The Soča River in northwestern Slovenia belongs, rightfully, in discussions about the most beautiful rivers in Europe and is renowned within the flyfishing community for its most mysterious resident—the marble trout. A subspecies of brown trout, marble trout evolved within the confines of the Soča watershed and other streams in the Adriatic Sea basin, and are known for their remarkable vermiculated color patterns, predatory behavior and an ability to grow very large, for a trout.

Yet the marble trout of the Soča might not inhabit the river today if not for a dedicated group of scientists and local anglers that, since the late 1990s, has spent countless hours every winter fighting what could have been the slow death of this unique species…

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above In November, female marble trout begin building redds; soon after, the males join them and fight for their spot, with brown trout interlopers sometimes sneaking in and creating the hybridized trout that the Marble Trout Action Plan has worked to mitigate.