The globally attractive Škocjanska jama cave system is part of the Reka river system, where the river descends into the Karst underworld. As far as Ilirska Bistrica it is relatively insignificant, but from there on it gains strength from its lowland tributaries and is transformed into a respectably potent river, which used to power sawmill sand mills. On its passage from its source in Gorski Kotar (Croatia), the Reka is home to the indigenous marble trout, hybrids and the predominant brown trout. There are two artificial lakes on its tributaries. The water of the Klivnik Lake accumulation is clear, clean and relatively cool. In it, in addition to the trout, the pike-perch is one of the most interesting fish.
The Unica river’s journey begins on the southern edge of one of the most beautiful and best-preserved Karst plateaus at the confluence of the Pivka and Malenščica. For many years one of the world’s best grayling waters in the world of fly-fishermen, the Unica winds its way several times back and forth across the whole width of Planinsko polje (valley), and thus it is as much as three times longer than the 6-kilometre long valley itself. Living conditions for fish are extremely good here. There are times between autumn and late spring when such are the volumes of water rising to the surface that the sinkholes cannot suck them all down below ground. At these times, much of Planinsko Polje is flooded for up to a month. In this way, the fish receive an additional source of food additional to their already well-stocked table. There are no rainbow trout in the Unica. Thus, even the best fly-fishermen and local experts have to confess their weaknesses in the face of nature. But it richly still rewards its most faithful adherents for their fidelity. At Mayfly time and again in early summer, after the birth of stone-flies and caddis-flies, fly-fishermen from all over the world congregate here. This is the time when it is possible, in the early morning breaking of the day, when the first rays of the sun appear, to trick a trophy grayling. Alternatively, in the evening twilight, a trophy colourful brown trout.
The Idrijca is surely one of the richest and fishing-friendly salmonid waters in this part of Slovenia. It is easily accessible from the road that runs parallel to it, while meanwhile it is also a very productive river, offering enjoyable fishing to fly fishers throughout the season due to its having a suitable water level. The brown trout is predominant, with hybrids and grayling. The marble trout is present in lesser numbers, but the individuals caught here are almost exclusively of trophy size. The Trebuščica is its tributary in the lower part of the valley. This attractive river with its numerous pools is suitable mostly for fishermen who love solitude. The marble trout is predominant, with hybrids also present.