Trout season arrives early this year in 18 eastern counties in Pennsylvania. The change in regulations, announced last year by the Fish and Boat Commission, marks the first time the open season for the state's most popular gamefish will not arrive simultaneously across the state.

The regular season for trout opens at 8 a.m. Saturday on approved trout waters in the newly declared Southeast Region, comprising the counties of Adams, Berks, Bucks, Chester, Cumberland, Dauphin, Delaware, Franklin, Juniata, Lancaster, Lebanon, Lehigh, Montgomery, Northampton, Perry, Philadelphia, Schuylkill and York.

The season starts at 8 a.m. April 14 on trout waters throughout the rest of the state. It ends simultaneously in Pennsylvania at midnight Labor Day.

"What we're trying to do is match the opening of the season to conditions in the water, which varies in different parts of the state," Fish and Boat Commission spokesman Dan Tredinnick said. "Air temperature correlates to fishing conditions. We looked at [data] from the National Weather Service showing the historical average last date in the year when it gets below freezing."

Biologists know that the earlier a stream experiences the final freeze, the sooner it warms up in the spring, influencing insect life and making the fish more active. Colder water also holds more oxygen. Southeast Region streams that thaw sooner also heat up earlier when the water becomes uncomfortable or even unbearable for cold-water trout, which like it right around 50 degrees.

"There's also the issue of overhead cover, which sprouts earlier in the southeast," Tredinnick said. "Spring weather comes a couple of weeks sooner in the southeastern portion of the state, and the earlier opening day [there] matches the season up with fishing conditions."

The Fish Commission anticipates some additional side benefits to the new regional opening day. Trout stocking in the southeast can be scheduled closer to the season opening, giving trout less time to migrate out and poachers less time to steal fish. It also offers a two week head start for fishing-related commerce in 18 Pennsylvania counties.

One variable that no one can predict is the number of anglers from the west who will migrate east the next couple of weeks to take advantage of the open waters.

"We'll be interested in how that plays out," Tredinnick said. "It wasn't a driving force in the decision to do it, but it's another side benefit. If fishermen travel east, we look at that as a good thing."

The introduction of a new opening day also impacts social tradition. Since the 1950s, anglers have anticipated a single season opener everywhere in the state.

In addition to checking for trout stamps and counting creel limits, Tredinnick said waterway patrol officers will be making field observations of angler pressure on eastern waters, gauging the impact of the new rules.

"We recognize some folks may see this as putting more pressure on [eastern] streams," he said.

Chuck Thompson, of International Angler in Aspinwall, Pa., doubts increased pressure will come from western fly anglers, who enjoy special fly and spin tackle regulations all year long.

"Opening day of trout season is not as meaningful to fly fishermen," he said, "because you have so much water available right now that's so excellent. And steelhead [fishing] is starting up again."

Just off the Schuylkill River in Philadelphia, Bob Vernitsky of Bob's Bait and Tackle said his customers are happy to get a two-week head start.

"It's kind of warm down here already," he said. "Usually, New Jersey opens its season before us and a lot guys go over there. But now Jersey opens a week after us for the first time in years."

Vernitsky said he has not heard complaints about the possibility of western anglers hogging spots on eastern streams.

"Basically on opening day, everything seems to work," Vernitsky said. "Fathead minnows, shiners, wax worms and spinners work well. Rooster Tails in white and grey, and look for the start of an April caddis hatch. If the water is muddy, go with small minnows."

Find a map showing stocked sections of Southeast Region trout waters at www.fish.state.pa.us.