Pollan (fish)

The pollan[3] or Irish pollan[2] (Coregonus pollan[2] or Coregonus autumnalis[3]) is a freshwater whitefish known only from five Irish lakes, Lough Neagh, Lower Lough Erne, Lough Ree, Lough Derg, and Lough Allen. The Irish pollan faces competition from introduced species such as pike, roach, and zebra mussel and the populations rely on restocking for survival.

Pollan
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Salmoniformes
Family: Salmonidae
Genus: Coregonus
Species:
C. pollan
Binomial name
Coregonus pollan
Synonyms
  • Coregonus autumnalis pollan Thompson, 1835
  • Coregonus elegans Thompson, 1839
  • Coregonus altior Regan, 1908 [2]

Conservation status

The pollan populations are threatened by ecosystem changes such as eutrophication and increases in species, including pike, roach, and zebra mussel.[4] Only the population of Lough Neagh in Northern Ireland remains abundant and supports a small fish commercial fishery. The other Northern Irish population in Lough Erne has severely declined.[4] The Lough Allen population was only confirmed for the first time in 2006.[5] Other populations rely on stocking for their survival.[6]

Description

The Irish pollan and other members of the Coregonus genus are very like herrings in appearance but the presence of an adipose fin distinguishes them. The mouth is relatively small and the teeth are deciduous and very small. The scales are of moderate size, the dorsal fin is of moderate length and the tail fin deeply forked. The different species are difficult to tell apart unless the lake from which they originated is known. This species grows to an average length of 9 to 10 in (22.9 to 25.4 cm) and a weight of 6 ounces (170 g).[7]

Ecology

The Irish pollan is a shoaling species. The diet consists small crustaceans and insect larvae. Breeding takes place in November and December, with spawning taking place over hard ground in deep water.[7]

Classification

In scientific literature and national biodiversity and conservation assessments, the Irish pollan are usually classified within the species Coregonus autumnalis. That is a widespread anadromous whitefish which inhabits coastal waters and rivers of Arctic Siberia, Alaska, and Canada and is there known as the Arctic cisco or Siberian omul.[3][5][8][9] C. autumnalis is not distributed elsewhere in northwestern Europe, and the pollan are often given a status of subspecies as Coregonus autumnalis pollan.[4][10] These classifications are based on the close genetic similarity of the Arctic and Irish whitefish populations.[11][12][13] By IUCN and in the FishBase, the Irish pollan is, however, listed as a distinct fish species Coregonus pollan.[6][2]

Unlike its Arctic relatives, the Irish pollan does not migrate to the sea.[7]

References
  1. "Ireland, Red List No.5: Amphibians, Reptiles & Freshwater Fish" (PDF). IUCN. Retrieved 5 March 2020.
  2. Froese, Rainer and Pauly, Daniel, eds. (2016). "Coregonus pollan" in FishBase. April 2016 version.
  3. Pollan IFI Inland Fisheries Ireland (accessed 1 June 2015)
  4. Ferguson, A: Northern Ireland Priority Species: Coregonus autumnalis pollan – Pollan habitats.org.uk (read April 2010)
  5. Harrison, A.J., Kelly, F.L., Rosell, R.S., Champ, T.W.S., Connor, L. and Girvan, J.R. (2010) First record and initial hydroacoustic stock assessment of pollan Coregonus autumnalis Pallas in Lough Allen, Ireland. Archived 2011-06-15 at the Wayback Machine Biology and Environment: Proceedings of the Royal Irish Academy 110B, 69-74.
  6. Freyhof, J. & Kottelat, M. (2008) Coregonus pollan IUCN Red List of Threatened Species. Version 2010.1. Downloaded 25 April 2010.
  7. Jenkins, J. Travis (1925). The Fishes of the British Isles. Frederick Warne & Co. pp. 240–242.
  8. All-Ireland Species Action Plan: Pollan (Coregonus autumnalis) Archived 2010-06-13 at the Wayback Machine Northern Ireland Environmental Agency 2006
  9. National action plan - Coregonus autumnalis (Pollan) UK Biodiversity Action Reporting System. (read April 2010)
  10. Andrew J. Harrison, Lynda Connor, Emma Morrissey and Fiona Kelly (2012) Current status of pollan Coregonus autumnalis pollan in Lough Ree, Ireland. Archived 2014-07-14 at the Wayback Machine Biology and Environment: Proc. Royal Irish Academy 112B, 1-9 DOI: 10.3318/BIOE.2012.09
  11. Ferguson, A., Himberg, K.-J.M., & Svärdson, G. (1978). Systematics of the Irish pollan (Coregonus pollan Thompson): an electrophoretic comparison with other Holarctic Coregoninae. Journal of Fish Biology 12, 221-233.
  12. Bodaly, R.A., Vuorinen, D.A., Ward, R.D., Luczynski, M., & Reist, J.D. (1991). Genetic comparisons of the New and Old World coregonid fishes. Journal of Fish Biology 38, 37-51.
  13. Politov, D.V., Gordon, N.Y., & Makhrov, A.A. (2002). Genetic identification and taxonomic relationships of six Siberian species of Coregonus. Archiv für Hydrobiologie: Special Issues Advances in Limnology 57, 21-34.
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