Notolychnus valdiviae (Brauer 1904)

High-oceanic, epipelagic and mesopelagic. Found between 375-700 m during the day and between 25-350 m at night (Ref. 4066). Size stratification with depth during the day only. Juveniles migratory; adults migratory, partially migratory or non-migratory. Feed on copepods, conchoecid ostracods and euphausiids.

Branchiostegal rays: 9 (Ref. 31422). Anal organs 8; a single deeply set translucent supracaudal gland present in both sexes, but no infracaudal gland; males have much larger eyes and a longer supracaudal gland than those of females (Ref. 39633).

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: 12 - 15; Vertebrae: 27 - 31

High-oceanic, epipelagic and mesopelagic (Ref. 4479). Found between 375-700 m during the day and between 25-350 m at night (Ref. 4066). Size stratification with depth during the day only (Ref. 4775). Juveniles migratory; adults migratory, partially migratory or non-migratory (Ref. 4775). Feed on copepods, conchoecid ostracods and euphausiids (Ref. 4775). Oviparous, with planktonic eggs and larvae (Ref. 31442). Also Ref. 58302.

Notolychnus valdiviae

This slender, diminutive lanternfish grows no larger than about 25 mm (Paxton, 1972; Clarke, 1973), the largest specimen in the Ocean Acre collections being 22 mm; few exceed 20 mm. Notolychnus valdiviae, one of the dominant lanternfishes of the North Atlantic subtropical region (Nafpaktitis et al., 1977), is very abundant in the study area and was one of the six most abundant myctophids in the area at each of the three seasons sampled. The collections contain 3999 specimens; 2870 were caught during the paired seasonal cruises, 1944 of these were from discrete-depth samples of which 1670 were in noncrepuscular tows.

DEVELOPMENTAL STAGES.—Postlarvae were 4–10 mm, juveniles 8–17 mm, subadults 15–22 mm, and adults 17–22 mm. Most juveniles smaller than 12 mm could not be sexed; nearly all of those greater than 13 mm were sexed. Some fish (larger than 18 mm) categorized as subadults appeared to be in a postspawning condition. Sexual dimorphism in subadults and adults is manifested externally in several ways: males have a larger supracaudal gland than females (Nafpaktitis et al., 1977); males larger than 16 mm have noticeably larger eyes than females of the same sizes; females average 1–2 mm larger for each of the three older stages and attain a larger maximum size than males 22 vs 21 mm; of the 54 sexed fish larger than 20 mm, 51 are females.

The dimorphism in size appears to be reversed for juveniles in late summer, when males averaged 0.4 mm larger than females. However, females may develop faster and, as a result, be recognized at a smaller size than males. Badcock and Merrett (1976:45) noted that in the eastern North Atlantic (30°N, 23°W) N. valdiviae was sexually dimorphic in “eye and snout characteristics” and that females grow larger than males.

REPRODUCTIVE CYCLE AND SEASONAL ABUNDANCE.—Notolychnus valdiviae appears to be an annual species that spawns primarily in spring and probably at low levels at other times. Most fish live about one year, but a few may survive into their second year. Abundance was greatest in late summer, when juvenile recruits were predominant, intermediate in winter, and lowest in late spring (Table 122). Subadults and adults were most abundant in winter. The low abundance in late spring probably was due to recruits being too small to be adequately sampled by the nets.

Although adult-size females were caught at each season, only in late April to early May did a large proportion (over 90 percent) have enlarged ovaries containing eggs mostly larger than 0.1 mm in diameter. This seasonal distribution of females with ripening eggs, together with the great abundance of 10–15 mm juvenile recruits in late summer, indicates that N. valdiviae spawns mostly in spring. Postlarvae, although only 19 specimens, were all caught from July to September, further indicating a spring spawning peak. Clarke (1973) noted that near Hawaii N. valdiviae has a similar cycle, with smaller juveniles (less than 15 mm) being most numerous in September, and the proportion of females with developed ova being greater in March and June than in September and December.

Winter collections were dominated by subadults, with juveniles and adults less and about equally abundant (Table 122). Subadults were spawned during the previous spring spawning peak, appeared as the large juvenile recruitment of the late summer, and matured and spawned during the subsequent spring. Most winter adults were spawned late in the previous winter or early spring, appeared as juveniles just approaching catchable size in late spring, and were the larger juveniles and smaller subadults of the late summer population.

