The fact that little Peters Lake recently yielded a 10-pound 1-ounce largemouth bass doesn't surprise Rick Lorson, the Pennsylvania Fish and Boat Commission biologist who manages the 35-acre Washington County-owned impoundment.

"Peters has a large bass population for its size," Lorson said. "Of course, you can catch a trophy in a one-acre pond. It's a combination of genetics, forage and the fact that today fewer fish are being harvested."

The bass reproductive cycle, which peaks when the weather starts to warm, presents a regulatory quandary.

Bass are more aggressive -- and more likely to be caught -- during the spawn when males are guarding nests, said Lorson. It's also a time when the fish are especially vulnerable. Because natural reproduction is critical in Pennsylvania (neither smallmouth nor largemouth bass are stocked), anglers should avoid casting to nesting bass.

But unlike walleyes and saugers, which have a closed season, or panfish and muskies, which can be harvested year-round, bass regulations include a legal gray area. During the so-call "catch-and-release season" (mid-April through mid-June), bass may be caught and returned as long as spawning beds aren't intentionally targeted. The regulation replaced a closed season eight years ago in an effort to balance science with angler preferences.

"Bass are spawning at a time of year when all other seasons are open and warm weather is bringing more people to the water, so it's inevitable that anglers fishing for walleyes or pike are also going to catch bass," said the agency's chief warmwater biologist Bob Lorantas. "We had requests from anglers asking for opportunities to fish for bass in what was historically the closed season."

It still is unlawful to target bass on their beds, but the catch-and-release season lets unwitting violators off the hook. The ban was practically unenforceable anyway, Lorantas said.

"Although you can expect beds to be near shore, sighting them can be challenging in Pennsylvania, where some waters are turbid in springtime," he said. "The intent of the change in regulations was to encourage anglers to leave beds alone to the extent possible."

Lorantas said spawning bass should be released -- ideally under water -- in less than a minute, which is all the time it takes for bluegills or other fish to raid an unguarded nest.

Although he said bass production is more affected by water quality and conditions than by fishing pressure, Penn State University fisheries biologist Tyler Wagner said not much is known about angler impact on the outcome of a spawn.

"How does [releasing] bass off their beds affect population levels? That's a critical question, and it hasn't really been studied," he said. "Nest predation is a concern, but without studies, it's hard to draw conclusions."

For that reason, some anglers won't take chances. Bob Clouser, one of the state's best-known bass guides, doesn't bass fish during the spawn and holds off guiding until July 4.

"Spawning bass have enough hardship. Why add to their demise?" said Clouser, who lives on the Susquehanna River and created the popular upside-down fly, the Clouser Minnow. "We're told there are so many bass in a fishery that removing one, even briefly, won't hurt. But how do we know? How do we know a bass will find its nest again if you're 100 yards away?"

To offset possible increases in springtime mortality, the commission, when it implemented the catch-and-release season, tightened bass creel limits and sizes October through December. It also bans bass tournaments during the spawning season.

Some anglers say ice fishermen should be more restricted, too.

"Ice fishermen are allowed to fish with five rods or tip-ups. Everyone else fishes with two, and when we're fishing a tournament we limit ourselves to one rod," said Don Wagner, tournament director of the Keystone Bass Buddy Circuit. "A lot of trophy bass come through the ice at lakes like Arthur and Wilhelm. A lot of our members who ice fish won't target bass."

Lorantas said the commission hears the same complaints but has to consider the interests of all anglers.

"Ice fishing is social. Your catch tends to be more on display for others to see," he said. "And the data suggests bass harvest rates are actually higher in summer than in winter, because more people are fishing."

Lorantas believes the current bass regulations are working.

"Angler impact during the spawn could be a problem where you have low density of bass and high density of angling pressure, but we're really not seeing problems," he said. "In fact, in 2007, smallmouth bass reproduction was up on rivers statewide, except for the lower Susquehanna."

Considering it generally takes bass four years to reach 12 inches (legal size in most waters), last year's successful spawn bodes well for fishing in three to four years.