CLARKE: DIETS OF FOURTEEN SPECIES OF MESOPELAGIC FISHES 



lar to each other, but quite distinct from the others. 

 Differences in size and depth distribution at night 

 probably reduce diet overlap among these species. 

 Triphoturus nigrescens and L. nobilis occur shal- 

 lower than do N. valdiviae and L. steinbecki, and 

 within each pair, one species is considerably larger 

 than the other. Other multispecies studies in the 

 tropical or subtropical open ocean also indicate 

 some degree of specialization among cooccurring 

 species. 



In contrast, Tyler and Pearcy's (1975) results 

 indicate that high latitude species have little or no 

 separation or specialization in diet. Confirmation 

 and further documentation of the apparent differ- 

 ence are certainly merited. If true, it could indi- 

 cate that tropical species are less likely to be com- 

 peting against each other for food or that species in 

 the highly productive waters off Oregon are not 

 food limited. The apparent difference in degree of 

 dietary specialization also has obvious implica- 

 tions relevant to differences in diversity — both of 

 the fish faunas and of their prey — between tropi- 

 cal and temperate oceanic communities. 



ACKNOWLEDGMENTS 



This research was supported by NSF GA-38423 

 and the Hawaii Institute of Marine Biology, Uni- 

 versity of Hawaii. I thank the officers and crew of 

 the research vessels Teritu and Moana Wave; the 

 staff of Ship Operations, Hawaii Institute of Geo- 

 physics; and the many people who participated on 

 the cruises for their assistance and cooperation. 

 Patricia J. Wagner capably assisted in the early 

 phases of the work. Euphausiids and decapods 

 were identified by K. Gopalakrishnan. 



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