Nannobrachium cuprarium (Tåning 1928)

10-11 AO photophores; 8-10 tooth patches on the lower limb of the second gill arch; 32-33 lateral line organs (Ref. 36121). Pectoral fin rays rather weak, flexible (Ref. 36121).

Oceanodromous. Migrating within oceans typically between spawning and different feeding areas, as tunas do. Migrations should be cyclical and predictable and cover more than 100 km.

Dorsal spines (total): 0; Dorsal soft rays (total): 16 - 19; Analspines: 0; Analsoft rays: 17 - 20; Vertebrae: 32 - 34

High-oceanic, mesopelagic species, found at 650-1,000 m during daytime, at 40-278 during the night (maximum abundance at 100 m at night). Feeds on amphipods, calanoid copepods, conchoecid ostracods, and euphausiid larvae and adults.

High-oceanic, mesopelagic species, found at 650-1,000 m during daytime, at 40-278 during the night (maximum abundance at 100 m at night) (Ref. 4479). Feeds on amphipods, calanoid copepods, conchoecid ostracods, and euphausiid larvae and adults (Ref. 4775). There are larger specimens reported for this species (11 cm by Gibbs et al. (1972) and 12.8 cm from the southwest Atlantic by Parin et al. (1974)) but these may be misidentifications (Ref. 36121).

Lampanyctus cuprarius

This is a large species reported to exceed 100 mm in length (Bekker, 1967; Kotthaus, 1972; Parin et al., 1974), but it probably does not grow larger than 80 mm (Zahuranec, 1980). The largest specimen taken during the study was 79 mm. Beebe (1937) listed the size range of L. cuprarius taken near Bermuda as 9–101 mm, but did not indicate whether total or standard length was measured. In either case, specimens near either extreme of the range probably were not L. cuprarius; transformation occurs at 16–18 mm.

According to Backus et al. (1977:275, table 5), this bipolar subtropical species is not a ranking member of the family in any of their Atlantic mesopelagic regions. However, in the study area L. cuprarius is common and was among the eleven most abundant lanternfishes at each season, ranking as high as fifth in late spring. There are 1462 specimens in the Ocean Acre collections; 584 from the paired seasonal cruises, 383 of these in discrete-depth samples, of which 340 were in noncrepuscular tows (Table 23).

DEVELOPMENTAL STAGES.—Postlarvae were 5–20 mm, juveniles 18–54 mm, subadults 46–74 mm, and adults 62–73 mm. Most juveniles smaller than 30 mm could not be sexed, and most larger juveniles had small but recognizable ovaries or testes. Some females larger than 65 mm and categorized as subadults may have been postspawning adults with regenerating ovaries. Adult females contained eggs as large as 0.5 mm, but mostly ova were 0.2–0.3 mm in diameter. There may be sexual dimorphism in size; all fish larger than 70 mm examined for sex and stage (10 specimens) were females, and the average sizes of subadult and adult females were 2.0 mm and 1.6 mm larger than those of subadult and adult males, respectively.

REPRODUCTIVE CYCLE AND SEASONAL ABUNDANCE.—The life span of L. cuprarius is two or more years, and sexual maturity is not attained until the second year. Although spawning may occur from spring to fall, it probably is minimal except from July through September, when reproduction is at its peak. Abundance was fairly stable over the three sampling periods, perhaps a result of the relatively long life span. Abundance was greatest in late spring and lowest in late summer (Table 88), which is incongruous with the pronounced spawning peak in summer. The low late summer abundance may be due to continuing mortality of postspawning adults and inadequate sampling of new recruits. The increase from winter to late spring was due mostly to juveniles and must be an artifact of sampling. Normal mortality from winter to late spring, together with continuing development into the subadult stage, must deplete the abundance of juveniles between the two times. Presumably the greatest abundance occurs in fall, with postlarvae and juveniles being numerically dominant.

Adult-size females were caught at each season, but greatly distended ovaries with eggs as large as 0.5 mm in diameter were observed only from July to September. Those taken in June had enlarged, but not distended, ovaries with ova up to 0.3 mm in diameter. Postlarvae were caught only during August-September, and juveniles 20–25 mm began to appear in October. Juveniles 25–30 mm were most abundant in winter. These data show that L. cuprarius reproduces mostly during the summer and that little additional recruitment occurs at other seasons.

