The hunter hunted

`There was never a pike. . . as yet engendered in all this countrey, nor in the adjacent parts of Mayo or Galway counteys," wrote Roderic O'Flaherty, gentleman naturalist, in 1682. He was talking of the region around Lough Corrib and its sister lakes, Mask and Carra, and of a fish whose name in Irish, gailliasc, then clearly marked it out as a foreigner in an Ireland abounding in trout and salmon.

Three centuries later, control of the pike is Ireland's longest-running venture in conservation management - not 300 years old, indeed, but now almost 50. In its newest phase of intensive culling of pike, the scientists of the Western Regional Fisheries Board are trying to halt the decline of the trout in the three western lakes and restore them as salmonid ecosystems, precious to Europe and almost unique in the world. The pike, Esox lucius, is the one freshwater fish that looks you in the face with both eyes at once, perhaps its most unsettling feature next to its jutting jaws and spiny teeth. It hunts like a tiger, moving from one clump of waterweed to the next, and then dashing from cover with a lightning propulsion of tail and fins. It swallows its prey head first, like a heron or a snake, and takes the rest of the day off to digest it, hanging still and huge in mid-water.

Neither ugliness nor menace are in the pike's disfavour. As a predator it has its own lithe and muscular beauty, "green tigering the gold" in Ted Hughes's image. Pike anglers go into raptures about its power and speed. Unfortunately, they would also set no bounds to its empire and become incensed at the heavy culling, year after year, that is needed to restrain its dominance in a lake.

The pike inhabits a great swathe of the northern hemisphere, right across Europe and Asia and the centre of North America. But, at the end of the last Ice Age, Ireland was severed from the continental land mass before any purely freshwater fish could recolonize its rivers or lakes. Up to the 12th century, these were almost exclusively held by salmon, trout and eels, which came in from the sea.

Pike was probably introduced first by the Normans, for food, and it now hunts through all our angling waters, with the notable exceptions of Lough Leane and Lough Melvin. By the 1950s, when the new Inland Fisheries Trust began its rearguard attempts at control, the toll of predation on the trout of Corrib and Mask was one of the telling statistics produced by fisheries scientists. Studying the prey in the stomachs of some 1,170 pike weighing more than five tonnes, they estimated that, in the year before they were killed, the fish had eaten over 46 tonnes of trout and 11 tonnes of coarse fish, mainly perch.

Pike culling continued on the western lakes from 1959 to 1983, part of a massive campaign against the fish in a dozen prime trout lakes across the island. But then netting in the west was stopped when money ran out in the early 1980s. Pike expanded rapidly, both in numbers and size, and by 1995 those in Lough Corrib were estimated to be eating more than 255,000 catchable trout in a year.

Their diet changes as they grow. In the rich Irish lakes the food of small pike, up to 40cm, is almost all invertebrates such as water-lice and shrimps, with a leavening of sticklebacks. After that size, even with other fish to choose from, the pike hunt trout selectively, and bigger pike catch bigger trout to get the best return on effort.

Why then (as the Pike Anglers Club has asked) is the Western Regional Fisheries Board admitting to throwing big pike back when it takes them alive from the gill-nets? The Board says it is actually making a concession to the pike lobby: any fish over 90cm gets tagged and released. With only perhaps another year to live, their appetites for trout and their spawning contribution will make little difference.

In any event, the intensive netting and trapping so far this year has yielded only 25 fish over 20lb weight - this despite the regular appearance of Mask and Corrib fish in the specimen pike statistics of the 1990s (a lake specimen weighs 30 lb, or 13.6 kilos). Another 700 smaller pike, found alive in the nets (which are of relatively soft, braided nylon), have been transferred to nearby lakes where coarse fishing dominates.

What is so wrong, some anglers ask, with lakes with mixed stocks of fish, such as the large Shannon lakes and Lough Neagh? The fishery scientists, with 100 man-years of Irish research on the subject, say that trout always end up as the minority species. At best, anglers can expect to catch a small number of big trout during the mayfly hatch - but this is not good enough to satisfy the game-fish angling tourist.

Keeping adult pike in the western lakes simply to win fishermen during the trout closed season would make nonsense of the Board's current work to restore the lakes' tributary rivers with trout-friendly redds and riffles and weirs: why double the trout for pike to eat? The aim of the new culling programme is to keep the pike population to a perpetual youthfulness, measuring 30 cm or less, and satisfied with shrimp.

Corrib, Mask and Carra are ecological treasures, not only for their rich limestone feeding but in their situation so close to a great ocean. Cool summers and strong winds keep the waters well mixed and full of oxygen from top to bottom, a regime essential to bringing brown trout to their prime and one quite missing from the warm summer lakes of the Continent. If the trout need a predator to weed out the small ones, let it be their own long-lived, fish-hunting "ferox" race, ancient in Ireland and already native to the Cor rib and Mask.