FEEDING HABITS OF STOMIATOID FISHES FROM 



HAWAIIAN WATERS 



Thomas A. Clarke 1 



ABSTRACT 



Stomachs were examined from over 2,800 specimens of stomiatoids collected near Hawaii. Small 

 Vinciguerria nimba ria ate mostly small copepods and ostracods, while large fish appeared to switch 

 to large amphipods and small euphausiids. The remaining planktivorous species, sternoptychids 

 and small gonostomatids, fed primarily on large calanoid copepods and small euphausiids. All of 

 these appeared to feed by active, visual searching, and preferred prey were probably more visible 

 than other zooplankton in appropriate size ranges. Diets and preferences of the planktivorous 

 stomiatoids were similar to or identical with those of one or more species of myctophids which share 

 the same habitat. The large gonostomatids ate micronekton but appeared to feed in the same manner 

 as the small individuals and species. 



The species from six other families, which appear to be morphologically adapted to ingest rela- 

 tively large prey, did in fact feed mostly on prey 20% of their body length or longer. Only two species 

 ate zooplankton as well. Most species with chin barbels were nearly or exclusively piscivorous, and 

 those without barbels ate few or no fish. The barbel and analogous structures appear to be used pri- 

 marily to attract and aid in the capture of relatively large fish. Apparent preferences for certain 

 types of prey by the piscivorous species indicate that interspecific differences in barbel features are 

 related to dietary specialization. Based on feeding incidence and estimates of stomach evacuation 

 time, the piscivorous stomiatoids appear to consume a large fraction of the standing crop of plank- 

 tivorous fishes each year. 



Stomiatoid fishes are important components of 

 the micronekton in most tropical and temperate 

 oceanic areas (e.g., Maynard et al. 1975). Most 

 species occur in the upper 1,000 m and undertake 

 diel vertical migrations (Clarke 1974 and others 

 cited therein). They include both small, plank- 

 tivorous species and generally larger forms with 

 certain morphological features apparently re- 

 lated to capture of relatively large prey. 



Little is known of the feeding habits of these 

 fishes and, consequently, of their role and impor- 

 tance in the pelagic food web. Diets of a few 

 planktivorous species have been reported, but 

 usually from few specimens and without identifi- 

 cation of prey beyond major taxa. Clarke (1978) 

 showed that some planktivores feed while at 

 depth during the day. Knowledge of the prey of 

 nekton-eating species has consisted mainly of in- 

 cidental reports scattered throughout the litera- 

 ture rather than systematic investigations of 

 large numbers of specimens. 



This paper presents results of examination of 

 stomach contents of over 70 species of stomia- 

 toids from an extensive series of collections near 



■Department of Oceanography and Hawaii Institute of Ma- 

 rine Biology, P.O. Box 1346, Kaneohe, HI 96744. 



Manuscript accepted November 1981. 

 FISHERY BULLETIN: VOL. 80, NO. 2. 1982. 



Hawaii in the north central Pacific Ocean. 

 Almost all the species are vertical migrators; the 

 abundant, nonmigrating species of Cyclothone, 

 Sternoptyx, and Argyropelecus (which are the 

 subjects of separate studies by other investiga- 

 tors) are not included. Diets of the planktivorous 

 species are compared with estimates of prey 

 abundance in appropriate depth ranges in order 

 to determine whether composition and apparent 

 preference are similar to those of cooccurring, 

 nonstomiatoid planktivores which feed in the 

 upper layers at night (Clarke 1980). Data from 

 the nekton-eating stomiatoids allows considera- 

 tion of preference, feeding methods, and the 

 impact of these predators on the planktivorous 

 micronekton in the community. 



METHODS 



Specimens for this study were collected ca. 20 

 km west of the island of Oahu, Hawaii (ca. lat. 

 21°20-30'N, long. 158°20-30'W) in waters 2,000- 

 4,000 m deep. Previous studies in this area have 

 considered the vertical distribution and certain 

 other aspects of the ecology of stomiatoids 

 (Clarke 1974) and the feeding chronology of five 

 species (Clarke 1978). Other investigations in the 



287 



