Marble trout - Salmo marmoratus
The Marble trout. For me, this beautiful fish is the most rewarding to catch. A decent-sized wild Marble trout is "smart" and very shy. Catching one takes effort, needs to be earned, and will surely not be handed over on a platter. It is Slovenia's national fish and once it was the only trout species in the Soca river and tributaries. The population came under pressure with the stockings of the Brown trout in the 20th century. They crossbreed and the offspring are fertile. Hybridization is one of the main reasons the population went downhill in the Balkans and Northern Italy. Due the hard work of the fishing club of Tolmin and others the Marble trout is back again in the Soca Valley. They found 8 pure Marble trout populations in some upper tributaries and are used in a well-organized breeding program that helped rebound the population. Now this is the last remaining place on earth where you can see and catch them frequently on a daily basis if you have some skill and know where to look for. Marble trout don't give away second chances so much, they are sensitive and easily spooked.
To fool them you need to surprise them with a stealthy approach, a precise cast and a drag-free presentation. The trout that offers a big challenge every time. They can grow to exceptional sizes around the 125cm mark and weigh up to 25 kilos.
The fish over a meter, however, are rare.
Brown trout - Salmo trutta fario & marble trout crossbreeds
The Brown trout is also present but no longer common since it is illegal to keep, breed, or stock them in the Soca river system. They are a big threat to the Marble trout population in terms of the crossbreeding and as competitors for food and space. I catch them during the hunt for Marble trout while fishing the tributaries. They also like a hiding place close by. Today it is more likely to catch a Marble trout than a Brown trout. They can grow to the 70cm mark.
The Hybrid trouts are my second most wanted trout species because they can be so beautiful in their color patterns. They can be very different in the way they look and sometime it is impossible to tell quickly what species it really is. They can look very similar to a Brown trout or look very much like a Marble trout. The most beautiful ones have some of both.
The combinations can be stunning. They can have the habits of a Brown trout or the Marble trout, but who cares?
They are all wild, beautiful, and a good sport on the fly. They can grow to the 1m mark.
Adriatic grayling - Thymallus thymallus
The Adriatic grayling is not named as a different species yet but it differs from the Danubian grayling that was introduced earlier. Both species have also crossbreeds. The hybrids are almost impossible to tell apart, especially when they have black dots on the front. The Adriatic grayling is the original species and the easiest to recognise. It has a light grey or golden-yellow body with few, or no black dots in the front. The two graylings behaviours differ from elsewhere in Europe. They are not that shy but the hard part is catching them. Mostly they are lazy and very picky, This gets worse when they become aware of your presence. The fly must be presented in close proximity to their feeding line. They are mostly found close to the bottom, so your fly needs to go deep. To catch a good sized grayling it can require a lot of patience. Once you have spotted one, don't give up quickly and give it some extra casts. They live in the slow middle and lower parts of the rivers and prefer a gravel or sandy bottom. They mostly hold at the ends of the pools where the current slows down and the gravel bottom comes up. When you hook one they often jump out of the water like the Rainbow trout and use tactile strategies like hanging in the current with their backfin unfolded to give you the feeling that you have hooked a brick.
They are a good sport as they can reach the 60cm mark.
Rainbow trout - Oncorhynchus mykiss
The Rainbow trout is introduced to make the fishing more interesting. They are aggressive and easier to catch compared to the native species. It often saves the day when catching Marbles or Graylings was too challenging. When hooked, they jump out of the water multiple times making them a good sport fish and a lot of fun to catch. At first they didn't reproduce in these rivers but they are now accustomed to these waters and it's now not uncommon to catch a wild specimen. The wild ones have perfect fins with white edges and are more light silver in color. They eat almost anything that is presented well. The average stocked size is "big" and can demand the most of your fishing equipment and skills. You will find them in the more easily reached parts of the river, in open pools. It is the most seen and caught species because of its aggressiveness and persistent hunger. Most of the time it is the first fish to reach your fly. Personally, I like to avoid areas that hold a lot of rainbow trout because they make the catch of Marble trout and Grayling more difficult. They can grow to the 80cm mark in these rivers.