See data on Catalog of Fishes here.
The barbel increases in relative length until about 70–80 mm SL, after which it is 30%–52% SL and does not change with growth. Pigment in the stem axis is light to moderate proximally, decreasing in density distally until only a few scattered melanophores are present. As much as one-third of the distal stem may be unpigmented. The external chevron–shaped or rounded striated areas on the stem are unpigmented.
The terminal bulb also apparently increases relative to SL until about 70 mm SL, after which it appears to decrease slightly from 1.0%–1.5% at less than 80 mm to 0.9%–1.2% in those larger than 100 mm. The bulb is almost flat proximally and has a solid black cap covering its base. This black cap is a persistent structure, remaining intact even when the rest of the bulb has been mutilated. The bulb itself, when intact, is shaped like a blunt–tipped cone.
The terminal filament decreases relative to SL from 3.6%–5.1% in specimens smaller than 85 mm to 1.6%–2.0% in those larger than 130 mm. The filament is unpigmented. There were tiny bulblets in the filament of only 1 specimen. Most filaments are simple, but some are bifurcated at about one-third or more of their length.
The postorbital organ of males increases from 0.6% SL, 24% of fleshy orbit at 104 mm SL to 1.1% SL, 46% of fleshy orbit at 136 mm.
On the anterior margin of the eye is a short projection extending very slightly over the eye and bearing a photophore at its tip.
A single cone-shaped terminal bulb, 0.9%–1.5% SL except in the smallest specimen. Barbel relatively short, 25%–52% SL except in specimens smaller than 70 mm. A single, simple or bifurcate, short terminal filament 5.1%–1.6% SL, decreasing relatively with growth. Proximal end of bulb almost flat, with a solid black cap. Axis of stem moderately to lightly pigmented. External chevron–shaped or roundish striated areas unpigmented. Middorsal paired spots between occiput and dorsal-fin origin 8 (rarely 9).
Northwestern and north–central Pacific between about 10° and 25°N, and south–central and southeastern Pacific between about 20° and 30°S.
Eustomias gibbsi is a member of the subgenus Nominostomias Reagan and Trewavas (1930). The following description applies to all member of Nominostomias.
Three well-developed, free pectoral rays. Seven pelvic rays. Barbel with slender stem having little or no external pigment (axis often pigmented), no row of dark spots, and no branches proximal to the terminal bulbs (E. multifilis may have a few short filaments on the stem near the bulb). One or 2 relatively small terminal bulbs, the distalmost with a projection or filament of variable complexity (the projection almost indiscernible in a few species). No wide ventral body groove posterior to pectoral–fin base (a narrow, shallow groove observed in some specimens). Photophore and vertebral counts high. Photophores in ventral series (IC) 69–80 (seldom fewer than 72, species modes mostly 75–78), in lateral series (OC) 63–73 (seldom fewer than 66, species modes mostly 69–72), VAV and VAL 15–21 (seldom fewer than 16, species modes 17–18 and 18–19, respectively). Vertebrae in continuous series 64–71 (seldom fewer than 65, species modes mostly 67–69). No paired photophores in lateral series. Number of teeth high: premaxillary 11–20, mandibular 14–29 in large specimens (fewer in many specimens less than 100 mm SL).
Counts of fin-rays, photophores, vertebrae, and teeth are of little use in distinguishing most species of Nominostomias, for even those species that show modal differences overlap the ranges of most other species.
None of the body proportions examined by Gibbs et al. (1983) showed convincing differences among species of Nominostomias. Differences in size or relative–growth patterns appeared to characterize a number of species for which few specimens were measured, but these are believed to be artifacts of sampling. The cloud of points of species with abundant measurements usually encompassed those of species with few measurements, and in those abundant species, isometric growth is indicated for almost every body part once metamorphosis is complete. The only body measurement to indicate allometric growth is the least caudal-peduncle depth, which decreases relative to SL.
Gibbs RH, Jr, Clarke TA, Gomon JR. 1983. Taxonomy and distribution of the stomioid fish genus Eustomias (Melanostomiidae), I: Subgenus Nominostomias. Smithsonian Contributions to Zoology 380:1–139.
To at least 156 mm SL
Eastern Philippine Sea [west of Pahan, Northern Marianas, Western Pacific], 17°47.7-50.7'N, 143°41.2-50.0'E, depth 0–525 meters.
Holotype: SIO 69-354.
