7.1 Background
7.2 Research Needs
Salmo gairdneri is by far the most widely distributed species of trout in Latin America, where it has been utilized mostly for stocking lakes and rivers as a sport fish. A commercial fishery operated successfully in Lake Titicaca until 1969.
Trout farming as a small-scale commercial venture exists in several countries. The main limitation to its more extended development appears to be the lack of adequate feeds, the high level of animal protein required making them expensive.
Unsuitable location and inadequate design of facilities have created problems for owners of trout farming enterprises in several countries. Parasites and diseases, which sometimes are associated to poor holding conditions, have been observed in the region. Nutritional disorders are reported to occur frequently at government stations and have also been reported in commercial ventures.
The vastness of high altitude lands available in the upland areas and the poverty of local populations who have very few employment opportunities have made rural development agencies in several countries consider the possibility of promoting semi-intensive trout fanning in conventional ponds. Limitations to the applicability of methods of organic and chemical fertilization of ponds utilized in warm-water fish farming to increase natural productivity, and the problems involved in formulating suitable feeds cheap enough for use under local conditions, make difficult the improvement of low yields obtained when systems of extensive culture are practised with this species. Intelligent research, however, could bring some positive results, particularly applicable to countries where large amounts of fish meal (the main animal protein ingredient now used in fish feeds) are produced in the region.
It is suggested studies on trout culture at the Centre's cold-water sub-centre in Campos de Jordão could deal primarily with the following:
(i) Research on feeds and feedingThe screening of locally available inexpensive ingredients that could be used in the formulation of a trout feed, including analysis of their nutritional quality, should be undertaken as one of the first tasks. Based on this information, the formulation of nutritionally complete feeds should be undertaken. The ingredients should be widely available throughout the region or easily substituted by local products. Economy is a very important consideration.
Next, the formulae should be tested at each stage of the trout's development.
(ii) Studies on the maturity and breeding of Salmo gairdneri under Latin American conditions. It is reported that the species can be bred throughout the year. This has to be verified. If this is feasible, and under local conditions a sustained growth rate is obtained under more or less constant temperature conditions, a well-phased year-round production programme may become possible.
(iii) Research on semi-intensive trout farming
In view of the need to develop a semi-intensive type of trout farming for mountain areas with good water resources, efforts along this line deserve careful consideration. Perhaps appreciable amounts of trout could be economically produced in conventional ponds through the use of supplementary feeds. This possibility should be weighed against the development of a culture system for one of the few indigenous species inhabiting cold waters.
During the first phase of experimental work at the Pirassununga Centre and while the required infrastructure for trout farming experiments become available at Campos de Jordão, simple field trials of semi-intensive pond culture could be carried out, including the following:
(a) development of a feed formula. Possibility of using locally available ingredients, like wastes from animal industries/processing, for the preparation of a feed that is cheap enough to be used in semi-intensive trout farming;(b) determination of the highest population density compatible with an acceptable growth rate of the fish; conversion factor; yield;
(c) management techniques;
(d) economics of the system. Benefits to be derived by rural populations through trout farming in rural areas.
(iv) Research on parasites, bacterial and viral diseases, and nutritional disorders.
Disease prevention and control plans should receive early attention to prevent deterioration of natural conditions conducive to trout rearing.
