Lough Neagh, some 150 square miles in area, has the distinction of being the largest lake in the British Isles. Its drainage or catchment basin takes in 40 per cent of the total area of Northern Ireland; within this basin live about 250,000 people. A survey of the lough undertaken for the Admiralty by a Lieutenant Graves in 1835 showed that most of it is very shallow with an average depth of less than 20 feet. An exception is the relatively deep trench in Toome Bay which goes down to slightly over 100 feet. The lough's level has fluctuated considerably at different times in the past but it is now maintained at 52 feet O.D. This large, almost rectangular lough dominates the lowland centre of Northern Ireland, but throughout history it has acted not as unifier but as a cultural divide and barrier to communications between east and west Ulster.
The lough shores show a remarkable continuity of settlement dating from about 6000 B.C. when Mesolithic arrivals from the coast began to fish its waters and hunt its wild fowl. Old customs allied to anthropometric evidence suggest that the present tightly knit fishing community may well be descendants of these first Irishmen.
In the 12th century Lough Neagh and the Lower Bann formed the frontier between John de Courcy's Ulidia (Antrim and Down) and the native Irish territories west of the inland sea. This frontier was marked by a line of mottes at Ballycairn, Mill Loughan, Harryville (Ballymena), Edenduffcarrick, Donegore, Antrim, Crumlin, Glenavy and Clanrolla. The motte on Coney Island was either an outpost or an Irish imitation.
During the 14th and 15th centuries Lough Neagh was dominated by the O'Neills. The great O'Neills of Tyrone lorded it over the western and south-eastern shores, while the Clandeboye O'Neills established themselves at Shane's Castle. However, in Elizabethan times this O'Neill supremacy was attacked. Sir Henry Sidney, the Lord Deputy, marched against Shane O'Neill, captured his treasury on Coney Island, and gave Lough Neagh a new name - Lough Sidney. In 1597 a force from Carrickfergus captured Shane's Castle which be-came one of the bases for Sir Arthur Chichester's naval task force of 'one barque, close decked, of 30 tons, one boat of 14 tons, and two at 10 tons ... the charge of the barque and boats, £721. 5s. 1½d...'
With these vessels attacks were made on the western shore and on Killultagh. The exercise of this 'sea-power', combined with Mountjoy's attack across the river Blackwater, led to the fall of Dungannon, the destruction of Tullahogue and the surrender of Hugh O'Neill in 1603. The Elizabethan conquest was consolidated by the building of forts at Charlemont and Mountjoy, "a fair castle of stone and brick ... compassed about with a good strong rampier of earth, well ditched and flanked with bulworkes." North-west of Lough Neagh the oak forest of Glenconkein, "a very fast country, by reason of the woods, bogs and bordering mountain" was at last subdued and planted with settlers by the Salters' Company. Their bawn, Salters' Castle, was a typical 'strong house' of the early 17th century, comparable to the Vintners' Bawn at Bellaghy and that at Movanagher on the Lower Bann.
The later 17th century saw the growth of such towns as Lurgan, Portadown and Dungannon and the building of country houses like Springhill (near Moneymore), Carrickblacker and Massereene. Lough Neagh now began to be looked on as the obvious centre for a system of inland navigation, and by the end of the 18th century it was possible to travel by water from Portadown and Lurgan to Newry, Belfast and Coalisland. Steamers appeared on the lake c. 1820 and William Dargan, the famous railway builder, completed the Ulster Canal from the Blackwater to the Erne at Wattle Bridge in 1842, and operated steamboat services from Kinnegoe to Ballyronan and Newport Trench: "By these conveyances Cabin Passengers by the Second Class railway carriages for 2 shillings , and with all the comforts of steamboat and railway travelling" ... "The Tyrone and Derry shores are all alive - sharp is the word - to Belfast and back same day, with the money in their pockets for the rates". (Belfast News-Letter, May 1842). The necessities of flood control led to the lowering of the lough level by nine feet in 1859 and the construction of locks on the lower Bann, 1860-3. This put a stop to the steamer services.
The isolation of the Lough was completed by the completion of the railway network in the seventies, and its shores and coves were left once more to the fishermen. As many as 350 fishermen using 160 boats still fish Lough Neagh (there were 900 fishermen at the beginning of this century). Eels are by far the most important catch although small quantities of trout and pollan are also taken. The fishing boats are clinker-built with fixed thole pins instead of rowlocks, also a feature of sea-going curraghs. They are usually found in sheltered, artificially deepened 'coves'.
Eels are fished by draft nets and long lines which have thousands of baited hooks. Those caught in the lough are yellow or immature eels unlike the mature silver eels which are caught at the weirs along the lower Bann when they migrate to spawn in the Atlantic. Disputes over fishing rights for eels reached the House of Lords on two occasions in the last 100 years. Today lough fishermen may fish for unrestricted amounts of eels provided they use legal gear. The use of illegal Dutch trawls is causing some concern about depletion of stocks. Pollan were once important but over-fishing probably caused some of the severe fluctuations in catch which mark its history. Once steam communications with English markets were established at the close of the last century eels became by far the more important attraction for the fishermen.
Lough Neagh's considerable potential is threatened by pollution or rather eutrophication (enrichment) by phosphates and nitrates which find their way into its waters as waste materials of urban, industrial and agricultural uses. They allow a population explosion to take place among certain of the algae which inhabit its shallow waters. Algae bloom, such as occurred in the summer of 1967, may look unpleasant on the surface of the lough but more seriously it can cause deoxygenisation of the lower layers which if prolonged could destroy the infamous Lough Neagh fly (Chironomous anthracinus and Glytotendipes paripes) and thus a major part of the food supply of eels and other fish. In terms of eutrophication, in some respects Lough Neagh is already ahead of Lake Erie.
Lough Neagh spotlights the complex problems of multiple use of an important natural resource. It acts both as a major source of freshwater and as a sink for increasing amounts of waste materials. It provides large quantities of sand and gravel, carries bird populations of international importance and its eel fishery, the largest in Western Europe, gives much employment.
In addition its waters and shorelands have an important re-creational potential especially in the Craigavon area. By 1990 an additional 150,000 people may be living in its catchment basin. It needs little stressing that a close check should be kept on all activities which might aggravate the Lough's problems.