Scotia Sea icefish, Chaenocephalus aceratus
The first dorsal fin has 5-9 flexible barb rays, the second dorsal fin has 37-42 articulated rays, the anal fin has 36-40 articulated rays, the pectoral fin has 23-26 rays, the caudal fin has 11 branchial rays; the lower part of the first gill arch has 4-6 gill rays; the total number of vertebrae is 60-64. The body is relatively large (11-18% of standard length). The head is very large, 33-42% of the standard length. The rostral spike at the tip of the snout is reduced to a button. The apex of the lower jaw is on the same vertical line as the apex of the upper jaw. The snout is very long, 46-57% of the length of the head. The mouth is large, the posterior edge of the upper jaw reaching to the level of the centre of the pupil or slightly beyond. The eye is rather large, the diameter of the eye socket 14-23% of the length of the head. Interorbital space moderately wide (16-23% of head length). First dorsal fin moderately high, higher than second dorsal fin. Both dorsal fins well separated by a wide interdorsal space. The body has two lateral lines without bony segments, along dorsal line and a very short medial line on the caudal peduncle. The pelvic fins are elongated (19-45% of standard body length), extending beyond the beginning of the base of the anal fin, and their relative length decreases with age. The caudal fin is rounded. The overall colouration of the body is greyish with a lighter pelvic side. There are 4-5 relatively broad dark stripes on the sides of the body, which are yellowish-green in immature individuals. The first dorsal fin is dark or blackish. The colouration of the other fins varies from light to dark.
It occurs off South Georgia, South Sandwich, South Orkney and South Shetland Islands, off Bouvet Island and off the coast of the Antarctic Peninsula.
It inhabits depths of 5 to 770 metres.
The total length of females reaches 76-77 cm, males - 61 cm. The maximum weight of females is 3.97 kg, males - 2 kg.
Life history and Behavior
Spawning takes place in the Antarctic autumn: on South Georgia in March-May and on the South Shetland Islands in May-June.
Food and feeding habits
Juveniles up to 25-35 cm in total length are predatory zooplankton eaters, feeding mainly on Euphausia superba, mysids and other small crustaceans. As it grows, fish begin to appear in the diet. Adult fish over 50 cm long are typical predators - ichthyophagous, feeding mainly on bottom and benthic-pelagic species of Nototheniidae - small Nototheniops larseni and Nototheniops nybelini, Lindbergichthys nudifrons, as well as juveniles of Gobionototothen gibberifron, Champsocephalus gunnari, Dissostichus eleginoides and juveniles of their own species. Luminescent anchovies and other fish are also found in small numbers in the stomachs.
Females reach sexual maturity at an average total length of 52 cm, males at 44 cm. Absolute fecundity varies from 3 to 23 thousand eggs, relative fecundity - 3.9-9.2 eggs. The diameter of mature eggs is about 4.4-4.9 mm. The eggs are demersal. Larvae hatch in spring, August-September.
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Tags: blackfin icefish