The pollan is endemic to Ireland, which means that it is a native species that is only found in Ireland, making it a very special part of our natural heritage. The pollan is usually classified as a species within the genus Coregonus, which are a diverse group of species known collectively as whitefish in the fish family Salmonidae, along with salmon, trout and char. The pollan (Coregonus pollan) is very closely related to the Arctic cisco (Coregonus autumnalis), which inhabits the Arctic regions of Siberia, Alaska and Canada.
The pollan is sometimes considered to be a subspecies (Coregonus autumnalis pollan) of Arctic cisco that has become a glacial relict, which means that pollan populations became isolated as the range of Arctic cisco contracted northwards following the retreat of colder environments at the end of the last ice age. Pollan populations are believed to have dispersed into Ireland's river systems thousands of years ago when they were connected by melting glacier water but subsequently became isolated as large lakes formed. Today, they only survive in Lough Allen, Lough Ree and Lough Derg on the River Shannon, as well as Lough Erne and Lough Neagh. The Lough Neagh population is the most abundant population and is fished commercially.
Pollan are a shoaling fish that feed on planktonic invertebrates in lakes and typically live for about five years. The conservation status of pollan in Ireland is classified as vulnerable. Pollan are threatened by introduced species, including predation by pike and competition for food with roach, as well as warmer water temperatures due to climatic change and nutrient enrichment that reduces the quality of the cool, well-oxygenated waters that they prefer to live in.