Soča is the biggest of our rivers, springing from the alpine valley of Trenta. The top part is mainly trout water. It flows through the picturesque gorge to the confluence with Lepena river. There also grayling joins the fish species in the river. It then gradually flows by Bovec and Čezsoča until it enters a narrower valley under Srpenica. There the flow builds up between large boulders, catching its breath in deep pools, before mellowing down by Kobarid, where the valley widens considerably. Here also the chub and barble join the already rich fish life of the river. There it starts to meander through the white sands, flowing softly towards Tolmin. After the confluence with Tolminka it enters a 7km long reservoir for HPP Doblar. In its depths live the largest marble trout as well as other fish species of our area.

Its uppermost part is managed by the Fisheries Research Institute of Slovenia. From Čezsoča to the confluence with Vogeršček, under the dam at Podselo its managed by the Angling club of Tolmin.