"The IDNR has studied smallmouth bass for many years, and we have moved a few, but mostly populations depend on river conditions, and that is out of our control," said Conover.

When heavy rain during spawning season brings dirt into the river, reproduction can be minimal.

The IDNR doesn't control the weather, but it can regulate anglers. Smallies are especially vulnerable to harvest, and many years ago the IDNR took two actions to help the fish live longer and grow bigger: It set a statewide 12-inch minimum-size limit on both small and largemouth bass in Iowa rivers, and implemented catch-and-release areas on sections of the Middle Raccoon, Cedar, Upper Iowa and Maquoketa. The Maquoketa catch-and-release area extends downstream from below the Lake Delhi Dam to the first county gravel road bridge. Catch-and-release sections of the other rivers are identified in the IDNR's fishing regulations booklet.

The regulations have helped bass and bass fishing -- especially on the Maquoketa. "The length limits have benefited both smallmouth and largemouth numbers and size of fish," said IDNR fisheries research chief Don Bonneau.

Catch-and-release fishing has gained popularity among dedicated smallmouth bass anglers. "We were considering eliminating the catch-and-release section on the Cedar River because our research didn't indicate that it was very effective there," said Conover, "but many anglers told us they like the regulation, so we kept it."

The regulation has certainly helped Maquoketa River smallies. "Catch-and-release fishing does not necessarily increase the number of fish," Kirby said, "but it can increase the number of large fish in areas where fish growth is good and there was heavy fishing mortality before the regulation. Paragamian's research in the late 1970s showed that anglers were keeping many fish, but today they release most smallmouth bass. That's helped.

"In the early 1980s, about 10 percent of smallmouth in the catch-and-release stretch were longer than 12 inches, but by 1990, it had increased to 40 percent. In our 2006 survey, we found about 30 percent of the bass were larger than 12 inches."

IDNR biologists Bill Kalishek and Mike Wade conducted research comparing smallmouth populations in the catch-and-release area and similar stretches of river where anglers can keep bass. "The catch-and-release area had higher numbers, larger size distribution and a greater percentage of fish over 12 inches than the kill area," said Kirby. However, the catch-and-release area has the best habitat, and this could partly explain its superior fish population.

Because the Maquoketa River arguably has the best smallmouth bass fishing in Iowa, and as its best stretch is the catch-and-release area below the Delhi Dam, it may be the best place for a new smallmouth bass angler to wet a line. Absent a lot of recent rain, April is a great month for bass fishing.