Atlantic Lanternfish

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): 10 - 12; Analspines: 0; Analsoft rays: 15 - 18

Oceanic, epipelagic to mesopelagic (Ref. 4066, 58302), found between 400-930 m during the day and between 18-1,050 m at night (with maximum abundance at 50-100 m and 500-700 m at night) (Ref. 4479). Larvae and juveniles non-migratory at least near the Canary Islands (Ref. 4479). Oviparous, with planktonic eggs and larvae (Ref. 31442). Minimum depth from Ref. 58018.

Diogenichthys atlanticus

This small lanternfish grows to a size of 22 mm in the study area, and very few specimens exceed 18 mm. Nafpaktitis et al. (1977) report it to attain 29 mm. An unevenly distributed tropical-subtropical species, it is one of the ranking myctophids in the North Atlantic subtropical region (Backus et al., 1977). Diogenichthys atlanticus is very abundant in the study area, being the second most abundant lanternfish in both winter and late spring and the fifth most abundant in late summer (Table 131). The collections contain 4013 specimens in all; 2824 were caught during the paired seasonal cruises, 1866 of these in discrete-depth samples, of which 1310 were from noncrepuscular tows (Table 23).

DEVELOPMENTAL STAGES.—Postlarvae were 5–13 mm, juveniles 11–16 mm, subadults 13–21 mm, and adults 14–22 mm. Even the smallest juveniles have recognizable ovaries or testes and, as a result, 95 percent of all juveniles examined could be sexed. Adult females contained ova as large as 0.5 mm in diameter, but most had eggs 0.2–0.4 mm. There was no apparent sexual dimorphism in size for any stage. Sexual dimorphism is evident externally at a size of 15–16 mm, with females developing infracaudal luminous tissue and males developing supracaudal luminous tissue and a larger Dn than females.

REPRODUCTIVE CYCLE AND SEASONAL ABUNDANCE.—Diogenichthys atlanticus has a life cycle of about one year. Spawning apparently takes place most or all of the year, but with very pronounced peaks in spring and fall. The population was dominated by young fish; postlarvae and juveniles together constituted from 59 percent of the catch in late summer to 92 percent in late spring. Total abundance and that of the three younger stages was greatest in winter. In late spring total abundance and the abundance of all stages, except postlarvae, was lowest. Adults were most abundant in late summer, when they accounted for nearly 18 percent of the total catch (Table 57). The maximum abundance of adults in late summer, and of postlarvae and juveniles in winter, suggests that most spawning occurs in fall.

Postlarvae were caught in the greatest numbers in June-July and January, and adults in August-September and February-March. This indicates that the most spawning takes place in fall and spring.

In late summer, juvenile recruits from the spring spawn accounted for about half of the catch, with the remainder being mostly adults and subadults. Postlarvae were at their minimum, indicating that spawning was reduced from late spring to summer. Adults, subadults, and probably large juveniles (larger than 14 mm) were spawned the previous late summer-fall and would soon mature and spawn.

In winter juveniles comprised half of the catch, and postlarvae, most of which were caught in January, made up about one-quarter. Most of these recruits from the fall spawn presumably would mature over the spring and summer and spawn in the fall at about one year of age. Adults, subadults, and perhaps large juveniles, most of which were spawned the previous spring, would soon mature, ripen, and spawn. The combined abundance of subadults and adults increased slightly from the late summer level, because those lost through postspawning mortality in fall were replaced in winter by fish that were juveniles in late summer.

By late spring the second spawning peak had passed. Few large fish remained, and postlarvae and juveniles accounted for slightly more than 90 percent of the catch. The estimate of the abundance of recruits probably is much too low, for the catch of postlarvae in July was considerable, and those fish probably were too small to be retained by the nets in June. This low estimate of the abundance of young fish, together with the virtual absence of fish larger than 15 mm (Table 57), resulted in the minimum abundance observed in late spring.

