San Juan National Forest - Colorado - <in swedish>
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It is mostly fishing for various types of trout that attracts the fishermen, but you will also find pike, karp and other spieces here.
The most pleasant period of fishing is usually the weeks before midsummer when the waters are going down after the spring flood and it is not too hot in the daytime. If you're lucky you can experience world class dry fly fishing when the Stonefly hatch.
My own travel report and my pictures from my trip to the area might inspire you to visit the San Juan National Forest yourself...