Lanternfish

Branchiostegal rays: 7-8 (Ref. 31442).

Oviparous (Ref. 31442).

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): 9 - 11; Analspines: 0; Analsoft rays: 16 - 19; Vertebrae: 35 - 40

High-oceanic, epipelagic to mesopelagic, at 375-650 m by day (most common at 500 m); nycto-epipelagic at surface and down to 200 m (Ref. 4775).

High-oceanic, epipelagic to mesopelagic, at 375-650 m by day (most common at 500 m); nycto-epipelagic at surface and down to 200 m (Ref. 4775). Neustonic at 0-200 m at night (Ref. 58302). Oviparous, with planktonic eggs and larvae (Ref. 31442).

Centrobranchus nigroocellatus

This slender-tail species is found between about 40°N and 35°S in the Atlantic Ocean, where it is a questionably tropical-subtropical species (Backus et al., 1977), in the Indian Ocean between 5° and 26°S (Nafpaktitis and Nafpaktitis, 1969), and in the South Pacific Ocean (Craddock and Mead, 1970; Wisner, 1976). It is moderate in size, growing to 48 mm in parts of its range (Nafpaktitis et al., 1977). The largest specimen in the Ocean Acre collections is 35 mm.

Centrobranchus nigroocellatus, a “common” lanternfish in the study area, was included in the twenty most abundant lanternfishes only in late spring, when it ranked eighth (Table 23). Most fish were taken at the surface by night. A total of 527 specimens was caught. Slightly more than 91 percent of the fish taken on the paired seasonal cruises (389 of the 434 collected) were from neuston samples. Only 29 individuals were taken in discrete-depth samples made below the surface, 23 of these from noncrepuscular times.

DEVELOPMENTAL STAGES.—Postlarvae were 4–12 mm, juveniles 12–20 mm, subadults 18–35 mm, and adults 28–33 mm. Several large females (larger than 30 mm) categorized as subadults had reduced, flaccid ovaries and apparently were spent adults. Nafpaktitis et al. (1977) reported that C. nigroocellatus reaches sexual maturity at about 34 mm, nearly the maximum size attained by the Bermuda population, suggesting geographic variation in both size at maturity and maximum size for the species. Subadult and adult males have supracaudal luminous tissue, and females of the same stages have infracaudal luminous tissue. There may also be a sexual dimorphism in size. Only females were greater than 32 mm, but the mean size of subadults and adults combined was similar for both sexes (males 25.0 mm, females 24.5 mm).

REPRODUCTIVE CYCLE AND SEASONAL ABUNDANCE.—This species lives about a year. Spawning probably takes place from fall to summer with a peak in intensity in spring. Abundance was greatest in late spring, shortly after the peak in spawning intensity, when recruits dominated the catch. In late summer total abundance and, except for postlarvae, abundance of all stages was least.

The winter population was predominantly subadults, with juveniles and adults less and about equally abundant (Table 34). The few juveniles caught were mostly 20 mm and smaller and probably represented the earliest spawn. Most subadults presumably would ripen and spawn in spring.

By late spring the peak in spawning was past, and the catch was dominated by juvenile recruits 20 mm and smaller. Most of the winter population had spawned and died. The abundances of subadults and adults showed little change from their winter levels (Table 34). Some earliest spawned recruits were now subadults, some recently spent adults were categorized as subadults, and the smallest subadults of winter were just maturing. Postspawning mortality was evident in the reduced abundance of 23–35 mm fish from that in winter.

In late summer all stages were at or near their yearly minimum. The reduced abundance of larger fish is understandable, and probably is attributable to postspawning mortality, with none of the recent recruits having yet grown large enough to replace them. However, the low abundance of all stages (Table 34) and sizes is perplexing and, clearly, is incongruous with the greater abundance of larger fish in winter. There is no evidence of additional spawning from late summer to winter, and the increased winter abundance cannot be accounted for in that way. Fishing effort at the surface was least in late summer, which may account for the small catch. However, only 2 of 14 nocturnal surface tows captured the species in late summer, by far the lowest proportion of positive neuston samples. This may be due to light conditions. It is well known that neuston species are not taken at the surface on well-lighted nights. Unfortunately, there are not enough observations on moon phase or cloud cover to pursue this in greater detail.

SEX RATIOS.—The sexes were about equally numerous in late spring and late summer, and males were much more numerous than females in winter, with male-to-female sex ratios of 1.2:1, 0.7:1, and 1.6:.1, respectively (Table 35). Juvenile males were more numerous than juvenile females at all three seasons, but not significantly so. Male subadults were more numerous than female subadults in late spring and winter, with only the latter difference being significant. Only ten adults were caught during the paired seasonal cruises.


VERTICAL DISTRIBUTION.—Day catches in all seasons were poor; a total of 12 fish was collected in the three seasons combined. Combining day samples from the three seasons yields a depth range of 501–800 m, with most fish taken at 501–650 m. Night captures were made mostly at the surface, but in each season a few fish (less than 5) were taken between 51–200 m. Nothing could be determined about stratification according to stage or size.

Apparently, most fish beyond the transformation stage migrate on a regular basis, as all night captures were from the upper 200 m. In late summer, fish 11–13 mm were taken only by day. Their absence from neuston samples at night might be due to nonmigratory behavior, but they were not taken at day depths either, and fish that size were taken in neuston nets in the other two seasons (Table 36).

Surface waters were occupied no later than about one-half hour after sunset in each season. Catch rates for C. nigroocellatus taken in neuston samples at hourly intervals are given in Table 37. In January 1971 C. nigroocellatus was taken at the surface between 1.0 and 1.5 hours before sunset (not shown in Table 37). In June 1972 and August-September 1971 the species was taken in neuston samples made between about the time of sunset and one-half hour after sunset.

PATCHINESS.—Patchness was indicated on the surface at night in all three seasons. In late summer two of 14 noncrepuscular samples captured a single fish each (there were other positive samples taken in the evening and morning crepuscular periods), which may indicate a low population density rather than a patch distribution. Table 37 shows that the abundance at the surface changed during the night in winter (January-March) and spring (June). This temporal change in abundance, which was especially prominent in winter, may be the major factor affecting the CD value.

NIGHT:DAY CATCH RATIOS.—Night catches were greater than day catches at each season, with catch ratios of 2.5:1 in late summer, 5.2:1 in winter, and 12.6:1 in late spring. At each season, the catch of all stages and most sizes taken was greater at night than by day (Table 38).

The small number taken in the Isaccs-Kidd trawl (and nonneuston trawls in general) indicates that C. nigroocellatus avoids trawls quite well at all times. This is the major factor for the observed night-to-day catch ratio.

USA to about 14°N, and from Brazil to Argentina

High-oceanic, epipelagic to mesopelagic, at 375-650 m by day (most common at 500 m); nyctoepipelagic at surface and down to 200 m.

nektonic