Cocco's Lanternfish

Usually occurs at depths of around 300 m (Ref. 26335). Mesopelagic (Ref. 5951).

Dorsal spines (total): 0; Dorsal soft rays (total): 10 - 13; Analspines: 0; Analsoft rays: 21 - 23

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.

Mature males with 6-8 supracaudal luminous structures; mature females with 3-6 infracaudal luminous patches.

Oceanic, found between 425-1,000 m during the day with maximum abundance at 425-650 m (Ref. 4479). Nyctoepipelagic from the surface to 175 m (Ref. 4479).

Gonichthys cocco

Although this medium-size lanternfish grows to 60 mm, the maximum size in the Ocean Acre collections was 45 mm, with very few exceeding 40 mm. According to Backus et al. (1977), G. cocco is a questionably tropical-subtropical species that is not found in the Caribbean Sea. Near Bermuda it is an “abundant” lanternfish. It is the most abundant one that comes to the surface at night, and ranks among the ten most abundant lanternfish at all three seasons. About 95 percent of all specimens caught were from night neuston samples. Of the 1326 specimens caught, 1112 were taken during the paired seasonal cruises, 1057 of these from surface samples. Discrete-depth samples made with the 3-m Isaccs-Kidd midwater trawl during the paired seasonal cruises accounted for only 35 specimens.

DEVELOPMENTAL STAGES.—Postlarvae were 5–15 mm, juveniles 13–32 mm, subadults 26–45 mm, and adults 34–44 mm. Most juveniles 13–20 mm have slender thread-like gonads and could not be sexed. Several fish larger than 40 mm that were categorized as subadults apparently were spent adults. Adult females contained eggs as large as 0.45 mm, but most eggs were 0.25–0.35 mm in diameter. Subadult and adult males had supracaudal luminescent glands and subadult and adult females infracaudal glands. There was no sexual dimorphism in size.

REPRODUCTIVE CYCLE AND SEASONAL ABUNDANCE.—Gonichthys cocco has a one-year life cycle, with very few, if any, individuals surviving much beyond a year. Spawning occurs from winter to early summer, with a peak in winter or early spring. Abundance was greatest in late spring (Table 61), when G. cocco was the fourth most abundant lanternfish, and juveniles were most abundant. Subadults and adults were most abundant in winter.

The winter catch was dominated by juveniles, but subadults and adults were at their yearly high in abundance. Spawning evidently was low over late summer and fall, as most winter juveniles were 20–30 mm, and transformation occurs at about 14 mm (Taaning, 1918). By late spring much of the winter population had matured, spawned, and died, resulting in a decrease in abundance of subadults and adults and an increase in juveniles; in late spring most juveniles were 18–21 mm. Subadults and adults (small juveniles of the winter) would spawn and die by late summer. As a result of postspawning mortality, the older stages virtually were absent at that season (Table 61), and most fish were 20 mm or smaller. This suggests that few fish live more than one year.

Abundance most likely was underestimated both in late spring and late summer, as several 8 mm postlarvae were taken, and fish less than 10 mm probably were not adequately sampled by the nets. In winter small juveniles (16–20 mm) were at a minimum and subadults and adults at a maximum. Continuing mortality in the recruit class should have resulted in a decrease in total abundance from late summer to winter but, because of the underestimation of the late summer population, no significant change was apparent (Table 61).

SEX RATIOS.—The sexes probably are equally abundant at all seasons. Total female-to-male sex ratios were 1.0:1 in winter and 1.3:1 at the other two seasons; only the difference in late spring differed significantly from equality (Table 62). Most of the difference in late spring was due to juveniles, of which about half could be sexed. Adult females outnumbered adult males in winter and late spring, and juveniles and subadults showed no consistent trend in numerical dominance of either sex. None of the sex ratios for individual stages differed significantly from equality.


VERTICAL DISTRIBUTION.—Diurnal catches in each season were poor; only 19 fish were taken in all daytime discrete-depth samples combined. The combined seasonal day discrete-depth samples give a depth range of 501–1000 m, with no apparent depth preference (Table 63). Gonichthys cocco probably was well dispersed vertically by day at all seasons, as all positive samples contained 3 or fewer fish. One specimen, a probable contaminant, was taken at the surface by day in late spring.

