The Hawaiian Archipelago, situated in the middle of the Pacific Ocean, is the most isolated landmass in the world. The west coast of the U.S. is 2,400 miles away and Japan is 3,800 miles away. These 376 small, torrential mountain streams are located on the windward side of the islands and represents the freshwater ecosystem that is home to our native stream animals. They are small compared to many of the larger streams on the US mainland. Hawaiian streams resemble a mainland trout stream but are generally shorter.
Numerous waterfalls characterize many Hawaiian streams.
Stream flow tracks rainfall pattern. Although year round orographic rainfall is the primary source of stream water, localized heavy rainfall and storms passing through the islands cause frequent flooding, called freshets or spates. There are only about 550 species of marine fishes, as compared to about 2,000 fish species in the Philippines. The fishes consist of two closely related familes, Gobiidae and Eleotridae , collectively referred to as 'o'opu in the Hawaiian language. These fishes are small, nearly scaleless bottom dwellers as adults.