The mean was 0.015 milligrams per liter. In open oceans, copper levels ranged from 0.1 milligrams per liter to 0.39 milligrams per liter, with an average of 0.8 milligrams per liter. These figures show how copper is effective in small quantities. To measure such tiny amounts requires a spectro photometer, an instrument that gauges matter by zeroing in all the way down to atoms in molecules. Scientists heat animal tissue to extremely high temperatures until atoms begin to emit light.
Different atoms produce light at different wavelengths.
Many of these species are part of the renewable foundation of fishing, a vast worldwide activity that helps meet a growing demand for protein. Commercial and recreational fishing is practiced just about every where in the world, including such land-locked countries as Bolivia, in South America, and Azerbaijan, in Asia. Bolivians have been fishing the waters of Lake Titicaca for centuries, and the valuable caviar industry of the world is centered in Azerbaijan, on the Caspian Sea. Almost a third of that catch was raised on fish farms in a fast-growing commercial process known as aquaculture. Fish grow under controlled conditions within enclosures and are fed a carefully balanced diet that invariably includes copper.