By late spring the peak of spawning was past, and the adults and most subadults of the winter population had matured, spawned, and died. This mortality was reflected in the decreased abundance of adults and subadults (Table 122) and of all individuals 16–20 mm. The combined catch of subadults and adults in late spring, which was about one-third of the winter catch of all stages, suggests that by late spring about two-thirds of the winter population had died. Subadults and adults accounted for 93 percent of the late spring catch and were about equally abundant (Table 122). However, many females categorized as subadults were judged to be spent adults with reduced, somewhat flaccid ovaries. Presumably postlarvae from the spring spawn were present in great abundance and dominated the population, but were not yet large enough to be sampled adequately by the nets.

In late summer juvenile recruits 10–15 mm accounted for more than 86 percent of the catch. Adults were spawned about one year earlier, appeared as juveniles in winter, as subadults in late spring, and soon would spawn and die, marking the end of the previous winter population. Adult mortality resulted in the decreased abundance of subadults and adults, and of all specimens larger than 17 mm from late spring to late summer.

Further confirmation of a one-year life cycle is in the seasonal progression of size dominance (11–13 mm in late summer, 16–19 mm in winter, and 18–20 mm in late spring) and in the lack of an annular ring on the otoliths of two 22-mm females caught in winter and late spring. Otoliths were not routinely sampled, these being the only two from individuals of maximum size.

SEX RATIOS.—Unbiased sex ratios could not be determined for any developmental stage during any season for two reasons: females generally could be recognized at a smaller size than males, and spent adults, especially females, may have been categorized as subadults. The total number of females was significantly greater than that of males at each season; juveniles accounted for most of the difference in late summer, and subadults for most of the difference in winter and late spring (Table 123).

Females were significantly more numerous than males for the following stages: juveniles in late summer and winter, subadults in winter and late spring, and adults in late summer. Males were significantly more numerous than females for adults in winter and subadults in late summer (Table 123). Considering only subadults and adults, females still were more numerous than males, but the ratios were nearly equal at any season. Because neither sex was consistently more numerous than the other for either of the two oldest stages, the observed differences in the numbers of males and females for subadults and adults probably were due to the criteria used to allocate individuals to stages rather than actual differences in the numbers of each sex.

The female to male ratio for juveniles in late summer, which is slightly less than 2:1, was due largely to fish 9–12 mm. However, less than half of the fish within that size range could be sexed. The predominance of females may be due to their developing faster and, as a result, being recognized at a smaller size than males. Males and females have been taken in about equal numbers off Hawaii (Clarke, 1973) and in the eastern North Atlantic at 30°N, 25°W (Badcock and Merrett, 1976).

VERTICAL DISTRIBUTION.—Daytime depth range in winter was 451–850 m (possibly shallower) with maximum abundance at 451–500 m, in late spring 400–700 m with a maximum at 451–500 m, and in late summer 451–750 m with a maximum at 501–600 m. Vertical range at night in winter was 30–1050 m with maximum abundance at 51–100 m, in late spring 50–250 m (one specimen also was caught at 751–800 m) with a maximum at 51–100 m, and in late summer 33–400 m and scattered between 651 and 950 m, with a maximum at 33–50 m (Table 124).

During daytime six specimens caught shallower than 400 m during the three seasonal cruise pairs combined were taken near the evening crepuscular period and may have been migrants. Two of the specimens were suspected contaminants and may have been taken during a previous tow. Day depths for N. valdiviae near Hawaii (Clarke, 1973) and in the eastern North Atlantic (Badcock and Merrett, 1976) were deeper than 400 m.

Stage and size stratification were evident day and night at all three seasons, except for stage stratification by day in winter. During the day in late spring and late summer the two older stages had greater depth ranges than juveniles, which were caught only in the shallower portion of the vertical range. In late spring only adults were taken deeper than 600 m (Table 124). During the day in each season, smaller fishes were caught mostly at or near the upper depth limit, and larger ones were found over most or all of the vertical range. In winter most (87 percent) fish smaller than 16 mm were caught at 451–500 m, in late spring all those smaller than 18 mm at 451–500 m, and in late summer all but one smaller than 17 mm at 451–600 m (Table 124).

Adults were not taken in the upper 50 m at night at any season, whereas juveniles were taken at that depth at all three seasons. Subadults were taken in the upper 50 m in late spring and late summer. Migrant subadults and adults were caught over a greater depth range than migrant juveniles at each of the three seasons, and the latter did not occur as deep as the former.

