Animalia Life

Trematomus bernacchii
FAMILY
Nototheniidae
TAXONOMY
Trematomus bernacchii Boulenger, 1902, Cape Adare and Duke of York Island, North Victoria Land, Antarctica.
OTHER COMMON NAMES
English: Emerald rockcod, bernak; French: Bocasson йmeraude; Russian: Trematom-pestryak; Spanish: Austrobacalao esmerelda.
PHYSICAL CHARACTERISTICS
Reaches a maximum length of 12 in (30 cm) and a maximum weight of 12.3 oz (350 g). It is thick-bodied (length/depth ratio, about 3:9) and light brown to pinkish brown on the sides, with irregular darker blotches; the belly is silvery gray. It is covered with ctenoid scales, except for a patch between the eyes, where there may be a single row of scales. Three distinct color varieties are known: • continuous white band across the nape and opercula • an interrupted band, consisting of a narrow medial stripe on the nape and on each operculum • no white marking
DISTRIBUTION
Coastal waters of Antarctica, including the Antarctic Peninsula and South Shetland and South Orkney Islands.
HABITAT
It is most common on boulder, rock, or gravel bottoms or in sponge beds at depths of 18–1,200 ft (5–370 m), but it has been caught as deep as 2,280 ft (700 m). Smaller individuals are found in shallow water, whereas mature fish are more common in deeper water.
BEHAVIOR
The emerald notothen is a sedentary demersal species, spending most of its time immobile on the bottom. It swims infrequently and slowly, sculling with the pectoral fins and making short excursions across the bottom or ascending about 3 ft (1 m) into the water column. In the aquarium, dominant individuals establish and defend territories.
FEEDING ECOLOGY AND DIET
This is an opportunistic feeder and scavenger, primarily on benthic invertebrates. Small crustaceans are the most common dietary item, followed by polychaetes, molluscs, fish, and fish eggs. It ingests seaweed, but its nutritional contribution is unknown.
REPRODUCTIVE BIOLOGY
The life span of the emerald notothen is 8–10 years; in McMurdo Sound, first spawning occurs at five years. Females spawn biennially; initial oocyte development takes one year and active vitellogenesis (deposition of yolk within the growing egg) another year. Spawning takes place over a brief period, from October to November in Adйlie Land and December to January in McMurdo Sound. Fecundity is on the order of 1,500– 3,000 eggs, which are attached to rocks, algae, or sponges; mature eggs are 0.16 in (4 mm) in diameter. There are reports that the emerald notothen tends egg masses in sponges.
CONSERVATION STATUS
Not threatened. The emerald notothen is widespread and common; considering its small size and high latitude, it is not likely to come under any significant pressure from fisheries. Its limited mobility probably would lead to extremely rapid depletion of any local populations that might be subjected to commercial fishing.
SIGNIFICANCE TO HUMANS
This species has played an important scientific role in the study of anatomical, physiological, and biochemical adaptations to the Antarctic environment. Most significantly, it has featured prominently in the elucidation of biological antifreeze compounds.

Other popular Animals