SEX RATIOS.—The sexes probably are equally abundant at all seasons. Males were more numerous than females in winter and late spring, and slightly less numerous than females in late summer, with male-to-female ratios of 1.1:1, 1.2:1, and 1.0:1 for the respective seasons. None of these differences were significantly different from equality (Table 58). Juveniles of each sex were taken in roughly equal numbers at each season. Subadult males were more numerous than subadult females at each season, and adult males were more numerous than adult females in late spring. The differences for subadults in winter and late summer and for adults in late spring were significantly different from equality. Adult females were more numerous than adult males in winter and late summer; the latter difference being significant. The differences noted for adults and subadults may represent a sexual dimorphism in rates of maturity rather than a real difference in the numbers of each sex. The nearly equal numbers of juveniles of both sexes at each season supports this view. Badcock and Merrett (1976) reported a sex ratio of 1:1 for D. atlanticus near 30°N, 23°W in the eastern Atlantic.

VERTICAL DISTRIBUTION.—Day depth range in winter was 501–850 m (and probably deeper) with maximum abundance at 601–650 m, in late spring from the surface to 1100 m with a maximum at 751–800 m, and in late summer 25–1150 m with a maximum at 601–650 m. Nighttime vertical range in winter was 20–1050 m with maximum abundance at 851–900 m and a secondary concentration at 51–100 m, in late spring 50–850 m (and probably deeper) with a maximum at 51–100 m and 751–800 m, and in late summer 30–1000 m with a maximum at 51–100 m and a secondary concentration at 851–900 m (Table 59).

Stage and size stratification were evident day and night at each of the three seasons. Except for postlarvae in winter, the diurnal vertical range of juveniles and postlarvae was more extensive than that of subadults and adults; the latter two stages never occurred at either depth limit and were confined to the 551–800 m stratum at each season. Postlarvae were most abundant below 750 m, while the depth of greatest abundance of each of the other stages lay between 551 and 750 m at each season. In winter juveniles and subadults were most abundant at a shallower depth than adults. In terms of size, fish taken in the upper 300 m were all 7–21 mm, and all those taken below 750 m in late spring and below 800 m in winter and late summer were 11–14 mm. Fish larger than 16 mm were concentrated at 701–750 m in winter and at 751–800 m in late summer, depths that accounted for less than 10 percent of the total catch but for more than 80 percent of the catch of larger fish (interpolated values are not included in these figures). The mean size of the catch from those intervals was noticeably larger than for any other 50 m interval at both seasons. Larger fish, although present, were not sampled by discrete-depth daytime tows in late spring.

At night postlarvae and juveniles were caught over a greater range of depths than subadults and adults (excluding the subadult and adult, both suspected contaminants, caught in winter at 1001–1050 m). Adults and subadults (again, excluding the suspected contaminants) were caught only in the upper 500 m and were most abundant in the upper 100 m at each season. Catches of postlarvae and juveniles were greater below 750 m than at shallower depths at each season, although in late spring greatest abundance of postlarvae was at 51–100 m. Fish smaller than 10 mm were taken only in the upper 150 m at all seasons. Those larger than 15 mm (excluding the suspected contaminants) were taken only in the upper 100 m in winter and late spring, and only in the upper 500 m, but mostly the upper 100 m, in late summer. Specimens 10–14 mm were taken over most of the depth range, and constituted the entire catch made below 100 m in both winter (excluding the suspected contaminants) and late spring, and below 650 m in late summer (Table 59).

Postlarvae were stratified by size, and probably either do not migrate vertically or undergo only slight changes in depth during a diel cycle. Those smaller than 10 mm appear to be confined to the upper 150 m, being found deeper than 100 m only in late summer. Postlarvae 10–11 mm were taken throughout the vertical range, but mostly below 750 m. With the exception of one 12 mm specimen taken at the surface during the day in late spring, all larger postlarvae (12–13 mm) were caught below 750 m. Obviously, initial development occurs at relatively shallow depths, and at 10–11 mm postlarvae descend to the greater depths where they transform into juveniles. Small postlarvae (less than 10 mm) may undertake limited vertical movements; in late spring they were taken in surface samples only at or near the time of sunrise. All nocturnal surface samples and all those taken during daytime (but more than 3.0 hours after sunrise) failed to catch this species (see “Night:Day Catch Ratios”).

