If you own a dozen fly rods, you probably couldn't care less about the opening of Virginia's trout fishing season at noon this Saturday, or Pennsylvania's opening at 8 a.m. next Saturday. Purists who delight in the beauty of a secluded mountain stream and the challenge of a head-to-head confrontation with the aristocrat of gamefish generally take a dim view of the carnival atmosphere that pervades these states' trout waters on the first and second Saturdays in April each year.

But the thousands of less picky anglers from Bristol to the Poconos, the openers are magic moments not to be missed.

No matter that throngs of brightly garbed anglers will be packed in like fingerlings in the hatchery troughs. No matter that the fish were bred in captivity and only recently plopped into the natural stream. No matter that they've been fed pellets from the hand of man, been spared the rigors of harsh spring torrents and cutthroat competition for food and living space.

It's opening day!

Young and old, male and female, once-a-year dabblers and life-time anglers will be out there on these two longed-for days. On these two Saturdays in April thousands of fisherman who have little other contact with trout throughout the year catch fish, often in exquisite mountain settings.

And for many of them, it's their only chance. most of the anglers out on the opener lack the skill, knowledge and patience required to take trout consistently once the fish have adjusted to their life in a natural stream and taken on a chary outlook toward the business of feeding.

The Virginia and Pennsylvania openers are prime times for family angling, also -- one time a parent can take a novice out for trout and expect him or her to catch at least a fish or two.

So yes, the opener is a bit artificial. And yes, it's crowded; but as long as they are with us, opening days can offer some old-fashioned fun for those who take them in the right frame of mind.

So bring a light and tolerant attitude first of all, if you venture out in Virginia this Saturday or Pennsylvania the following Saturday. Secondly, bring bait.

The bulk of the million-plus trout in Virginia and the 2.7 million trout in Pennsylvania that have been stocked by the fish commissions were raised on ground meal pellets. They're usually suckers for a lazily presented natural bait -- at least during the first few hours, before the sting of a few hook barbs makes them cautious about wolfing down all that "meat" drifted in front of them.

Salmon eggs, cheese ball (yuk!), night-crawlers, garden worms and live or salted minnows will draw solid, pecking takes from the hungry fish. Impale them on a short-shank No. 8 or 10 gold hook and crimp on a tiny split shot or two a foot above the hook for weight.

Light line is best, say two- to six-pound test, so the offering will drift naturally in the flow. Toss the bait upstream and quartering across. Let it drift down easily, without any manipulation, through slow pools, deep runs and pockets in fast water. Under-cut banks and swirling eddies off the main current are also attractive to the trout, since they've had to fight little current before in their hatchery lives, and are eager to escape the main tugging flow in the middle of the stream.

As the line drifts below you, slowly reel in and cast again, covering a different section of water. More work is involved in this technique than simply anchoring your bait on the bottom and waiting for a bit, but the "natural drift" approach will yield far more fish. When you feel a nibbling trout or see your line twitching or moving upstream, strike back quickly or the fish will make like a thief with your bait and be gone.

Rainbows are the fish you'll most likely encounter on the opener, but some browns and brookies are stocked in both states. (The recent fish kill in Virginia, which took the lives of half a million young trout, will not affect this year's stockings, since these were fingerlings destined for planting in '81.) In Pennsylvania you may even luck into a cream-colored palomino trout, a hybrid of the rainbow. Stocked specimens normally run 9" to 12", but a few bigger brood fish are customarily dumped in. And there are always some holdover trout and occasional wild fish in the better streams to add spice to the creel.

The creel limit in Virginia is six fish in most waters, five trout in a few lakes listed in the fishing regulations. There is no size limit. In Pennsylvania the limit is eight trout a day, with a statewide 6" minimum size limit. In Virginia a trout stamp is required, in addition to the regular fishing license.

Don't expect solitude or a spiritual communion with nature if you venture out for the openers in Virginia and Pennsylvania, but for high odds at creeling a few fresh trout for the skillet, the next two Saturdays are good bets.