WRW #33: Trout and About
The cache, a small camo-taped, screw-capped pot, is hidden just down from the road-side on a mini-trail used by anglers accessing the river for a spot of fly-fishing.
The Wharfe is probably the most famous of the Yorkshire rivers, maybe because of the top quality fly fishing it provides, or perhaps because it is surrounded by the most outstanding scenery. It is a similar size to the River Ure and like all the Yorkshire Dales rivers it runs with a peat stain 'giving it the appearance of Yorkshire bitter'.
Fly fishing on the river is outstanding and it is regarded as one of the finest brown trout rivers in the UK with fish of a high average size present in abundance. It also holds good stocks of grayling in places, particularly from Ilkley downstream and in decreasing numbers upstream of Ilkley.
There is good access to the best fly fishing on the River Wharfe with many angling clubs. The Bolton Abbey Estate area - just north of the cache location, beyond the bridges - is one of the most popular with about 5 miles of double bank trout and grayling fishing. It is particularly suitable for fly-fishing newbies and for instruction, with well-defined pools, relatively easy wading and good stocks of fish that respond to most methods of fly fishing.
Fly fishing on the River Wharfe started a long time ago with anglers using wet flies, or North Country Spiders as they are known. These spider flies were invented for the Yorkshire Dales rivers and other northern, fast flowing, rain fed rivers, using simple, locally available materials. They are still very much in use today due to their success rate, and it is a very enjoyable and relaxing way to fish, however, it also requires a high level of fly fishing skill to fish effectively.
Other more modern methods are also very successful. The Wharfe responds particularly well to the duo method of fishing a dry fly and nymph together and also to fishing a single dry fly - the Wharfe trout and grayling are very free rising. Czech nymphing works very well in the faster flowing pools and the upstream nymph is a very exciting tactic to employ for fly fishing the riffles and shallow runs.
Brown Trout: The main fish targeted is the brown trout (Salmo trutta), a European species of salmonid fish that has been widely introduced into suitable environments globally. It includes both purely freshwater populations, referred to as the riverine ecotype, Salmo trutta morpha fario, and a lacustrine ecotype, S. trutta morpha lacustris, also called the lake trout, as well as anadromous forms known as the sea trout, S. trutta morpha trutta. The latter migrates to the oceans for much of its life and returns to fresh water only to spawn. Sea trout in the Ireland and Britain have many regional names: sewin in Wales, finnock in Scotland, peal in the West Country, mort in North West England, and white trout in Ireland.
Its native range extends from northern Norway and White Sea tributaries in Russia in the Arctic Ocean to the Atlas Mountains in North Africa. The western limit of their native range is Iceland in the north Atlantic, while the eastern limit is in Aral Sea tributaries in Afghanistan and Pakistan.
It has been widely introduced into suitable environments around the world, including North and South 
America, Australasia, Asia, and South and East Africa. The introduced fish have established self-sustaining, wild populations in many countries. It can grow up to 1m long and weigh up to 20kg or more. In smaller rivers 1kg is a typical size. It is an adaptable freshwater fish and a fearsome predator with rows of sharp pointed teeth. It can live for 15-20 years.
Cover or structure is important to trout, and they are more likely to be found near submerged rocks and logs, undercut banks, and overhanging vegetation. Structure provides protection from predators, bright sunlight, and higher water temperatures. Access to deep water for protection in winter freezes, or fast water for protection from low oxygen levels in summer are also ideal. Trout are more often found in heavy and strong currents.
Brown trout are active both by day and by night and are opportunistic feeders. While in fresh water, their diets frequently include invertebrates from the streambed, other fish, frogs, mice, birds, and insects flying near the water's surface. The high dietary reliance upon insect larvae, pupae, nymphs, and adults allows trout to be a favoured target for fly fishing. They can be caught with lures such as spoons, spinners, jigs, plugs, plastic worm imitations, and live or dead baitfish.
Whilst they will happily eat maggots and worms, trout along with salmon are known as game fish and for the purists, should only be caught with a fly. There is a considerable art and skill involved in fly fishing which involves using nothing more than hook attached to the line. The hook is dressed usually with bits of feather and other materials as an imitation of shrimps, small fry, insects and other water invertebrates that make up the fishes natural diet. It is also an art to dress/tie your own hooks. The ultimate satisfaction and Holy Grail of fly fishing is using the hook, convincing the ever wary and very clever fish that it is real prey/food, hooking, playing and then landing the fish.
For more information see here and here.