Myctophidae
by P. A. Hulley
Generally small-sized fishes. Head and body compressed. Eyes large and lateral (dorsolateral in Protomyctophum (Hierops)). Mouth terminal (sub-terminal in Centrobranchus, Gonichthys, Loweina), extending beyond the vertical through middle of eye; with upper edge formed by premaxillary only. Teeth small. Rudimentary spine at base of dorsal, anal, uppermost pectoral and outermost ventral finray. Adipose fin present. Origin of anal fin close behind base of dorsal fin. Scales cycloid or ctenoid. Photophores present (absent in Taaningichthys paurolychnus), arranged in distinct groups on head and trunk. Smaller 'secondary' photophores on head, trunk and fins in some species. Luminous organs of various shapes and sizes on head or caudal peduncle or both.
High-oceanic mesopelagic/bathypelagic or pseudoceanic pelagic/epibenthic from arctic to antarctic waters. Mesopelagic and pseudoceanic pelagic species exhibiting diurnal migration to between the surface and 100 m at night; some showing size stratification with depth and some with juveniles/adults non-migratory; bathypelagic and pseudoceanic epibenthic species not exhibiting vertical migration. Mainly opportunistic feeders on copepods, amphipods, ostracods, euphausiids, chaetognaths, fish eggs and fish larvae; some species showing a degree of selectivity. Number of eggs in ovaries very variable according to the species. Period of spawning also very variable. Changes occur during development: larvae and post-larvae differ from adults in their pigmentation, number of photophores (the groups of which appear gradually) and in some features of the head. Larvae may be stylophthalmoid, having the eyes supported by a peduncle more or less long.
Mostly abundant, some species rare, limited exploitation only in South-east Atlantic (Lampanyctodes hectoris) and Southern Ocean (Gymnoscopelus species), but potentially important for the production of fish oil and fish meal.
Genera 30; in Clofnam area 20.
Recent revisions: Wisner (1976); Nafpaktitis et al. (1977); Nafpaktitis (1978); Kawaguchi and Shimizu (1978); Hulley (1981).