A dramatic concentration takes place at night. More than 95 percent of the nocturnal catch in each season came from the surface (Table 63). In winter fish also were taken at 101–200 m and at 751–900 m, in late spring a single specimen was taken at 51–100 m, and in late summer one fish each was taken at 1–50 m and 851–900 m.

Only fish smaller than 20 mm were taken below 750 m day or night at all seasons (Table 63). Because day catches in each season contained mostly one developmental stage and night catches were mostly from the surface, little can be said concerning stage stratification.

Although most migrants were found at or close to the surface, at each season migrants also were taken well below the surface. These individuals were most abundant in winter, when juveniles, subadults, and adults all were taken at 101–200 m (Table 63). In late spring and late summer only a single migrant juvenile was taken well below the surface (at 90 m and 33 m, respectively).

Apparently, regular migratory behavior is assumed at about 16–19 mm. Larger sizes were all migrators, and a few 16–19 mm juveniles were taken at day depths by night in winter and late summer. Nonmigrants accounted for about 2 percent of the winter night catch, and less than 1 percent of that in late summer.

Migrations could not be traced in any season due to poor diurnal and evening crepuscular catches. In late summer one fish was taken at 501–550 m between 2.3 and 1.3 hours before sunset and another at 101–150 m between 1.5 and 0.5 hours before sunset. Surface waters were occupied 1.5 hours or less after sunset in each season. In late spring fish were taken at the surface between 1.5 to 0.5 hours before sunrise, and in late summer samples taken up to 45 minutes before sunrise were negative. Samples were not taken within 1.75 hours of sunrise in winter. Table 64 gives the catch rate (specimens/hour) for selected times for the five cruises during which neuston samples were taken.

PATCHINESS.—Significant patchiness was indicated at the surface by night in each season. Table 64 shows the great variation in catch rates even when samples taken from the same times on different days are combined. Examination of individual samples revealed even greater variation. Sequential samples often had catch rates that differed by a factor of 2 or more. Additionally, on several occasions negative samples were interspersed amongst several positive samples.

A significant CD also was obtained for late spring day surface samples. However, this was due to the capture of a single fish, a probable contaminant. This obviously is not indicative of a patchy distribution even if the capture is a valid record for G. cocco.

NIGHT: DAY CATCH RATIOS.—Night catches were consistently larger than those of day, with ratios of 13.6:1 in winter 70.3:1 in late spring, and 9.9:1 in late summer (Table 65). The large night catches must be due, at least partially, to the great constriction of the vertical range at that time, Net avoidance is the obvious explanation for the virtual absence of this species from daytime samples; its effect at night cannot be evaluated.

Gonichthys cocco és una espècie de peix de la família dels mictòfids i de l'ordre dels mictofiformes.

Gonichthys cocco, often called the Cocco's lanternfish, is a species of oceanodromous lanternfish.

El pez-linterna de cocco (Gonichthys cocco),​​ es una especie de pez marino de la familia de los mictófidos o peces linterna.​

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Gonichthys cocco Gonichthys generoko animalia da. Arrainen barruko Myctophidae familian sailkatzen da.

Il pesce lanterna nasuto (Gonichthys cocco) è un pesce abissale della famiglia Myctophidae.

Gonichthys cocco is een straalvinnige vissensoort uit de familie van de lantaarnvissen (Myctophidae). De wetenschappelijke naam van de soort werd in 1829 gepubliceerd door Cocco.

柯氏星灯鱼（学名：Gonichthys coccoi）为輻鰭魚綱燈籠魚目灯笼鱼科星灯鱼属的鱼类。分布于大西洋、印度洋、太平洋以及海等，常生活于广泛生活在热带和亚热带海洋，屬深海魚類，棲息深度0-1000公尺，體長可達6公分。该物种的模式产地在意大利的墨西拿。

Western Atlantic: about 50°N, east of 40°W or south of the slope water region west of 40°W to about Brazil (absent over the minimum region off Brazil and lower abundance in the South Sargasso Sea)

Nyctoepipelagic species, migrates from daytime depth of 500- 1000 m to between 0- 175 m at night.

nektonic

Known from seamounts and knolls