Comephorus

Comephorus
File:Comephorus baikalensis.jpg
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-like 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.

Description

Comephorus have translucent bodies with no scales. 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. Lack of a swim bladder, high lipid content and porous bones allow the fish to tolerate varying pressure extremes as they move through the water column. Over a third of their body weight (38.9%) is oil. The common name golomyanka literally means 'naked.

Species

There are currently two recognized species in this genus:

• Comephorus baikalensis (Pallas, 1776) (Big Baikal oilfish)
• Comephorus dybowskii (Korotneff, 1904) (Little Baikal oilfish)

Biology and ecology

They are the principal ecological competitor to the omul, and represent a primary food source for the nerpa seal. They are easily identifiable, and are large enough (at 15-20 centimeters) to be easily seen. Golomyankas are unusual for their habit of moving throughout the entire water column of Lake Baikal without much regard for changes in pressure, although they can exist only within a very narrow range of temperatures. They are considered the world's most abyssal freshwater fish. They are also known for rapidly decomposing in sunlight, leaving behind fat, oil, and bones.

The biomass of the golomyanka population is estimated at 100 to 150 thousand tons, making it one of the most populous forms of vertebrate life in Lake Baikal. They are extensively preyed upon by nerpa, for which the golomyanka are the primary food source. Food sources for the golomyanka are fairly varied, including their own young and pelagic crustaceans. Shoaling behavior is not known for this species, and the females do not lay eggs; rather, they are viviparous, producing a swarm of 2000-3000 larvae when they reach sexual maturity at two to three years.

Relationship to humans

Due to their solitary lives, golomyankas are not harvested commercially, although their fats and oils are used medicinally when storms toss them up on shore. They are valued primarily as the principal food source for the Baikal seal nerpa, which are harvested commercially. They are so numerous and spawn so rapidly that they represent the largest concentration of fish biomass within the entire lake, and would seriously unbalance the ecosystem of Lake Baikal if not constantly fed upon by predators.

See also

• List of fish families

References

• Ichthyofauna of Lake Baikal from Baikal Web World, accessed May 5, 2006 (with a photo of the golomyanka).
• Lake Baikal FAQ Irkutsk State University Lake Baikal FAQ, accessed May 5, 2006
• Animals and plants of Lake Baikal from Irkutsk State University, accessed May 5, 2006<
• Lipids and fatty acids of two pelagic cottoid fishes (Comephorus spp.) endemic to Lake Baikal, T.A. Kozlovaa and S.V. Khotimchenko, accessed July 31, 2010