FISHERY BULLETIN: VOL. 81, NO. 2 



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STANDARD LENGTH (mm) 



FIGURE l.— Otolith height vs. standard length curve for Ichthyo- 

 coccus irregularis. Solid circles represent specimens collected by 

 midwater trawls , from which the curve was drawn. Open circles rep- 

 resent otoliths found in the dolphin stomachs, from which the fish 

 sizes were estimated. 



dolphin stomachs, and at least three genera are rep- 

 resented. Comparative material of these little-known 

 fishes is rare, since adults are seldom captured 

 (Rofen 1966) but the abundance of their larvae 

 (Ahlstrom 971, 1972) and juveniles suggests that 

 they are quite numerous. These fishes are inade- 

 quately sampled by current trawling gear and our 

 knowledge about their ecological relationships is 

 meager. The sizes of the otoliths that we found in the 

 dolphin stomachs indicate that they were feeding on 

 barracudinas of a size range uncommon in trawling 

 collections, but because little comparative material 

 is available, we cannot reliably estimate their lengths 

 except to say that the majority of individuals were 

 probably between 200 and 300 mm long. 



Evermannellidae 



Evermannellids are also midwater predators whose 

 adult stages and ecology are poorly understood be- 

 cause of a scarcity of material. In contrast to the 

 paralepidids, their larvae are less common in the 

 eastern tropical Pacific (Ahlstrom 1971, 1972), yet 

 they outnumbered barracudinas in the dolphin sto- 

 machs. Evermannellids are known to consume ver- 

 tically migrating micronektonic fishes and squids, 

 but apparently they do not migrate regularly them- 

 selves. Their sagittae are quite distinctive, and based 

 on comparative material from the western Pacific, we 

 estimate the sizes of the ingested fish to range from 

 35 to 90 mm long. 



Scopelarchidae 



Like the two preceding families, the "pearl-eyes" 

 are mesopelagic predators, adept at eluding trawling 

 gear. Based on the size range of the otoliths, L. hosei 

 had been feeding upon large, adult specimens. At 

 least three kinds of scopelarchid otoliths are present 

 in the material; the most numerous are most likely to 

 be from Scopelarchus guentheri. We estimate the size 

 range of these individuals to be from 80 to > 160 mm, 

 based on an extrapolation from trawl-caught spec- 

 imens from the western Pacific. This greatly exceeds 

 the known size range of S. guentheri (Johnson 

 1974). 



Myctophidae 



Lanternfishes of the family Myctophidae are found 

 throughout the world ocean as more than 225 species 

 in a wide variety of niches and depth ranges. Myc- 

 tophids commonly provide the bulk of the vertically 

 migrating fish fauna which contribute to sound scat- 

 tering layers. At least 10 genera are represented by 

 the otoliths we found in the dolphin stomachs, but the 

 majority are from Lampadena and Lampanyctus. In 

 addition to being the most numerous, the otoliths 

 from these two genera were obviously from much 

 larger individuals than those of the less abundant 

 myctophids. We believe that most of the smaller 

 otoliths, many of which are heavily eroded, may have 

 entered the dolphin stomachs secondarily as sto- 

 mach contents of predatory fishes or squids. Among 

 these smaller myctophids are several vertically 

 migrating types and surface-oriented species (e.g., 

 Diogenichthys laternatus, Benthosema panamense, 

 Symbolophorus evermanni). 



The Lampadena otoliths represent three species: L. 

 luminosa, which is by far the most abundant; L. 

 urophaos; and a form which has not yet been de- 

 scribed (Fitch and Brownell 1968; Nafpaktitis and 

 Paxton 1968). We estimate the size range of the in- 

 gested individuals of L. luminosa to be 75 to 105 mm 

 and that of L. urophaos to be 60 to 70 mm. Lampanyc- 

 tus otoliths are also divisible among three species: L. 

 nobilis, L. idostigma, and L. parvicauda. Large in- 

 dividuals of these two genera often live as deep as 

 1,000 m, and either forego the vertical migration pat- 

 terns typical of other myctophids or are easily able to 

 avoid trawling gear near the surface. 



Melamphaidae 



Adult melamphaids are generally robust fishes 

 found at mesopelagic depths in all oceans. They are 



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