The streams have shrunk in their beds, mere vestiges now of the spring freshets. April's rain-clouded pools and bulging currents have been replaced with transparent flats and ankle-deep runs.

Vulnerable hatchery trout, so common and so cooperative during spring, have dwindled to a hardy few survivors that are now nearly wild, and schooled in telling the real from the ersatz. And the truly wild trout are even more skeptical about what they eat than they were before.

They are vulnerable, these trout lurking in the thin, sunbaked pools. And they know it.

The big, erect-winged mayflies and large fluttering caddis that we drifted over them in May now look as out of place as a yacht in a farm pond. Heavy spoons and gaudy spinners that scored in spring now send trout scurrying for shelter. And if the spoons don't, all too often the shadows and vibrations of a clumsy angler traipsing up the stream's edge do.

A bleak setup for trout fishing, it seems. And the response of many anglers to this challenge is to simply give up trout fishing until the easy sport of April returns next year. Still, a few anglers have discovered that with alterations in their approach, surprisingly fine trout fishing can be enjoyed, even now. Best of all, since their numbers are so few, these anglers can have broad reaches of water all to themselves.

But to catch the late trout requires respect for the changed conditions the fish face. Their world has shrunk; its clarity has intensified, and the successful late trouter will stalk his quarry like a cat. Your knees and back will ache at day's end from hunkering down and creeping toward the quarry, but the effort will pay off in fish on the line.

Tackle that worked in spring must also be replaced with refined gear suited to the heightened clarity of the water. Two-pound line is best for spin fishermen, and rods must be light-tipped models that will not snap such fine monofilament on the strike. Lures, too, should be scaled down; often the same varieties that scored in spring -- jigs, spinners, grubs, spinnerbaits, banana-shaped wobblers -- will still produce, but only in smaller sizes. Live baits can still produce fish, too but again it's the smaller, less obtrusive varieties that work best. Red wrigglers and earthworms are perfect; so are grasshoppers and crickets. Thread them loosely on a No. 8 or 10 hook, crimp a tiny split shot a foot above them, and drift through deep runs and where riffles merge into pools.

Fly fishermen have the best chance of all, in part because many "fish-for-fun" waters nearby are reserved for them. These regulated areas almost always contain a greater abundance of trout at this time of year than waters with normal rules, because almost all of the trout must be released unharmed.

Fly fishing also offers the best method for delivering those tiny, refined offerings that duplicate the common late-summer trout foods. Midges in both pupae and dry patterns, sized 20 to 26, will dupe trout in any stream now. Hatches of tiny mayflies, such as the Tricorythodes, which emerges so profusely on Pennsylvania's Falling Spring Run each morning, also offer prime fly fishing now -- on this stream dun and spinner immitations tied on No. 24 and 26 hooks and delivered on gossamer tippets will fool trout as long as your forearm. Getting such fish in on lines testing less than some brands of sewing thread is another matter entirely, but it's fun to try.

Terrestrials are perhaps the most important flies of all for the summer angler, since these foods are available to trout in almost unlimited quantities throughout the entire day. Ants, beetles, crickets, hoppers, true bugs, caterpillars -- all are grist for the mill of the hotweather trout. Deliver the larger of these patterns with a tiny "splat" to imitate the entrance of the naturals into the stream, the smaller ones with a gentle, traditional presentation, and hearty rises are guaranteed, in spite of the heat that's dried their streams to a trickle.