The guys from AEG, who brought you Trout Bum Diaries: Patagonia and Trout Bum Diaries II: Kiwi Camo, are back. The team heads to Mongolia in search of the elusive and endangered taimen. They are opening new doors to the world of adventure angling, doors that now demand a trip half-way around the world. For two months the guys travel to five rivers that potentially no other fisherman has floated down in search of a mysterious fish. Their travels in this fly fishing adventure movie take them into inner Mongolia by horse, camel, Russian military vans, and hiking boot in search of the taimen, also known to Mongolians as River Wolf. The taimen is the world's largest salmonid—the family of fish that includes salmon and trout. The species can live for more than 50 years, but they grow slowly, not reaching maturity until seven to nine years of age. They are not known to be exceptionally migratory, but tend to stay in a small section of river for their entire lives. This has put the future of the species at risk due to years of over-harvest and lack of management.

After tackling the fish of Patagonia, the titular Trout Bums journey to New Zealand's backcountry, where they search for the world's biggest and most elusive brown trout. Along the way, the quartet encounters wondrous sights and dangerous wildlife. The four-month expedition features jaw-dropping photography of some very big fish, as seen through crystal-clear waters. Fly anglers will be easily hooked.