ABSTRACT
Species or strain selection is a most important decision for the aquacultural entrepreneur. A knowledge of that species' biological needs must be considered in relation to site-specific climatological considerations and quality and quantity of water. Some tilapia species may be cultivated easily in high-salinity waters although they are originally freshwater species. It is generally impractical to control ambient temperatures in aquaculture systems. In temperate climates, thermal minima are often serious constraints to aquaculture. The chapter reemphasizes the fact that aquatic species require oxygen-rich waters for optimum growth and survival. It argues that many species tolerate a wide spectrum of water temperatures, the optimum temperature range for good growth rate, low feed conversion ratios, reproduction, and disease resistance. A rapid growth rate that permits harvest in the shortest time is highly desirable in any species. The market potential for any aquaculture crop must be checked and specific buyers targeted before a cost-and-return analysis can be made.