For juvenile and older stages, diel migrations were evident at all seasons but, as indicated above, not all individuals migrated. Recently transformed juveniles 11–13 mm are mostly nonmigrants, being caught mainly below 500 m both day and night. Most juveniles appear to become regular migrants at about 14 mm, as the majority of juveniles of that size were caught below 550 m in the daytime and in the upper 200 m at night. Except for the suspected contaminants in winter and possibly a few subadults at night in late summer, all nonmigrants were postlarvae and juveniles smaller than 15 mm (Table 59).

About 83 percent of the late spring, 40 percent of the late summer, and 76 percent of the winter populations were nonmigrants. Most nonmigrants were found at depths greater than 700 m (Table 59). In late spring about 33 percent of the nonmigrants were postlarvae found within the upper 100 m.

Times and rates of vertical migration were not estimated for late spring because more than 80 percent of the population apparently did not migrate, and almost all fish caught during the day were the size of nonmigrants (less than 15 mm, Table 59). Migration times in winter and late summer were based only upon the capture of specimens larger than 14 mm. In winter such fish were caught at 535 m no more than 2.3 hours before sunset, and at 95 m no later than 2.7 hours after sunset (the time that the earliest night sample taken in the upper 100 m ended). This gave a maximum of 5.0 hours for the evening migration. Other captures, made near 225 m and at 130 m within 1.2 and 0.8 hours after sunset, respectively, indicate that night depths probably were reached no later than 1.5 hours after sunset, a 3.8-hour migration. In late summer fish larger than 14 mm were caught near 500 m no more than 1.2 hours before sunset, and at 75 m no later than 1.2 hours after sunset, giving a maximum evening migration of 2.5 hours. Based upon this estimate and the 5-hour migration for winter, upward migrations occurred from day depths (650 m) to night depths (100 m) of maximum abundance at minimum rates of 220 m/hour in late summer and 110 m/hours in winter. Downward migrations apparently commenced between 0.7 and 1.7 hours before sunrise in winter and late summer, as fish were taken in the upper 100 m between those times at both seasons. Day depths were reached no later than 2.0 hours after sunrise in winter, giving a maximum migration time of 3.7 hours and a minimum rate of migration of about 150 m/hour from night (100 m) to day (650 m) depths of maximum abundance of migrant fishes. Fish larger than 14 mm were not caught at day depths by 3 hours after sunrise in late summer; therefore, no estimate of morning migration time was made.

PATCHINESS.—Daytime patchiness was indicated in winter at 551–650 m and in late summer at 601–650 m, the depths of maximum species abundance at both seasons. Juveniles (which accounted for 71–86 percent of the total catch there) and subadults had their greatest abundance at those depths.

Patchiness at night was indicated in winter at 40–100 m and 851–900 m, in late spring near 100 m, and in late summer at 51–100 m and 851–900 m. These are the depths of maximum abundance of each stage in winter, of postlarvae and subadults in late spring, and of all stages except postlarvae in late summer. In winter and late summer patchiness in the shallower stratum probably involved subadults and adults, which together were more than 70 percent of the catch taken in those strata, while at 851–900 m postlarvae and juveniles were involved. In late spring patchiness involved mostly postlarvae and to a lesser extent juveniles.

Significant CD values obtained for day samples at 701–750 m in winter and at the surface in late spring, and for night samples at 551–600 m in winter and 151–200 m and 301–350 m in late summer, may have been a result of distributional features other than patchiness. The variation in catch in samples taken at 701–750 m during the day in winter and at 150–200 m at night in late summer was attributed to a single sample taken near twilight, and probably indicates a change in population density at both depths due to vertical migrations. Although depths of 551–600 m in winter and 301–350 m in late summer were sampled during each of the two cruises made during the two respective seasons, all or nearly all of the catch was from one of the cruises, indicating that year-to-year variation in population density was responsible for the large variance in the catch at both of the 50-m intervals in question. Four postlarvae were caught in 27 daytime surface (neuston) samples in late spring. This indicates the rarity of D. atlanticus in superficial waters rather than patchiness.

NIGHT:DAY CATCH RATIOS.—Night-to-day catch ratios for discrete-depth samples were 0.7:1 in winter, 1.0:1 in late spring, and 1.1:1 in late summer (Table 60). Although the total ratios were not significantly different from 1:1, at each season the night and day catches for one or more stages (Table 60) and for several sizes were significantly different. It is not likely that D. atlanticus can avoid the nets with any great success; the observed catch ratios can best be explained by diel differences in patchiness, extent of vertical range, and sampling inequities.

