Cocco's Lantern Fish

Anal organs 10-11; mature males have supracaudal gland consisting of a series of 6 large, well-defined scale-like structures flanked by 5 pairs of smaller, triangular ones; the infracaudal gland of mature females consists of 2 heart-shaped scales; flanked by smaller, triangular luminous scales (Ref. 39633).

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 - 18; Analspines: 0; Analsoft rays: 13 - 15

High-oceanic and mesopelagic (Ref. 4066), found between 300-800 m during the day and between 25-100 m (juveniles 14-22 mm) and 200-300 (adults 50-56 mm) at night (Ref. 4479). Size stratification with depth both day and night (Ref. 4775).

High-oceanic and mesopelagic (Ref. 4066), found between 300-800 m during the day and between 25-100 m (juveniles 14-22 mm) and 200-300 (adults 50-56 mm) at night (Ref. 4479). Size stratification with depth both day and night (Ref. 4775). Oviparous, with planktonic eggs and larvae (Ref. 31442). Reach sexual maturity between 40 and 45 cm (Ref. 47377). Also Ref. 58302.

Lobianchia gemellari

This medium-size myctophid seldom exceeds 35 mm in the study area; a few grow to 48 mm. Two specimens nearly 100 mm were caught. Nafpaktitis (1968) noted that a few individuals found in the slope water off New England and further north all with undeveloped gonads were 85–100 mm, and Hulley (1981) commented on the presence of large, sexually undeveloped specimens north of 40° in the eastern Atlantic. There is a question as to whether these large specimens are expatriates or represent a separate population, for they have high gill-raker counts. A tropical-subtropical species (Backus et al., 1977), L. gemellarii has a more or less complementary distribution to that of its congener L. dofleini in the Atlantic, but when both are found in the same area, one will be much more abundant than the other (Nafpaktitis et al., 1977). This species, although common in the study area, never ranked among the top 10 lanternfishes in abundance. The Ocean Acre collections contain 627 specimens; 222 were caught during the paired seasonal cruises, 146 of those in discrete-depth samples of which 112 were in noncrepuscular tows.

DEVELOPMENTAL STAGES.—Postlarvae were 6–12 mm, juveniles 11–38 mm, and subadults 29–98 mm. The sex of only a few (∼12 percent of those caught during the paired seasonal cruises) specimens could be determined; even those had barely recognizable ovaries or testes. Only nine specimens exceeded 40 mm, the reported size at sexual maturity (O'Day and Nafpaktitis, 1967). Most specimens lacked luminous tissue on the caudal peduncle, a secondary sex characteristic of L. gemellarii found in the spawning area (12°-26°N) of the Atlantic Ocean (O'Day and Nafpaktitis, 1967).

REPRODUCTIVE CYCLE AND SEASONAL ABUNDANCE.—Lobianchia gemellarii is a nonbreeding resident of the study area. Abundance was greatest in winter and decreased with the progression of the seasons (Table 116). In winter and late spring juveniles were predominant, making up about 79 and 92 percent, respectively, of the catch.

The paucity of specimens of adult size (larger than 40 mm), the lack of ripe females, the absence of luminous tissue on the caudal peduncle of most specimens, and the presence of the two “giant” specimens showing very little sexual development indicate that L. gemellarii is a sterile expatriate, whose numbers in the study area must be periodically replenished, presumably from the spawning area to the south.

Recruitment was greatest in winter. The catch at that season consisted almost entirely of specimens 20 mm or smaller. Juveniles comprised nearly 80 percent of the catch in winter. Postlarvae had their peak abundance at this season, accounting for about 17 percent of the catch (Table 116). The small size of winter specimens indicates that the parent population was at a peak in spawning in fall. The relatively high abundance in winter in the study area presumably reflects a peak in abundance in the spawning area.

In June almost all fish were greater than 20 mm; none were smaller than 16 mm. Abundance was only about two-thirds of that in winter. Specimens taken at this time either were winter recruits at an older age or were recent recruits from the parent population, or both. The paucity of small specimens at this early summer season indicates that most spawning was completed by winter.

By late summer most specimens were larger than 25 mm, although a few were 10–20 mm. The smaller specimens may reflect a smaller spawning peak for the parent population in late spring–early summer or may signal the advent of a new spawning season. Abundance was quite low, being about one-sixth of that in winter.

The relatively low abundance at each season probably resulted from very few recruits reaching the study area. Apparently most specimens could not survive long under the prevailing conditions; none had reached sexual maturity. It cannot be determined if the “giant” specimens had survived in the study area for any length of time. The “giants” examined by Nafpaktitis (1968) were taken in slope water off southern New England or further north.

VERTICAL DISTRIBUTION.—Daytime depth range in winter was 1–50 m and 451–650 m with maximum abundance at 451–500 m, in late spring 351–800 m with a maximum at 601–650 m, and in late summer 451–600 m. At night the vertical range in winter was 51–150 m and scattered sporadically between 301 m and 600 m with maximum abundance at 51–100 m, in late spring 51–300 m with a maximum at 201–250 m, and in late summer at scattered intervals between 51 m and 450 m with no apparent concentration (Table 117).

