Fishing for trout in summer on one of the rare, idyllic chalk streams of Southern England is something all too few anglers experience these days – the expense and difficulty of booking puts it out of the reach of most. But should the chance come your way, you’ll find it pays to understand what makes chalk streams special.
Since all rivers and streams owe their existence to rain, you might expect them all to have a similar flow and appearance — but this is far from the case.
The streams that thread their way down mountains and hillsides and tumble through valleys – although fed to a certain extent from springs – rely almost entirely for their water on rainfall and snowfall. They trickle down or run in spate according to how little or how much water has fallen to swell the flow. Chalk streams are quite different. Their water comes mainly from springs fed by deep underground resources (aquafers) which collect and hold huge amounts of rainwater.
As a direct result the true chalk stream offers fish one of the richest, most stable of all freshwater habitats. The chalk stream is bora’ on the downlands of eastern and southern England. Rain works its way through the porous chalk, gathering calcium, phosphates and other nutrients, and comes to rest in aquafers deep below the surface. Eventually the water appears in springs at ground level, creating the infant chalk stream. It can take four months — or even longer – for the water to surface in a spring after falling as rain.
This process of delay creates a variety of special features. The temperature of the water is remarkably stable. Even in the warmest weather it is rare for a chalk stream to rise above 12°C (54°F) – or to fall lower than 9°C (48°F) in cold weather.
The ever-present system of springs, often along the river’s entire length, provides a con- water crowfoot and banks of starwort that create excellent lies in the channels—perfect resting and feeding places for the fish. Man-made hatch pools and weir pools, with their reverse flows and overhanging trees, are all-important fish-attracting features. The hatch pool pushes water through a small controlled opening, creating a mini weir pool. This makes for a fast central cur- sistent level of water and also a permanent saturation of vital calcium, nitrates and carbon dioxides. These, in turn, give rise to the startling clarity and purity of chalk streams. Speed of flow is also fairly constant. A chalk stream is far less likely to flood or suffer the huge variation in flow of other rivers. Flow in a chalk stream is balanced, though swift – it runs at about 4mph (fast walking pace) along its length from source to mouth. Flow of water at the surface is much faster than it is deeper down.
Finding trout lies
These rich, stable conditions mean plant and animal life prospers. Anglers often think chalk streams are for game fish only -even now most of the larger rivers have salmon and sea trout runs, though they are more familiar as trout rivers. But the richness of chalk streams in fact encourages most running water fish – roach, dace, barbel, chub, pike and grayling can all reach specimen weights here. Weed growth in chalk streams is heavy, rooted in the gravelly or pebbly bed. Look for trout sheltering among the thick swathes of rent which divides and reverses to either side. Trout lie in this highly oxygenated area, waiting for food to come their way. Overhanging trees on any water offer fish abundant security and shade. They are not so important in chalk streams, but they are still places the canny fly fisherman finds well worth investigating – lots of flies and grubs fall on the water from them and the fish appreciate the shade when the rest of the stream is in bright sunshine. Undercut banks Trout favour holes and lies tucked under the banks and hollowed by erosion and water movement. The fish are often shielded by reeds, grasses and other plants that also harbour a variety of insects on which the fish feed. These are places you should explore, though because they are so close to the bank, you’ll need to exercise extreme caution and stealth. Follow the feeding The lush weed growth, which has to be cut at regular intervals on most streams to regulate flow and avoid localized flooding, harbours a vast array of aquatic insects. Most chalk streams have a healthy population of ephemerals (upwinged mayflies) and caddis (sedges), as well as small two-winged flies (diptera) such as midges and smuts. Every time you go down to the water to fish, check to see if the trout are feeding on one insect to the exclusion of others. When they are – imitation is the order of the day. Most fly fishing on chalk streams is concerned with the use of an imitation of an upwinged nymph (wet) or a dun (adult, dry), though a dry sedge, especially near nightfall in the summer, can be deadly. You’ll find that fishing upstream with a dry fly is the only permitted method on most chalk streams until August, when a nymph may be used. Check the flow Although the variation of flow in a chalk stream is not as dramatic as it is in other types of river, different depths do affect the speed of the water. Some sections offer elongated shallows which the fish seem to favour during the evening. Slower, deeper sections often hold larger trout, but don’t be deceived into choosing larger flies. Colonies of small diptera and other insects mean it’s essential to use tiny flies (size 18-20) on fine tippets of VA-2 lb /0.7-0.9kgb.s.
Overall, however, a chalk stream averages a depth of 1.2-1.8m (4-6ft) and is fairly uniform along its length – making trout location fairly constant.