The abundance of postlarvae almost certainly was artificially low in winter and in late spring day samples, because depths of significant concentrations of nonmigrators at night (851–900 m and 801–850 m, respectively) were not sampled during the day. But in late spring the catch of postlarvae at 51–100 m at night was nearly 13 times larger than the day catch at that depth (Table 60), even though the sampling effort during the day was half again greater than that at night (Table 2). All of these postlarvae were taken at 91–96 m; depths that were adequately sampled (4 or more hours) in the daytime. Clearly postlarvae in the upper layers must undergo at least limited diel vertical movements. Because there were no day samples made between 100 and 150 m, a diel shift of as little as 10 m could explain the virtual absence of postlarvae in day samples in the upper layers at that season.

Although the day catch of juveniles was about 1.5–2.5 times larger than the night catch, at each season there was a depth of considerable concentration of juveniles at night (between 751 and 900 m) that was not sampled during the day. At each season some juveniles migrated into the upper 200 m at night, but the catch from these depths was always small. It is possible that at night juveniles may have been concentrated at some depth that was not sampled, or that they were relatively uniformly distributed over a broad depth range. For example at night in winter a total of three fish was caught in discrete-depth samples made shallower than 40 m. But 46 specimens (mostly subadults and adults with a mean size of 17 mm) were taken in an oblique tow from 19 m to the surface which lasted about 25 minutes (a catch rate of 110.4/hour).

分布於世界三大洋熱帶及亞熱帶海域。臺灣則發現於西南部及東部周邊水域。

一般以底拖網捕獲，不具食用經濟價值，通常做為下雜魚用。

體中等延長，背鰭前方較高，側扁，後部略細。頭中等大。吻很短，鈍圓。眼大，大於吻長。口大，上頜骨狹長而延伸至前鰓蓋後緣，末端擴大；上下頜具絨毛狀齒，後部一行向前彎，鋤骨、腭骨及中翼骨均具齒。體被大而薄圓鱗，易脫落；側線平直。背鰭單一，位於體中部，具軟條10-12，後部另具一脂鰭；臀鰭基底長於背鰭基底，具軟條14-17；尾鰭叉形，尾鰭副鰭條柔軟。各部位之發光器位置於下：鼻部背位發光器(Dn)小而圓形，位於眼前上方；鼻部腹位發光器(Vn)無；眶下位發光器(So)無；鰓蓋位發光器(Op)2個，位於前鰓蓋後緣下方，Op1較Op2小，均在眼眶下緣縱線之下；鰓被架位發光器(Br)3個；胸鰭上方發光器(PLO)位於胸鰭與側線之中部；胸鰭下方發光器(PVO)2個，二者幾在水平線上；胸部發光器(PO)5個，幾為一直線；腹部發光器(VO)4個，VO2位置略高；腹鰭上位發光器(VLO)位於腹鰭和側線之間，接近腹鰭基部；臀鰭上方發光器(SAO)3個，三者排列略呈彎線狀，SAO1位於VO4的後上方，SAO3位側線下緣；體後側位發光器(Pol)1個，在脂鰭下方，側線下緣；臀鰭前部發光器(AOa)5-7個，沿臀鰭基部依次排列；臀鰭後部發光器(AOp)2-3個，沿尾柄腹側水平狀排列；尾鰭前位發光器(Prc)2個。尾上腺(SUGL)呈橢圓形；尾下腺(INGL)較小；二者周圍皆具黑色素。

大洋性中、底層巡游魚類，具日夜垂直分布習性，白天一般棲息於400-930公尺以上，晚上則上游至水深50-100公尺附近處覓食，以小蝦等甲殼類為食。

The longfin lanternfish (Diogenichthys atlanticus) is a species of oceanodromous lanternfish that is oviparous, and a host of Sarcotretes scopeli.

Atlantic Ocean: widely but unevenly distributed between 50°N and 48°S, less abundant or absent in regions of low productivity

oceanic, epipelagic to mesopelagic, found between 400-930 m during the day and between 18-1,050 m at night (with maximum abundance at 50-100 m and 500-700 m at night)

nektonic

Known from seamounts and knolls

Epipelagic