Wild Trout In Rivers
Almost all trout spend part of their lives in rivers and streams. Even trout that migrate to sea-the steelhead and sea-run cutthroat of North America and the Atlantic sea trout of Europe-are born in rivers, where they may spend a year or more as parr before making their journey downriver to salt water; when fully grown, the urge to reproduce drives them back to their natal rivers. Similarly, lake trout may spend the bulk of their lives in still water but most are born and return to breed in the lake's feeder and outflow streams.
The true river trout, however, never leaves its native river system, and may indeed spend much of its life in precise locations or 'lies' in the river. These lies are chosen by the trout because they provide some shelter: possibly a swathe of river weed, or a deep hole under a high bank, or by a large boulder, or the fast streamy neck of a river pool, or beneath overhanging tree branches. Lies are also chosen by the river trout because they provide the fish with a steady supply of insect food that is being carried down the river.
This is one major difference in behaviour between river trout and trout that feed in lakes, estuaries or at sea. The latter must often swim some distance during the course of a day in their search for food, and because many pairs of eyes are better than one, most lake, estuary and sea trout feed in shoals. Not the river trout; the stream brings the food to the trout. But because of the irregularity of the flow down a stream, due to the flow being broken by large boulders, weirs, the meandering of the river banks and so on, some parts of the stream will carry more food than others. The trout compete for the best positions: the more food and the better the cover provided by a lie, then usually the bigger the trout in that lie. An older, larger trout will vigorously defend its lie against a lesser trout.
All river trout anglers can cite examples of such lies from their own rivers. Lies where there will be a good trout. Lies that often give the trout the sort of cover that makes catching them difficult. Lies that, once a big trout is removed, are never left vacant for long: another trout, perhaps not quite as large as the earlier occupant, will soon move in having abandoned its previous, lesser lie. It is as though there is a peck order based on the trout lies on each stretch of river. When the trout at the top of the peck order disappears (by dying, or being caught by man or another predator) all the other trout move up one place.
In Minor Tactics of the Chalk Stream (1910), the famous angler-naturalist G. E. M. Skues wrote of one trout which seemed never to leave its lie.
There are many similar tales of river trout, often known personally by name, that inhibit quite distinct lies: hatch pools, beneath bridges, below overhanging branches, above and below weirs, and so on. Every time the angler passes he raises his hat, wishes the trout 'Good Morning!', makes a token cast at his old friend, and then moves on upstream.- So it goes for the whole season from April to September when he waves cheerio to the river and wishes his finny friend farewell. And often, on the first day of the next season, our angler returns to the river. There, in the same place, is the trout. 'A Happy New Year' he shouts as he raises his hat and prepares for the token cast!
Contrary to angling myth, however, no river trout remain permanently in one lie, year after year; in certain water conditions and on some rivers even a well-established trout may have two lies: a feeding lie and a resting lie. During high summer, when the river is very low and the light bright through the day, the shallow flow which produces a potentially good food supply may be dangerous during the daytime. In the glare of the bright sunlight streaming through the shallow clear water the trout may be easily seen, yet unable to see potential predators approaching. Unlike humans, trout cannot contract the pupil of the eye to reduce the glare of bright light. In such conditions the trout may therefore seek cover in the shade of riverside vegetation.
Come evening, as the light fails, the trout -Will leave the cool dark daytime lie and swim into the shallow streamy water to feed, under cover of darkness, on the evening hatches of mayflies and the night hatches of sedges. During drought. conditions on Scotland's River Nith, one large brown trout (that could be identified by a very pale pectoral fin) was followed on seven consecutive evenings for nearly 200 yards, as it swam from its daytime lie amongst the roots of a riverside alder to its evening he beside a boulder in four inches of open water. In July 1975 a tributary of the Madison River. in Wyoming seemed fishless until dusk, when the cutthroat trout moved from their daytime lies in the deeper pools to feeding lies in the shallow, faster Water.
Through the year many river trout move even further afield. The upper reaches of spate streams often seem devoid of trout through the spring, when the fish are feeding lower down the river. A visit to the river may be marked by the year's first large hatches of flies, but not one fish breaks the surface; in June or July the same length of stream is alive with trout. However, the major movement of river trout tends to occur in winter, between October and April, when the trout move on to the redds to spawn. For some trout, this means a short trip to the nearest patch of fine gravel. For many it may be an upstream journey of several miles, from the deep silty pools of the lower reaches to the fast gravel-strewn runs of the headwater streams. Even trout that remain faithful to one particular lie for most of the year, will leave that he to spawn.
The notion that trout commonly remain faithful to a particular lie is therefore quite unfounded. The vast majority of river trout move from lie to lie as they ascend the peck order, sometimes passing from one length of river to another, even swimming the whole length of the river system during the course of a year. Equally mythical is the much vaunted intelligence of wild trout in rivers. When anglers refer to trout as being educated or wily they Hatter fish whose intellect is similar to that of a farmyard chicken; possibly even less.
Nevertheless, to survive by eating and avoid being eaten trout have evolved a highly acute set of sensory organs. They have a system of nerve endings in the lateral line that can detect the approach of danger through vibrations in, the water. Watch a trout in the river while you stamp on the bank: though it may not see you, its lateral line will warn the trout that you are there. Its fins may quiver; it may sidle under a patch of weed; it may even flee.
Trout also have remarkably keen eyesight which enables them to scrutinise potential food items and to see predators approach. Many anglers, thwarted despite carefully selecting a trout's favourite fly and casting with consummate skill, have credited the fish with intelligence. But it is more likely that the trout has actually seen the bend, point and eye of the hook, and the monofilament leader extending from the hook: features the natural fly does not have. It may be that trout which have been caught and released can grow wary of what they will and will not take from the water surface. They examine their food more carefully; and are more likely to spot the deception in the angler's fly than fish that have never, been caught before. But that reaction does not demonstrate intelligence. Exactly the same survival trait is exhibited by birds feeding on a bird table in a garden frequented by cats, or rabbits in a warren when a fox trots past.
Lake trout rarely enjoy the same reputation for intelligence as river trout. Yet this is almost certainly attributable to differences in the environment rather than the fish themselves. In a river the water flow acts as a conveyor belt carrying food to the trout in its lie; the trout selects what it wants from the stream. When the water is clear and carries plenty of food, the trout can afford to be choosy; angling is then at its most difficult. By contrast, lake trout cannot lie in one spot and wait for the food to arrive; they must actively seek food by hunting for it and possibly Covering large distances in the process. Sometimes there may be a fall or hatch of flies at the lake surface that the trout will select. But large supplies of natural insects are much rarer on most trout lakes than on rivers. So, as it moves through the water, the lake trout will more often be prepared to take anything that might be edible.