Jewel Lanternfish

Distinguished from other species of Lampanyctus by the pattern of its photophores and by its short pectoral fins located just behind gill opening (Ref. 5571). Photophores along ventral post-anal region (AO): 6 (7) + 8 (7-9) = 14 (13-16) (Ref. 4775).

Apparently spawns in deepwater.

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 soft rays (total): 13 - 14; Analsoft rays: 16 - 18

Depth distribution: larvae most abundant in the upper 50 m (Ref. 5573); post larvae and juveniles between 45-150 m (Ref. 4775); adults from 700-1,000 m (Ref. 4775; 5571). Adults may migrate to shallower waters at night (Ref. 4775) but they remain essentially in mesopelagic depths (Ref. 5574). The jewel lanternfish may be demersal in the Hudson Canyon off New York, U.S.A. (Ref. 5571).

High-oceanic, between 700-1,000 m during the day (with juveniles in the upper 200 m) and 45-250 m and 4000-1,000 m at night (Ref. 4479). Depth range from 318-1192 m in the eastern Ionian Sea (Ref. 56504). Epipelagic to bathypelagic, feeds on zooplankton (Ref. 58426). Catches of lanternfishes off the west coast of South Africa: 1,134-42,560 mt (Ref. 5571). Minimum depth from Ref. 58018.

fisheries: of potential interest

Lampanyctus crocodilus

This large myctophid grows to 200–300 mm (Taaning, 1918); the largest Ocean Acre specimen is 56 mm. Lampanyctus crocodilus is a temperate-semisubtropical species (Backus et al., 1977). Although categorized as “common” in the study area, it was found in moderate abundance only in late spring, when it was the eleventh most abundant myctophid; at other seasons it was uncommon (Table 131). The Ocean Acre collections contain 350 specimens; 142 were caught during the paired seasonal cruises, 97 of these in discrete-depth samples, of which 76 were caught in noncrepuscular tows.

DEVELOPMENTAL STAGES.—Postlarvae were 6–22 mm and juveniles 19–56 mm. Few specimens exceeded 40 mm in length.

REPRODUCTIVE CYCLE AND SEASONAL ABUNDANCE.—It cannot be determined if the entire life cycle is passed in the study area. The parent population probably spawns from winter to summer, with the greatest intensity in winter and late spring. Although the life span cannot be determined, the catch data show that the species lives for more than one year and that sexual maturity was not attained by that age.

April collections were solely of postlarvae, which may reflect a spawning peak in the parent population. By late spring some postlarvae had transformed, and most of the catch was 19–24 mm, at or near the size at transformation. A few specimens were 25–35 mm, and two were about 50 mm, none were 36–49 mm. In late summer the IKMT catch was exclusively 25–37 mm juveniles, presumably 5–6 months old. At that season the Engel trawl caught a similar size group and two fish about 50 mm, but none of intermediate size. In winter most specimens were 34–45 mm and about one year old. Apparently, the larger specimens (50 mm) taken in late spring and in late summer were spawned early.

Seasonal abundance reflects the above sequence of events. Abundance was greatest in late spring when recruits 19–24 mm predominated, and decreased as the year progressed as a result of the end of spawning and of continuing mortality in the recruit class (Table 86).

The absence of large fish in the collections is puzzling. Even the Engel trawl failed to catch fish larger than 56 mm, despite fishing to 1000 m. Fish more than 100 mm in length apparently remain below 1000 m (Goodyear et al., 1972), and may stay as deep as 2500–3000 m (Krefft, personal communication). It is possible that near Bermuda fish larger than 50 mm live below the depths sampled during the Ocean Acre program. Specimens about 100 mm long were observed from a deep submersible near or on the bottom in the slope water off New England (J.E. Craddock, personal communication). If large fish live near the bottom in the Bermuda area, they would not appear in the collections because no samples were made near the bottom. Alternatively, large fish may not occur in the area, remaining in their more temperate habitat, while smaller specimens enter the area, but never reach spawning size.

VERTICAL DISTRIBUTION.—Depth by day in winter is 801–850 m (1 specimen), in late spring 751–1000 m with maximum abundance at 751–800 m, and in late summer 801–950 m. Nocturnal depth in winter is 751–900 m, in late spring about 50–300 m and 551–850 m, and in late summer 201–950 (Table 86). As indicated earlier, L. crocodilus may inhabit greater depths than these.

There is no evidence for stratification by stage. In late spring juveniles and postlarvae were taken over similar depth ranges, and at the other two seasons only juveniles were taken (Table 86).

Lampanyctus crocodilus may stratify according to size. At night this stratification was related to the extent of the vertical migrations performed by this species. During the day in late spring the two largest specimens (50 and 52 mm) were caught at the greatest depth, and smaller fish were taken throughout the depth range. At the other two seasons too few specimens were taken during daytime to note whether or not size stratification existed (Table 86). Goodyear et al. (1972) noted that in the Mediterranean Sea juveniles smaller than 34 mm were found at shallower depths than larger juveniles and subadults.

Postlarvae probably were stratified by size. The few taken in the upper 200 m at night were smaller than 14 mm, and those caught below 700 m both day and night were larger than 14 mm. This suggests that, as with other myctophids, postlarvae do not undergo extensive diel vertical migrations during initial development which takes place at superficial depths, and at about 14 mm postlarvae descend to greater depths to complete development and metamorphosis.

Diel migrations apparently commence soon after metamorphosis and continue for a limited time, after which they gradually diminish in extent until there is no change in depth during the diel cycle.

Vertical migrations occur only in fish 20–33 mm, with those 20–24 mm migrating to 50–100 m, and those 28–33 mm migrating to intermediate depths (Table 86). The catch at night in late spring consisted of migrants 20–24 mm, partial migrants 28–32 mm, and nonmigrants 19–23 mm, the size at which metamorphosis takes place. In late summer the night catch consisted of partial migrants 29–33 mm and nonmigrants 25–36 mm, and in winter of nonmigrants 34–42 mm (Table 86).

PATCHINESS.—Clumping was indicated for the depth of maximum abundance by day in late spring (751–800 m) and by night in late summer (851–900 m).

NIGHT:DAY CATCH RATIOS.—Night-to-day catch ratios for discrete-depth captures (including interpolated values) are 4.0:1 in winter, 0.6:1 in late spring, and 2.4:1 in late summer (Table 87).

The difference in diel catch rates for winter samples probably was due to poor sampling effort within the presumed day range, 751–1000 m (Table 86). In late spring there were diel differences in clumping and extent of vertical range, which might account for the greater daytime catch. Also fish 35–52 mm were sampled only by day. In late summer several depths within the diurnal vertical range were not sampled and clumping was noted by night but not by day.

Lampanyctus crocodilus, the jewel lanternfish, is a lanternfish of the family Myctophidae, found in west Mediterranean Sea and north Atlantic Ocean (above 50° N). Bathypelagic between 400 and 2000 m.

Feeds on ostracods, euphausiids and copepods

Western Atlantic: reported from as shallow as 46 m in Ungava Bay, Canada, in slope water region

High-oceanic, between 700-1,000 m during the day (with juveniles in the upper 200 m) and 45-250 m and 4000-1,000 m at nigh.

nektonic