Fish culture in ponds is an old profession, with earliest practice going back to prehistoric times. It has assumed various levels of importance in different civilizations, but has risen presently to greatest relative importance as a national source of food for the peoples of Israel, China, Formosa, Indonesia, and the Philippines. Pond fish culture is being promoted widely in Asia, Africa, and Central and South Americas as a method of improving the nutritional levels of present and future populations.
As a world-wide source of food, fisheries, both marine and fresh water, are of relatively minor importance as compared with agriculture since they furnish an estimated average of only 10 kilograms of edible fishery products per person per year. Of this total, fresh waters are believed to contribute only less than 10 percent, but the high quality of fish proteins makes this resource of great importance in areas of dense populations where the bulk of human food must consist of grains and vegetables.
Studies of population increases indicate that low population densities are of a temporary nature and that human populations tend to increase to the maximum “carrying capacity” of the ecological niches that they occupy. Carrying capacity itself is a variable and depends upon the type of diet consumed. Thus, as population density increases, food consumed changes from a diet high in animal proteins to one high in plant proteins. With this change, the importance of sources of high-quality animal protein to fortify the lower quality plant protein diet increases.
The fish culturist must realize that fisheries in general, or pond fisheries in particular, are merely one possible source of these high-quality proteins. Pond fisheries require use of land and water, both usually in scarce supply in areas of dense human populations. Each may be put to alternate uses for food production by agriculture. For too many years, fish culturists have been content to claim that if land were surrounded by dams and inundated, production by fish culture would be higher than that of agriculture from the same land. At a primitive level of both cultures, this is probably true if we compare production of fish proteins to production of animal proteins, but not true if we compare it to production of vegetable proteins.
The tremendous amount of research devoted to agricultural production has given agriculture capabilities far beyond its primitive abilities to produce. Plant and animal breeding have developed superior and higher producing strains, whereas the fish culturist still must use what are in effect wild unselected species. Studies of soils, fertility and fertilization, feeds and feeding, irrigation, plant and animal physiology, and related sciences have yielded vast sources of information upon which the agriculturist may draw to push production to higher and higher levels. Combined with this scientific information, organized groups of agricultural specialists are available that by demonstration and by teaching can bring relatively rapidly new procedures and scientific information into general use by farmers.
For pond cultures relatively few individuals working with inadequate experimental ponds have the responsibility for devising, by research procedures, improved fish cultures that are capable of successful competition with agriculture for land, water, fertilizer, feeds, and human labour. That they are successful to a certain extent is in part the result of adaptations of research-accumulated agricultural knowledge to fish culture. Soil science, botanical science, and animal sciences are basic to both. Pond fish culture is both competitive with agriculture for certain resources and supplemental to agriculture in conservation and utilization of others.
Even in land usage they may be both competitive and supplemental. Since run-off waters must be impounded and held in relatively flat lowland areas, it is inevitable that pond culture here may be in competition with agriculture for use of highly productive lands. It becomes increasingly necessary that these flooded lands produce more than they could under agricultural usage to replace lost agricultural products and to repay the added capital costs of dams and other costs of impoundment. Pond culture may in other areas supplement agriculture in effective land usage by making use of lands too wet, too poor or too saline for agriculture.
Where fish are produced by feeding, again this is competitive with agriculture for the limited supply of animal feeds. We can justify their usage in fish culture only if these feeds are used as efficiently or more efficiently than in agriculture to produce high quality animal proteins for human consumption. Fortunately, we can do this, as certain fishes are among the most efficient of animals in conversion of low quality feeds into high quality proteins. However, efficient conversion can only be attained by combined usage of efficient fish, efficient feed mixtures, and most efficient rates of feeding, all of which must be determined by careful research.
Fish cultures also may be supplemental to agriculture when agricultural wastes are used directly or indirectly as fish feeds, and fish wastes are used in animal feeds.
Fish culture is competitive with agriculture and industry for labour. The returns for this labour in terms of kilograms agricultural or fishery products per man-day must be high if the labourer is to enjoy a high standard of living. Agriculturists and industrialists strive for maximum production per man-day of labour since the wealth of a nation is the sum total of the productivity of its citizens. In fisheries, we have often ignored this, assuming that fisheries was a means of supplying enough food for survival. While this is important, the low level of income of fisherman in all nations emphasizes the need for maximizing production and minimizing labour required per hectare of water for growing and harvesting the crop. Israel deserves much credit for the mechanization of operations and for devising labour-saving procedures for their system of pond culture.