Almost all specimens caught in late spring were either 30–50 mm or 59–74 mm. The smaller group consisted mostly of juveniles approaching one year of age. The age composition of the group of larger fish was uncertain; there may have been more than one age class represented. Those smaller than about 70 mm were approaching two years of age and were about to spawn for the first time. It is possible that fish in excess of 70 mm are more than two years old, but they may be faster-growing fish approaching two years old.

In late summer postlarvae and juveniles smaller than 20 mm begin to appear in the catch. These fish apparently represent offspring from the earliest spawn. Most fish in this group were too small to be sampled adequately by the gear and probably were much more abundant than the samples indicate. Most of the other specimens were either 45–54 mm or 62–71 mm and represented the two size groups noted in late spring (but were slightly older). The smaller group consisted mostly of juveniles about one year old, and the larger one mostly of subadults and adults about two or more years old. Several females larger than 65 mm and categorized as subadults appeared to be spent adults. The abundance of both juveniles and subadults was about half of that in late spring. The abundance of juveniles decreased because some had grown to subadults and others were lost to mortality, and also because recruits were not yet large enough to be sampled adequately. The decrease in subadults is most likely attributable to most having matured, spawned, and died by late summer.

Spawning was completed by winter when adults were least abundant and no postlarvae were caught (Table 88). Most specimens were either 20–40 mm or 56–74 mm, very few were 41–55 mm. The smaller group mostly consisted of juvenile recruits from the recent spawn with the larger group containing subadults and a few adults at least a year older than the recruits. Older fish were slightly more abundant than the recruits (Table 88), which is the reverse of what would be expected, suggesting that the abundance of juveniles in winter was underestimated. The apparent increase in abundance of juveniles from winter to late spring further suggests that the abundance of juveniles in winter was underestimated.

SEX RATIOS.—The sexes were equally abundant at each season. Female to male ratios were 1.3:1 in winter and late spring, and 0.7:1 in late summer. None of these ratios is significantly different from equality (Table 89). Except for juveniles in late summer and subadults in late spring, there were no significant differences from equality for any stage at any season. Despite the differences noted above, the sexes probably are equally abundant for the three older stages.

VERTICAL DISTRIBUTION.—Diurnal depth range in winter was 601–1050 m (possibly deeper) with maximum abundance at 801–850 m, in late spring 751–1200 m with a maximum at 751–800 m, and in late summer 701–950 and 1451–1500 m with a slight maximum at 801–950 m. Nocturnal depth range in winter was 200–1000 m with maximum abundance at 200–350 m, in late spring 100–1100 m with a maximum at 100 m, and in late summer 33–1000 m with maxima at 33 m and 851–900 m (Table 90).

Stage and size stratification were evident at all three seasons. The daytime depth of greatest abundance of juveniles was shallower than that of adults at all seasons and of subadults in winter and late spring. In winter only juveniles were caught at 601–750 m, and in late summer all stages except adults were caught at 701–850 m. In late spring adults were not taken as deep as juveniles and subadults. Size stratification was well developed in winter and in late summer, when the mean, minimum, and maximum sizes all increased with depth. In late spring fish smaller than 49 mm were taken only above about 1000 m, and in winter those larger than 35 mm were caught at depths greater than 800 m (Table 90).

At night the depth of greatest abundance of juveniles was shallower than that of the other stages in winter and in late spring. In late summer postlarvae were most abundant in the upper 50 m, and the three older stages at 851–900 m. Except for one subadult caught at 51–100 m, only juveniles were taken at either extreme of depth in late spring, and in late summer only postlarvae were taken at extremes of depth (Table 90). Size stratification was well developed only in late spring when all fish larger than 50 mm were caught above about 600 m and smaller fish were taken over the entire vertical range. In the upper 600 m fish also were stratified by size; those taken at 51–100 m had a mean size of 39.8 mm, and those taken at 101–600 m were mostly larger than 45 mm with a mean size of 54.5 mm. Most sizes were taken throughout the depth range in winter and late summer, but the catch below about 700 m consisted mostly of fish larger than 45 mm (Table 90).

