Dollaghan are a variety of brown trout

Brown trout

The brown trout and the sea trout are fish of the same species....

 (Salmo trutta) native to Lough Neagh

Lough Neagh

Lough Neagh, sometimes Loch Neagh, is a large freshwater lake in Northern Ireland. Its name comes .-Geography:With an area of , it is the largest lake in the British Isles and ranks among the forty largest lakes of Europe. Located twenty miles to the west of Belfast, it is approximately twenty...

, Northern Ireland

Northern Ireland

Northern Ireland is one of the four countries of the United Kingdom. Situated in the north-east of the island of Ireland, it shares a border with the Republic of Ireland to the south and west...

, and many of its tributaries. They are a potamodromous

Fish migration

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 thousands of kilometres...

 migratory

Fish migration

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 thousands of kilometres...

 trout spending much of the year in the lough, returning to the rivers in autumn to spawn

Spawn (biology)

Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...

. Dollaghan are much sought after by anglers in County Antrim

County Antrim

County Antrim is one of six counties that form Northern Ireland, situated in the north-east of the island of Ireland. Adjoined to the north-east shore of Lough Neagh, the county covers an area of 2,844 km², with a population of approximately 616,000...

 due to their greater size in comparison to the non-migratory trout found in streams such as the Kells Water

Kells Water

The Kells Water is a small river in County Antrim, Northern Ireland. It flows through Moorfields and Kells and is a tributary to the River Main. The river rises above Glenwherry. It is a continuation of the Glenwhirry River and eventually joins the Main, which in turn flows into Lough Neagh. The...

, Six Mile Water

Six Mile Water

The Six Mile Water is a river in southern County Antrim, Northern Ireland. It was historically called the Ollar and is known in Irish as Abhainn na bhFiodh. The Six Mile Water is an indirect tributary of the River Bann, via Lough Neagh...

, Moyola River

River Moyola

The River Moyola or Moyola River stretches for approximately 27 miles from the Sperrin Mountains to Lough Neagh. The Moyola starts a small river for the first few miles of its length and proceeds to expand to a medium sized river and then to a large river for its last couple of miles before...

 and River Main. They are often caught at in the dark in methods very similar to that of fishing for sea trout.
Many anglers regard them as an elusive species and call them 'sea trout of lough neagh'.
Their weight varies greatly - from small fish of aroiund 1/2 lb to large specimens of over 10 lb.
There is generally 4 species of brown trout in Ireland. Dollaghan, Gillaroo

Gillaroo

Gillaroo , is the name of a species of trout which eats primarily snails and is only proven to inhabit Lough Melvin in Ireland.Gillaroo is derived from the Irish for Red Fellow ; this is due to the fish's distinctive colouring. It has a bright, buttery golden colour in its flanks with bright...

, Sonaghan and Ferox

Ferox

Ferox is a Latin word meaning "fierce". It may also refer to:*Cannibal Ferox, a 1981 film by Umberto Lenzi *Aconitum ferox, a flowering plant of the Ranunculaceae family...

. The Dollaghan is thought to have evolved from sea trout which were land locked many years ago.