A reservoir, be it an urban concrete bowl or dammed river valley, remains a closed book until you can decode its ripples, read its contours and translate its obscure features into fish
Locating feeding fish can be a daun-ting business, particularly when you visit a water which you have not fished or seen before. There may be up to 15 miles of bank and 1,000 acres of water to choose from.
Catching reservoir trout in this situation depends on making a quick and accurate assessment of the water and its geography, together with the effects which wind, temperature, and other weather conditions will have on the water and the fish. Such an assessment will usually offer a number of options which you will learn to arrange in order of priority. The angler is faced with probabilities arising from a water’s topography and the weather conditions. If he could deal in certainties, he would hardly find trout fishing the challenge it is.
Your first choice of spot may prove to be wrong, and each must be tested in turn. Most anglers make a mental note of the pitches they propose to fish and then arrange to visit each as economically as possible in the time available, until success is finally achieved.
Signs of feeding
Occasionally you will be lucky enough on arrival to see rise forms caused by moving or feeding fish. Trout rising to surface flies generally break surface in a clearly visible. Way. Sometimes, too, they take sticklebacks or fish fry in the upper layers. Their slashing attacks are plainly heard and seen, and the small fish leaping and scattering on the surface clearly indicate where you should fish.
Less obvious are fish taking nym-phs a foot or so below the surface. Often a slight bulge, whirl, or a break in the normal ripple pattern is all that can be detected. The angler must study the surface carefully to spot such movements, and it takes an experienced eye to detect them.
But you must often try to locate feeding fish without any kind of rise to guide you. Success must be based on your appreciation of what can be observed of the topography and weather, and their effects on the habits of trout.
You do not have to be a geologist to know that features of the land-scape do not suddenly cease to exist when they are covered by water. You can infer fairly accurately from the slope of the land, and from hollows, ridges and hummocks, how the bottom of the reservoir, at least at the margins, and often farther out, is likely to look. Deep water is often indicated by a steep bank. There may be one or several shallow shelves at the c water’s edge, formed by wind and by wave erosion at different seasonal periods.
Distant shallows may be identified by a distinct change in the surface ripples, and in high wind, small white-tipped wavelets often reveal them. Features such as this may be checked by plumbing from a boat on later visits to the water.
In waters where levels change a great deal over the season, hedgerows often extend into the water levels. Deep water in itself does not guarantee fish, but together with adjacent shallows over the eroded shelves, an ideal trout habitat exists.
Deeper water provides cover when fish are not feeding, and from here they sally forth to feed on the aquatic life inhabiting the weedy shallows. Fishing directly among the weed invites the loss of flies, but fishing the gaps, and along the margins or across the deeper adjoining water, is often productive. If the angler wishes to wade he must do so very carefully, feeling around him with a wading stick or landing net handle, as a shelf may plunge abruptly and unexpectedly.
Steep banks often peter out after a few hundred yards, giving way to a flatter shoreline with bays. A bay may be a continuation of a hollow on shore, or it may arise from a stream entering or leaving the lake. Search into the water with polarized glasses and you will discern weeds, especially in the shallow fringes of the bay. These provide both food and shelter. Marginal sedges, reeds and other bankside plants offer cover to the wading angler and present, often on several sides, fishable gaps, especially where other anglers have already a path to the water.
Good wading position
A bay is often enclosed on both sides by a small headland or promontory. Such spots offer commanding positions for wading, enabling you to fish both into weedbeds in the bay, or along the banks on each side of the bay, depending on the wind.
Before wading, it may be worth checking for inflows or outflows within the bay. Inflowing ditches and culverts often become slightly tainted with washings of oil from roads and with other minor impurities which are unattractive to trout. Towards the end of the season, when fish move towards and into minor streams prior to spawning, heavy rains will quickly clear these impurities.
A group of hillocks in line towards the bank suggest a similar underwater formation. They may form small islands when levels are low, or may create attractive, fish-holding water. These, as well as submerged tree stumps from bankside copses, cut before the land was flooded, provide cover, and it is worth risking a few occasional snagged lines to fish near them.
