Testing flies in Slovenia on Idrijca and Soca rivers

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A few days ago I went in Slovenia with two friends and TroutLine team members to test some flies on Soca and Idrijca rivers. We planned to fish 3 days on these beautiful but difficult rivers and to make a new selection of flies for starting season. The weather was not the best, 20-25 Celsius degrees with deep blue clear sky . No wind, no clouds, just a super strong sun. The rivers where super clear and low ( like they are in Autumn time) and all fish were extremely spooky. Zoran, the river keeper told us that we will have difficult days, due to full moon and high pressure generated by weather. He knows very well when trout eats because he raises marble trout for re-population the Idrijca. He showed us how his big marble trouts behave in the big breeding pools: spooky, no interest in insects from the water film…

Anyway we started the first day with fishing on Idrijca. We tried with stimulators and hot spotted nymphs, buggy nymphs, PT nymphs and all kind of micro streamers. The fishing was more difficult and demanding than I expected. To catch a few trout I needed to stay low profile, go close to the targeted spot very slow and careful. The water was extremely clear and I had to walk on my knees almost all the time. Even today my legs are hurting me 🙂

I had up to 30-35 fish in that day with a size between 30 and 45cm. I had to use Stroft Fluorocarbon in size #12 to be sure that I will be able to catch some fish. Any kind of other type of line like Stroft ABR or GTM was not suited.

The second day was dedicated to Soca. I met the same fishing situations like on Idrijca. Super clear water, clear sky and hot weather. My teammates had a few nice rainbows up to 65-68cm, no marble and no brown trout. In certain moment we stopped fishing, too many boats and rafting guys, so we went to enjoy some nice and tasty local food.

In that day we used streamers mainly and the fish caught where bigger compared with those on nymphs. We fished only in big pools to hunt some big fish. One time I tried to cross the river to fish a nice spot but the current washed me away 🙂 No water hydration in that day 🙂

Bellow is my wet equipment, even my camera had a few strops on the lenses 🙂

When I wa walking on the river bank I met a couple of italians, they complained about fishing conditions and the lack of fish in the water. No grayling, no brown trout like 5 or 10 years ago… But the surroundings where spectacular 🙂

In the last day we went again on Soca and low part of Idrijca, where we caught a lot of rainbow on nymphs. Jan, a good Slovenian friend, advised us to fish in the low part, usually fishermen go to fish on special stretch from upper part but the lower part of the river has less fishermen. Lots of beginners start looking from the bridges and when they see fish in water they jump with the rods on them. Those fish know all fishing catalogues and they are the most educated 🙂 Is almost impossible to catch those fish ( maybe late in the day when the sun goes down). Usually beginners remain there and start cast all flies from all boxes. It is better to avoid those places…

Jan was right, we started to catch big fish, over 60cm and marble. Each of us had 2-3 fish in these sizes. So we had the possibility to make a nymphs classification :

for me:

For Mihai :

For Gaby:



2 Comments
  • Darius Adomaitis
    December 2, 2024

    Hello, thanks for nice post. Im wondering what size nymphs worked best. Thanks in advance for your response

    • Lucian Vasies
      December 3, 2024

      Hi Darius,
      Thanks for your comment. Size #14 and #16 are most used sizes for sight fishing ( peche a vue ) . In very very strong currents you can go to size #10 and #8, sometimes even #6 for big rainbow and marble.

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