Norway pollock
| Norway pollock | |
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T. finnmarchica
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| Theragra finnmarchica Einar Koefoed, 1956[1]
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Theragra finnmarchica or Norway pollock is a rare fish of family Gadidae (codfish) only known from the Barents Sea. Until recently, its known range would have made it an endemic species to Norway, but one specimen was captured from Russian waters in 2004.[2] Moreover, current evidence suggests that T. finnmarchica is the same species as Alaska pollock (Theragra chalcogramma or Gadus chalcogrammus). The range of T. finnmarchica is fully separate from Alaska pollock, and the history of T. finnmarchica in the Barents Sea remains a mystery.[3]
Description
Theragra finnmarchica was described as a new species to science by Norwegian zoologist Einar Koefoed in 1956,[1] based on two specimens landed in Berlevåg, northern Norway, in 1932 (hence the Norwegian name, "Berlevågfisk"). Based on morphological differences, Koefoed considered T. finnmarchica a new species related to but separate from T. chalcogramma.
Current status
Until recently, Theragra finnmarchica was known only from very few specimens. Between 1957 and early 2002, seven specimens were caught.[4] However, in 2003–2004, 31 new specimens were caught. All specimens were large (465–687mm in total length) and caught in the coastal waters between Vesterålen in the west and Varangerfjord in the east. By 2006, 54 individuals had been recorded.[5]
Sequencing of mitochondrial DNA of two specimens of T. finnmarchica and 10 T. chalcogramma revealed no significant genetic differences, leading Ursvik et al.[6] to suggest that T. finnmarchica and T. chalcogramma are the same species. An analysis of a much larger material (44 T. finnmarchica and 20 T. chalcogramma) using both genetic and morphological methods led to similar conclusions.[5] While the putative species could not be separated genetically, they showed some consistent differences in morphological characters. Nevertheless, only one character showed no overlap. Byrkjedal et al.[5] conclude that T. finnmarchica should be considered a junior synonym of T. chalcogramma. These analyses also suggest that T. finnmarchica is a near relative of the Atlantic cod, and that both Alaska and Norway pollock should be moved to genus Gadus.[5]
T. finnmarchica is listed as Near Threatened in the 2010 Norwegian Red List for Species[7] based on criteria D1: "Very small or geographically very restricted population: Number of mature individuals". It is currently not listed in the IUCN Red List.
References
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