Hucho taimen, is the world's largest salmonid (with reports of 200-pounders), and also one of the most outrageously aggressive. Swimming in streams across Siberia and Mongolia, they pound gigantic streamers or floating bugs, and then tear up the surface. Thad Robison of the Angling Exploration Group reports catching and releasing a 20-inch lenok, also known as Manchurian trout, only to see it smashed by a much larger taimen.

For more information: AEG Media

Atlantic salmon the size of fireplace logs run up the clear streams of Quebec's Gaspe Peninsula. "For reasons not understood," says writer and editor Tom Dickson, these ostensibly nonfeeding fish "will take dry flies." Dickson himself watched a 35-pounder rise from the bottom of the Petite Cascapedia River to engulf his deer-hair Bomber. "Unfortunately, [my fly] had a dull hook point… and even with two hard hook sets the hook pulled free and the fish sank back down to the bottom."

For more information: St. Lawrence Lowlands Fishing Lodges and Resorts

Don't compare rainbows of Alaska's Kvichak River with those in the Lower 48. Think instead of torpedoes. "The strike indicator disappeared with a violent jerk, and I stared into the water where I had last seen it, only to see a leaping rainbow trout out of the corner of my eye," says Keith Curley, Trout Unlimited's development coordinator. "A moment later I realized it was the same fish." In addition to rainbows, which can exceed 30 inches, the broad Kvichak harbors chinook, sockeye, chum, coho and pink salmon.

For more information: Alaska's Clearwater Lodge

Intimate streams, huge trout—that characterizes the fishing in the mountains near Queenstown on New Zealand's South Island. "Every stream in New Zealand is a trout stream," says fly-fishing instructor and author Gary Borger, "but those of the southern district of the South Island are special. Roaring off the shoulders of the Southern Alps through heavy bush and tussock grass land, they offer a primal, peaceful, and extraordinary experience in tranquility and wildness that can be found no place else on earth."

For more information: Fishing in New Zealand

Atlantic salmon, brown trout and arctic char all swim in the barren-ground streams that flow seaward off the Kola Peninsula in northern Russia near Murmansk. Watersheds of the Karlovka, Eastern Litza, Rynda and Zolotaya make up the roadless two-million-acre Atlantic Salmon Reserve. The fishing, especially for Atlantic salmon, ranks among the world's best and draws anglers from all over the world beginning in late May through September. But the price to pay is the difficulty in navigating this remote country.

For more information: The Atlantic Salmon Reserve

Rainbow trout turn up in surprising places in the vastness of Patagonia, including landlocked Jurassic Lake. Chowing on scuds, they grow to blimp-like proportions, reports photographer and fly-fishing fanatic Tim Pask. Wading into the lake and stripping streamers through the shallows, Pask and his companions caught beefy fish that averaged 10 pounds and occasionally broke 20. They are, he reports, some of the "strongest rainbows in the world… There are no bad days on Jurassic Lake."

For more information: Loop Tackle

The West Branch of the Delaware River, flowing some 40 miles through New York's Catskill Mountains, explodes with hatches of green drake, sulfur and March brown mayflies. Browns and rainbows respond ravenously—but selectively. "Matching the hatch becomes paramount here," says Trout Unlimited's Erin Mooney. "Sometimes fish will turn their noses at a hackle-heavy fly or one too sparsely tied. It's their meal and they'll tell you how to cook it.&quo

The South Fork of the Snake, upstream from its confluence with the better known Henry's Fork, "might be the West's best dry-fly trout paradise," says Chris Hunt, Trout Unlimited's western press secretary. Best of all are the steam's beefy native cutthroats. Fly-fishers can have 50-fish days on dry flies. In June and July cutthroats, as well as browns and rainbows, smash thumb-sized salmonflies. In late summer, they turn their attention to wind-blown hopper

Yellowstone National Park's Firehole River is the favorite frustration of John Ross, author of "Trout Unlimited's Guide to America's 100 Best Trout Streams." He's especially enchanted by Muleshoe Bend. "Steaming mud pots, strings of bison, bugling elk, snow showers one moment, sun the next, and rainbows that humble me still. I do not know of a more fascinating place to fish in the United States."

For more information: Yellowstone Park

Here, in the isolated backcountry of Tierra del Fuego, on the banks of Chile's Rio Grande, the sea trout reach 20 pounds or more. Imagine them on a wood-fired range, alongside fresh lamb and beef, perhaps paired with a hearty malbec. As for the fishing, says author John Ross, "I'd hunt wild browns in the tributaries with my three-weight, throw dries for sea-runs with my six, and wrestle the big boys with streamers with my eight."

For more information: Angler's Aventuras