Stage stratification was most pronounced at night in late summer, when juveniles accounted for more than 95 percent of the catch from the upper 50 m, a decreasing percentage of the catch from each deeper 50-m interval to 300 m, and none from 301–400 m (Table 124). A smaller scale stratification existed in the upper 100 m in late summer. An upper, predominantly juvenile, layer at 33–60 m apparently was isolated from the remainder of the population. No adults and very few subadults were caught in that layer. No specimens were taken at 60–70 m. There were no samples taken between 70 and 90 m. The deeper layer was sampled at 90–92 m, where only 42 percent of the individuals were juveniles. In late summer both a seasonal thermocline and halocline were developed at about 25–75 m, and dissolved oxygen content at those depths was greater than at shallower and deeper waters (Morris and Schroeder, 1973). Perhaps these relatively large changes between 25 and 75 m inhibited subadults and adults from migrating up to shallower waters.

Diel vertical migrations occurred at all three seasons, but not all of the population migrated regularly. Nonmigrants were most abundant in winter, when nearly 32 percent of the night catch was from day depths. Less than 3 percent of the night catch in late spring and late summer came from day depths. Nonmigrants were predominantly subadults and adults in winter and juveniles at the other two seasons (Table 124). Nonmigratory behavior of adults and subadults in winter may be associated with the approaching spring spawn. Nonmigrants also are known to occur in the eastern North Atlantic (Badcock and Merrett, 1976) and near Hawaii (Clarke, 1973). Nonmigrants were abundant in winter but not in late spring near both Bermuda and Hawaii. However, in late summer about 70 percent of the population near Hawaii remained at daytime depths at night (Clarke, 1973), in contrast to about 3 percent near Bermuda (Table 124). Partial migrants and nonmigrants were found in the eastern North Atlantic at 30°N, 23°W in late March-early April (Badcock and Merrett, 1976), but not off Fuerteventura (Canary Is.) in October-November (Badcock, 1970). Partial migrants and nonmigrants found in both Atlantic localities were mostly subadults and adults. Near Hawaii they consisted of a higher proportion of larger fish than migrants in late summer but not in winter. The proportion of ripe or nearly ripe females in the partial-migrant and nonmigrant element was not noticeably different from the migrant fraction of the population at any of the three localities.

Evening migrations apparently begin between 1.5 and 2.5 hours before sunset in winter and late spring and between 2.2 and 3 hours before sunset in late summer. Because night depths were reached no later than 1.5–2.5 hours after sunset at each of the three seasons, upward migration times were about 4 hours in winter and late spring and 4.5 hours in late summer. These estimates of migration times indicate upward migration between day and night depths of maximum abundance averaging about 100 m/ hour in winter (500 to 100 m) and late spring (500 to 100 m), and about 115 m/hour in late summer (550 to 30 m).

Morning migrations apparently begin within about 1.5 hours before sunrise at each season. Because in late summer fish were caught in the upper 100 m possibly as late as 0.3 hours before sunrise or later and none were caught in the upper 50 m within 1.3 hours of sunrise, the starting time of migrations may depend upon depth. Day depths were reached no later than 2.5 hours after sunset in winter (650 and 750 m) and late spring (600 m), and by 3.5 hours after sunset in late summer (580 m), possibly an hour or more earlier. Assuming a starting time of 1.5 hours before sunset in each season, total downward migration times probably were not greater than 3.5 hours in winter and late spring and 4.5 hours in late summer. These estimates of migration times indicate that the average rate of descent from the depth of maximum abundance at night to that during daytime is about 115 m/hour at all three seasons, which is similar to the upward migrations.

PATCHINESS.—Patchiness by day was indicated in winter at 451–500 m and 601–650 m, and in late summer at 501–600 m. Juveniles, subadults, and adults were all taken in greatest abundance at 451–500 m in winter and at 501–600 m in late summer. In winter the catch of each stage at 451–500 m was similar, with subadults slightly more abundant than the other two stages, suggesting that each of the three stages had a patchy distribution. Because there were only two samples, each from different depths (456–469 m and 469–504 m), these conclusions must be accepted with reservation. The catch at 501–600 m in late summer was dominated by juveniles (over 79 percent), for which the variation in catch rates was much greater than for either subadults or adults. This suggests that only juveniles had a clumped distribution.

Patchiness at night was indicated at 51–100 m at each of the three seasons; subadults accounted for most of the catch at this depth in winter and late spring, and juveniles were dominant in late summer (Table 124). Juveniles, subadults, and adults were most abundant at that depth in winter, subadults and adults in late spring, and adults in late summer.

Other significant CD values were thought to be due to factors other than a patchy distribution. The CD values for day samples in winter at 801–850 m and in late spring at 451–500 m were significant. Only 6 specimens were caught at 801–850 m during daytime in winter, and all but one were from a single sample. Such a small catch and barely significant CD (3.5) suggests that significant clumping was unlikely. Three samples were taken at 451–500 m in late spring, two of which caught no fish. The CD value probably reflects year to year variation in abundance or vertical distribution rather than patchiness.