For overall efficiency of the world's food-producing capacity, fisheries are an essential supplement to agriculture. The food-producing capacity of soils resides primarily in their ability to provide annually in a soluble form the salts essential for plant growth. However, as rain falls upon land, a portion of these soluble salts are taken from soils by run-off waters and transported downhill towards the oceans. The world-wide average loss of salts per hectare of land is 575 kilograms per year, and such annual leaching has made necessary fertilization of soils to maintain high agricultural production. Yet when fertilizer is added to soils, inevitably a portion is lost in run-off waters. As the farmer gradually improves fertility of his lands, he loses increasing amounts of plant-essential salts to these waters. These water-borne salts furnish the basic fertility supporting productivity in ponds, lakes, rivers, and brackish waters. They can be effectively recovered for human use through fresh-water and marine fisheries, but most efficiently by pond culture.
In certain areas of Asia, Africa, Europe, and Central and South Americas, populations already exceed local abilities to produce food required for an adequate diet. Within the next 50 to 100 years, predicted increases in populations will make this a severe worldwide problem unless methods greatly increasing productivity are developed for both land and water areas.
Tal (1965) effectively points out the problem ahead of all of us. 1 In Israel by intensive pond management and supplemental feeding, average production rose from 1,570 kg per ha in 1952 to approximately 2,000 kg in 1957. Despite intensive research on pond management, no further increases were obtained up to the present.
A plateau has been reached where intensive research is required to devise procedures to bring production to higher levels. At various levels of management factors limiting production must be identified and procedures for their elimination must be developed (Swingle, 1964).1
It is desirable to clarify our thinking upon fish culture in ponds by considering two levels of management - ponds where all fish food is produced within the pond and ponds in which natural fish food organisms are supplemented by daily feeding.
The maximum annual production that can be achieved in ponds where all food for fish is produced within the pond seldom exceeds 1,000 kg per ha. This includes both unfertilized and fertilized ponds. In areas where the growing season includes eight or more months, this plateau may be reached in most ponds by procedures of liming and fertilization combined with efficient combinations of fish. To what extent this plateau of production can be exceeded can only be determined by research. Unfortunately, in most areas the above maximum is seldom achieved, partly because of inefficient species and ineffective management methods.
Where supplemental feeding is used to obtain higher production, the second level can achieve annual maximum production of approximately 2,500 to 3,000 kg per ha in ponds without flowing water (to remove wastes) and if the growing period is eight or more months. Here, production is determined partly by ability of the pond to produce fish foods, and partly by the quality and amounts of organic materials that can be produced elsewhere and added as daily feeding. Such feeding is usually based upon an efficient agriculture that can produce an excess of food above requirements for direct human consumption. For this reason, this level of pond management is difficult to achieve in areas where high production is most needed. For these areas, methods of using as fish feeds agricultural wastes and food of poor quality for human consumption must be devised. This is a field in which little has been accomplished by research, yet became the basis for the traditional Chinese pond cultures. Research within a few years must produce better methods than traditional cultures developed over centuries of time.
We can briefly summarize our present position as follows: In many areas, pond culture is still a primitive art, scarcely producing sufficiently to justify use of the water and land it utilizes. Sufficient information is presently available to raise productivity to a level that is competitive with present agricultural usage in these areas and in addition can repay the costs of impoundments and management. However, where supplemental feeding is not possible, after we reach the plateau of 1,000 kg per ha of fish production, we have at present insufficient knowledge of limiting factors and no procedures to increase productivity materially beyond that point.
Supplemental feeding is at present principally useful in areas with a surplus of agricultural products, whereas highest fish production is most needed in areas having no such surpluses. Research must give us the answer to higher production in these areas by providing methods for developing efficient fish feeds from organic wastes and low-quality feeds.
Research must also proceed at a rapid pace upon methods of increasing fish production at all levels of management to enable the fish culturist to earn a higher standard of living and to ensure adequate food for coming generations.
After research has developed the needed information and effective methods for increasing fish production, the monumental task remains of getting this information into use by people. This is a most difficult task, requiring intensive and continuing effort, including effective demonstrations of actual pond management and its results by extension specialists at village and regional levels. People must see to learn. In situations where the techniques demonstrated have not been tested experimentally, it can be predicted that demonstrations often will principally demonstrate to villagers that the extension specialist did not know how to manage a pond. Demonstrations that do not succeed are best conducted on experimental stations of the fishery departments so that research workers can devise improved methods of management. The extension specialist is supposed to carry experimentally developed knowledge to the people, not a fishery department's lack of knowledge.
We have met at this Symposium both to pool our knowledge and to explore our lack of knowledge so that our progress into the unknown may be more rapid. From our common knowledge should come reliable instruction and procedures that can be used to improve pond cultures in all countries. From our glimpses into the unknown will come the research needed for the advanced and highly productive fish cultures of the future.
1 Tal, S., 1965 Current problems in fish culture. Bamidgeh, 17(1): 3–8
