FISHERY BULLETIN: VOL. 74, NO. 3 



almost every conceivable intermediate pattern is 

 represented as well. 



Four of the common species, Bregmaceros 

 japoHicKs, B. macclelland} , Scopelogadus 

 mizolepis, and Melaniphaes danae, are typical 

 migrators. Both juveniles and adults move from 

 well below 500 m during the day into the upper 250 

 m at night. The data indicate that four rarer 

 species, Rondeletia loricata, Melaniphaes indicus, 

 M. "janae" and Scombrolahrax heterolepis proba- 

 bly perform similar migrations. 



The first four species were the most abundant of 

 all considered here and ranked with all but the 8-10 

 most abundant myctophids and migrating 

 stomiatoids (see Clarke 1973, 1974). The night 

 size-depth patterns of the four were similar to the 

 general types observed in the latter groups. Breg- 

 maceros japouicKs cooccurred with similar-sized 

 individuals of several abundant myctophid species 

 and Vinciguerria nimharia, whWe B. macclellandi 

 and the melamphaids had patterns similar to those 

 of deeper-living species, e.g., Lanipauycfus niger 

 and Gonostoma spp. In the case of the Bregmaceros 

 spp. and M. danae, the adults occurred throughout 

 the depth range instead of primarily at the lower 

 end as was usually the case with the other fishes. 



During the day, the four migrating species 

 exhibited a trend for increased size with depth. 

 The day depth range of B.japon reus was similar to 

 those of many other migrating species, but the 

 other three were the only migrating species be- 

 sides the myctophid Lampangctus nobilis whose 

 day depth range extended well below 1,000 m. 

 La})ipa}n/ct}is nobilis, B. macclellandi, and 

 Scopelogadus mizolepis are relatively large 

 species, but M. danae is one of the smallest species 

 of fishes encountered in our study area. 



The species for which there was no indication of 

 diel change in vertical distribution are a rather 

 heterogeneous group. Opisthoproctiis soleatus 

 inhabited a relatively shallow depth range and 

 cooccurred with several stomiatoid species with 

 similar, and probably convergent, morphological 

 features (see Clarke 1974). Other nonmigrating 

 species {Scopeloberyx spp.; Poromitra oscitans, 

 Photostylus pycnopterus, Bathyleptus lisae, Eury- 

 pharynx pelecanoides, and probably Barbourisia 

 rnfa) occurred mostly below 600 m. Many of these 

 species are commonly referred to with the too 

 casually used adjective "bathypelagic," which has 

 the connotation (if not always the denotation) of 

 extremely great depths well removed from direct 



influences of surface phenomena. Our data in- 

 dicate that most of these should more properly be 

 considered members of the mesopelagic commun- 

 ity. Even taking into account the relatively few 

 hours of sampling below 1,000-1,200 m, the only 

 species which appear to occur in any abundance 

 below this depth are Poromitra oscitans and E. 

 pelecanoides (of course, other fishes not covered 

 here do occur deeper and some, e.g., certain cera- 

 tioidsand the eel Cyema appear to occur only below 

 1,000-1,200 m). In "fact, B. lisae, the Scopeloberyx 

 spp., and probably all the others except P. oscitans 

 have their primary centers of abundance above 

 1,000-1,200 m. During the day, they cooccur and 

 presumably interact with vertically migrating 

 species. Thus at least some aspects of their ecology 

 must be aff'ected by diel light changes. 



Four species showed limited diel changes in 

 depth distribution. Sfylephorvs chordatus moved 

 somewhat shallower at night, but did not occur in 

 the upper 250 m. Juveniles of P. crassiceps and 

 Anoplogaster cornnta undertook fairly substantial 

 upward migrations at night, but the adults shifted 

 only slightly shallower. Juvenile P. megalops 

 occurred somewhat shallower at night, but there 

 was no conclusive evidence that the adults moved 

 at all. Juvenile Scopeloberyx robustus, considered 

 a "nonmigrator" above, may also move up at 

 night. Since only P. crassiceps and P. megalops 

 were taken in even moderate numbers, the pat- 

 terns for the other species must be regarded as 

 tentative. Size-related diff"erences in migration 

 have been noted for some myctophids and stomia- 

 toids (Clarke 1973, 1974). As examples, the adults 

 of Bolinichthys distofax (identified as B. superla- 

 teralis in Clarke 1973) appear not to migrate while 

 the juveniles do, and the larger individuals of 

 Gonostoma elongatum appear to occasionally 

 remain at depth during the night. 



Interpretation of data on the gempylid-tri- 

 chiurid species is limited because, with the excep- 

 tion of Diplospinus, only the small juveniles were 

 collected, and even these either avoided the net 

 during the day or occurred so shallow that they 

 were not sampled by our program during the day. 

 The data indicate that all sizes of Gempylus 

 serpens (to 148 mm) and Nealotus tripes (to 173 

 mm) collected probably remain in the upper layers 

 during the day. Although the deep day catches of 

 small Scombrolabrax heterolepis may have been 

 made in transit, the absence of this species from 

 day tows above 750 m suggests that it may mi- 



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