Comephorus

Comephorus
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Scorpaeniformes
Superfamily:	Cottoidea
Family:	Comephoridae Günther, 1861
Genus:	Comephorus Lacepède, 1800

Comephorus, known as the golomyankas or Baikal oilfish, are a genus comprising two species of peculiar, sculpin fishes endemic to Lake Baikal in Russia. Comephorus is the only genus in the family Comephoridae. Golomyankas are pelagic fishes which make the main food source of the Baikal seal.

Comephorus have translucent bodies with no scales, but appear dull when dead. The big Baikal oilfish (C. baikalensis) can reach up to 21 cm (8.3 in) in length and the little Baikal oilfish (C. dybowskii) up to 16 cm (6.3 in). They have long pectoral fins, and although pelvic bones are present, they lack pelvic fins. They have a strong lateral line. The lateral line system on the head consists of large cavities linked by narrow, bony bridges with small external pores. High lipid content and porous bones result in an almost neutral buoyancy and lack of swim bladder allows the fish to tolerate varying pressure extremes as they move through the water column. Over a third of the body weight (38.9%) of C. baicalensis is oil, but C. dybowski contains far less (4.7%). It has been said that they decompose in sunlight, leaving behind only fatty oil and bones, although the accuracy of this claim has been questioned. Some of the adaptions in golomyankas resemble those seen in deep sea fish.

There are currently two recognized species in this genus:

The common name golomyanka originates from the old-Russian golomen, meaning "far from the shore" in the local dialect and referring to their pelagic behavior. They are the principal ecological competitor to the omul, which also eat small golomyankas, and represent a primary food source for the Baikal seal, at more than 90% of its diet. They are easily identifiable, and are large enough to be easily seen. Golomyankas are unusual for occurring pelagically throughout the entire water column of Lake Baikal, ranging from depths in excess of 1 km (0.6 mi) to near the surface, but they primarily occur deeper than 100 m (330 ft). During the night they move up the water column to feed, often occurring as shallow as 10–25 m (33–82 ft). They are considered the world's most abyssal freshwater fish, together with certain Lake Baikal deep-water sculpins (Abyssocottidae). They move without much regard for changes in pressure, although they can exist only in cold temperatures, preferring water up to 5 °C (41 °F) and dying at 10 °C (50 °F).

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