Night samples taken in winter at 151–200 m and 451–500 m and in late summer in the upper 50 m, 151–200 m, 201–250 m, and 301–350 m also had significant CD values. Differences in the catches in samples at 151–200 m and 451–500 m in winter and 151–200 m in late summer probably were due to changes in population density that were related to migratory movements. In each case the significant CD value resulted from a single sample taken near dawn that had a much larger catch than the remaining samples from the particular depth. The significant CD values for samples at 201–250 m and 301–350 m in late summer apparently were due to year to year variation in population density. Samples at both 50-m intervals were taken in two different years; CD values calculated for each year separately at both depths were not significant.

Two samples from the upper 50 m in late summer leave doubt as to whether the variation was due to upward migrations or to patchiness. There was a series of three one-hour samples starting at 0.5 hours after sunset taken at 33 m that caught 1, 76, and 156 specimens, respectively. The difference in catch between the first and second samples probably was due to migratory movement, because the first sample was taken during twilight and was not considered in the analysis. The difference between the second and third samples, although probably due to migration, may reflect patchiness.

NIGHT:DAY CATCH RATIOS.—Night-to-day catch ratios including interpolated values were 0.5:1 in winter 0.8:1 in late spring, and 1.9:1 in late summer (Table 125). The greater night depth range at each season (Table 124) may explain in part the catch ratios obtained for winter and late spring. In late summer the catch at night from the upper 50 m, which accounted for 67 percent of the total catch at night, was greater than the entire day catch. However, the value given for the upper 50 m at night, is based on two samples and may not be representative of the entire 50 m, as both samples were made at 33 m. Although no samples were taken between the surface and 33 m, the catch from oblique samples and from samples taken near sunset suggests that N. valdiviae does not inhabit depths shallower than 30 m. This indicates that abundance at 33 m was much greater than at shallower depths. There are no reliable catch data for 34–50 m at night.

廣泛分布於世界三大洋熱帶及溫帶海域。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。

體延長，側扁，後部略細。頭中等大。吻短，前端尖。眼中等大。口大，上頜骨狹長而延伸至前鰓蓋後緣，末端擴大；上下頜呈絨毛狀齒帶。鰓蓋後上緣圓角，不具鋸齒狀突起。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；臀鰭基底略等於或長於背鰭基底，具軟條12-14；胸鰭軟條11-14，尾鰭叉形。各部位之發光器位置於下：鼻部背位發光器(Dn)小而圓形；鼻部腹位發光器(Vn)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)，在側線上方，近背部；胸鰭下方發光器(PVO)2個，兩者互為斜線排列；胸部發光器(PO)5個，PO3及PO4位置明顯昇高；腹部發光器(VO)4個，VO1明顯昇高；腹鰭上位發光器(VLO)位於腹鰭和側線之中間；臀鰭上方發光器(SAO)3個，三者排列呈斜線，SAO3在側線上方，近背部；體後側位發光器(Pol)2個，Pol2在脂鰭下方，側線上方，近背部；臀鰭前部發光器(AOa)3個，水平排列；臀鰭後部發光器(AOp)4個；尾鰭前位發光器(Prc)2個，垂直排列，各位於側線上下緣。尾部發光腺，雄魚與雌魚皆具SUGL而無INGL發光鱗。

大洋性中層巡游魚類，具日夜垂直分布習性，白天一般棲息深度可達350-700公尺左右，晚上則上游至水深25-350公尺附近處覓食，以小蝦等浮游性甲殼類為食。

Notolychnus valdiviae, the topside lanternfish, is a species of lanternfish found in the oceans worldwide. This species grows to a length of 6.3 centimetres (2.5 in) TL.

El pez linterna de Valdivia (Notolychnus valdiviae),​​ es una especie de pez marino, la única del género Notolychnus, de la familia de los mictófidos o peces linterna.​ Su nombre científico procede del griego: noton (espalda) y lychnos (antorcha),​ por la posición de sus órganos luminiscentes.

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Notolychnus valdiviae Notolychnus generoko animalia da. Arrainen barruko Myctophidae familian sailkatzen da.

Smailiasnukės švytulės (lot. Notolychnus) - žibintūninių (Myctophidae) šeimos žuvų gentis.

Feed on copepods, conchoecid ostracods and euphausiids

Western Atlantic: Canada to Argentina

High-oceanic, epipelagic and mesopelagic, found between 375-700 m during the day and between 25-350 m at night.

nektonic

Known from seamounts and knolls

Epipelagic