Oysters are found throughout the tropics and subtropics and are commonly harvested from wild populations. In spite of their adaptability to cultivation, oyster farming has developed in only a few tropical countries. The expansion of oyster culture has been hindered by limited awareness of its potential among fishery development promoters and the need for more widespread dissemination of information on the technology of oyster culture, processing and marketing. Hopefully this publication will contribute to overcoming some of these obstacles.
The oyster is probably the most studied invertebrate organism and much is known of its biology in temperate waters. Galtsoff provides an excellent coverage of its general biology, based on the American oyster, Crassostrea virginica. Quayle has provided an extensive bibliography dealing with tropical oyster biology and culture. More recently Breisch and Kennedy produced a bibliography covering the entire subject of oyster taxonomy, biology and culture with over 3,000 citations.
The taxonomy and phylogeny of tropical oysters remain confusing in some areas, but the application of modern methods of protein electrophoresis and hybridization using state-of-the-art hatchery technology will help to clarify these relationships. Identification keys based on regional species groupings would be most useful for oyster culture developers, but are beyond the scope of this paper.
While much of the biology of tropical oysters is comparable to that of their temperate counterparts, the effects of their warm environment on reproductive cycles are not well understood.
Temperature may play a minor role in stimulating gonad maturation, as will be pointed out in following sections. Oysters, particularly of the genus Crassostrea, must adapt themselves to the sometimes rapidly changing salinity and heavy silt loads brought about by the monsoonal climate of much of the tropics.
Tropical oyster farmers are confronted with the difficulty of predicting spatfall from populations of oysters that may be spawning continuously. Sometimes they must avoid excessive setting.
Fouling is a serious problem in the tropics and culture systems must be evolved which can economically overcome it Many of these problems are compensated for by the extremely fast growth (compared to temperate species) of tropical oysters. The farmer can usually obtain marketsize oysters in less than one year, often in as little as six months, and with the continuous spatfall common in many areas, can produce a steady flow of product for customers.
Although disease has not been a serious problem in tropical oyster culture, siltation and pollution have reduced production and pose a continuing public health hazard that must be addressed if the industry is to thrive. Problems of both technology and infrastructure have to be overcome.
Oyster production is slowly increasing, but tropical production is still dominated by a few countries, most notably Mexico, and its production comes mainly from one species, Crassostrea virginica. However, the potential is great. Culture technology utilizes low-cost materials and is adaptable to rural development.
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