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DescriptionMolva molva is the largest fish of the cod family, growing up to 200 cm in length and 30 kg in weight. Both its head and eyes are small and the upper jaw projects beyond the lower. The lower jaw bears a distinct sensory barbel. Unlike most other cod species, Molva molva has two instead of three dorsal fins. The first dorsal fin is short with 14-15 fin rays; the second is considerably longer and has 61-68 fin rays. The elongate anal fin has 58-64 fin rays. This species has between 63-65 vertebrae. The caudal peduncal and the pelvic fins are short, the latter not extending beyond the pectoral fins. It is marbelled greenish-brown on its upper surface becoming lighter on its flanks and underside. The anal and dorsal fins have a distinct white edge and bear a dark spot at the rear. However this spot is more conspicuous on the first dorsal fin. Juveniles tend to be lighter in colour often having pale purpleish irridescent lines.Spawning occurs offshore between March and August at a depth of 100-300 m. The females produce between 20-60 million pelagic eggs ca.1 mm in diameter. Each egg contains a single pale green oil globule, which enables them to stay in the upper layers of the water column to develop and eventually hatch after about 10 days. The fry of Molva molva have a downward faced head and the paired fins are both long (Dipper, 1984). Juvniles stay in coastal waters until the 2-3 years of age (Dipper, 2001; Wheeler, 1969). Growth is initially rapid: up to 20 cm long in the first year; 35 cm in the second; 55 cm in the third and up to 83 cm in the forth year. Subsequent annual growth is between 8-10 cm until the ninth year. Females invariably grow faster and live longer than males. Females reach maturity at 90-100 cm or 6-8 years of age and can live up to 14 years. Males reach maturity at ca. 80 cm and rarely live over 10 years of age (Wheeler, 1969).
Molva molva primarily feeds on other fish such as Trisopterus esmarkii, Gadus gadus, Clupea harengus and flat fish, and invertebrates such as crustaceans and starfish may also be consumed, but more likely by the inshore juveniles. This species is commercially fished using longlines and trawls around western Scotland. It is salted and dried as klipfisk and then exported to southern Europe (Muus & Dahlstrom, 1974; Wheeler, 1969). Molva molva maybe mistaken for Merluccius merluccius, although this species does not have a barbel. There are two other Molva species: Molva dypterygia and Molva macrophthalma with the former present only in UK waters. Molva molva can be distinguished from Molva dypterygia by its barbel being longer than the eye, and by having 59 to 70 second dorsal fin rays, whereas Molva dypterygia has 69 to 83 rays (Muus & Dahlstrom, 1974).