The Roogagh River is one of the main tributaries for Lough Melvin. It flows through Garrison, a small village in County Fermanagh, Northern Ireland, 5 miles south of Belleek, at the eastern end of Lough Melvin.
Lough Melvin is home to the Gillaroo or 'Salmo stomachius' - a species of trout which eats primarily snails. Gillaroo is derived from the Gailge or Irish for Red Fellow (Giolla Rua). This is due to the fishes distinctive colouring. It has a bright buttery golden colour in its flanks with bight crimson and vermilion spots. The gillaroo is characterised by deep red spots and a "gizzard" which is used to aid the digestion of hard food items such as water snails. Experiments carried out by Queens University, Belfast established that the L. Melvin cannot be found anywhere else in the world. They feed almost exclusively on bottom living animals (snails, sedge fly larva and freshwater shrimp) with the exception of late summer. It is at this time that they come to surface to feed and may be caught on the dry fly. Other lakes reputed to contain the gillaroo are L. Neagh, L. Conn, L. Mask and L. Corrib. However the unique gene found in the L. Melvin trout has not been found in some 200 trout populations in Ireland and Britain.
Legend has it that St Brigid was offered chicken to eat on a Friday as she walked through Garrison (a big no-no to Catholics) and she was so enraged she threw the entire bird into the river where it changed into a fish, hence the "gizzard".
The sonaghon trout (Salmo nigripinnis) is another species unique to Lough Melvin. It can have a light brown or silvery hue with large, distinctive black spots. There are sometimes small, inconspicuous red spots located along its posterior region. Its fins are dark brown or black with elongated pectorals. Sonaghen are found in areas of open, deep water, where they feed on mid-water planktonic organisms.