Good angler behavior is critical, or such special stretches of river will become off-limits. Public water and access are found within the confines of Casselman River State Park.

To obtain an accurate picture of the Casselman's trout fishing, I recently spoke at length with fishing guide and fly tier Harold Harsh. Contact him at (301) 387-6587 about the Casselman and other trout waters in the area, or visit www.springcreekoutfitter.com.

"The Casselman is heavily stocked with trout by the DNR," noted Harsh. "And many of the fish are large ones over 3 pounds. Trout over 6 pounds have been taken there, too.

"The DNR stocks both brown and rainbow trout. And there's a pretty good swim-up of brook trout from Pennsylvania's portion of the river."

The Casselman flows from Maryland into Pennsylvania. In the Quaker State, it is managed as a trout water from the state line down to the Moser Road Bridge.

"In the spring," said Harsh, "it's a very good fishery. As long as there's enough water to keep the trout alive, the fishing will continue into the summer. Then once again in the fall, around the beginning of October -- provided there is enough water flowing to sustain the fish -- it will be stocked again.

"Stockings then continue in January, February, March and sometimes as late as April. So it gets a pretty significant infusion of trout. Something like 15,000 trout end up in that four-mile stretch."

Harsh says that like many anglers, he starts his focus on the Casselman during the late winter or early spring.

"I'm out there early, as soon as conditions allow," said Harsh.

"Once the snow melts and the river conditions become decent, the Casselman comes up fairly quickly. But it also falls quickly."

Harsh's early-season outings are tailored to the coldwater conditions that prevail at this time. Your best early tactic is to fish slowly.

"Fly-fishing is my thing," he noted, "so during the early season, I'm going with big stonefly nymphs and Woolly Buggers -- something you can get down and get in their face with.

"The water is cold, so trout are going to be more lethargic. This is pretty much the deal from January through early March, until water temperatures start to rise."

Fly-fishing tactics begin to change around mid-April, when the coming of spring begins to accelerate the food chain.

"The caddis hatch will start once the water temperature reaches the 50- degree range," said Harsh.

"This is usually in early to mid-April. Shortly thereafter, when the water gets up to 52 degrees or so, various mayfly hatches occur."

Harsh said that the Casselman features several good mayfly hatches, though their frequency and strength varies from year to year.

"There's a really good dry-fly fishery once the water warms up," he said. "It starts with the caddis hatch. After that, there are midges, Quill Gordons, March Browns and a pretty good sulphur hatch. There can also be a good green drake hatch in the middle of May, if the water doesn't warm up too quickly."

The nearby Savage River and Youghiogheny River trout projects have cold-water influences from tailraces (in the case of the Youghiogheny, discharge from Deep Creek Lake).

But unlike them, the Casselman is a natural free-flowing river. Once typical summer weather arrives, it's subject to low flows and warm water temperatures.

"That's why Delayed Harvest regulations make sense on the Casselman," said Harsh. "The fishing is good during the springtime. But by the time summer rolls around, often it dries up to a trickle. People can keep fish after June 15 because during a normal year, they won't survive."