Approximately a million years ago, during the Ice Age, most of Patagonia was covered in wide masses of ice. The ice flows dug away at the rocky floor yielding enormous depressions and valleys. At the end of the Ice Age (14,000 BC) the glaciers retreated, rivers changed courses and these depressions gradually filled with water providing the origins of most Patagonia lakes.

In general most of these lakes are quite deep with a visibility and clarity that varies between 20 to 50 feet with some lakes as much as 70 feet. The water is extremely clean, almost distilled, and with virtually no salinity or hardness. For the majority of lakes this is the result of rain and snow on hard insoluble rocks that have few salts or ions that can cause contamination.

Low water temperatures, low quantities of nutrients, steep valleys and wind action impede aquatic vegetation except in those areas that are closest to the shore line. The majority of these small and medium sized lakes are easy to navigate. They have many bays and abundant vegetation. Fishing close to the shore yields numerous large trout.

It is important to utilize the appropriate type of boat to find the best places to fish. Lake Paimun has the incredible backdrop of Mount Lanin , an ancient volcano. The Lake Epulafuen mirrors the volcano Achen Niyen that had its last eruption 300 years ago. From the lake one can observe how the lava decended into its cold water Famous Lake Huechulafquen captures the grandeur of the largest lakes inside the National Park.

The fishing techniques vary: trolling from the boat, fishing along the banks, casting near the outlets of rivers and streams, and casting dry flies under leafy trees that line the shores of the lake.

Necessary equipment is a number 6 or 7 weight fly rod with lines such as Teeny 130 or 200, shooting sinking lines and floating lines in some cases. Recommended flies include Wooly Buggers in a variety of colors and sizes, Zonkers, Muddlers, Matukas, and Morin.