Technological and Ecological Problems Limiting the Production of Freshwater and Marine Fishes in Latin America

Abstract

Most of Latin America, with the exception of northern Mexico, Chile, Argentina, Uruguay, and the southern tip of Brazil, is located between the Tropic of Cancer and the Tropic of Capricorn. The tropical oceans have been considered to be less productive than those of the Temperate Zone because of certain environmental factors. The principal factor is the presence of a permanent thermocline in tropical waters. Surface waters are warmer throughout the year and the temperature of the water decreases gradually with increasing depth until reaching the thermocline, a zone of rapid decrease in temperature with moderate increase in depth, which, in effect, separates the colder and denser lower water mass from the warmer and less dense waters above. In temperate waters, the thermocline forms during the summer months; but during the cold season, the surface waters cool down and sink because of their increased density until the temperature in the water column becomes uniform and the thermocline disappears. Because the water column has a uniform temperature and is of equal density, surface waters and bottom waters mix, bringing to the surface nutrient-rich waters from the bottom layers. This process is called overturn, and provides a nutrient-rich environment for the phytoplankton to grow in during the following warm season (1,2).