ROSEBURG Lunchtime along the Umpqua River was just as enjoyable as the fishing itself.

Sitting around a table on a slab of lava rock, we sipped a glass of wine and watched a pair of great blue herons land across the river.

Farther downstream we could see two osprey nests containing noisy young. Next, we were served salad and fresh bass fillets.

Over lunch our guide Gary Lewis, owner of Gary’s Guide Service out of Roseburg, explained why the smallmouth fishing is so good on the Umpqua in southwest Oregon.

”The drop-off structures in the river really attract the bass,” he said. ”You can catch smallmouth just about anywhere on the main Umpqua and South Umpqua.”

The fish also have a good prey base of crayfish, dace, shiners and insects.

We floated a nine-mile section of the Umpqua River downstream of Roseburg and saw only five other boats. August is one of Lewis’ favorite times to go after smallmouth.

My wife and I caught more than 100 bass, including a couple of 15-inchers. Even the smaller fish were very aggressive fighters. Bouncing purple plastic worms off the bottom worked best, although casting Rapalas also produced fish. Lewis showed us how to use a variety of flies and poppers as well on the fly rods.

Even before we put the drift boat in the river, I knew it was going to be a great day.

While shuttling vehicles between boat launches, a group of turkeys crossed the road ahead of us. A mile farther, two spotted fawns ran up the yellow line.

Lewis likes to cast the Rapala and let it set for a few seconds, then give it a couple of twitches. This will attract the attention of a hungry smallmouth, and the fish usually explodes on the lure. Instead of just reeling in the Rapala normally, he keeps it moving erratically to resemble a wounded minnow.

On every cast that day, several bass followed the lure to the boat, even when a fish was hooked. Many fish were in the 5- to 10-inch range, but the larger fish were lurking just below and would often plow through the school of smaller fish and hit.

Dave Loomis, a Roseburg-based biologist with the Oregon Department of Fish and Wildlife, said smallmouth bass were illegally introduced into the Umpqua River system sometime in the early to mid-1960s. The fish could have entered the river during the 1964 flood, when many private ponds on the tributaries overflowed.

The bass are now present in the entire South Umpqua, the mainstem Umpqua and several of the tributary streams. Although the ODFW hasn’t surveyed for bass in many years, Loomis said there are more than 1,000 fish per river mile. He’s seen hundreds of bass at once in some of the pools.

Besides ospreys and herons, we also saw bald eagles, cormorants and a variety of ducks. At one spot on shore, several turkey vultures fed on a large salmon. Western pond turtles basked on rocks jutting out of the water.

The scenic Umpqua River flows through a steeply forested canyon and has much lava rock in and along the river. A motor for the boat is a must, as there are several long stretches of calm water that could make rowing a struggle.

The river level was much lower than normal, but according to Lewis low water helps the fishing by concentrating the fish. The main Umpqua has been running about 800 to 900 cubic feet per second. Normal levels are about 1,200 cfs.

For the South Umpqua, which is now running about 40 cfs, normal levels at this time of year are about 120 to 140 cfs.

Although the fishing is great at low levels, the problem is having enough water to drift the boats. Many boat ramps are getting tougher to launch from. Call the ODFW in Roseburg (541-440-3353) or Gary’s Guide Service (1-800-672-2460) to check river conditions and best drifts.

Loomis said smallmouth numbers have leveled out over the last few years. There aren’t as many larger fish in the river as there used to be, for a couple of reasons: The bass have balanced their population, and anglers are keeping some of the bigger fish.

There is a limit of 10 bass per day and two limits in possession, but Loomis said he rarely sees anglers keep that many fish. He’s seen several fish over 5 pounds come out of the river and a few of about 22 inches. He hears of many bass of 17 to 19 inches being caught.

The average-size smallmouth (5 to 8 inches) are 2 years old. Most of the mortality occurs in the third or fourth year.

According to Lewis, the fish become active when the water reaches about 63 degrees and stay active no matter how warm the water gets. Ideal water temperatures for catching bass are about 68 to 70 degrees. Below 60, the bite slows tremendously, and at 56 the bass quit biting. That’s also the magic number when the fall chinook really start hitting, Lewis said.

The bass spawn in the spring when water temperatures reach 60 degrees. They choose spawning sites within bedrock shelf areas that contain pea-sized gravel pockets. The early spawning leads to good growth in the first year.

Loomis said September offers the best fishing for larger bass, which become more aggressive. Earlier than that, anglers have to get through all the smaller fish before they reach the larger ones, he said. Last year, anglers were still catching bass in early November. As long as the water stays warm and relatively clear, the smallmouth will bite.

”Bass fishing is good throughout the entire river system,” Loomis said. ”If you get on the river, you’ll find bass.”

There are miles of bass fishing to be had in the Umpqua drainage. Roseburg is at river mile 117 from the mouth. There are 80 to 90 miles of good bass habitat. The lower 25 miles is estuary.

On the South Umpqua, there is a stretch of about 40 to 80 miles of bass fishing. Another 30 to 40 miles on Cow Creek support smallmouth, as do several other tributaries.

Loomis recommends bringing along your entire tackle box.

”That’s the fun part about bass fishing,” he said. ”You can throw out a white grub one time, imitation crayfish the next, then top water with Rapalas. See if the fish are near the surface or on the bottom. Try slow retrieve, then fast. Sooner or later, you will catch fish. Anything small and on the bottom works best this time of year, such as crayfish.”

He pointed out that there is no reason to buy several dozen worms when plastics work just as well.

Some fly anglers who recently went out with Lewis landed four fish of 16 to 18 inches. For fly fishing, he uses poppers and pencil flies on the surface. Girdle bugs, wooly buggers and shad imitations work well under the surface.

For those interested in just catching lots of fish, he recommends 4-inch purple plastic worms jigged on the gravel bottom. Six-pound test line is used on his spinning rods.

”The diverse habitat is what makes the Umpqua such a unique river system,” Loomis said. ”It starts in the Cascades coming down the North and South Umpqua to the valley floor, to the coastal range and finally to the estuary.”