The principal site for cage culture proposed by the staff was the irrigation channel (locally called the “dead branch”), an old river bed four km in length near the FCRI presently used to conduct water for rice irrigation, fish culture and duck culture. No oxygen/temperature data were available on this body of water, so a profile of these factors was obtained four times daily for one week. Daily determinations of these factors was recommended for the remainder of 1975 and all of 1976. Twice each month the four-a-day determinations were obtained. The profile for one week indicated that at periods of low water, the fertility of the water from the nearby duck culture was quite high. The dissolved oxygen at dawn was as low as 2 ppm. Water with a high fertility and periodic low dissolved oxygen is not suitable for cage culture of fish. The added stress of low oxygen can at best cause poor feeding and slow growth and may likely cause complete mortality. When the channel was full of water and the flow of the water across the enclosures of ducks was away from the cages, there was no problem with low oxygen. Even though the low-water situation was rare, there only has to be an oxygen depletion around the cages one day in the year and an entire research project can come to an end as a result of mortality of the caged fish. Without duck culture on the irrigation channel, fertility would be lowered and this body of water would be excellent for cage culture.
The two staff members of the Institute assigned to cage culture were Mr. Laszlo Varadi and Miss Eszter Buz. Mr. Varadi has a master degree in mechanical engineering and Mizz Buz has completed a three-year programme in technical agriculture. Mr. Varadi's position is that of mechanical engineer and he was assigned part-time to the design and construction of cages. Miss Buz was assigned full-time to carry out the daily operation of cage culture.
In order for the staff to gain experience with cage construction, stocking, feeding techniques and data recording, one cage was built and stocked during the second week of the mission. Three hundred carp, averaging 158 g each, were stocked into the cage and feeding was begun. Carp were used in the initial trial because they were available and are relatively hardy fish. About 10 percent mortality occurred during the first week as a result of handling and hauling the fish for stocking, but no mortality occurred after the first week. Since only sinking pellets were available, a feeding tray was designed to contain the pellets and the carp quickly adapted to feeding from the tray. Floating pellets would be a decided advantage but none are available in Hungary.
Twelve cages were constructed during the last week of July and the first week of August. These twelve cages were to be used for a short-term experiment for the remainder of the warm period of 1975. The staff at FCRI was consulted about research priorities and a research project was designed as shown in Table 1. In essence, the project is a study of two types of feed, three designs of feed containers for sinking pellets, and four genetic strains of carp.
EXPERIMENTAL DESIGN OF FIRST CAGE CULTURE TRIALS FISH CULTURE RESEARCH INSTITUTE, SZARVAS, HUNGARY
| Feed #1 30% protein | Feed #2 35% protein | ||
| Double basket | Poultry feeder | Double basket | Single basket |
| 1 | 4 | 7 | 10 |
| 2 | 5 | 8 | 11 |
| 3 | 6 | 9 | 12 |
Each cage contains four strains of carp for a total of 1 200 fish/cage.
The two types of feed, selected by the personnel working in feed research, were chosen in order to establish a suitable feed for cage culture utilizing locally available ingredients. As recommended by the fish feeds consultant, the pellets were made to be water stable for at least one hour.
Conversion ratios are partially dependent upon how much feed is wasted, so the design of the feed container is important. A simple basket has been utilized previously in cages but other designs may improve efficiency. Two other types of feeders were selected to determine if they would improve feeding efficiency. The double basket feeder was constructed in the same way as the single basket except that a smaller basket was built into the centre. A staff member was of the opinion that the double basket design would reduce the amount of feed the fish would swirl out of the feed container. A cylindrical, standard poultry feeder, which was adjustable, was also selected as a design to reduce the feed loss caused by the activity of the fish.
The personnel in the genetics section of FCRI had developed four strains of carp which they wanted to test in cages for rates of growth and feed conversion efficiency. These four strains were marked for identification and 1 200 were placed into each of the cages.
The above described research project will terminate in November, 1975 at the time the irrigation channel is drained. Further testing of the variables will be discussed after results of the present study are evaluated.
As a method of imparting knowledge about cage culture to a majority of the staff, lectures were held and slides were shown. Lectures were given on specific research projects using cages, general cage culture, and general aquaculture. Mr. Csávás was the interpreter and discussions were held at the end of each lecture.
Several of the senior staff members were of the opinion that other Hungarians who do not read other languages would like to know something about cage culture. To fill this need a generalized article was written about cage culture; it was translated into Hungarian and will be published in the autumn of 1975 in a Hungarian fisheries magazine. Engineering drawings and photographs were included in the article, a copy of which is appended (Appendix 1).