Except by day in late summer, size stratification was evident day and night at each of the three seasons. During the daytime in winter all specimens from the upper 50 m were 7–8 mm postlarvae and those from greater depths were 10–29 mm. During the day in late spring there was an increase in maximum size with depth and the mean size tended to increase with depth. At night in the upper 350 m the mean size at 51–100 m was noticeably smaller than at other 50-m intervals. The largest specimens were taken only between 251 m and 350 m (Table 117).

Postlarvae seemed to be stratified by size; those from the upper 150 m were 7–8 mm and those from greater depths 10–12 mm. As with other species of myctophids, initial development apparently occurs in the upper layers and, at a size of about 10 mm, postlarvae descend to about 500–600 m, where they transform. Postlarvae probably do not undertake vertical migrations of any great extent, but there is little evidence to support this.

Diel vertical migrations occurred at each of the three seasons. Only two specimens were caught at day depths at night, one postlarva and a 12 mm juvenile; this suggests that the smallest juveniles were not regular migrants.

Little could be determined concerning the chronology of vertical migrations. In winter and late spring specimens were caught in the upper 250 m during the evening crepuscular period and in the upper 200 m during the morning crepuscular period. Thus at least some specimens begin upward migrations prior to about 1.0–1.5 hours before sunset, and some do not commence downward migrations until shortly before sunrise.

PATCHINESS.—A patchy distribution was indicated at 451–500 m during the day and at 95 m during the night in winter. The day CD was based upon two samples at different depths within the 451–500 m interval and probably reflects different population densities within that interval. One sample fished at 451–470 m had a catch rate of 2.0, and the other fished at 469–500 m had a catch rate of 13.0.

Eleven samples were taken at 51–100 m at night, three at 68 m, three at 95 m, and five at 100 m. Samples from 68 m and 100 m caught either one specimen or no specimens, and their individual CD values were not significantly greater than 1.0. At 95 m the first of three consecutive samples had a much lower catch rate than the following two. The first sample was taken shortly after the evening crepuscular period, when fish still may have been migrating up to their nighttime depths.

NIGHT:DAY CATCH RATIOS.—Night-to-day catch ratios for discrete-depth captures were 0.4:1 in winter, 0.8:1 in late spring, and 4.2:1 in late summer (Table 118).

Because juveniles smaller than 20 mm dominated the winter catch both day and night, and specimens smaller than 30 mm accounted for most of the difference in day and night catches in late spring, it is unlikely that diel differences in net avoidance had much, if any, effect on the diel differences in catch. Apparently, the species concentrates in a narrow stratum both day and night. Most of the catch in each diel period came from a single depth range, and positive samples from other depths contained only one or two fish. The observed diel differences in abundance, then, probably were due to sampling inequities.

Catches in late summer were poor both day and night. Most specimens captured were 30 mm and larger, sizes that may have been able to avoid the net. Avoidance by day was suggested by the fact that only two fish were taken in all discrete-depth diurnal samples combined, despite good sampling effort within the presumed depth range (Table 117). However, even at night few specimens were caught; the difference may be due to chance.

分布於世界三大洋熱帶及亞熱帶海域。臺灣則發現於東部周邊水域。

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，鈍圓。眼大。口大，上頜骨狹長而延伸至前鰓蓋後緣，末端略擴大；上下頜、鋤骨、腭骨均具齒帶。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17-18，後部另具一脂鰭；臀鰭基底略短於背鰭基底，具軟條13-15；胸鰭具軟條11-12；尾鰭叉形，尾鰭副鰭條柔軟。各部位之發光器位置於下：眶前發光器(Ant)無；鼻部背位發光器(Dn)小而圓；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明顯較Op2小，上下相接近；鰓被架位發光器(Br)3個；胸鰭上方發光器(PLO)，位於側線與胸鰭基部之中間；胸鰭下方發光器(PVO)2個，兩者與PO1成一斜線；胸部發光器(PO)5個，PO4位置昇高；腹部發光器(VO)5個，VO3位置最高，VO4及VO5下降；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，三者排列呈斜線狀，SAO1高於VO5；體後側位發光器(Pol)1個，在脂鰭下方，靠近臀鰭；臀鰭前部發光器(AOa)5個，AOa1位置不昇高，最後一個昇高；臀鰭後部發光器(AOp)5-6個，沿尾柄腹側水平狀排列，最後一個不昇高；尾鰭前位發光器(Prc)4個，四個依次昇高呈半弧形排列，Prc4在側線下方約發光器直徑的2倍處。尾部發光腺具在，雄魚具5-6個覆瓦狀的SUGL，雌魚則具2個心狀的INGL。

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300-800公尺左右，晚上則上游至水深25-100公尺(幼魚)及200-300公尺(成魚)附近處覓食，以小蝦等甲殼類為食。

Cocco's lantern fish (Lobianchia gemellarii), also called Gemellar's lanternfish, is a species of lanternfish.

Western Atlantic Grand Bank to the Antilles and Argentina, but absent between 17°-3°N east of 30°W

High-oceanic and mesopelagic, found between 300-800 m during the day and between 25-100 m (juveniles 14-22 mm) and 200-300 (adults 50-56 mm) at night.

nektonic

Known from seamounts and knolls