FERNAN - Roughly two minutes after John Rankin released thousands of rainbow trout into the east end of Fernan Lake, a small squadron of ospreys swooped in for a snack.

Searching for prey, the sharp-eyed birds soared and circled. Every so often, a hungry osprey would tuck its wings and plunge like a dive bomber, talons outstretched, a rainbow in its sights.

"They like the hatchery fish. They know," said Rankin, an Idaho Fish and Game fish hatchery manager. "They'll clean 'em out of the little ponds sometimes."

Fernan Lake is normally stocked in April, May, June and September - twice each month. Rankin drove a tanker truck up Fernan Lake Road on Monday afternoon, backed down the boat launch and loosed 3,600 young trout.

Flushed through a green tube, the silver-sided fish - all 9 to 10 inches in length - flipped, flopped and splashed into Fernan's calm waters. Before long the wriggling rainbows would disperse to every corner of the scenic lake.

"They're put out there for people to catch," Rankin said. "We always put (the fish) in at this end of the lake in the spring."

The west side of Fernan drains under Interstate 90 toward Lake Coeur d'Alene, he explained. If IDFG released the trout at the main boat ramp, near the Forest Service building, the small fish could be sucked out of the lake.

Despite cool and snowy conditions, a fair number of anglers were casting lines into Fernan Lake on Monday. Small boats patrolled open water, while shore fishermen huddled along the stony banks. Crappie, bass and northern pike are starting to hit lures this time of year.

Spring, summer or fall, Fernan is a popular fishing hole.

"For being so close, it grows nice fish and it's got a great diversity," said Jim Fredericks, regional fishery manager.

Every stocking month, IDFG releases about 4,000 catchable trout at Fernan Lake, Fredericks said. About 30-40 percent of those rainbows are caught by fisherman within one year - the "return to creel" percentage, in Fish and Game terminology.

"The higher percentage that get caught, the better," Fredericks said.

Rankin's rainbows traveled many miles to reach their new home. Raised at the Nampa Fish Hatchery, the trout were trucked to another facility in Sandpoint, then transported south to Fernan.

A Fish and Game transport truck is specially-equipped for carrying trout, Rankin said: An aerator circulates water inside two tanks, and a supplemental oxygen system keeps the fish healthy - without it, 3,600 rainbows would quickly deplete the oxygen supply.

In mid-April the water is cold enough to simply drop off the fish. But later in the year, when the weather grows milder, Rankin will pump lake water into the truck, slowly warming the tanks before releasing his trout.

Fish that are suddenly thrown into a much warmer environment can be shocked by the temperature change, Rankin explained.

"We really don't have to do that (water pumping) until June," he added.

IDFG stocks 104 lakes, reservoirs and creeks throughout the Panhandle Region. Hatchery trout are dropped off at Elsie, Hauser, Cocollala, Twin and Mirror lakes, among many others.

Every other year, Fish and Game personnel will hike the backcountry and release trout into high alpine lakes.

State revenue from fishing license sales funds the IDFG stocking programs, Fredericks said. Essentially, fishermen pay for the hatchery fish they catch in local lakes.

"A lot of people want to see their fishing waters stocked," he said. "They want more fish where they fish."

It's not always so simple, however.

IDFG is evaluating local lakes to determine the effectiveness of the stocking programs, Fredericks said. In places where the return-to-creel percentage is low - which could indicate predation or low fishing pressure - stocking may not be the best strategy.

As the circling ospreys hunted from above, Fernan Lake's newest residents scattered about the bay. They broke the surface intermittently, cutting a small wake as their tails slashed through the water. Rankin's truck rumbled back up the ramp, mission accomplished.

Many of the slender rainbows, only a year old, would soon be on someone's dinner table.

"In a perfect world, every one of them will be harvested by anglers," Fredericks said.