Postlarvae also were stratified according to size in late summer. Those caught in the upper 150 m were 6–15 mm, mostly 6–11 mm, and those caught deeper than 700 m were 9–20 mm, mostly 15–20 mm. All postlarvae caught at the shallower depth, and all but two from deeper depths, were taken at night. Based upon the maximum size of postlarvae (20 mm) and the minimum size of juveniles (18 mm) in the collections, metamorphosis probably occurs at 17–20 mm. A few transforming postlarvae 16.4–18.8 mm were taken during the program (H. Zadoretzky, personal communication). Thus, initial development takes place in the upper 150 m. Upon reaching 12–15 mm postlarvae descend to depths greater than about 700 m where they transform into juveniles. Postlarvae probably do not undergo diel vertical migrations of any great extent, but additional daytime catches are needed to verify this.

Diel vertical migrations occurred at each of the three seasons, but only part of the population migrated to waters shallower than the minimum day depths at night. Excluding postlarvae, nonmigrants accounted for about 33 percent of the total night catch at each season. The stage and size composition of nonmigrants varied seasonally. In winter nonmigrants included juveniles and subadults 20–71 mm, in spring all but one were juveniles 43–49 mm, and in late summer they included all stages and were 9–68 mm. Fish larger than 49 mm were predominant among the nonmigrators in winter (69 percent) and late summer (86 percent).

PATCHINESS.—Significant CD values were obtained only for depths at which small catches were made (abundance ranged from 1.3 to 3.9) and at which one or more samples failed to catch the species. It is not likely that significant patchiness occurs at such low population densities.

NIGHT:DAY CATCH RATIOS.—Night-to-day catch ratios, including interpolated values, were 1.1:1 in winter, 0.4:1 in late spring, and 2.6:1 in late summer (Table 91). Except for juveniles in winter and adults in late summer, ratios for the individual stages followed the seasonal trends. The ratios most divergent from 1:1 were obtained in late summer for postlarvae and juveniles and in late spring for subadults and adults.

The lack of consistency in the total night-to-day ratios from season to season indicates that several factors may have been responsible for the observed differences in catches. Vertical range during daytime was smaller than that at night at each season, suggesting that compression could result in larger diurnal catches than nocturnal catches. However, only in late spring did the total day abundance exceed the total night abundance. In late summer, when the diel difference in vertical range was greatest, the night catch was 2.6 times greater than that of day. At that season part of the difference was due to postlarvae and juveniles smaller than 20 mm, for which the ratio was 8.4:1. Large fish (mostly subadults) also were more abundant in night than in day samples, possibly due to enhanced net avoidance during daytime. In winter fish larger than 50 mm also were more abundant in night samples, but in late spring the reverse was true, complicating avoidance as an explanation.

Nannobrachium cuprarium (Tåning, 1928)

Lampanyctus cuprarius Tåning, 1928:68 [original description, North Atlantic],—Parr, 1928:88, 106–108 [key, western Atlantic, description, figure],—Bolin, 1959:33–34 [discussion, distribution].—Backus et al., 1965:144 [western Atlantic],—Bullis and Thompson, 1965:28 [northern Gulf of Mexico].—Bekker, 1967a:116-ll7 [distribution].—Backus et al., 1969:95 [western Sargasso Sea],—Nafpaktitis and Nafpaktitis, 1969:42 [discussion, figure of lectotype].—Badcock, 1970:1039 [off Canary Islands].—Gibbs and Roper, 1971:129 [diurnal vertical migration].—Gibbs et al., 1971:43, 103-104 [key, vertical distribution near Bermuda, figure].—Krefft and Bekker, 1973:87 [biology, synonymy].—Nafpaktitis, 1973:41 [redescription, figure and designation of lectotype].—Briggs, 1974:328 [tropical Atlantic endemic].—Merrett and Roe, 1974:117, 119–125 [depth and feeding habits].—Nielson, 1974:38 [listing of lectotype].—Parin et al., 1974:106–107 [in part?] [southwest Atlantic].—Roe, 1974:107, 110 [vertical migration].—Bekker et al, 1975:314 [distribution, Caribbean Sea],—Badcock and Merrett, 1976:42–43, 45 [depth].—Brooks 1976:569, 575, 581 [swimbladder size].—Nafpaktitis et al, 1977:197–199 [description, distribution, figure].—Backus et al, 1977:267, 275, 277 [zoogeography].—Paxton, 1979:14 [lectotype].—Hulley, 1981:193–195 [description, Atlantic distribution]; 1984b: 462 [description, northeast Atlantic distribution].—Moser et al, 1984:239 [relationships, larval description],—Hulley and Krefft, 1985:36–37, 42–46 [North Atlantic zoogeography].—Karnella, 1987:52, 107–110, 149–159, 163–165 [ecology and biology near Bermuda],—Gartner et al, 1987:86, 88–89, 91, 95 [eastern Gulf of Mexico].

