Unfortunately, there is little information on the exact depths inhabited by most midwater 

 fishes in the eastern Pacific Ocean; the vast majority of captures have been made with nets 

 that fished open at all times, many fishing from the surface to 1000 m or more. (This range 

 certainly contains most myctophid fishes.) Thus, the depths of capture given in this work are 

 often necessarily imprecise. Also, many of the depths listed for earlier collections, particularly 

 for the Isaacs-Kidd Midwater Trawl (IKMT), were derived from calculations based on wire 

 angles measured at the surface (Clarke, 1963). The resulting depths range from near-surface 

 to 4000 m or more, with the net fishing open at all times. Such records are uninformative of 

 depths actually inhabited by a species, even if the maximum depths calculated are correct. 

 Occasional captures with the opening-closing, paired zooplankton net (Bongo-net, McGowan 

 and Brown, 1966) have given more precise information. However, this net has a much smaller 

 mouth opening and requires a much slower towing speed than the IKMT, and captures consist 

 mostly of the smaller specimens. In this report it is to be assumed, unless otherwise stated, 

 that captures were made with nets that fished open at all times. Depths of capture are thus 

 simply given as "To .... m" or "O ... . m". If known, it is stated whether captures were in 

 daylight or darkness. Data refer only to adults or young adults. 



Some information on the approximate levels inhabited by lanternfishes in the eastern 

 Pacific Ocean is offered by Paxton ( 1967 ) and Pearcy ( 1964). Paxton sampled to about 900 m in 

 the San Pedro Basin, southern California, and Pearcy mostly to 200 m, with a few trawls to 

 1000 m. Unfortunately, both studies were made with nonclosing nets, and both areas have a 

 rather sparse myctophid fauna. 



The only major sampling effort with opening-closing trawls was made in the Atlantic 

 Ocean near Bermuda, during the Ocean Acre Project. Gibbs, Goodyear, Keene, and Brown 

 ( 1971 ) provide capture data for 52 species of lanternfishes collected with discrete-depth sampl- 

 ing gear. 



The distribution charts are based mainly on material in the Marine Vertebrate Collection 

 of the Scripps Institution of Oceanography. This is particularly true for species that are poorly 

 known or easily confused with related forms. Distributional data from recent revisions have 

 been accepted and credited to the authors. 



Discussions of zoogeography are offered only in individual species accounts rather than in 

 one formally designated section. Detailed discussions on this aspect of myctophid fishes of the 

 Pacific Ocean have been presented by various Russian ichthyologists, principally Andriashev 

 (1962), Parin (1968), and Becker ( 1964b). 



The extensions of range of several species of the genus Diaphus, known previously only 

 from the western Pacific and the Indo-Pacific areas, are reported for the first time; most of 

 these new occurrences appear to be confined to tropical and subtropical regions of the central 

 Pacific. In some instances too few collections were available to permit firm zoogeographical 

 statements, or too few specimens to permit adequate assessment of specific relationships. 



Perhaps the most interesting finding was the absence of certain species from a wide area of 

 the extreme eastern Pacific between Baja California and central Chile. Some species were 

 absent throughout this broad area but others from only the northern sector. These absences 

 were evident only for species that are numerous around the periphery of the area but were not 

 taken there despite considerable collecting effort. Thus far involved are the species 

 Diogenichthys atlanticus, Myctophum nitidulum, the four species of Centrobranchus, 

 BoUnkhthys photothorax and B. longipes. 



The reasons for these absences are not clear, and a solution or detailed discussion of the 

 problem is beyond the scope of this publication. However, I am inclined to believe that the 

 absences are related to the layer of oxygen-deficient water (containing 1.0 milliliter or less of 

 oxygen per liter of water, ml/1) underlying a large part of the east-central Pacific Ocean, from 

 about central Baja California to central Chile and extending in a narrowing wedge into the 

 central tropical region. Austin ( 1960) delineated this oxygen minimum in the central area, to 

 170° W, and Wyrtki (1967) presented a detailed analysis for the eastern area. Wyrtki placed 



