szeged will cooperate in the design and interpretation of laboratory results. Preliminary work will focus upon young carp fed low and intermediate levels of these PUFAs and the effects of various thermal stresses in the laboratory. Electron microscopy coupled with gas-liquid chromotography to identify the fatty acids involved should identify the sites and physiological states of the phospholipid moieties affected by the nutritional treatments. Results should furnish critical information on the type and amounts of fatty acids required in diets for carp or catfish to assure maximum health and survival of fish exposed to low temperature stresses or to physical handling.
Studies on the amino acid requirements of catfish and of carps will be continued. Amino acid analysis of fish feed commodities and of finished feeds will supply the exact knowledge necessary for formulating diets which will support maximum growth of the fishes under each husbandry technique. Least cost feed formulations by computer for experiments involving carps or catfishes will be based upon these amino acid profiles. In addition, assays will be made of various natural waters and fish pond systems to indicate, the availability of amino acids in these systems.
The EIFAC-IUNS bulletin on Standardization of Techniques for conduct of fish nutrition experiments was reviewed in detail with Dr Csengeri. These techniques will be implemented to assure reproduceable results between tests and between stations. Standard experimental design for fish nutrition experiments was also reviewed and recommended for adoption by the entire Haki staff.
Major efforts of the group will be directed toward requirements for specific nutrients. One area which needs exploration is that on micro nutrients such as the vitamins and the minerals needed by production fish. The staff is too small to assign responsibilities for this area of research to anyone now there. More staff is needed or the work must be done elsewhere. Some interfacing between the fish health group and the nutrition physiology group will result in an awareness of the importance of these elements in fish nutrition and diet development. Much of the vitamin requirement of the fish can be supplied by natural food organisms present in ponds and in natural waters, but as the intensity of production develops, supplies rapidly become exhausted and the fish must then rely upon supplementation in the diet. To satisfy this need for vitamin in the intensive culture system proposed for the joint venture at Bikal, a vitamin premix formula was designed for this particular application. This formula is given in Appendix 1.
