Vertical Zonation of Inshore Fishes in the Upper Water Layers of the Hawaiian Islands

The Hawaiian Islands are in the trade wind belt; they have about a 1—m tide. Along open coasts the effect of the tide on the zonation of inshore fishes is minor compared to that of the surge. Above sea level, pools depend primarily on wave splash for replenishment. The higher splash pools have few species of fishes, and those that occur there are ecologically well differentiated. On the exposed rocky benches just above sea level, there is usually abundant seaweed, but one herbivorous blenny is the only fish that lives there. For some 6 m or more just below sea level on open coasts horizontal water movement frequently scours the bottom, often with the abrasive action of sand added. The bottom here is of rock or sand. Most of the species of the area are herbivores which graze on such short algal stubble as exists on the rocks. Indeed, in both species and individuals, the maximum number of herbivorous fishes would seem to occur in this zone. In the quiet water offshore from, and just below the surge zone the best live coral formations in the Hawaiian waters grow. Here there is also a fishes below this point are scarce. Preliminary information suggests that the differentiation of the fish fauna at deeper levels is far more gradual, and that there is still a considerable number of species to at least half a mile in depth. Around the high Hawaiian Islands the waters protected by fringing reefs appear to have a mixed zonal fauna containing partly surge zone fishes, partly fishes that come in from quiet, deeper water, and partly forms restricted, so far as known, to such areas.