The pollan or Irish pollan (''Coregonus pollan'' or ''Coregonus autumnalis'' IFI Inland Fisheries Ireland (accessed 1 June 2015)) is a freshwater whitefish known only from five Irish lakes,
Lough Neagh
Lough Neagh ( ) is a freshwater lake in Northern Ireland and is the largest lake in the island of Ireland, the United Kingdom and the British Isles. It has a surface area of and supplies 40% of Northern Ireland's water. Its main inflows come ...
, Lower
Lough Erne
Lough Erne ( , ) is the name of two connected lakes in County Fermanagh, Northern Ireland. It is the second-biggest lake system in Northern Ireland and Ulster, and the fourth biggest in Ireland. The lakes are widened sections of the River Erne, ...
,
Lough Ree
Lough Ree () is a lake in the midlands of Ireland, the second of the three major lakes on the River Shannon. Lough Ree is the second largest lake on the Shannon after Lough Derg. The other two major lakes are Lough Allen to the north, and Loug ...
, Lough Derg and Lough Allen. The pollan faces competition from introduced species such as
pike
Pike, Pikes or The Pike may refer to:
Fish
* Blue pike or blue walleye, an extinct color morph of the yellow walleye ''Sander vitreus''
* Ctenoluciidae, the "pike characins", some species of which are commonly known as pikes
* ''Esox'', genus of ...
,
roach
Roach may refer to:
Animals
* Cockroach, various insect species of the order Blattodea
* Common roach (''Rutilus rutilus''), a fresh and brackish water fish of the family Cyprinidae
** ''Rutilus'' or roaches, a genus of fishes
* California roach ...
and zebra mussel, and the populations rely on restocking for survival.
Conservation status
The pollan populations are threatened by ecosystem changes such as
eutrophication
Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus. It has also been defined as "nutrient-induced increase in phytopla ...
and increases in species, including
pike
Pike, Pikes or The Pike may refer to:
Fish
* Blue pike or blue walleye, an extinct color morph of the yellow walleye ''Sander vitreus''
* Ctenoluciidae, the "pike characins", some species of which are commonly known as pikes
* ''Esox'', genus of ...
,
roach
Roach may refer to:
Animals
* Cockroach, various insect species of the order Blattodea
* Common roach (''Rutilus rutilus''), a fresh and brackish water fish of the family Cyprinidae
** ''Rutilus'' or roaches, a genus of fishes
* California roach ...
and zebra mussel. Only the population of Lough Neagh in
Northern Ireland
Northern Ireland ( ga, Tuaisceart Éireann ; sco, label= Ulster-Scots, Norlin Airlann) is a part of the United Kingdom, situated in the north-east of the island of Ireland, that is variously described as a country, province or region. Nort ...
remains abundant and supports a small commercial fishery. The other Northern Irish population in Lough Erne has severely declined. The Lough Allen population was only confirmed for the first time in 2006.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. Biology and Environment: Proceedings of the Royal Irish Academy 110B, 69-74. Other populations rely on stocking for their survival.Freyhof, J. & Kottelat, M. (2008 ''Coregonus pollan'' IUCN Red List of Threatened Species. Version 2010.1. Downloaded 25 April 2010.
Description
The Irish pollan and other members of the '' Coregonus'' genus are very like
herring
Herring are forage fish, mostly belonging to the family of Clupeidae.
Herring often move in large schools around fishing banks and near the coast, found particularly in shallow, temperate waters of the North Pacific and North Atlantic Oceans, i ...
s 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 and a weight of .
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.
Classification
In scientific literature and national biodiversity and conservation assessments, the Irish pollan are usually classified within the species ''
Coregonus autumnalis
Arctic cisco (''Coregonus autumnalis''), also known as omul russian: Омуль, is an anadromous species of freshwater whitefish that inhabits the Arctic parts of Siberia, Alaska and Canada. It has a close freshwater relative in several lakes of ...
''. That is a widespread
anadromous
Fish migration is mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousan ...
whitefish which inhabits coastal waters and rivers of Arctic
Siberia
Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a part of ...
,
Alaska
Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...
, and
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
and is there known as the Arctic cisco or Siberian omul. ''C. autumnalis'' is not distributed elsewhere in northwestern Europe, and the pollan are often given a status of
subspecies
In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...
as ''Coregonus autumnalis pollan''.Ferguson, A Northern Ireland Priority Species: ''Coregonus autumnalis pollan'' – Pollan habitats.org.uk (read April 2010) These classifications are based on the close genetic similarity of the Arctic and Irish whitefish populations.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. By
IUCN
The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
and in the
FishBase
FishBase is a global species database of fish species (specifically finfish). It is the largest and most extensively accessed online database on adult finfish on the web.
, the Irish pollan is, however, listed as a distinct fish species ''Coregonus pollan''.
Unlike its Arctic relatives, the Irish pollan does not migrate to the sea.