Lampanyctus (Lampanyctus) cuprarius.—Fraser-Bruner, 1949:1086 [illustrated key].—Bekker, 1983:87, 89, 193, 200, 201 [key, description, distribution].

COMPARATIVE DIAGNOSIS.—Nannobrachium cuprarium (Figure 15) can be distinguished from N. lineatum by its fewer AO photophores, lateral line organs, and vertebrae (Table A10). In addition, its caudal peduncle is shorter than the upper-jaw length (longer than the upper jaw in N. lineatum), and Prc3 lies on a line connecting Prc2 and Prc4 (but is below that line in N. lineatum). Nannobrachium cuprarium can be separated from all other species of Nannobrachium by the combination of characters in Table 1.

DESCRIPTION.—Counts are based on up to 25 specimens from the Atlantic Ocean and are given in Tables A2–A8 and Table A10.

Proportions: Given in Table 13.

Fins: Origin of anal fin before vertical from middle of base of dorsal fin. Pectoral fin not reaching vertical from PO4, its rays rather weak, flexible. Adipose fin above or slightly before end of anal-fin base.

Luminous Organs: PLO –2 photophore diameters below lateral line. PO4 slightly higher than level of PVO2, above and usually behind vertical from PO3. VLO not more than its diameter below, frequently nearly touching, lateral line. SAO2 approximately above AOa1, AOa1, somewhat depressed; AOa1–2 interspace enlarged. AOp1, at or near end of anal-fin base. Pol2 well before vertical from origin of adipose fin. Pre continuous with AOp; Prc2–3–4 on straight line at angle of about 110° to line connecting Prc1–2. Supracaudal and infracaudal luminous scales well developed, very rarely single separated scale before infracaudal gland; prominent covering of black pigment on posterior tips of infracaudal and supracaudal glands resembling hood or cap. Solitary minute secondary photophores in horizontal rows, one such photophore on each posterior margin of at least some enlarged lateral line scales and on at least some scales below lateral line on anterior part of body; rows of minute photophores between rays of caudal fin.

Size: This appears to be a small-bodied species of Nannobrachium, seldom longer than 80 mm. The largest specimen examined here was 79 mm. Bekker (1967a) reported individuals as large as 92.7 mm, whereas Parin et al. (1974) reported one of 128 mm from the southwest Atlantic, and Kotthaus (1972a) reported one sample with a specimen of 110 mm. Gibbs et al. (1971) found the maximum size of the N. cuprarium collected in the Bermuda Ocean Acre study to be 79 mm, whereas Nafpaktitis et al. (1977) reported gravid females 70–75 mm. Hulley (pers. comm., 1980) examined 28 specimens from collections made by the Walther Herwig in the South Atlantic. Although his largest specimen was a 78 mm female, he judged it was not fully mature because the eggs lacked oil droplets, and he suggested that maximum size for the species might be about 90 mm. Given these recurrent findings (that virtually all specimens of N. cuprarium are approximately 80 mm or less), it may be that those larger specimens listed by Parin et al. (1974) and Kotthaus (1972a) are misidentifications.

Material: 534 (14–78 mm) specimens were examined, including the lectotype, a 63 mm female, ZMUC P2330213, Dana sta 1231 I, 24°30′N, 80°00′W, 6 February 1922 (Nafpaktitis, 1973).

DISTRIBUTION AND GEOGRAPHIC VARIATION.—Nannobrachium cuprarium is restricted to the Atlantic Ocean (Figure 16), where it is a bipolar, subtropical species. It is reported to occur during the day at 600–1200 m near Bermuda and at 700–900 m near the Canary Islands and during the night at shallower depths at both locations (Nafpaktitis et al., 1977). Kamella (1987) reported similar depth distributions in Ocean Acre material near Bermuda but with a maximum depth to 1500 meters in late summer. No consistent variations could be detected in specimens examined from the eastern and western North Atlantic, Gulf of Mexico, or South Atlantic.

Feeds on amphipods, calanoid copepods, conchoecid ostracods, and euphausiid larvae and adults

Grand Bank to Emerald Bank

Found at depths of 40- 1100 m.

nektonic