Most reservoirs hide submerged buildings which, even if crumbled to a few feet in height, offer good shelter and feeding for trout. Ruined or demolished buildings or masonry on the bank are a good indication of sunken ruins nearby. Also worth trying are concrete sills or ledges. These absorb even poor sunlight better than does water. They reflect whatever heat there is into the nearby water, providing warm spots where fish may feed when the rest of the water is too cold.
An OS map (as large a scale as possible) covering the area prior to flooding provides an excellent picture of the bottom. The angler should seek out, in particular, underwater contours revealing small plateaux or hills not identifiable by studying the water itself.
The reservoir fisherman must normally depend on the lie of the surrounding land to distinguish fish-holding underwater features. But they may also be pin-pointed by the presence of fish fry or large numbers of insects attracted by their shelter and food-rich weed. Sometimes the merest tips of weeds, well-rooted in the bottom, and some distance from the shore, can be discerned in still weather. These islands of deep weed indicate large weedbeds for food. Polarized glasses may help reveal the extent of such weed.
Wind is a most important factor to be taken into account once the general topography of a water is understood. It has far-reaching effects on feeding fish, either because it cools water in summer when temperatures are too high, or because it provides a large surface drift area which is itself, as moving water, attractive to trout.
Generally, trout do not feed at temperatures above about 21 °C (70°F), or below about 4.4°C (40°F). Exceptions can always be quoted by anglers, but trout need well-oxygenated water, and since oxygen levels fall as temperature rises, they instinctively seek out water layers and levels where extremes can be avoided, especially during periods of hot weather.
In their more natural river conditions, trout, like all fish, will face upstream to assist breathing. When surface drift occurs in reservoirs (and this happens whenever there is any wind beyond a mere breeze) they seek out a suitable temperature – often occurring at the surface drift – and instinctively move slowly upwind. Sometimes, the surface temperature is conducive to excellent oxygenation and fish may become inclined to feed. If so, they will do so heavily, feeding on the many creatures active at this level, and upon land and water flies, such as olives, alder flies, daddy-longlegs, and sedge flies, and other insects such as nymphs which are blown across the water, often drowning in the waves or becoming trapped by surface tension.
If there was no compensatory movement of water, surface drift would cause the level at one end of the lake to be higher than at the other. But water displacement takes place at a lower level, perhaps across the bottom if the water is less than 20ft deep. This simple and con-tinuous circulation carries free-swimming creatures, including snails and caddis larvae, up to the surface layer where it meets the lee shore of the reservoir.
The surface drift also builds up a preponderance of food on or by the weather shore as it starts its downward circulation. Here, many insects, crustaceans and other food items will have collected as a result of surface drift. Wave action may also have washed other prey, such as caddis, chironomid larvae and other creatures out of the marginal bottom weed or mud.
Fish stimulated by the circulation, its changing temperature levels, and its increased oxygen content, will generally be found moving against the drift – upwind on the surface, and downwind on the bottom. At the same time they are frequently stimulated to feed.
As a result of these conflicting trends, there tends to be a build-up of fish on each shore as they move along the banks in search of food, before moving again in the opposite direction, against the drift.
For the angler, these patterns are probabilities, and it is tempting to fish along the sheltered shoreline, especially if the ripple line – where the ripples begin at the edge of the calm water near the shore – is within reasonable casting distance, and the trout can be seen moving there.
But there could be just as good fishing on the windward side, with trout feeding on the food stirred up by a strong, long-lasting wind. It is not necessary here to cast directly out in the teeth of the wind, and casting up or down, parallel to the shore, will often take fish as they move close in under the bank in response to food. Towards evening, the wind may drop a little, enabling you to cast more easily and cover more water, but sometimes it merely strengthens, thereby defeating all your efforts.
Do not despair over your first attempts at reading a water. No angler learns a great deal about a reservoir on his first visit, but each subsequent trip adds to his knowhow, and with information from other anglers, bailiffs and perhaps from maps, a picture builds up fast. Another trip, with a boat, will often confirm some of your assumptions and eventually you find yourself regarding what was once a new water as one of your familiar favourites.