Spring is a magical time on the rivers and streams of Southwest Montana. Trout slowed to a virtual standstill by the frigid temperatures of winter awake from their dormant state to feed on the bounty of insect hatches that mark the changing of the season.

Beyond the borders of the Big Sky state, many anglers have heard of the famed Mother's Day caddis hatch. But the insect of choice for anglers and trout alike during the drizzly, overcast days of spring is certainly the baetis mayfly.

Commonly referred to as blue-winged olives or BWOs, these tiny mayflies are the first substantial food source trout seek out after feeding for months on even tinier midges.

"It is nice to have a good hatch and see fish rising," said Nathan Guffey of The River's Edge fly shop in Bozeman, Mont. "A lot of people have a hard time fishing midges. The fish are a lot more active with baetis, a lot more aggressive."

Popular fly patterns for the spring baetis hatch include the Sawyer pheasant tail, batwing emerger, parachute Adams and CDC emerger in sizes 16-20.

For anglers interested in fishing bigger flies, the March brown hatch is the answer.

"March browns typically hatch the first part of March through May," Guffey said. "It depends on the year and they are a little more sporadic, but I have seen pretty good hatches on the Gallatin and on the Yellowstone. They come off on the upper Madison as well."

With the change of season, the fish - and the fishermen - pick up the pace.

"The baetis and March browns, it is definitely those hatches that draws people out to the rivers."

--Ben Pierce