Pollan Fish

The Pollan (Coregonus autumnalis) is a freshwater salmonid fish and is one of the few Irish species that is not found elsewhere in western Europe outside Ireland.

From a conservation viewpoint, it is one of the most important components of Irish biodiversity.

Over the past 20 – 30 years, a dramatic decline in pollan fish numbers has been observed, especially in Lough Erne and Lough Neagh – the largest lake in Britain and Ireland and holds the healthiest population of pollan in Ireland.

This reduction has prompted a number of conservation and restoration measures (e.g. the UK Biodiversity Plan). This project aims to use modern molecular methodologies to provide essential genetic information required for the proper management and conservation of this important member of the native Irish fauna.

Where To Find Pollan Fish

Elsewhere, populations may be found in Loughs Ree and Derg and on the Shannon system in the Irish Republic. Little is known about the status or abundance trends of these populations.

The Pollan fish has a silvery body with an adipose fin (typical of the salmon family). Very similar to other white fishes such as Vendace, Schelly and Powan, which occur in Britain. The Pollan fish can weigh up to 1.2 kilograms, however, 170 grams (10 ouces) is its more usual size.

The Pollan fish diet varies from river to river – in the Lough Neagh it feeds upon Mysis relicta and other insects, whereas in the Lough Derg it typically feeds upon planktonic crustaceans.

The perceived threats are the usual suspects, namely, water enrichment and introduction of non-native fish species (particularly roach).

Distribution outside of Ireland includes the Arctic and is an anadromous species around Alaska, Northern Canada across to eastern Siberia and is known as the Arctic cisco. A landlocked population similar to that in Lough Neagh occurs in Lake Baikal.

Appearance and Physical Features

The Pollan is a slender, streamlined fish well suited to life in the open water of large lakes. Its body is covered in fine silver scales that give it a bright, almost metallic sheen, and the belly is pale white. The back is a darker grey-green, which provides some degree of camouflage from above. Like all members of the salmon family, the Pollan has a small fleshy fin on its back known as the adipose fin, positioned between the main dorsal fin and the tail. This feature is one of the most reliable ways to identify it as a salmonid.

The mouth is small and positioned at the front of the head, reflecting the Pollan’s feeding habits as a filter feeder and plankton consumer rather than an active predator of larger prey. The tail is forked and the overall body shape is typical of a fish built for sustained, energy-efficient swimming in deep, open water.

Behaviour and Habitat

The Pollan is a shoaling species, meaning it tends to move and feed in groups rather than as solitary individuals. These shoals can be found at a range of depths depending on the time of year and the availability of food, but the fish generally favours the cooler, deeper water of large lakes during the warmer months. As temperatures drop in autumn, the fish moves into shallower areas, and it is during this season that spawning takes place, which is reflected in the species name autumnalis.

Pollan prefer clear, well-oxygenated water and are sensitive to changes in water quality. This sensitivity makes them a useful indicator species, as a decline in Pollan numbers often signals wider problems with the health of the lake ecosystem in which they live. The species does not tolerate poor water conditions well and tends to disappear from lakes that have been significantly affected by pollution or nutrient enrichment.

Conservation Challenges

The decline of the Pollan in Ireland is a serious conservation concern, and the reasons behind it are not always straightforward. Water enrichment, also known as eutrophication, is one of the primary factors. When excess nutrients from agricultural run-off or sewage enter a lake, they encourage the growth of algae and aquatic plants, which reduces water clarity and lowers oxygen levels. These changes make the habitat less suitable for a species like the Pollan that requires clean, well-oxygenated conditions.

The introduction of non-native fish species has also played a significant role. Roach, which were introduced to Irish waters relatively recently on an evolutionary timescale, compete directly with Pollan for food and have been shown to have a considerable impact on Pollan populations in lakes where both species coexist.

Efforts to protect the Pollan have included habitat management, water quality improvement schemes and research into the genetic diversity of remaining populations. Maintaining healthy and genetically varied populations across multiple lakes is seen as essential to the long-term survival of the species in Ireland, as it reduces the risk that a single damaging event could wipe out the entire national population.

Sources & References

• Animal Diversity Web — Coregonus pollan
• Wikipedia — Coregonus pollan

Joanne Spencer (2026, April 9). Pollan Fish. Animal Corner. Retrieved 2026, October 10, from https://animalcorner.org/animals/pollan-fish/

Joanne Spencer. "Pollan Fish." Animal Corner, 2026, April 9, https://animalcorner.org/animals/pollan-fish/.