Glacial Lanternfish

Males with single black-bordered supracaudal gland; females with two infra-caudal luminous patches; occasional specimens with both. Luminous organs in the anal area, 5-6 anteriorly and 5-7 posteriorly, 11-13 total.

Spawns both north and south of the Polar Fronts in the eastern North Atlantic. Reported to perish after spawning (Ref. 9707).

Dorsal spines (total): 0; Dorsal soft rays (total): 13 - 14; Analsoft rays: 17 - 19

Endemic in the Mediterranean (mainly western basin) and Atlantic.

High-oceanic, mesopelagic at depths between 375-800 m during daytime and 12-200 m during night. Depth range from 0-850 m (Ref. 4479) and from 541-1085 m in the eastern Ionian Sea (Ref. 56504). Photophores present. Feeds mainly on calanoid copepods, also euphausiids and copepodites. Feeding occurs at night in Norwegian fjords (Ref. 9209) and in northwest Africa (Ref. 9194). Mature from about 3 cm onward. Spawning peaks in the Mediterranean in late spring with east-to-west progression. Female produces 160-2,000 eggs depending on her size (Ref. 35388).

fisheries: of potential interest

Benthosema glaciale

This subarctic-temperate species (Backus et al., 1977) is thought to be the most abundant member of the family north of about 37°N in the Atlantic Ocean (Bolin, 1959; Halliday, 1970; Nafpaktitis et al., 1977). It attains a moderately large size near Bermuda; maximum length in the Ocean Acre collections is 60 mm. Maximum size and, presumably, life span increase with latitude; B. glaciale grows to 68 mm off Nova Scotia, to 84 mm off Greenland (Halliday, 1970), and to 103 mm off Norway (Gjosaeter, 1973). The species is uncommon in the study area; 97 specimens were collected during the program, about half of these during the paired seasonal cruises. Discrete-depth captures numbered 35, of which 28 were from noncrepuscular times.

DEVELOPMENTAL STAGES.—Juveniles were 20–36 mm, subadults 33–60 mm, and adult males 48–60 mm SL. All but two fish could be sexed; one was the smallest specimen, the other was badly damaged. There were 48 females and 47 males. External sexual dimorphism was evident in fish 25–30 mm, with males having supracaudal and females infracaudal luminous tissue.

REPRODUCTIVE CYCLE AND SEASONAL ABUNDANCE.—Based upon the low abundance and peculiar vertical distribution of B. glaciale in the northern Sargasso Sea, Jahn (1976) concluded that the species was an expatriate and did not reproduce successfully in that region. The Ocean Acre collections, which contain no adult females, or juveniles at the transformation size, or postlarvae, seem to support Jahn's conclusion.

Fish 20–30 mm were caught in small numbers in March, April, and June and were most numerous in April (cruise 6). According to Halliday (1970), fish of this size found off Nova Scotia were about six months old. Assuming that the Ocean Acre population had a similar growth rate, one would expect to catch fish about 11–12 mm (the size at transformation (Taaning, 1918; Halliday, 1970) in fall or winter if they were spawned in the study area. Few fish of any size were taken those seasons. The entire catch from October to March consisted of 15 specimens 36–56 mm SL.

Abundance was at its yearly low in winter (Table 24). The entire catch was three specimens. Abundance increased to its maximum by late spring when subadults were dominant; juveniles and adult males were about equal in number but less abundant. The catch was mostly of fish larger than 40 mm, which, according to Halliday (1970), would be one to three years old. By late summer, abundance had decreased to an intermediate level and, as in late spring, the catch was mostly larger than 40 mm.

The conspicuous absence of 10–12 mm juveniles and the predominance of specimens larger than 40 mm in the collections suggest that all fish were at least six-months old and most were more than a year old before they reached the study area (Halliday, 1970). Otoliths from three fish (40, 53, and 56 mm) had two, three, and three transparent rings, respectively, indicating that they were two and three years old (Halliday, 1970).

VERTICAL DISTRIBUTION.—Although B. glaciale is known to migrate from day depths of 250–800 m into the upper 200 m at night off Nova Scotia (Halliday, 1970) and in the Mediterranean Sea (Goodyear et al., 1972), near Bermuda the species was taken only deeper than 750 m day and night at all seasons (Table 25). The maximum depth of occurrence is uncertain because of poor samples below 1000 m (Table 2); the deepest catch by day was at 1001–1050 m and by night at 1201–1250 m (Table 25). Maximum abundance was at 951–1000 m by day and 851–900 m by night (Table 25).

Most positive samples (including open net and oblique IKMT tows) caught one fish, a few caught 2 to 4, and one caught 13, indicating a patchy distribution.

Benthosema glaciale, or glacier lantern fish, is the most common species of lanternfish and important part of the midwater ecosystem of northern North Atlantic.

It feeds on small crustaceans, including copepods, krill and amphipods, along with other small invertebrates.

Feeds on copepods, euphausiids and copepodites

Baffin Bay to northern edge of Gulf Stream

Nyctoepipelagic species, migrates from daytime depth of 375- 800 m to 12- 200 m at night.

nektonic

Epipelagic

Mesopelagic

Bathypelagic