wildlife species living in the riparian zones the salmon reach. The nutrients can also be washed downstream into estuaries where they accumulate and provide significant support for invertebrates and estuarine-breeding waterbirds. Background Most salmon are anadromous, a term which comes from the Greek anadromos, meaning "running upward". Anadromous fish grow up mostly in the saltwater in oceans. When they have matured they migrate or "run up" freshwater rivers to spawn in what is called the salmon run. Anadromous salmon are Northern Hemisphere fish that spend their ocean phase in either the Atlantic Ocean or the Pacific Ocean. They do not thrive in warm water. There is only one species of salmon found in the Atlantic, commonly called the Atlantic salmon. These salmon run up rivers on both sides of the ocean. Seven different species of salmon inhabit the Pacific (see table), and these are collectively referred to as Pacific salmon. Five of these species run up rivers on both sides of the Pacific, but two species are found only on the Asian side. In the early 19th century, Chinook salmon were successfully established in the Southern Hemisphere, far from their native range, in New Zealand rivers. Attempts to establish anadromous salmon elsewhere have not succeeded. The life cycle of an anadromous salmon begins and, if it survives the full course of its natural life, usually ends in a gravel bed in the upper reaches of a stream or river. These are the salmon spawning grounds where salmon eggs are deposited, for safety, in the gravel. The salmon spawning grounds are also the salmon nurseries, providing a more protected environment than the ocean usually offers. After 2 to 6 months the eggs hatch into tiny larvae called sac fry or alevin. The alevin have a sac containing the remainder of the yolk, and they stay hidden in the gravel while they feed on the yolk. When the yolk has gone they must find food for themselves, so they leave the protection of the gravel and start feeding on plankton. At this point the baby salmon are called fry. At the end of the summer the fry develop into juvenile fish called parr. Parr feed on small invertebrates and are camouflaged with a pattern of spots and vertical bars. They remain in this stage for up to three years. As they approach the time when they are ready to migrate out to