General Marine Habitats in Hawaii
In arbitrary divisions, there exist three general marine habitats in Hawaii. The pelagic or deep-sea habitat supports the least number of marine species and is the most uniform of these environments. The majority of its species are found in its epipelagic surface layer whose temperature and chemical composition is kept generally constant by trade winds, sometimes to depths of 100 fathoms (600 feet). Interestingly, a number of reef and inshore species’ larva and juveniles can be found in these waters, most abundantly in its inshore, neritic zones. Surgeonfish are an example of a species whose pelagic larva feed on zooplankton in the open ocean for a period of roughly 2.5 months, after which they return to their adult, reef habitat.
The Benthic or bottom habitat is the marine environment least known to scientific exploration. Unlike the unrestricted and roaming species of the pelagic habitat, the species of this region are like reef fish in the sense that they are confined to specific areas because of the location's physical characteristics. The benthic area is roughly between 30 to 150 fathoms, just below the reef habitat, which fades at around 20 to 30 fathoms (Gosline, 1960).
Just as its fish species, the coral of the Hawaiian Islands is less diverse than those of other islands found in the Pacific, largely due to the chain’s extreme isolation of being at least 2000 miles from any major land mass. The hindered development of Hawaii’s reefs is similarly the result of geography as the islands border the northern edge of the tropics, just below the subtropic zone, where coral growth can be compromised by sensitivity to low temperatures. On Oahu, as on Kauai, Molokai, Lanai, and Maui, over half of the shoreline is fringed with reef, which at some areas extend as much as 300 meters from the shore (Kay, 1987). Of the roughly 680 known types of fish in Hawaiian waters, there are around 440 species that can be classified as inshore or reef fish (Randall, 1985). Within the inshore habitat, coral and reef fish ecosystems can vary for example between leeward and windward sides of an island to the extent that deviations of physical conditions such as wave action, or chemical conditions such as light exposure due to depth occur (Gosline, 1960).