NATURE AND EVOLUTION — HAWAIIAN INSHORE FISH FAUNA 349 



If cold water were the principal limiting factor in the differentiation 

 of Hawaiian shore fishes, then greater variation would be expected 

 within the Hawaiian chain than between the northern Line Islands 

 or Wake and Hawaii. This, however, does not occur. On the contrary, 

 the fish fauna throughout the Hawaiian chain seems to be quite homo- 

 geneous. Except for slight indications of racial differentiation in two 

 species (Kuhlia sandvicensis and Istihlennius zebra), attempts to dis- 

 tinguish even races of fishes within the Hawaiian chain have been un- 

 successful. 



As to number of species, there are several a priori reasons for sus- 

 pecting that it might differ at the two ends of the Hawaiian chain. 

 One is the great differentiation in winter water temperatures within 

 the chain noted above. A second is that the southeastern islands are 

 high and volcanic, whereas the northwestern are low coral atolls. Pre- 

 sumably all the atoll habitats are present around the high islands; how- 

 ever, the volcanic rock habitats of the eastern islands are absent from 

 the whole western part of the chain. Finally, there is the possibility 

 that the low western islands have a larger fauna because they are older. 

 Unfortunately, it is impossible to say whether the number of species 

 at the two ends of the Hawaiian chain actually does differ, for the low 

 leeward islands have been very poorly collected and the absence of 

 species records from these islands means nothing. Consequently, it be- 

 comes necessary to fall back on general impressions for what they are 

 worth. After collecting at most of the islands from Hawaii to Midway 

 it is my personal feeling that there is a decrease, though probably not 

 an evenly graded one, in the number of species from southeast to north- 

 west. Indeed I have collected no species in the leeward islands that 

 I had not already collected in the high Hawaiian islands. (On the other 

 hand the number of individuals of a species seems to increase from 

 south to north. Also, judging from a few non-commercial species, the 

 maximum size of individuals within at least some species increases from 

 south to north.) If, however, there are species on the high islands 

 restricted to lava rock habitats, I do not know them. In Oahu, the great 

 majority, at least, of the species found over lava rock may also be en- 

 countered over coral or coralline limestone areas. It seems necessary 

 then to fall back on winter temperatures as the cause of the decrease 

 in number of species in the leeward group, if indeed such a decrease 

 really takes place. 



Current Systems 

 The adults of most Hawaiian inshore fishes are bottom feeders that 

 would presumably starve in the open sea. It is generally believed. 



