Conserving the Wild Trout

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The River Tees, in northeast England, once had prolific runs of Atlantic sea trout. Now  gross pollution of the estuary prevents the fish from entering the river. The upper reaches too have been ruined: one accidental spillage of creosote into the river in 1983 destroyed 34 miles of trout stream.


The saddest trait of modern man is that he selfishly takes from the world around him without much thought either for his fellow creatures or for the generations that will follow him. The fact that, during the present century, the rate of extinction of plants and animals has been higher than in any preceding century, and that the vast majority of these losses can be attributed directly to human activity and were avoidable, will testify through the rest of time that 20th century man was an environmental vandal. What hope then is there for conserving the wild trout?

Living in an aquatic environment that is highly vulnerable to any interference, the wild trout populations of the industrialised world have been repeatedly damaged by human pressures. The water that flows through lakes and rivers may have been affected by acid rain, by agricultural fertilizers or industrial effluents. The riverbed and banks may have been disturbed by damming, dredging or deforestation. And where the water passing downstream is contaminated, it may affect the estuary and even the sea, sometimes for miles around. Outflow from the Rhine, Europe's filthiest river, has destroyed much of the marine life over large areas of the southern. North Sea.

Today both national and international efforts are being made to clean up those waters that have suffered from gross pollution since the Industrial Revolution. Man is becoming more 'environmentally conscious'. The general public are demanding that their countryside should be protected; that where lakes, rivers and seas are contaminated, efforts should be, made to clean them up. Industries that cause pollution have had to respond. Often their action is slow. Sometimes the situation appears to worsen before it gets better. However, now that there are votes in 'green' issues, we are certain to see a reduction of direct water pollution over the next few decades.

Provided that some remnant population of wild trout survives when a lake or river is made clean, the fish can soon respond and begin to restock the water. Within a few years they can spread back to areas where formerly they could not live. The bull trout and sea trout of the River Tyne in Northern England were virtually exterminated by estuarine pollution during the first half of the present century, but the pollution was removed in the 1970s and both sea trout and bull trout currently are on the increase.

Acid rain is a more intractable problem, since the industrial gases that cause this form of. pollution may have been carried many hundreds of miles before they reach the ground, dissolved in rain water. Gaseous emissions from Germany and the United Kingdom are destroying the life, in lakes and rivers in Scandinavia; acid gases from lowland England are affecting the, lakes and rivers of English and Scottish u lands; atmospheric pollutants from the industrial centres of the USA are damaging waters in the Canadian wildernesses. Industrialists, and. the governments of industrialised countries, have been reluctant to act quickly to reduce the damage. After all, this would be extremely expensive and might benefit their neighbour's countryside but not their own. So although there are international agreements on controlling such pollution, they are very weak affairs giving the polluters many years to reduce the problem. It seems that acidification is likely to b6 a hazard well into the 21st century. In the meantime, more and more lakes and rivers will lose trout stocks and other aquatic life.

Yet pollution is no longer the biggest threat to wild trout. Paradoxically, there are probably more trout worldwide today than there -have ever been before. Trout have been introduced to regions that formerly had no trout, such as New Zealand, Tasmania, South America and southern Africa. The introductions have produced feral stocks and, in many cases, because of the genetic variation within these stocks, the feral populations have diversified further, to produce varieties of lake trout, river trout and sea trout. Even in Europe, the natural range of the wild brown trout and its varieties, and in western North America, the natural ranges of the wild rainbow and cutthroat trout and their allies, there are possibly more trout today than there were a century or more ago. However, it is in these regions, the homelands of the truly wild trout, that the fish are most endangered. Although the total trout population may have increased, this is due less to environmental improvement than to the wholesale stocking of wild trout rivers and lakes with alien varieties. The numbers of wild trout have seriously declined, and are still falling.

Sea-going trout-the coastal cutthroat, steelhead and Atlantic sea trout-have probably been the least affected. Although there has been some reduction in population in parts of their ranges, and although the estuaries of some river systems are too polluted to allow the fish to pass between freshwater and the sea, sea trout overall are thriving. This situation is due, at least in part, to the economic value of sea trout waters, which are consequently accorded special protection. Populations are bolstered by fish of the pure sea trout variety raised in commercial hatcheries.

It is the freshwater varieties of trout that face the greatest danger. In the USA and Canada, the populations of many of the scientifically accepted varieties of wild trout have crashed since man arrived in the western wildernesses; many rivers have been taken over by introduced forms of trout or by hybrid populations. Ten of the fourteen forms of freshwater cutthroat trout are now so rare that they appear on either State or National lists of endangered animals. A century ago most were abundant. Likewise some varieties of rainbow trout. In his book Native Trout of North America, Robert H. Smith sadly describes the Apache trout and 'Gila trout as: 'Now very rare as pure populations'; and other forms such as the golden trout of Volcano Creek, the Gilbert golden trout and the mountain strain of the Kamloops trout as occurring only 'above barriers' which introduced, non-indigenous trout cannot pass.

The danger is exacerbated because those forms of North American freshwater trout that are thriving, such as the Yellowstone and the Snake River cutthroat, and the South Fork Kern River golden trout, have been used to stock waters vacated by the declining trout varieties. This has reduced the chances of the native trout ever recolonising their traditional ranges; and where the remnant has hybridized with the introduced trout, the genetic purity of these rare forms has been ruined.

The freshwater trout of Britain and Europe-the brown trout and their allies-have generally not suffered to the same extent as some of the North American varieties, though they have been excluded from part of their pre-Industrial Revolution range. Most clean lakes and rivers still have populations that are clearly identifiable as 'brown trout', and some lakes maintain their own quite special varieties. What we do not know is whether there were far more local varieties like the sonaghen and Loch Leven trout two hundred or more years ago. Nor do we know if forms such as the gillaroo, that are today known from just a handful of lakes, were once more widespread.

There is growing concern, however, in both North America and Europe, as rivers and lakes continue to be stocked with trout from hatcheries. On stocking day a wagon carrying several thousand trout may set out from the fish farm and disgorge its load into three, four or more completely separate river systems. This may satisfy the requirements of the anglers: they now have plenty of trout to catch in their beat. And the fishery owner may be quite content because heavy artificial stocking means that plenty of permits will be sold. But these trout are not the native trout of that river; they are not wild trout.

In the worst cases, European brown trout are used to stock lakes in North America and American rainbow trout to stock rivers and lakes in Europe. But even where the local species is used, it is common practice to stock one lake or river with trout that have originated from other lakes and rivers. Current evidence suggests that this is wrong. If a wild trout lake or river cannot be stocked with its own strain of trout, it would be better not to stock at all, but to protect the natural head that remains until the population recovers.