Frank Clark was up on Hunting Creek near Thurmont, Md., last week enjoying what he likes to call the "total trout experience."

That entails a clear, cold stream thundering down from the Catoctin Mountains; deep pools and busy riffles; and great stretches of empty space where there are no picnickers, minibikers, canoers, hikers or geology field-trippers.

It means getting up early in the morning, sorting out the right flies for the season, packing hip waders and fly fisherman's vest, clippers and pliers, varying weights of leader line for proper presentation of the fly, driving 75 minutes up I-270 and spending hours casting and retrieving, listening to the song of spring runoff greeting the rocks and rills.

These are stiff requirements, but something seems lacking.Like how many total trout in this total trout experience?

"A couple came up and bumped my fly," said Clark as he happily emerged from the woods, "but I couldn't set the hook."

In short, no fish. And even if Clark had enjoyed a banner day on Hunting Creek's speical fishing area, he'd have brought home at the absolute tops one trout. This is the phenomenon called fish-for-fun, civilized man's answer to the face, that wild trout no longer can withstand the intrusions of sport and meat-hungry man in the crowded East. The state stocks Hunting Creek every year, but not with the colossal supplies it dumps into "put-and-take" streams like Seneca and Beaver creeks. A thousand fish will be tossed into Hunting this year. The idea is to provide stock for a reproducing population, not meat for the cheese-ball fisherman's table.

The limit on Hungting Creek is one fish per day over 15 inches, which essentially is a no-fish-per-day rule. Trout rarely reach that length in these waters. In addition, fisherman are barred from using anything but the most demanding tackle - fly rods.

Just downstream from the fish-for-fun area is a dam and a pond of a couple acres - Frank Bentz Pond - where different rules apply. Fish are stocked on a put-and-take basis. Anglers can use any gizmo they want to catch them: worms, marshmallows, rotten liverwurst. The limit from the pond is five fish per day. Last week cars filled the little parking lot at Bentz Pond, but no one was fishing. "What's up?" two anglers were asked. "Waiting for the stocking truck," they said. It never came.

Meantime Clark, vice chairman of the Maryland Coldwater Coalition and vice president of Potomac-Patuxent Trout Unlimited, was reading the rushing waters, doping out where real trout would lie, walking, wondering and getting lost in time and the miracle that is the quiet invasion of some other creature's world.

Fish for fun. Even getting skunked can be a pleasure.