REXBURG, Idaho (AP) — The Piper Tomahawk looks much the same as other aircraft taking off from the Rexburg Airport.

But when Steve Roberts pilots the plane into the sky, he's on a mission.

He provides one of the components in a comprehensive creel survey by the Idaho Department of Fish and Game.

"As famous as it (the Henry's Fork) is, this is the first time we will have a complete and comprehensive study of the river," says Dan Garren, the regional fisheries manager who is overseeing the project.

Roberts' task is to complete 120 flights of the river, doing what Garren describes as "instantaneous counts" of the number of fishermen, boats and pelicans in the river, which is divided into five sections.

He flies from Rexburg to the base of Island Park Reservoir on a random schedule twice a day for two days each week. Earlier this month, he had logged 40 flights. He started the flights April 18 and will end in October.

"It's an amazing perspective," Roberts said of the upper valley from the air. Within Federal Aviation Administration rules, he flies close enough to count all that's on his list.

Sometimes that requires circling an area if pelicans are in clusters or there are lots of boats and anglers in a section.

"One day, I counted 63 in a cluster," he said of the pelicans that have a 9-foot wingspan.

"They have to be in or above the river for me to count them," he said of all three survey subjects.

So far he hasn't been able to discern any sort of pattern as to how the river is fished. Weather and streamflow have probably been big factors in where the anglers and boats have been located so far this spring, he said.

"The thing I'm learning is that it's absolutely unpredictable," he said.

One day last week, the wind was blowing at 28 knots with gusts to 39 knots when he took off from Rexburg. That day he saw a lot of fishermen hiding out in a protected cove downstream from the Ashton Dam.

But if the stonefly hatch is out, even high water and stormy conditions don't stop anglers from launching their boats and hunting for trout. He counted 33 boats from the stretch from Warm River to the Ashton Bridge a couple of weeks ago.

In the course of the surveys he has seen some beautiful scenery and wildlife. He watches bald eagles perched in treetops or soaring above the river. One day his plane alarmed a sow black bear and her cubs near Sheep Falls, and the cubs scurried to the very top of a lodgepole pine.

"They got closer to me," Roberts said.

He has flown in all kinds of weather as long as it has met the personal limits he sets on his own flying. But the weather generally has not been sunny and calm. Most of the flights have been bumpy, and two of the three people who have taken up his offer of joining him have made use of the airsick bags.

But the zigzagging bumpy flights don't faze Roberts. "I love it," the longtime pilot said.

His counts of anglers and boats will be used with information gathered by a ground crew that is talking to anglers from the riverbanks and in canoes about their success rates.

Through the Harriman State Park stretch, the Henry's Fork Foundation has partnered with the state to conduct an angler opinion survey that also will be used to help manage the fishery. The two people conducting the on-the-ground part of the survey have been entering the data continuously, which will help reduce the amount of time the agency will take to produce the completed study.

When complete, the study will be "groundbreaking and thorough," Garren predicts.

As for the pelican count, it's being used in another statewide study of the effects the birds might be having on the state's fishery.