6.1 Background
6.2 Research Needs
The Israeli strain of the common carp (Cyprinus carpio) has been introduced into Latin America and is cultured on an experimental or subsistence scale in Mexico (Obregon, 1961), Ecuador (Departamento de Limnología, 1977), Brazil (Nomura and Castagnolli, 1977), Paraguay (División Caza, Pesca y Piscicultura, 1977), Bolivia (1977), Colombia (Acero-Sánchez, 1977; Nión, 1977; Noreña, 1977) and Chile (División de Pesca y Caza, 1977). Carp has been cultured in different parts of the world for centuries, thus techniques for its culture are well established. It is relatively easy to reproduce and problems in obtaining fry are few. However, the season of spawning must be taken into account. In Europe, carp spawn in the spring, whereas in tropical areas, such as Indonesia, they spawn all year round. Climate may also affect maturation ages, which in turn can affect the management techniques selected. "Wild spawning" can occur, disrupting the culture plan and resulting in stunted populations and reduced yields. The main advantage of carp is its ability to utilize a variety of feeds as supplements to the natural food that develops in the pond. Good results can be obtained by feeding simple carbohydrate feeds like sorghum or other cereals, or even agricultural by-products such as ricebran, etc. Carp can, therefore, be cultured at different intensification levels according to prevailing conditions. The prime need, however, is to determine the level of intensification that will provide the most economic returns in a particular locality, and 1.0 conduct an inventory of supplies of feedstuffs that could be used, keeping in mind the ability of the carp to consume and utilize plant by-products.
The degree of intensification of fish culture in stagnant warm-water fish ponds is determined by economic conditions. If land, water and labour are abundant and inexpensive, but feed is expensive, culture must be more extensive relying more on natural food and less on supplementary feed. However, if land, water and labour are expensive, intensification is necessary even at the cost of higher expenses for feed. Extensive farming will involve the use of a larger pond area than that used in intensive culture to obtain the same yield. Recent studies have shown that considerably high yields can be achieved by the use of chemical fertilizers and organic manures. Partly intensive culture may be feasible in many areas, by using simple feeds such as cereal grains or farm by-products.
Carp has been distributed in many Latin American countries, though there is opposition to introduction in some countries. High yields can be obtained in carp culture, alone or in a polyculture system. As mentioned above, the techniques have already been developed, and it is more the problem of adaptation to Latin American conditions that the Centre should be dealing with. These should involve:
(i) Breeding studiesThese studies should be concerned with natural breeding in ponds, and hatchery breeding procedures
(a) the seasonality of carp breeding and its effects on the maturation age. This may be of importance both from the point of view of fry supply and from that of prevention of "wild spawning" of carp in ponds;(b) the survival of fry during nursing and ways of increasing it. Loss of fry can be incurred by many causes, such as diseases, parasites and pests. Water-bugs, frogs and water snakes may decimate fry severely. Ways should be found to control diseases, parasites and pests;
(c) hatchery-induced spawning. This should be attempted if the loss of eggs and fry in the first days is very heavy and its control is difficult or too expensive.
(ii) Feeding studies
Since carp can utilize carbohydrates well, the studies should concentrate on finding local low-cost carbohydrate sources. At a later stage these can be incorporated into a diet containing proteins for more intensive culture. Here the studies should be concerned with the following:
(a) inventory of local feeds and their acceptability to the carp;
(b) digestibility tests;
(c) growth studies in running water tanks.(iii) Culture studies
The interaction between fertilization, manuring and feeding and stocking rate should be studied in ponds, and the effect of the environmental conditions on the fish, their rate of growth and yield should be ascertained.
(iv) Pilot-scale trials
Early attempts should be made to undertake trials of sufficiently large a scale as to permit the collection of adequate costing data for economic analysis of the system.
(v) To overcome any consumer resistance to the product, quality control, marketing, and product development studies should also be undertaken.
