Lough Neagh Pollan: Difference between revisions

Latest revision as of 14:26, 3 December 2018

A member of the Salmonid family, Lough Neagh Pollan is the name given to the lacustrine fish of the species Coregonus pollan which are harvested as a wild fish. Lough Neagh Pollan have been genetically ascribed as unique to Lough Neagh. As a consequence, they can only be harvested from the defined geographical area of Lough Neagh.

In appearance, the Lough Neagh Pollan are bright silver in colour, with dark dorsal colouration and pale fins. They are physically distinguished from other Coregonids in the British Isles by having:

— a lower jaw that does not project

— 41-48 gill rakers

— 74-92 lateral line scales

The minimum marketable size limit for Lough Neagh Pollan is 205 mm in length. Fish of this size typically range in age from 3-4 years and 76-210 g in weight. Lough Neagh Pollan are sold whole gutted or filleted, which are either fresh or frozen. Uncooked, Lough Neagh Pollan has a mild, delicate fish aroma. The flesh is a glossy, pale white colour with a slight pink tint and the descaled skin is a shiny silver. After cooking, the flesh is white and shiny. The aroma and taste are delicate with a pleasant earthiness and mild fish flavour. The texture is smooth with medium softness, and often considered as quite meaty, for a fish of this size.

Lough Neagh Pollan must be caught and processed in the defined geographical area using the traditional draft netting and gill netting (known locally as trammel netting) method. Processing occurs in two ways depending on customer requirements; whole gutted or filleted.

— Processing of whole gutted Lough Neagh Pollan involves descaling, evisceration and cleaning

— There is no set procedure for the filleted version and filleting can be completed by hand or in larger operations, using industrial equipment

The geographical area consists of Lough Neagh, Northern Ireland and includes the on-shore area incorporated within a 2-mile (3 km) perimeter of the lough’s shoreline, within which all processing of Lough Neagh Pollan occurs. Pollan are the only European vertebrate found uniquely in Ireland, where their entire distribution is limited to the following five loughs:

— Lough Allen

— Lough Ree

— Lough Derg

— Lough Erne (Lower)

— Lough Neagh

Lough Neagh, with an area of 151 square miles (392 km2), and an average depth of 8,9 m, is the largest lake in the British Isles and one of the largest lakes in north-western Europe. It is fed from eight afferent rivers and drains to the sea via the Lower River Bann at its northern end. Lough Neagh Pollan are a lake-only species and are not found in the surrounding tributaries. The characteristics of the Lough Neagh Pollan are linked to the environment where it grows, which in turn have contributed to the development of the traditional draft netting and gill netting (known locally as trammel netting) methods used in its capture.

The characteristics of the Lough Neagh Pollan are a product of genetic divergence from its closest living relative, the Arctic Omul (circa 200 000 years ago), and its survival and subsequent confinement in a restricted geographical area. As the sea temperature and salinity increased, Pollan lost its migratory behaviour and became restricted to freshwater habitats such as that of Lough Neagh. Unlike all other members of the Cisco whitefish family, which are found in Arctic climes, Pollan evolved to exist in temperate waters. DNA analysis indicates that Pollan colonised Lough Neagh after the Saalian ice age, circa 200 000 years ago, whilst the other Irish populations became resident during the Devensian glacial period circa 40 000 years ago (pers comm. Ensing). Pollan are the only European vertebrate found uniquely in Ireland, whilst those in Lough Neagh are the only viable population of commercially exploitable Pollan in the world.

A genetic study into Irish Pollan (Coregonus pollan) stocks from Loughs Ree, Allen, Neagh and Erne using a suite of 10 microsatellite markers indicates relatively large genetic differentiation at these markers among the three main genetic clusters; Lough Neagh, Lough Erne and Lough Allen/Ree. Such results demonstrate that the Lough Neagh Pollan is genetically distinct from all other Pollan populations.

The large number of rivers flowing into Lough Neagh result in high sediment deposits. These sediments are very dark and are composed of silts and clays, organic matter and diatom frustules. The silts and clays are primarily derived from river-borne suspended material whilst the organic matter originates partly from catchment sources and partly from material produced within Lough Neagh. As a result Lough Neagh is rich in nutrients (hypereutrophic) and is continually aerated by circulating winds, which ensures that the enriched nature of the lough does not precipitate a dramatic loss of oxygen in the warmer months.

The combination of feedstuffs and retained oxygen levels means that Lough Neagh sustains an enhanced invertebrate population, which in turn supports the production of the only commercially exploitable Pollan population in the world. The nature of the sediment makes it a suitable habitat for the multitude of invertebrate life resident in the Lough.

Lough Neagh Pollan feed on plankton, insect larva (mainly chironomids) and the glacial relict crustacean Mysis salemaai which constitutes the major proportion of the diet of Lough Neagh Pollan. The ready availability of this invertebrate-based diet, together with the hypereutrophic status and well-mixed nature of the lough, contributes to the Lough Neagh Pollan’s characteristically fast growth rate. Lough Neagh Pollan exhibit a wide distribution throughout the lough, but have preferred habitats, linked to life history stage, topography, substrate, water depth and season.

No similar fish species to Pollan exist in Lough Neagh; however, the other Lough Neagh resident Salmonid, brown trout (Salmo trutta L.) reaches a length of 99 mm end of year 1, and 162 mm end of year 2. Brown trout mature at age 3 (living up to 8 years) and leave Lough Neagh to spawn during autumn in the surrounding afferent rivers. Compared to such fish, Lough Neagh Pollan are fast-growing and short-lived, averaging 140 mm at the end of their first year, and 170 mm at the end of their second year. Maturing at 2 years of age and with an average life span ranging 3-4 years, Lough Neagh Pollan spawn in December in shallow areas of Lough Neagh, depositing eggs on gravel or rock sub-strata.

Only Lough Neagh contains sufficient stock to support a commercial fishery, as the other Irish loughs contain only small residual populations. Before 1900, the harvesting of Lough Neagh Pollan dominated fishing activities on the lough. It is still considered an economically important species and depending on the time of year Lough Neagh Pollan makes up a significant proportion of catches. While various historical records indicate that Lough Neagh Pollan have been a key component of the food heritage of the region for hundreds of years, it is still revered for its unique appeal among the most discerning of consumers today, in the 21st century.

Reference: The European Commission

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